VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

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VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 08 2010 8:56pm

Image

This pack came from Bluestreak, unpacking shown here:
http://www.endless-sphere.com/forums/vi ... 94#p329294
Image
It had a failure of the 4th string up, down to about 0.4V or so, measured at the balance taps. Not likely to be a simple broken balancing wire because it caused his trike to cut out (LVC?) at any real current draw.

I was suspecting a mechanical failure of cell connection inside, perhaps tab weld failures, based on the assembly of the BMS:
Image
That melted wire and bad soldering is from VPower/CammyCC. :(

I decided to disassemble the pack by unwrapping the duct tape, rather than cutting it off, as this tape has nice strong adhesive *but* doesn't stick that well to it's own top surface, making it ideal for unwrapping and saving/recycling the tape itself (either in rewrapping this pack or just as bits and pieces as I need duct tape :lol:). I just used an empty tape roll to put it on, though I didn't keep it lined up with the edges very well as I went.
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One layer of tape (about half a roll!) later, I get down to the corner-tape edges, and the cardstock protective layer.
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A little struggle getting the corner tape off; I couldnt' save much of it as it tore up in little pieces. Down to the bare cardstock, now very sticky with leftover duct tape adhesive--so much so that I had to wiggle it to pick it up off my table. :lol:
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Peeling the cardstock back took a little doing in places, as there is a LOT of glue (hotglue I suspect, haven't tested the theory) in crisscross lines securing it to a *second* layer of duct tape underneath.
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I suspect that based on the way it peels away from the duct tape on the four large sides but not on the two small, that it was applied directly from the glue gun on those two small ends to the tape, with the end pieces of cardstock then pressed onto the glue. The glue was probably applied directly to the cardstock on the larger sides, and then folded over onto the tape underneath.
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There's pretty much no way short of ripping the tape up to remove it from the ends, so I decided to leave it in place for the entire pack at this stage,
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especially as you can see the cardstock dividers that separate the two halves of the pack
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so I don't have to guess where things begin and end.
It's also clear where the balancing wires go in, and that they lay under the top layer of this duct tape
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(and that there is at least one nicked wire there, from the original pack build AFAICT). Given that, I decided I would not peel the rest of the tape off, but leave it as-is, and just trace the two balance wires on either end of the bad string,
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then cut away the tape around that string so I could diagnose it
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I'm holding the two balance wires there, plus the tape away from the cells. Turns out they use 18 parallel 18650-sized cells, presumably 1.1 or 1.2Ah each.
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The "top" two rows in that pic are the problem string. I tried to just peel the series-connecting tabs on each end away from the problem string, but it pulled away so easily that I damaged the paralleling tab welds on the end cells of the neighboring string it was attached to, and ended up pulling the series tabs off entirely. :(
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My 80-90W soldering iron is going to be thoroughly tested on heating this fast enough to solder it down without damaging cells. :?
I only meant to remove the series tabs so that I could test each half of the bad string to see if one was higher voltage than the other.

I found that the "top/right" half of the string is about 0.44V, and the "bottom/left" half is about 0.39V. So if there is a bad cell it's probably in the lower-voltage section, right?

Anyway, I left them that way for half-hour, unconnected to each other or anything else, but neither half recovered anything (I didn't really expect it to).

Given that plus the tab weld quality I already saw on this side, I decided I'd better take a look at the other side, seeing as a poor connection might cause something like this problem, where it doesn't charge the string right at least sometimes, and it fails to supply power to a load. I slit the tape down the whole black-lined section, and found two *more* problems, both mechanical. :roll:
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The first was the balance wire you see loose in the above pic--it just fell out of the "upper" half of the pack; it goes to the end-most inside cell ends. The solder joint is not apparently very good, although you can't see it well in this pic
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even though I circled it in red.
Worse, the main power output connector's crimps are terrible--they didnt' even hold the wire in when I opened the pack up and it pulled just a little on them, at the angle you see in the pic. The black came out first, and the red came out while I was holding the connector trying to see into the black heatshrink to see what had happened.
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The crimps basically aren't crimped at all. It almost looks like they just pushed the wire into it, then heatshrunk around it hoping that would hold the wire in. :roll: :(
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If Bluestreak had had to unplug/replug that BMS-input power connector more than a time or two, I expect it'd've come apart in his hands like this.


Anyway, I checked the other side (forgot a pic) and found no tabs broken off of cells or anythign AFAICT. So I started voltage testing individual cells, after having very easily pulled the paralleling strips off on the negative (outside) ends. I tested each cell in both halves of the string, and found my earlier measurements about the same for every cell in each string, whcih I didn't expect.
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I thought I'd end up finding only a cell or two or few that were still the lower 0.39V, and the rest at the higher 0.44V.
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So the only good way to test these was going to be to apply external voltage to them, and see if they charge up, or react normally vs in unusual ways.

First, I simply set my little Sorenson to 500mA at 3.60V, and hooked it's positive plus meter positive to the positive paralleling tabs for this string. The negative side of the Sorenson and meter I clipped together, and applied to each cell's negative end for 30 seconds while watching the meter.

In doing so I found only one cell that reacted differently.
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Each of them except that cell slowly climbed to about 2.6 to 2.7V, just as 30 seconds was up. The X-marked cell climbed in about 4 seconds to 3.6V, same as the Sorenson was set to, so it is probably dead.

