Used A123 packs. Good or risky choice?

Hi

The older (2012) Volt packs came with seven 2 Kw - 12S Modules and two 1 Kw 6S modules

I'm going between 3.5v and 4.05v - so the 12S modules are 42v to 48.6v and the 6S modules are 21v to 24.3v

When you say 96v - if you are talking Lead Acid then they will be 104v to 112v

So using a 1kw unit and 2 2kw units would get you 105v to 121v

Or just the 2 x 2kw units 84v to 97.2v

You could "Lose" a cell easily on the volt modules - just carefully short it out and leave it shorted out

Bit of a waste but quite easy

The later batteries are more "S" in each module - but I don't how many

If you get a complete battery there is a lot of other good stuff you can use

The seller indicates he has over 500 of these modules and they are located in Canada, so many are available and shipping is more convenient. Back in july 2012 there was this press release about converting the Canadian busses from cylindrical to prismatic cells, and making retrofit in the field. That may be the source of these cells, and they may be 6 years old. The price seems okay and it might be smart to buy just one in order to test capacity before spending too much for weak or worn out cells.

Pro: Location
Con: possibly weak or worn out cells

edit: noticed these are the ANR26650M1A, here is a test of the M1B:
http://lygte-info.dk/review/batteries2012/A123%2026650%202500mAh%20(Green)%20UK.html


Press Release
=====================
A123 Systems, a developer and manufacturer of advanced Nanophosphate lithium ion phosphate batteries and systems, signed an agreement to supply lithium ion battery packs based on the company's prismatic cells to BAE Systems for its HybriDrive Series propulsion system.
The new design is initially expected to be deployed on city transit buses, and, as part of the new agreement, A123 will also supply lithium ion battery packs for additional versions of BAE's HybriDrive system for other commercial applications.

A123's battery packs are currently deployed in BAE HybriDrive systems on nearly 3,000 buses globally that have amassed more than 300 million service miles to date. The current HybriDrive system utilizes battery packs based on A123's cylindrical cells, but under the new agreement, A123 will deliver packs featuring the company's prismatic cells to satisfy BAE's requirements for a more compact and economical solution. The agreement also formalizes the terms of a previously announced customer warranty campaign through which A123 and BAE Systems are sharing in a program to retrofit and upgrade battery packs on hybrid busses in the field.
================

Once again, good info. Thanks. It sounds like that fellow completely disassembled the pack. I wouldn't need to do that but I would need to take four cell strings off to make them work. To use them as is would be farther off than the volt cells. 3 modules in series would be 120v fully charged and 2 is only 80v. The blocks are 12s8p, so 36s for three. 32s would be perfect at 106.5v charged. The other 4 cell strings could possibly be used for the 12v system. Still, it might be more difficult than I think.

Duncan, thanks. Your numbers were the same as I had came up with except that I thought Volt cells charged to 4.1 volts. If I used Volt cells, my thought was to break the 96s pack into a 24s4p pack, but 84-97 volts is a little lower than ideal. It should work okay but the controller is marginal for power already and maginal voltage on the pack won't help. If I go with Volt cells, I think that would still be the best option. 120v is too high and I don't like the idea of shorting out cells. The other thing about Volt cells is the water cooling. I may need to build a pack in two parts and that could cause problems.

I'm still weighing pros and cons now anyway and there are still too many unknowns I need to figure out. I'm supposed to be getting an older conversion (no batteries but was lead acid) from a guy next month so not sure exactly what all will need to be done and how much room I have to work with either. I just saw these modules and wondered if they might be a good option.

puddleglum said:

Thanks Danny. Nice to find someone who's actually worked with these. Since you offered, I do have a few questions. Did you have to completely disassemble the pack to find the bad cells or did you discover them by capacity testing the parallel strings? Did you do capacity testing? You said it was easy to take apart. Are the top and bottom covers removable and the cells just tab welded together? Would it be quite a job to replace a bad cell if the pack without completely disassembling the pack? What about to remove some cell strings to make some lower voltage packs?
I've read a fair bit on bottom balancing and it seams to be the best option for a low (No) budget build.

Click to expand...

I didn't bother with capacity testing, mostly because when buying a used cell, I expected old/low capacity cells to present themselves during the bottom balance process. I am gifting the Moped that these cells power to my brother, and wanted to use these specific LiFePO4 due to their good reputation in terms of safety.

Breaking down the pack. I accomplished this by using a heat gun to peel off the adhesive sides. This exposed the screws (6 or 8 ). After removing the outer shell screws I removed all screws BMS/busbar screws as well. The plastic casing simply snaps into place which requires some patience and a good amount of gently prying. ( I used a pine baton that I found lying around the shop). Once you get one side off, the other will still be snapped in place. This one comes of easier, Simply turn it upside down with the plastic case facing up and while gripping the case and letting the cells dangle, shake / vibrate the plastic cover off of the remaining cells.

The whole process takes maybe 10 minutes and you are left with 96 cells wired 12s8p. (Capped & welded)

I left one pack as is, and cut the other pack into (3) 4s8p groups.
After balancing each group I I then cut & reused the plastic casing for the 4s packs.


Hope that helps. I don't have any pictures at the moment but if you request anything specific I'll snap a few upon request if I can.

Good luck with your project!