Any local builders in Northern California???

[Angry Andy]

Hello everyone Im glad to find this forum...

Im new to the battery pack design and build, and I would like to find people near me in the SF bay area (I live in Concord) to possibly help me build up a powerwall, and I can also help them with used 26650 cells....possibly if we can work together I will supply cells for the both of us and we can both benefit each other.

I have found a bunch of 12v 16ah battery packs in the recycle bins at work. I have a huge supply of them. They were used in parking meter stations. They are two cells glued together and connected in parallel via a busbar with connector. I have removed the busbar and connector and took a picture of the cells.

I took a dozen or so home and started testing them. Some are dated, some are not. Found some dated from 2020, so I assume they dont have many cycles on them.

I have a hobby charger I used to rebuild a couple Prius battery packs with, but not sure how to use it to charge/discharge these 26650 packs. Got a Lii 500 and a Opus c3400 on order to get these batteries tested....but working tonight with my current hobby charger (pic attached)

https://www.amazon.com/gp/product/B07LF1SC63/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I think I might have figured out what settings to use with my current chargers, but not sure still...

So I cut one open, and found it has a BMS inside, and its a 5p4s pack with blue batteries labeled "HTCF-26650-3200mAh-3.2V" date 2018-05-30

Some of the packs I tested came out great at the posted 16ah, but about half have not. Im not sure if it is a BMS issue or bad cells, or whatnot. Hence I cut open a couple packs and took pictures.

when I try to seperate the cells from the pack, the glue they used tends to break the shrink wrap in spots....from reviewing videos that is not good and those cells should be re-wrapped.

But they are already spot welded in parallel, and I kinda want to keep them as such and test the parallel group.....but maybe I should break the whole pack down to single cells and test them all that way??? But if I do that then I have the spot weld on top and I dont want to tear that off. Can I keep them in a parallel pack (with shrink wrap torn) and just tape the whole group with some electrical tape? Scotch33+ is what I use.

So this is where I am at now, learning, reading, watching videos, reading posts......and asking.

I would love it if there were people nearby me that we can work together with.....

Im looking to make multiple 48v packs in metal enclosures or ammo cans or whatever to wire them all in parallel.

thanks to all for helping here.

 

[Angry Andy]

the pack is glued together, and when I used plastic interior panel tool to seperate them the shrink wrap tore off as shown.

So I did not tear down the pack anymore....

 

[Oberfail]

But they are already spot welded in parallel, and I kinda want to keep them as such and test the parallel group.....but maybe I should break the whole pack down to single cells and test them all that way??? But if I do that then I have the spot weld on top and I dont want to tear that off. Can I keep them in a parallel pack (with shrink wrap torn) and just tape the whole group with some electrical tape? Scotch33+ is what I use.

For a better overall Powerwall, i highly reccomend to individualize all cells and spotweld them back together later on. You can then be sure, that all cells work as intended and balance the capacity better.

Often, you can safely rip off the spotwelded metal strip, try it with some defect cells first.
Leave the leftovers of it on the cells and dont try to scratch it off, as they will catch rust faster when you scratch the protective thin metal layer on the cells.

You can leave them with the damaged wrap, but its generally suggested to rewrap them, to make the handeling more secure. The whole body of the cell is the negative connector, if it comes in contact with the positive connection you might damage the cell. For my Powerwall, i just leave them as they are and only rewrap cells, that have a damaged wrapper around the positive connector.

 

[floydR]

On some LFP 26650's (A123 26650's) the case is positive. Always check. I would rewrap the cells before you build the packs.

Also not sure if the Lii 500 has a switch or a mode that will work with LiFePo4 cells. The Opus BT-C3400 does have a switch the switch is not accessible from outside the case. I cut a hole above the switch in back of the Opus I have set up for LiFePo4 testing. https://secondlifestorage.com/index.php?threads/26650-build.7727/#post-65048
Later floyd

 

[floydR]

Found the datasheet for the cells https://www.cebabattery.com/wp-cont...2v-IFR26650-3200mAh-Cylindrical_Datasheet.pdf
Later floyd

 

[Angry Andy]

Thanks Floyd! I found the same datasheet earlier today with a different front page.......good to know though..

Got my older RC chargers working. I had to put the setting to LiFe (1s) and it defaults to charge cutoff at 3.65V and discharge cutoff at 2.5v

running tests now, have some cell holders on order to get my two hobby chargers and the new opus running.

I realized I should break the whole packs down as others mentioned its the best way to gather as much info and group cells accordingly.

I have in IR tester, and according to the datasheets they say greater then 30m is acceptable.

Every cell so far has tested in the 17-18m range.

Started to break down the packs trying to minimize the shrink wrap damage, and using some super fine side cutters to clip away the nickel strip and then tapping it down with a rubber mallot. It comes out quite clean I must say.

 

[floydR]

Lower the better for IR. What IR tester do you have? wolf's tests of common hobby level 4 wire IR tester https://secondlifestorage.com/index.php?threads/ir-meter-recommendations.10361/#post-71639 I have a YR1030+

Since ≤30mΩ is standard 17-18mΩ is good

On testing I have found that not much capacity under 3.1v but that is from testing 60280,60290 LiFePO4 cells you may get different results. Not sure on the A123 26650 cells, I did watch a few finish up on the discharge part of the Charge/discharge/charge test and they seemed to finish discharging around 3v.

Heat shrink wraps are fairly inexpensive.
later floyd

 

[Angry Andy]

I got the YR1035+

also some shrink wrap on order from china

 

[jgilly69]

Hey Andy - how is your build fairing? I am up here in Norcal Sacramento area. Keep pulling those batteries! That looks like a good pack and if you can get more that is a great plan. That blueish goo on the side of the battery is leaked electrolyte, so don't touch that unless with some gloves.

 

[skpro]

Hey, I'm in the area (mtn view) and have worked extensively with the 26650 a123 batteries. I have a bunch of modified Opus 3400s I used for testing those cells, and also have a couple bench testing machines. I also have a kweld spot welder that could be useful, but I haven't used it too much. PM me if you want to connect.

I also agree you should tear down the packs that aren't testing well. And that green stuff looks like it is electrolyte or chemical offgassing, I would be careful with those cells.