I am now individually charging each of the other 17 cells at the same Sorenson settings for 30 minutes per cell, to see what voltage they reach and then will leave them for a while and see what they drop to, or if they hold that voltage.
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After I took the pic I decided to dig out the Fluke and use that instead, as it in theory is more accurate than the one in the pic, and that may matter in this case.

It'll be a while before I have them charged up this way, at least 8.5 hours, and then I will probably be trying to sleep to get up early in the morning, so likely no new news on this for at least another day. I might not even finish charging them up before I have to sleep. :)


.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by dnmun » Nov 08 2010 10:22pm

why are they pink? the ones on the vpower pack i am working on are all silver grey.

i had the same non crimped power connector.

the pack i am working on had a crushed cell on the end where someone had dropped the group of cells after they wrapped the first band of tape around them.

when the end cell was crushed, the cell next to it shorted out the metal strip to the case from the top of the cell, and that burned out the strip so that the balance wire was separated from the other cells in parallel.

but that was row#1, and i was able to charge it back up and it held a charge.

but the second row, #2 was totally dead just like the one you have. voltage at .37V and it would not take charge at all.

i think you will be better served to expose the entire pack and find everything wrong with it now, then figure out what to do.

all those cells are dead, you can't solder them either. you gotta find a spot welder. the welds on this one were so bad that the spot welds pulled apart when i pulled the tape off and 3 cells fell out of the pack loose, about a dozen in the pack have such bad weld that they are either loose on one end and flopping around, or in the middle with the tape separated from the cell. really bad.

plus it weighs as much as a SLA.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by BLUESTREAK » Nov 08 2010 11:22pm

HI AMBERWOLF: I am sorry that I did this to you. :mrgreen: :mrgreen:

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by Samba » Nov 09 2010 12:55am

Thanks for sharing, that battery makes me want to swear off duct tape forever. At least the first pic has a good lookin dog in it.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by dnmun » Nov 09 2010 1:01am

they spend more money on duct tape than on the cells. if they had just left the duct tape off then most of the bad welds woulda remained intact.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 09 2010 2:01am

dnmun wrote:why are they pink? the ones on the vpower pack i am working on are all silver grey.
I guess somebody wanted prettier cells the day they made this one, and they were depressed the day they made yours. :lol:

Actually I wondered about that too, because silver-grey is what I have seen on all the pics of these packs so far, and what I expected to see when I opened it up. I am curious as to what the difference in cell or cell origin is.

Any advice you have about workign with this pack is welcome, although I may not follow it. ;) I definitely want to hear (read) it.
the pack i am working on had a crushed cell on the end where someone had dropped the group of cells after they wrapped the first band of tape around them.
Great. :( And of course being in a hurry and not really caring about the quality of the product, they didn't bother to unwrap and check it. :(
i think you will be better served to expose the entire pack and find everything wrong with it now, then figure out what to do.
I will, but first I want to check the "dead" part of it. That is easier and safer if I can't accidentally short out other cell groups while I'm working with it. :lol:
all those cells are dead,
I'm not convinced of that yet, based on the revival others have said they've been able to do for LiFePO4 cells if they were not reversed or dead-low for very long (these haven't been, if I understand Bluestreak's problem and timeline correctly). I don't expect them to have the same kind of capacity or C-rate they had before, but they may still operate well enough for my purposes.

I have been charging up the cells as a test since my last post, and have gotten all 5 of the ones I've been working with up to 3.4xV, which is the same as the rest of the cell strings are at right now. That's just with 30 minutes per cell at 250mA. (I'd intended to do 500mA but decided to halve that, because even 250mA is probably is too fast a charge). I won't know more till tomorrow or the next day, as I need to try sleeping now and have to shut it all off for the night (to ensure dogs don't bump it and cause a problem).

All the cells I'd spent the 30 seconds with up to 2.6-2.7V before are all still at that voltage, a few hours later, except the cell with the X, which is back to about 0.35V. It's definitely dead.
you can't solder them either. you gotta find a spot welder.
Yeah, I realized right after I did it that removing the strips instead of just cutting them between cells was really stupid. :( :oops: But I sort of half-expected to find the entire string dead or useless anyway, and thus irrelevant what I did to it. ;)

I can almost certainly make a spot welder based on the thread about that. I have enough very large capacitors plus a few high-current linear power supplies to charge them up that all I need is the SCR, and I think I have one of those, too. The dead cell can serve as my test bed for welds. I expect my welds will be of the same quality (hopefully better, but...) as what it came with, so I can't really make it much worse. :)

I'm also willing to experiment with potential solder methods (if any exist) on the dead cell. Too bad brazing requires such high temperatures or that'd work great on the steel casings. :lol:

I'm also considering the methods used in "building a cylindrical pack for dummies" thread, taking the entire pack apart and doing that instead. It's already built in basically 2x 24V packs in series, so I can do it the same way, as the spring-contact boxes. Might go with 12V packs, though, just so it's easier to stack them and such.

the welds on this one were so bad that the spot welds pulled apart when i pulled the tape off and 3 cells fell out of the pack loose, about a dozen in the pack have such bad weld that they are either loose on one end and flopping around, or in the middle with the tape separated from the cell. really bad.
I'm not terribly surprised at that, given what I've seen already. I fully expect to find stuff like that in here once I get that far.
plus it weighs as much as a SLA.
Not really, though it is very heavy! Also it has way more capacity and capability than an SLA, given how badly Peukert affects the SLA vs LiFePO4. ;) My 48V of 17Ah SLA is around 55lbs, IIRC. This definitely doesn't weigh nearly that; probably half, maybe a bit more? Have to put it and then the SLA on a scale later just to see. :) Also the 48V 13Ah of NiMH.

