Blown BMS discussion (originally Wanted thread)

(edit: originally this was a wanted thread, but is moved to save the discussion bits)



I'm looking for BMS boards to support 10-15 LiPo cells, and as long as the PCBs are not actually burned to unusability, I could repair blown FETs, etc. If they're MCU-based BMS boards, I'd need the MCU part to be working, but I could replace most any other component with parts out of my other junk laying around here.

I can afford almost nothing for payment (seriously, I shouldn't even be considering this right now but need more range and to lighten the bike from my SLAs), so if you have one you were going to throw away anyway, or is sitting around in that fried battery pack you're never going to do anything with, I could pay postage and maybe a bit more (to Phoenix, AZ, USA, 85051).

I'm going to attempt to build packs for my CrazyBike2 out of individual LiPo cells, and I think it'd be a lot safer if I had BMS boards for every set to ensure HVC and LVC protection, given the reputation LiPo cells have for "celebratory lightshows" when those are exceeded.

I'll probably start with 36V nominal packs, preferably with each individual series set having it's own BMS, then parallel all those packs together to get the current needed to run the bike. I might end up wanting to use 48V packs by the time I'm done, but it runs fine on 36V now, and would require regearing anyway if I went to 48V to keep the total max motor speed at 20MPH.

So for those willing to help out, post here what you have and what you want for it and we'll figure it out from there.

I am testing my BMS. If it is shagged, you can have it for the price of P&P, from Ireland, which will be around $20 I guess. If I can get it cheaper you can have it cheaper. That said, the BMS might work.

QUestion: The BMS which came with my 48v 20AH unit, would that work as well on my 36v 20Ah unit?

The Mighty Volt said:

I am testing my BMS. If it is shagged, you can have it for the price of P&P, from Ireland, which will be around $20 I guess. If I can get it cheaper you can have it cheaper. That said, the BMS might work.

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If it does turn out to be bad, then whatever the cheapest option to ship is (even if it takes a long time to reach here) is the best way. It may be a little bit before I can arrange payment if it does turn out that way, as I am super strapped right now. Too many odd jobs are not working out like they are supposed to, and not getting paid or jobs get cancelled.

QUestion: The BMS which came with my 48v 20AH unit, would that work as well on my 36v 20Ah unit?

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I don't know; it depends on how it implements an LVC, I suppose. If it uses the LVC for each cell only, and not a pack-level LVC, then I see no reason why not. But if it uses the pack LVC, then 36V pack's highest voltage will probably be below the 48V BMS's LVC, or near it, and the BMS will shut off the pack as if it were drained even though it's not.

That might be a question you'd have to ask the supplier of the units, because some BMSs are "smart" and programmable for different packs via a cable, and others are "programmed" by a resistor value, while still others don't have a pack-level LVC at all, just per-cell, so they are easily swapped between different voltage packs (as long as all have less than or equal to the current draw ratings as the pack it came from or it's ratings).

I'm no expert on BMS at all; only going by what I've read, so some of what I say may not be as correct as I think it is.

There are only a few ways of implementing an inexpensive BMS, but those few ways have a lot of minor variations that make for some complicated troubleshooting if you don't already know which version and variation you're dealing with.

your stater made it. ill see if i have a dead bms in my box of stuff

the stater is much smaller than the pics. may only get it to work with 36volts wee shall see.

cheers

karma said:

your stater made it. ill see if i have a dead bms in my box of stuff

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that would be way cool. Based on problem reports I read here on ES, most of them seem to blow the FETs rather than anything "important" (meaning, anything I can't fix).

the stater is much smaller than the pics. may only get it to work with 36volts wee shall see.

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No problem there, as my pack currently is 36 anyway, and I am currently planning 36V packs with the li-ion cells (or sets of 12V packs, depending partly on what BMS types I'm able to find or make).

