dnmun
1 PW
the cell man 12S BMS is the headway 12S BMS with analog shunt transistor control. the new 16S BMS is digital and uses the RUI chip 190A 3.4mohm 80V mosfets. like ten of them.
A123 20AHr Pouch Cell Battery Build & Info Thread
- Thread starter bigmoose
- Start date
arkmundi
10 MW
Anyone want to split a carton of cells from Victpower?
In my latest exchange with Xin, its apparent Victpower wants to ship cartons of 14 cells and won't ship fewer. Understandable that the ecnomics of handling & shipping would require such economies. I used my 2 extra cells from the orginal shipment to replace bummed out cells in my pack. I'd like to have replacement cells on hand, but not 14. Anyone interested in splitting a carton? USofA only. Because of the devries group buy experience, I'll accept payment at the time I ship to you, so after I have cells in hand and fully tested each. These will be short-tab cells.
In my latest exchange with Xin, its apparent Victpower wants to ship cartons of 14 cells and won't ship fewer. Understandable that the ecnomics of handling & shipping would require such economies. I used my 2 extra cells from the orginal shipment to replace bummed out cells in my pack. I'd like to have replacement cells on hand, but not 14. Anyone interested in splitting a carton? USofA only. Because of the devries group buy experience, I'll accept payment at the time I ship to you, so after I have cells in hand and fully tested each. These will be short-tab cells.
megacycle
100 kW
I want some, but i live on the butt of the planet.
999zip999
100 TW
Arkmundi I saw a pic of short tabs and one tab looked like a cheese grater. Are the ones you gotten have clean half tabs ? And what size are the tabs you got as I'm going to do the Drutledge build with the four threaded rods. Will they work ?
And just one of my cells in a 24s pack is a little bit odd I have an extra cell but would like to follow the behavior of this cell.
And just one of my cells in a 24s pack is a little bit odd I have an extra cell but would like to follow the behavior of this cell.
arkmundi
10 MW
Yea, the tabs will be like that. Don't worry - they work fine, as far as my experience goes. Just to repeat, the ONLY genuine A123 AMP20 nano-LiFePO4 cells available on the open market are via the salvage of already constructed batteries. That means the tabs are welded, requiring them to be cut out for the salvage. Expect that there may be some external damage, which may or may not effect the internals. Hence cartons from Victpower may have duds, or poorly performing cells, or perfectly fine, up-to-spec cells. There's some risk spread over everyone involved and is par for the process. But at $16.50 to $18.50 per cell, what's there not to love?999zip999 said:
999zip999
100 TW
Yea and what size are these taps ?
arkmundi
10 MW
They're consistently coming in around 9mm, so adequate for Agnius' kit, which calls for 8mm. Can't say how adequate for other connections.999zip999 said:
Michall2008
10 mW
Hi to all,
I got some cell from vpower today and want to share the experience, some pics first:
All cells in bubble wrap and protective plastic case (not seen in photo)
The two top cell are curved, i guess because poor packaging
close look
All 14 cells are at 3.28v
I shuld get my hypirion 1420i soon and start capasity testing.
Im bulding 12s1p pack, it is my firs pack bulding so i'll need some adult supevision from you guys.
Suggestions are welcome
Michael
I got some cell from vpower today and want to share the experience, some pics first:
All cells in bubble wrap and protective plastic case (not seen in photo)
The two top cell are curved, i guess because poor packaging
close look
All 14 cells are at 3.28v
I shuld get my hypirion 1420i soon and start capasity testing.
Im bulding 12s1p pack, it is my firs pack bulding so i'll need some adult supevision from you guys.
Suggestions are welcome
Michael
dnmun
1 PW
no, don't be doing capacity tests on a new pouch for no reason. place the curved pouches on a flat surface and put something heavy and flat on the other side and leave it for awhile until it flattens out.
you don't have to be led along by individual instructions since there are tons of pack building threads you can read. you do have to balance them together initially by shorting them all together to the same voltage. then you use the bulk charger to charge them up under the BMS so they will balance quicker.
you don't have to be led along by individual instructions since there are tons of pack building threads you can read. you do have to balance them together initially by shorting them all together to the same voltage. then you use the bulk charger to charge them up under the BMS so they will balance quicker.
agniusm
1 MW
Those tabs just looks wrong. i wander how much current they would hold until acting as a fuse?
Ypedal
100 TW
dnmun said:
How about parallel..
ohzee
100 kW
I knew what he meant.. hehe good catch I read that and it didn't even register.
Michall2008
10 mW
SLA do have some use (something heavy):
dnmun: OK, I'll do my study on the forum.
No capacity testing? how will I know the true capacity ?
There will be no BMS in the pack, CA for LVC.
dnmun: OK, I'll do my study on the forum.
No capacity testing? how will I know the true capacity ?