The 32V (10 cells) of TS60Ah LiFePO4 cells weigh around 42lbs. 48V of them would be about 63lbs (15 cells), and would be three times the capacity of this pack, and more than 3.5x the capacity of the SLA pack even not counting Peukert losses. :lol:

dnmun wrote:they spend more money on duct tape than on the cells. if they had just left the duct tape off then most of the bad welds woulda remained intact.
Because they wouldn't have had pressure on them in different ways than when the welds were made?
Samba wrote:Thanks for sharing, that battery makes me want to swear off duct tape forever. At least the first pic has a good lookin dog in it.
I guess duct tape on a prismatic pack makes sense, given that some kind of pressure needs to be kept on the cells. But on one of these the only reason is to save money that would have been spent on other types of enclosures that would probably have kept the whole pack safer and more mechanically sound.
BLUESTREAK wrote:HI AMBERWOLF: I am sorry that I did this to you. :mrgreen: :mrgreen:
I'm not--it's interesting, and if I can fix it right I'll have a nice battery to run a bike on, or the trike. :)

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by dnmun » Nov 09 2010 3:15am

wow, he gave you that for free? i gotta start asking for free stuff too. greg gave me the signalab BMS he burned up with a lipo booster pack. since it was ruined already i didn't have to destroy a new one to see how they were designed. jerry garcia gave me some headway chargers to fix too. the only way to learn the stuff, imo.

look at how the pack is laid out and you may be able to reorganize it so you can cut out that group of dead cells. then find a spot welding guy at a battery repair shop and let him weld it together in the new format.

i think this pack is will have to be rebuilt that way. it is 36V 20Ah so 12 rows of 18 cells, so i can cut out the dead row(#2), and row #1 has only 16 left since the two on the end were destroyed.

so excluding the first 2 rows, i can cut 6 off each remaining row so i would then have 11 rows of 12 each and 10 sets of 6 each plus 4 left from #1 above the 12 needed.

then build 5 sets or rows of 12 each outa the 10 sets of 6 which leaves an extra set of 4 spares, add those 5 rows of doubled up sets to the others to get up to 16 rows 16S of 12 wide or 13Ah wide. so it would then be a 48V 13Ah pack, and i would use the ping v1 signalab on it with a 48V charger.

i think they dropped this pack before it was wrapped with the final outer layer of duct tape and cardboard since i saw no dents in the exterior where the cell was crushed, so it happened during assembly in china.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by MrKang » Nov 09 2010 6:01am

Good job Amberwolf ! i hope only one cell is dead instead of the entire cell-string
i had a pack with the same problem, only mine also were silvergrey and a whole cell string was defective.
but i replaced it with a new cell string for only 20 dollars from V-Power. Now it's working like a charm again.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by texaspyro » Nov 09 2010 7:50am

Dog says "Gee, this pack smells craptastic..."

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 09 2010 1:54pm

That's certainly a possible thought-bubble caption. :) Or "How many licks will it take to get to the chewy center?" ;)
dnmun wrote:wow, he gave you that for free? i gotta start asking for free stuff too.
Well, I didn't ask for it, but did take the offer when it was given. :)

When I do ask, I only ask for stuff that is broken or otherwise probably not going to be used anymore (like when people change out chainrings or other stuff, or burn something up and say they're not going to fix it), and I offer payment or trade but I don't have much to offer either way these days. Sometimes I get things cheap, sometimes they are outright donated. A fair bit of stuff that has been donated was not asked for at all (wouldn't have thought to do so).

greg gave me the signalab BMS he burned up with a lipo booster pack. since it was ruined already i didn't have to destroy a new one to see how they were designed. jerry garcia gave me some headway chargers to fix too. the only way to learn the stuff, imo.
I've still got a couple of damaged Signalabs that I need to get around to fixing. One of them mostly works but has a few badly-behaving slots, the other I forgot what is wrong with it, and would have to look it up. I was originally hoping to figure out how to change the off-chip reference voltages so I could use it with the LiCo cells (as the chips on there were designed for that range AFAICR).


look at how the pack is laid out and you may be able to reorganize it so you can cut out that group of dead cells. then find a spot welding guy at a battery repair shop and let him weld it together in the new format.
Only place around here I know of that does spot welds charges at least a buck a weld, at Batteries Plus. Given how many welds this will probably need, I would be better off building up my own welder and learning how, even if I end up having to buy some parts to make it (like the SCR).