So it would be 36V at what RPM? (KV? I forget the terminology)


EDIT (ADDED): BTW, is that memory stick just a keyfob, or do you use it as a wire-tucking tool?

heh you will need to run tests when its completed. i can set it up for 36v 30amps the rest is up to you. i have no way of testing the rpms.
im looking forward to seeing it in action :wink:

Yeah, tha'ts true. I forget that you don't have the housing there to put magnets in and check. And since it's a definitely non-standard motor for this, there is nothing to compare it to!

Amber

I have a couple really fried one's which I will send you FOC

One was actually fried over easy in a bike bag. :wink:

They probably would only yield a few good parts but what the hell!

Where do you want them?

PM'd

The batteries arrived, and I tested a few just to see what they're like, so far they work ok. I know that some of them are supposed to be no good, and those are in a separate section of the shipping boxes.

I stuck seven of the most-charged pink (Sanyo?) ones out of the top row of the 80% box in series in a papertowel roll tube and put the no-longer-installed 2-pole motor on them for a few seconds, and they turn it just fine with little sag, at about 26V.

Didn't test it for long, since I don't know their exact SOC and couldn't hold the batteries, meter leads *and* the motor wires at the same time well enough.

Now just have to devise a minimal BMS (or at least warning system and/or automatic shutoff of charger via relay) to charge them up "unattended" and something for an LVC and a current-limiter on the bike itself.

I have someone looking for one of the really small aluminum beer kegs for me as a possible unique-looking battery box; that way I can have Power On Tap.

I'm testing cells one at a time, and so far the handfull of already known good ones I've gone thru seem fine, with slightly varying capacities. One of the dead ones is really really dead, 0V and barely a trickle of current will flow into it; one has high current flow but never goes above about a volt. I'm afraid to keep trying with that one since it gets pretty warm.

I have not yet built a timer or other system to turn the charger off so I have to be there to monitor it. I've been doing it while working on the rear suspension system, in a room separate from the dogs and one remaining unadopted puppy so they'll be safe should something go wrong (and can't cause anything to go wrong, either!).

A couple of people have volunteered some BMS parts, so whenever those arrive I can start figuring out how to make them work again, and then to work with this chemistry, if possible. Or just use them for parts to make one from scratch.

when i send your stater back. it will have a ping bms with dead fets. the bms still balances the cells that's about all you need :wink:

works if you bypass the negative.

Cool! And I can replace FETs, so even that's not a big deal. All I need to do is figure out what to change on it to make it's HVC/LVC match the cell chemistry I'm using, which is different from that of LiFePO4. Shouldn't be too hard, I'd guess.

I've been playing with the one BMS I got so far (sent by Jules), which is from a Ping LiFePO4 pack. Have not yet figured out a way to change or offset the LVC and HVC on it to match the LiPo style levels. My mind keeps telling me there is something simple I am missing, but it hasn't yet let me in on what that actually is.

So the call for other types of blown BMS boards is still being sounded. I can still use even blown Ping boards, once I figure out a way to get around the voltage differences.

Well, in my playing with the one Ping BMS I have, and reading more about it's specs, it's supposed to be based around a chip that is for LiCo (which I guess is actually the kind of Li cells I have), and so should work for them. However, when I actually test it, it starts shunting around 3.98-4.0V on each cell, so that means something is setup differently on it than just the way the chip works.

Since these LiCo cells I have are used in laptop batteries too, I checked out some that I have and they charge them up to 4.1-4.2V to get them full.

So I could use the Ping BMS boards after all, for anyone out there that has dead ones they're willing to let go cheap.

It'd be nice if I could get one BMS for every series string of cells, rather than directly paralleling any cells at all. Then I can just hook up as many sets of cells+BMS as I need, and charge each one without worry that a cell failure will kill multiple parallel cells. First I need to fix the one BMS I already have (has two bad channels, plus something in the charge fet control that's not working).

I have 2 blown Ping 2.0 BMS's. ??

wineboyrider said:

I have 2 blown Ping 2.0 BMS's. ??