There will be no BMS in the pack, CA for LVC.
arkmundi
10 MW
Hey, those pics are what's being delivered. I've been working with them all along. They hold current just fine. There's more than enough metal protruding to pass even 30C currents. I put a new one into my pack today, so needed to extract the old. Doing so, I'm looking at the tabs from three cells - the one being replaced and two adjacent. There is absolutely no indication of melting or anything else that would suggest its "acting as a fuse." Pure speculation. Until there is actual evidence, "fusing" tabs is pure kakkaa.agniusm said:
Ypedal
100 TW
arkmundi said:
Hehe.. try shorting out a Nano-tech pack fully charged... and the weakest tab goes away like magic.
megacycle
100 kW
Agniusm, I'm with you, they butchered those tabs to take the crimp off, by the looks of it.
Not much csa left.
In saying that, looks like there is about 2 or 3mm clear near the seal, if you clamp that with a copper clamp, i'm reckoning should still be able to run high amps, but not sure what happens with sinking heat away at really high amps?
Never tried it but has anyone cut away a little of the top seal to access more tab?
Not much csa left.
In saying that, looks like there is about 2 or 3mm clear near the seal, if you clamp that with a copper clamp, i'm reckoning should still be able to run high amps, but not sure what happens with sinking heat away at really high amps?
Never tried it but has anyone cut away a little of the top seal to access more tab?
agniusm
1 MW
arkmundi said:
I hope you are right for the sake who bought them. 30C thats 600 amps
They might be OK up to 30 amps, just my view. Don't count the whole area, just the line with the holes.We'we yet to see..
megacycle
100 kW
Ratio of thickness of connection to length of overlap of connection needs to be minimum of about seven to make a proper connection, because the tabs are so thin say 0.4mm or so, 2-3mm of overlap if clamped down hard should be the close to the same as a full size tab, heatsinking at 30C should be ok with a copper bus connection.
Suppose test maybe the go, i can go gineau piggy
I blew all but a few mm of one of my A123RC's a couple of months back , be interested to know myself, i could use it for my spot welding
Suppose test maybe the go, i can go gineau piggy
I blew all but a few mm of one of my A123RC's a couple of months back
, be interested to know myself, i could use it for my spot welding
arkmundi
10 MW
My motor's max draw is 33 amps. Motor/controller are rated 20 amps continuous. So yea, there's no worry for me. That should be a clear warning for people using these short-tab cheese grater salvage cells from Victpower. I don't believe there would be a problem for higher amp applications, but buyer beware. What's the max amps for a really wacked tab? No one knows yet. Someone with a 72V pack and 1000 Watt motor, if any, should let us know.agniusm said:
megacycle
100 kW
Ok guys did some testing.
I had to remove the thin plastic coating, at the base, as the tab didn't have any exposed area left, it initialy looked like but it was down to the seal.
What i did manage to get after a lot of very careful scraping was about 2mm.
Its been seen before in this thread, i think, when you dig into this area, have to be careful as it exposes the foil packaging and i did see a little spark, when connecting for the test.
I'll post results later, out for dinner
I had to remove the thin plastic coating, at the base, as the tab didn't have any exposed area left, it initialy looked like but it was down to the seal.
What i did manage to get after a lot of very careful scraping was about 2mm.
Its been seen before in this thread, i think, when you dig into this area, have to be careful as it exposes the foil packaging and i did see a little spark, when connecting for the test.
I'll post results later, out for dinner
megacycle
100 kW
Geez Im full need to veg out for a while following dinner.
First photo of blown tab, not a good idea to short circuit two cells together .
Cut, scraped and cleaned.
Ok after scaping back a bit of the plastic coating on one side of the tab, i buffed up the couple of mm of tab making sure it was all cleaned off.
The test set up was a bit basic, but was 2 lengths of 25mm x 1.3mm bright copper bus clamped around each tab, which was a little difficult for the 2mm, but managed after pushing the bus downwards,
Used a couple of bits of 3mm aluminum to equalize the force under the clamp on the 2mm side clamping at the same time, with max force i could squeeze the vice grips with, which was a hell of a lot in the end, it didn't slip around any.
I used a fluke DVM which i cal'd as about +0.15% out on volts.
Clamp is an old Hioki which sorry can't vouch for, but i know from using it for charging measurement,
would say if it was out for these test +/-5% not gonna make much diff.
First test got a piece of fencing wire and connected across
The steel wires got a real negative coefficient, suppose being so thin too, started about 170A and dropped very rapid to the value shown as it was glowing, stopped test about 10 secs in.
The next was 2 bits of paralleled wire
Current started off scale at 200A+ initialy and ended up several secs later at the value shown.
Final test was a short length of 16mm2 cable, complete with insulation, silly me
See video highlights
:lol:.
Would have to say that was probably 350 to 400A range.