-i think this pack is will have to be rebuilt that way. it is 36V 20Ah so 12 rows of 18 cells, so i can cut out the dead row(#2), and row #1 has only 16 left since the two on the end were destroyed.
-so excluding the first 2 rows, i can cut 6 off each remaining row so i would then have 11 rows of 12 each and 10 sets of 6 each plus 4 left from #1 above the 12 needed.
-then build 5 sets or rows of 12 each outa the 10 sets of 6 which leaves an extra set of 4 spares, add those 5 rows of doubled up sets to the others to get up to 16 rows 16S of 12 wide or 13Ah wide. so it would then be a 48V 13Ah pack, and i would use the ping v1 signalab on it with a 48V charger.
That's a thought in case my attempt to recover the other 17 cells in the row doesn't work, but I'd do this one as 48V at whatever Ah it ends up as if I take off enough cells to make a new row.

If it does work with just the one dead cell removed, then at least for first testings I will leave the rest of the pack as-is and use it as 48V 18.9Ah (or whatever capacity that damaged row ends up as). After I do some test runs/cycles I'll open it up fully and reconfigure anything else that doesn't work right. :)

MrKang wrote:i hope only one cell is dead instead of the entire cell-string
i had a pack with the same problem, only mine also were silvergrey and a whole cell string was defective.
but i replaced it with a new cell string for only 20 dollars from V-Power.
Plus what shipping cost? I do hope it is just one cell, but I suspect there are other pack problems, possibly other cells within the pack that are not 100% either, which I will hopefully find before they kill other strings. Even this string could all be bad and just look like they're charging up ok.

I left the whole pack unpowered last night from my last post above till now, nearly 12 hours. The 5 cells I'd gotten charged partly up (1/8 charge if I figured correctly) are still at the same voltages I left them at, so they are retaining the charge so far (with no load). Same for the rest of the cells that I left with the 30-second charge. The dead cell is still dead at the same voltage.

So there is some small hope. :)

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by bigmoose » Nov 09 2010 6:29pm

Amber I have to tell you I am impressed with your systematic approach in repair. You sure know how to document it also. Your pix provide an ongoing commentary. That said, I remember a time when you were worrying about work hours and such. What came to mind was an offer to me from a guy who resold laboratory equipment. He "contracted" out the repair and calibration. He was a one man shop with a warehouse. His contract repairmen either worked in his facility, or took the equipment home and brought it back repaired. He told me his head repairman was making over $140 K/yr and that was 8 years ago.

My thought is there any "little guy" doing this type of work/service in your area? You have skills amberwolf, I just think things should be easier for you!
Last edited by bigmoose on Aug 07 2011 5:53pm, edited 2 times in total.
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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 09 2010 10:42pm

I dont' know if there is anyone like that around here, but I suppose I could look around. :) I haven't done much fixing of test equipment so far (though I have a fair pile of such like my old Tek 531A that all need some TLC to work better or at all), so I don't exactly have lots of experience at that. Might not matter depending on the employer. ;)

Documentation I used to do even more detailed than I do these days, but have been highly discouraged from that over the years by various employers who really don't care about documenting *at all* but just want the work done and out the door. :( It was only appreciated at Honeywell CFSG where the more paperwork the better. :lol: So I learned to skimp a lot on the details, and it's hard to get back into doing it again even for myself (I keep waiting for someone to yell at me to get more work done and quit "screwing around"). If this were 20-25 years ago, I'd have six pages on the disassembly of the pack, with pics of every step and possibly long boring full video, and minutiae that would impress the most deskbound bureaucratic paperpusher. :P

As for work hours, I am currently getting almost a full work week (one reason I don't have enough time for my projects, the other being taking care of the dogs and being mroe and more tired these days in general), but it is still not quite enough to make all the bills all of the time without being *extremely* thrifty as well as lucky with dog and people food clearance sales and such (getting ~$420 worth of puppy munchies for ~$140, for instance, last week, which ought to last about 3 months or so, I hope). I still take side work when I can get it, but that's harder and harder, as so few people are willing to actually pay for work and seem to expect it for free or nearly so--I'd rather just keep my time for myself and do my own projects or rest if it's less than $10/hour! (I almost make that much at my dayjob) Depends on how close my budget is running or if there are things I need to get outside normal budgets.

Mostly, there just isnt' enough time in the day when I am able to do stuff (my time on ES is when I am in bed anyway, either trying to sleep but unable to or not feeling well enough to be up and around doing other things). I'm not as bad off as Dogman in that respect yet, but I can see the day when I will be. :(

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by bigmoose » Nov 10 2010 8:16am

Glad to hear the work is up to full hours. Surprisingly your pix and documentation style is very close to what we used to contract out for the preparation of assembly and repair manuals 20 years ago. We were the first at our company back then to go away from line drawings by artists to color photos with callouts and text.

Thanks for the update, and wishing you all the best Amberwolf. Keep up your creative repurposing. We enjoy and learn from your threads!
Last edited by bigmoose on Aug 07 2011 5:53pm, edited 2 times in total.
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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 10 2010 9:06pm

Thanks for the encouragement. :) I need that sometimes.

The cells seem to be operating normally so far. I am up to 10 cells partially charged and each previous one is still holding the voltage it was left at. I'm hoping to have the rest of them charged by tonight.