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What do you want for them, including cheapest postage to Phoenix, AZ 85051?

Also, in reference to:
Subject: 2 Ping Batteries and a Kollmorgen motor for sale!

wineboyrider said:

I only have 1 36v charger as the 2 I did have are smoke and 2 more on the way from China.

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If they're for sale, how much for the dead chargers, too? I might be able to fix them and use them to charge the packs I'm trying to build, or at least for parts for something else.

Just keep in mind I have zero actual budget for any of this.

AmberWolf,
I think you are AMAZING what you do with this stuff. I saw your post in the money saved ebike section and was blown away at your talent for making good out of others junk!



I am in the process of going through my ebike stuff and have parts that maybe you could use/ Maybe you should start a thread
with what you need. I will send it and pay the postage. Tell me if you need any of the below listed items.

two HighPower brand ( good brand aluminum case) NIMH chargers that work 24 volt
two high power brand NIMH 36 volt that I blew connecting reverse.
crytal lyte controllers two blown and some early ones never used.

PM me

PM sent to wineboyrider and re-sent to ianmcnally2.

Still on the lookout for LiPo (vs LiFePO4) BMS, any condition, cheap.

Any other kind of BMS (or other stuff) is welcome, too, but LiPo/LiCo is what I need it for.

As an update, still looking for any old/blown BMS boards, and also a note about a failure mode I've noticed.

I have a 16s Ping v2 BMS sent to me as failed that I've worked with a bit, and it has a couple of slots that shunt *all the time*, so they'll kill the cells attached to them to 0V when it's not on the charger. It also has failed FET(s); I don't know which failed first or if any of the problems caused the others.

From what I have seen of various posts around ES, this doesn't seem like an uncommon failure mode for these, and is probably one reason for the change to the v2.5 by Ping, though I think I read of the same problem with one of those (can't remember for sure).

I'm not sure if it's the transistor that failed to short the shunt "on", or the voltage reference failed to keep the transistor biased off, as I didn't finish troubleshooting it yet. (I'd intended to work out how to use it for LiCo/LiPo instead of LiFePO4 but after the failures started working on other ideas instead.)

Poke a screwdriver between the gate and source to short them together on the suspected failed transistors. If the short doesn't disapear, then you know the transistor is bad. If the short disapears, you know it's the signal to the transistor. (and potentially a much harder problem to solve).

Sorry I did not get back to this yet to reply. I still need to do what you describe to check it out; seems an easy way to do so.

I am still as always looking for more BMS in whatever condition, and really of whatever type you've got for any number of cells. Even if I can't fix them I may learn from them and be able to use parts from them, as long as they're really cheap.


I'm looking for the rest of the parts to finish a pair of v2.6 F/G BMS, one for LiCo and one for LiPo, here:
http://www.endless-sphere.com/forums/viewtopic.php?f=8&t=18333&start=0

amberwolf

sorry for my late reply too..

im just taking pictures of what i can send you..

if you want tell me where to look more specifically on the bms,to see if they have the parts you looking for..

i will be back with some pics in ten minutes.
ALex

ok amberwolf

here are some pics ,note the cells are for another forum member.
99% sure they are li-mn chemistry,the pack was a 36v 10ah...all the bms,s should be ok.i havnt tested them though(not sure how to)..
View attachment bms,s for amberwolf 005.JPG

View attachment bms,s for amberwolf 006.JPG

i should at least be able to send you one of them if not both bms,s of the li-mn bms,s (given the other forum member doesnt need them for his pack he is reassembling)..

now i have 2 bms,s of lifepo4 chemistry,one works and the other i ruined,attempting to resolder the single bms cell wiring ..
here are some pics

View attachment bms,s for amberwolf 003.JPG



hopefully you could put them back to life again,also let me know if there is any particular numbering/wording/coding to look out for you on the bms,s..

send me a p.m if you still want them...
sorry about the picture quality,
Alex