I carefully touched both bus sections and large tab was pretty warm, fingers couldn't stay on long, with no clamping no aluminum helping sink, the 2mm tab no noticeable temp rise
https://www.youtube.com/watch?v=w8SmBEJ6Wzk&feature=youtube_gdata_player.
Edited too much and all the expletifs :lol:
Well looks like streamline effect in overlapping clamped connections is a fact, though contra to popular belief and those cells you bought Michael, those tabs will be fine, but would suggest you connect close to the base of the tab, if your using a clamped connection and collect a couple of mm of the full un damaged tab width, to get the full contact width.
With these tabs being so thin, a gnats appendage of continuous tab width of a connection eg 2mm, well clamped can carry full load similar to a full size tab.
following dinner.First photo of blown tab, not a good idea to short circuit two cells together
.Cut, scraped and cleaned.Ok after scaping back a bit of the plastic coating on one side of the tab, i buffed up the couple of mm of tab making sure it was all cleaned off.
The test set up was a bit basic, but was 2 lengths of 25mm x 1.3mm bright copper bus clamped around each tab, which was a little difficult for the 2mm, but managed after pushing the bus downwards,
Used a couple of bits of 3mm aluminum to equalize the force under the clamp on the 2mm side clamping at the same time, with max force i could squeeze the vice grips with, which was a hell of a lot in the end, it didn't slip around any.
I used a fluke DVM which i cal'd as about +0.15% out on volts.
Clamp is an old Hioki which sorry can't vouch for, but i know from using it for charging measurement,
would say if it was out for these test +/-5% not gonna make much diff.First test got a piece of fencing wire and connected across
The steel wires got a real negative coefficient, suppose being so thin too, started about 170A and dropped very rapid to the value shown as it was glowing, stopped test about 10 secs in.
The next was 2 bits of paralleled wire
Current started off scale at 200A+ initialy and ended up several secs later at the value shown.
Final test was a short length of 16mm2 cable, complete with insulation, silly me
See video highlights
:lol:.Would have to say that was probably 350 to 400A range.
I carefully touched both bus sections and large tab was pretty warm, fingers couldn't stay on long, with no clamping no aluminum helping sink, the 2mm tab no noticeable temp rise
https://www.youtube.com/watch?v=w8SmBEJ6Wzk&feature=youtube_gdata_player.
Edited too much and all the expletifs :lol:
Well looks like streamline effect in overlapping clamped connections is a fact, though contra to popular belief and those cells you bought Michael, those tabs will be fine, but would suggest you connect close to the base of the tab, if your using a clamped connection and collect a couple of mm of the full un damaged tab width, to get the full contact width.
With these tabs being so thin, a gnats appendage of continuous tab width of a connection eg 2mm, well clamped can carry full load similar to a full size tab.
agniusm
1 MW
Cool stuff mate. This is what i had in mind. Full cross section of the tab allows for rated current of these cells but as soon as you start puling that load through a tab that's one fifth or less of the total cross section i think that's where people would start having melting issues and tab length does not play any role here. Regarding your suggestion cleaning tabs i bet you had nice time scraping teflon of those tabs, and imagine doing 16 of them or more. There is a lot less to play with which makes building complicated and a risk of shorting outer casing. I was just suggesting to pay more just to save on tons of work given that these cells are not the easiest to terminate.
megacycle
100 kW
Spot on there.
I wouldn't normally suggest scraping that area off normally, or use this in a build.
I didn't realize that was Teflon Duh, but now you mention it, understand why it is and was so bloody hard to clean off.
Though what it did prove, is a cell is good for full current if its only got 2mm or more of connection length, though i had it clamped under a lot of force, which could be tricky to line up right in a pack and not accidently clamp on the Teflon and could come adrift with pack movement, unless as with Michael's cells you've got a bit more of length above it, like that cheesegrated section.
It also confirms the streamline effect, which is really good useful for builds that dont draw, i guess, 250A+ tab heating currents, could be cheap and light to clamp onto the top say 4mm of tab and still draw high C's.
I wouldn't normally suggest scraping that area off normally, or use this in a build.
I didn't realize that was Teflon Duh, but now you mention it, understand why it is and was so bloody hard to clean off.
Though what it did prove, is a cell is good for full current if its only got 2mm or more of connection length, though i had it clamped under a lot of force, which could be tricky to line up right in a pack and not accidently clamp on the Teflon and could come adrift with pack movement, unless as with Michael's cells you've got a bit more of length above it, like that cheesegrated section.
It also confirms the streamline effect, which is really good useful for builds that dont draw, i guess, 250A+ tab heating currents, could be cheap and light to clamp onto the top say 4mm of tab and still draw high C's.
megacycle
100 kW
Just an additional, note a tab with 1/2 its width compromised, should still be good for a few hundred A's, what do you reckon guys not 100% on this.