BTW, I accidentally left out the connection method for the cell-by-cell charging from the previous posts. I borrowed the idea mentioned somewhere in another battery thread (about A123 I think) that since the cases are steel, they're magnetic. So I just used a little button magnet off one of my old work badges (we use clip-on ones now, which look stupid and wrinkle and break all the time), to hold the negative wire in place.
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The positive wire is alligator-clipped to the tab on the positive side of the cell string.
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Also, early on I found the Sorenson's current meter has a bad connection inside, so sometimes shows zero current even when it is supplying full power. I put one of the Harbor Freight meters in series set to the 10A range to monitor current instead--at least it will be consistent, if not necessarily perfectly accurate.
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All I need is to know if it is still pushing current into the cell or not, and about how much proportionally to what I had it set to. :)

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by grindz145 » Nov 10 2010 9:24pm

Amberwolf do you srsly work in retail? You could definitely be working in engineering somewhere :mrgreen: Of course you may or may not be better off doing that.... Either way nicely done!

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by icecube57 » Nov 10 2010 10:51pm

With a hot enough iron and some sand paper I was able to wet the ends of konion cells with a nice rounded bead of solder. It didnt take long for for the solder to grab maybe 2-3 seconds tops. And you could run some solid copper conduit or braid to link them back together again. Soldering is possible. They are already held in place.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 10 2010 11:17pm

Are the konion cells steel-cased, or are they nickel-plated or something? How hot an iron did you use?

Since there are still tiny little dots of nickel tab welded to each cell end, I *might* be able to get solder to grab those, and work from there. But I dunno if that's enough.
grindz145 wrote:Amberwolf do you srsly work in retail? You could definitely be working in engineering somewhere :mrgreen: Of course you may or may not be better off doing that.... Either way nicely done!
I get from a fair number of people (including prospective employers) that I ought to be doing somethng "important" but really none of them have any options or intentions of letting me work for them to do that. :( Lots of those prospective employers don't want me around because (I suspect) they think I'm smarter than they are, which might or might not be true, but they sure don't want me there as competition for them. They just don't realize that I am happy to be doing something that earns enough money to stay afloat (I don't care about being rich or even well-off, as long as I have a place to stay and can keep myself and the dogs fed and whatnot, and do my projects).

I don't *want* to move up in a company, and have zero desire to be in charge of other people at all. I'm happy to stay at the bottom of the food chain, especially since that's where I've always been anyway. Besides, no one would let me implement my ideas for changing things in businesses anway, since they would not result in short-term profits, which is all they ever care about, rather than long-term customers and whatnot.


I've been in retail since getting laid off from a final test tech job at Honeywell CFSG back in 93/94 (I forget exactly when now) along with a few thousand other people, and having been unsuccessful for various reasons at a couple of component-level repair shops shortly afterward, as well as an inventory counter and other odd (boring) jobs, until late 95 when I started at Computer City as a pc tech and "upgrades" salesperson, then moved to CompUSA when they bought out CC, until CUSA finally died from terminal executive stupidity in 2007. Took a couple months off from working at all with the "bonus" for staying to the end they gave, and then tried hard to find work in just about any field at all around here, with some places telling me I'm overqualified and to go away, and the rest never responding at all.

But I don't have an engineering or bachelor's degree (just AASET), so I don't qualify for most of the positions that would involve the kind of work I'd probably enjoy doing. Plus I don't get along with math very well--it's a brain thing, I guess; I also don't get programming too well either.

Retail doesn't care, so here I am. :roll: At least it's a job. And I actually like some parts of it; just that retail in general can be a very sucky job, knowing that you'll never be allowed enough time to finish any task you're given, nor enough people to do all the tasks that must be done, because if you have enough people then obviously you're spending too much money and wasting profits. :roll:

Mostly I gave up years ago trying to find a good place to work, and just stick with whatever I have, since I know that in general I will probably outlast the company itself, certainly outlasting all the people I don't like to work with, :) and that it's good enough. When it is too much to deal with and I have somewhere else to go, I will, but mostly that hasn't happened. I'm better at dealing with people now than I was years ago when I last quit something due to people conflicts, although I still don't understand a lot of what is going on between people around me beyond the general impressions.

That last is part of why I probably don't interview well enough to get a job; I can't read people well enough to suck up to them like many other interviewees can, so I stick to truth and facts and clear answers, which seem to never be what interviewers are looking for. :(

Being deliberately carless has cost me some jobs for sure; I've been told outright a few times that if I had a car they'd hire me, even though the desk job does not require travel, and they even encourage people to take the bus all the time instead of driving in due to insufficient parking at the locations. :roll: But they dont' want people riding bicycles to work, for whatever stupid reasons. That's ok--I wouldn't want to work at a place with people that have that kind of attitude.

Anyway, that's probably a lot more info than you were expecting in response, so I'll stop now. :) :oops:

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by grindz145 » Nov 11 2010 8:50am

amberwolf wrote:
I've been told outright a few times that if I had a car they'd hire me, even though the desk job does not require travel, and they even encourage people to take the bus all the time instead of driving in due to insufficient parking at the locations. :roll: But they dont' want people riding bicycles to work, for whatever stupid reasons. That's ok--I wouldn't want to work at a place with people that have that kind of attitude.

Anyway, that's probably a lot more info than you were expecting in response, so I'll stop now. :) :oops:
Hah, that pretty much says it all. It just shows how much better off industry could be with a different attitude.

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 13 2010 1:49am

I have not been doing well at all the last day or so, so I didnt' get much done with this. All the cells in the string except the dead one are now charged to the same approximate voltage (3.38 to 3.42V). I went back for a second round of charging at 500mA, and if I calculated correctly, each of them now has about 1/2 full charge, or about 0.5-0.6Ah. I probably should have actually measured this with a wattmeter, but I didnt' think of it till I'd already done the first partial charge on most of the cells. Figured it doesnt' matter at that point.

They've also all held these voltages for today. Maybe I'll get to testing them with a small load tomorrow. Assuming they hold voltage at the load current, then I will work out a way to connect them all at least temporarily (with magnets and wires if I have to) and hook the pack back up to the BMS and try to charge it with the Sorenson 55-55 as a power source, with a wattmeter inline to monitor total input. I am sure most of the cells are full other than this string, so I expect all the shunts to get warm except the one for it.

Assuming this appears to work normally for a few minutes, I will then disconnect it and charge only this string as a string until it's theoretically full, monitoring with a wattmeter, and then after it's at that state, reconnect to BMS and Sorenson and see if it thinks it's full or if it tries to do further charging, etc.

Then I'll work on reconnecting the string to the pack in a way that can take an ebike-class load, and test it with that, to see about voltage drops, etc.

If it still works after that, I should probably open up the rest of the pack to examine tab welds and whatnot everywhere in it, and fix anything I find. I also should replace these ribbon-cable BMS wires with the teflon wire I've got from the aircraft panels. Then if something somehow goes wrong and a balancing wire heats enough it wont' melt the insulation and short to cells or whatever, and they'll be much less likely to get nicked by anythign I do with the pack.

I am also probably going to see how many of the thicker clipstrips I have around, saved from old product displays at the store, and make some better encasements for the pack, since I dont' trust duct tape and cardboard to prevent a puncture/scratch that could short out cells. The clipstrips won't stop everything either, but they'd be better than that (I've used them on the NiMH packs and been saved from at least one almost-incident because of them, when I was installing them on CB2 for the race and a hoseclamp slipped as I was tightening and I didn't notice till later. It'd've shorted across four series cells if I had not had the plastic there!).

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by Ypedal » Nov 13 2010 7:51am

Aaah the evil duct tape pack repair ....

The pink/beige cells are older stock ( 2008 or so ) , the newer batch are grey..

http://www.ypedal.com/cammycc/Index.htm

I was able to solder them up, rough up with a sanding disk, some flux and a hot iron..

word of caution on the magnets ( I made that post a few weeks ago, DrBass also does this lol ) be carefull they don't slip and bridge cells you don't want bridging, the magnetic properties makes it hard to knock off in a hurry.. :wink: Lay a piece of tape across the cells nearby to prevent accidents imo !

More than likely the cells that went below 1.5v will not recover with any usable capacity, they sag horribly on any that i have tried to salvage... nothing to loose by trying tho !
ES site status page:
http://www.ypedal.com/ES/ES.htm
----------------
http://www.ypedal.com

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 13 2010 7:29pm

I can imagine the magnet bridge becoming unmagnetic quickly as it heats up from teh short, but then the heat would make it hard to pull off. :lol: Not likely a big problem on stuff other than A123 because of C-rate, but I can still imagine it.

I left all the duct tape as you see in the pics, so it covers all cells that would be bad to connect across. Only cells taht were originally connected have ends exposed where this could happen, so it should not be a problem. :)

The faster charging went ok (I coudln't sleep well so I kept rotating between cells thru the night). I wasn't awake enough to remember the wattmeter much less charge them as a string, so I just did it one at a time. I think they are probably about full at this point, and all of them are around 3.38-3.41v with no load.

I have not hooked the BMS to it yet, or charged as a pack with the Sorenson. To use it I have to lift the Sorenson up onto the top of the washer in the utility room, then plug it into the dryer receptacle over my head height. Neither one of those is possible at the moment, and I also probably couldn't lift the pack itself up to sit on top of the charger.

So today, in the last hour or two, I only tested it for individual cell voltage under load with some paralleled 2W resistors, which got too hot to keep holding after a few seconds (I think I was off by a decimal place in the final resistance value, because the current ended up about 9A on that test, a lot higher than I intended--ok for a few seconds I guess). But the cells held 3.30V on every cell; they went back up to 3.33-3.38V afterward. Burned off surface charge I guess.

Then I decided to try soldering on the bad cell, using the 80W 900F Weller fat chisel tip iron,
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and found that it soldered VERY easily to both positive
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and negative
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ends of the cell, with less than 3 seconds on the negative end and about a second on the positive. The cell itself was still quite cool to the touch all over immediately after soldering. Room temperature is about 65F at the moment, perhaps a degree or two warmer than it was when I started I'd guess since the iron has been running for at least half an hour, probably 45 minutes, and the lights and other stuff have been on for several hours, plus me and the dogs in the room warming it up before that. The cell felt like it was about 70F at the most, at the soldered ends, through my highly calibrated digital fingerprinting thermometer. ;)


Since that went so well, I figured it'd be ok to solder right to the other cells, and that worked even easier, since the pack held them in place for me.
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One row I used the original nickel strip, but the other one I have somehow lost so I used some of the flexible braid off the outside of old 75-ohm RF cable I'm pretty sure I'll never use for it's intended purpose again. :)
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Same stuff I'm using to make the interconnects for the TS60Ah cells once I get back to that. Also used that stuff to connect the fixed strip back to the pack on that side (I'd left it connected on the other side).
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I tried to make a video but it didnt' come out right, stupid autofocus on the camera blurs everything I try to show into invisibility; you can see my hands moving and some shiny stuff but tha'ts it. Can't even tell what stuff is much less what's happening.

So some text description is the best I can do, since I can't take a still pic of it as I need to hold the camera to do that (or at least press it's buttons, and the timer is too short to setup the shot), as well as the soldering iron, solder, braid, and some needlenose. The last four are relatively easy to juggle, but there's no fingers left for the camera button. :lol:

--First I tinned each cell endcap, then tinned the end of the nickel strip.
--Then hold the nickel strip with the needlenose by pinky and thumb of left hand so that I can keep it level on the negative cap of the first cell
--Hold solder with my forefinger and middle finger of left hand to guide into the joint as needed,
--Hold the iron with my right hand to levelly press down onto the nickel strip.
--Just before I press the strip down to the cell, I insert a 1/4" of solder under it, so that the strip will heat and melt the solder and fill anything under the strip,
--Press down iron tip and count 1-1000 2-1000 and pull away the iron,
--Push with the needlenose on either side of the solderspot until I see the solder crystallize.
--Check temperature with finger after this (2-3 seconds) and verify it's only warm, perhaps body temperature at most.

After the first cell it was easier as the strip is now affixed to the first cell, and held at the right angle and whatnot for easy press-down with the needlenose without having to hold it with them first. I just spread the needlenose out so the tips are about 1cm apart, and hold it just above the strip, ready to press down just before I pull the iron tip away.

This let me quickly and easily solder all the strip cells, and it was nearly as easy for the braid. If I had had to do the positive ends instead of negative, it would have been harder, trying not to melt the plastic ring around the cell cap that insulates the negative cell body from the connections at the positive end. Could make for bad juju. ;)

The only issue I had at all was that at one point I was stupid and pulled the pack-interconnect braid *down* over the positive end of the last cell on the string next to the fixed one, and slightly melted into the pink tubing over the cell, at the positive end, so I got a small spark before I pulled it away. :oops: No KFF or anything though, must have been a VERY small connection area that shorted.

Verified voltage across the string as 3.34V at this point; about 3.41 to 3.48V on other strings.

Then I tested the pack as a whole using the 24V powerchair motor and gearbox I'd removed a little while ago from CrazyBike2. The gearbox places some load on the motor, and it's heavy enough to not flop around too much on the bench without being secured. To do the test, I clipped from motor wire positive to pack positive, and motor wire negative to one HF ammeter lead, then other HF ammeter lead to Fluke Voltmeter negative. Fluke Voltmeter positive was inserted into the pack positive cliplead.
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Got 54.2V with no load. Under 6.6A-ish load (varied from 7A down to 6.2A as HF meter heated up), 53.2V, unvarying.

Same test with Fluke Voltmeter across the damaged string gets 3.30V, unvarying.

I'd say it works ok for now. Have to see about capacity and voltage drop under a heavier load, but so far it looks pretty hopeful! :)
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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 13 2010 7:47pm

Ypedal wrote:The pink/beige cells are older stock ( 2008 or so ) , the newer batch are grey..

http://www.ypedal.com/cammycc/Index.htm
I have read that page before, when going thru all the info on your site one day. :) Probably been several months, so I didn't remember where I'd seen some of this stuff before but I guess that was it. ;)

Anyway, I am likely to rebuild using the coroplast like yours but I am probably going to make the sections by cutting some old signs up using the cardstock I peeled off as a pattern. I would be putting the coroplast directly against the pack rather than ducttape or cardstock, as the coroplast is less likley to accumulate any moisture/humidity and create leakage paths within the pack to cause charge loss over time.

To hold it together, I'll be reusing the duct tape I peeled off, which just about all of it is as intact as when it came off the original roll.

But to strap the cells together (once I've filled the end gaps like you did with coroplast strips) I've got some of those nifty plastic bands they use to strap pallets together, along with the metal spring clips that can be used to tighten them down kinda like motorcycle helmet chinstraps (and some other buckles) do. They won't loosen or stretch, and can't come undone either--I used some on CrazyBIke2 for some of the SLA straps during experiments before hoseclamping them in place, and never had a problem with them. The Curtis controller was held on that way the entire time I had it on there, without shifting. Better than tape, as long as I don't crush the cells with it. :lol:

Then if I need to open it up again to fix something in the future, I will not have to peel it open in layers again, but can just slice the outer tape along an edge, and lift the coroplast away, to get to the cells inside. Or if I can save the tape I can unwind it just like this time; given the Phoenix summer heat I doubt the tape will peel off this time around, if it lasts up until summer in the first place. :lol:

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by texaspyro » Nov 13 2010 11:25pm

amberwolf wrote:One row I used the original nickel strip, but the other one I have somehow lost
Dog said nickel strip tastes yummy... check the, uhhh, output ports...

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 13 2010 11:42pm

Haha...yeah, that could be bad. I doubt the dogs got it, as nothing else near where it should be is disturbed enough for them to have done it (it'd be quite a mess if they did), but I can imagine my crazy sister would pick it up to throw it out if it looked like trash, or play with it, or some crazy thing I can't even imagine. :(

I found enough oompf to move the pack to the bike, and place a bucket under the BB to hold up the front end off the ground. Connected the pack up thru the breaker and wattmeter (TWM2), and ran it no-wheel-load at full speed, which turns out to be 36.8MPH at the 53V the pack stayed at for no-load (1.1A).

Using the rim brake, I varied the load from about 10A (51.2V) to 39.8A (48.6V), and held the loads until the rim was hot enough to creak as the tire began expanding. Figured I better let go and let it cool off each time for that. :lol: Didn't take long since the air temperature is down to 58F in the living room right now (I don't heat rooms I'm not in, and most of the time I'm in bed when not doing stuff these days, so I just stay under the covers with dogs around me and I'm warm enough).

Using some rubber bands to hold full throttle and to hold the brake at various levels of load, I then measured as quickly as possible the voltages at the BMS end of the balancing wires, at the PCB. They varied from 3.30 to 3.32V, most of them at 3.30 or 3.31V, including the repaired string, for currents below 4-5A. Up around 10A they were still all the same, from 3.19V-3.21V.

Up at 30-40A they dropped to 3.02-3.04V, except for that repaired string around 2.97V. I expected more voltage drop from it, but am glad it's not that bad. Might be a lot worse later, and I have no idea what capacity it'll have. We'll see.

I left it at zero braking (load) and full throttle for a little while, until it was at 1.1Ah of usage, still with just about no voltage drop (from starting voltage) at that load level. I shut it off, and by then I felt ok enough to move the pack to the utility room and setup the Sorenson to try charging it back up.
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Unfortunately it's max voltage is only 56.8V, as opposed to the ~61V these should get for charging (per Bluestreak's notation about the original charger for it). I set the Sorenson for the max it would do, and 5A current limit. When hooked up and running, it dropped down to 54.4V (at BMS input) and 4.9A according to the Sorenson's front panel meters. Measuring across the actual battery connections, it's 54.1V according to the Fluke, so there's about a 0.3V drop across the BMS shunts and FET(s) and stuff.

EDIT: Actually, going back to check on it, I found by checking with the Fluke and the Watts Up WU1 that it really only outputs 55.9V.


When I was measuring the cell voltages during the bike load tests, I noted a couple things I hadn't seen while the protective covers were on the BMS:
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No idea what caused that, the shunts show no sign of a problem or smoke damage, so I'd guess it happened to the PCB before they were even installed. Or they are new ones put in after old ones were vaporized in some manufacturing mistake. :lol:

Then this one, the battery negative wire, doesnt' even have all the strands stuffed into the PCB.
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A better pic than before of the melty main positive wire, whcih is a manufacturing issue, overheating the wires trying to solder them in, and not even getting all teh strands in or soldered. :(
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This BMS uses IRF3710 FETs, which have RDSon of 23mohm, max Ids of 57A, and max Vds of 100V. 175C operating temp.
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There's 16 FETs, although I'm not sure if they are all wired in parallel or not (haven't traced them out) so I dont' know what the RDSon cumulative is. Bolted to little aluminum blocks, there's not really much heatsinking going on. I don't know what this BMS is rated for for current, but I suppose I could add a big heatsink to it and a fan, and help it out if I end up needing a lot of current out of it for whatever reason, or if it gets hot at typical loads of my existing bikes.


More to come in a little bit once charging is done (not sure how long that will take). Also, I just now remembered I forgot to put the stupid wattmeter inline with the charger, so I have no idea how much power has already gone back into it while I've been typing this up. :roll: :oops:

Well, not NO idea, but only a guess--assuming 5A constant since I started, it's been almost an hour since I began that, paid some attention to the dogs, and came in here to start typing and whatnot. So maybe 5Ah. Dunno if it was constant though. Gotta go see I guess, and stick the wattmeter in there. :(

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Re: VPower / CammyCC 48V20Ah LiFePO4 Repair by Amberwolf

Post by amberwolf » Nov 14 2010 12:02am

Well, it has nearly stopped charging. It shows 0A on the front panel but after inserting the Watts Up WU1 inline, I get about 0.22A still going in, at 55.9V. That's only 3.494V per cell, so it probably isn't even shunting anything at this point (the BMS certainly isn't warm anywhere, although it's 55F in that room so it'd be cooling off fast anyway even if it did warm up, especially with the draft caused by the high-volume (and loud) fans in the Sorenson. ;)

I guess I'm going to have to either dig out one of my isolated 5V high-amps power supplies to stick in series with the Sorenson, and get almost 60V, or live with slower charging times and use one of the little 0-750mA 0-40V Sorensons in series with the big one. Or just use both of the smaller ones in series, since it won't go higher than the current from one anyway, and that would let me keep the whole main charging setup in the front room.

I suppose I could even do bulk charging at higher currents up to the 55.9V on the big one, then hook up to the little ones for the rest of it, and balancing. Hmm. I think that's what I am going to do for the moment. Once the charging has dropped to 0A on the WU1, I'll move the pack to the smaller Sorensons in series for 60.1V at whatever they'll output (I think they actually will do 900mA or so, but they do get hot enough to want fans at that point, IIRC from my early NiMH experiments).

I'll go set that up to get it read for when the big one is as far as it can go.

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