Prep work for larger battery from harvested cells

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Apr 6, 2018
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I am trying to get some good power into a pit bike build so I know I need to start with cells that can handle a good amount of current. The current plan was to harvest LG MH1 cells from a online reseller and then stick them in NESE modules.

I know it is good practice to at least cycle test them once before sticking them in a parallel pack together. Can anyone recommend a reliable set up for that? Looking at around 120 cells to start so it would be months to get through all of them at 4 at a time. I'd like to do more if I can safely.

Also had a silly noob question for way earlier in the process. If I put a balancing BMS on the pack, can I just find any old lithium charger at the correct voltage and charge through the BMS? Leaning toward something from Daly as those are pretty popular around the internet.
 
A bms should be put on a balanced battery pack do not have a wack out battery and things to be a mess is going to magically balance this whacked-out battery. balance the battery first then put the BMS on.
 
MorbidlyObeseKoala said:
I am trying to get some good power into a pit bike build so I know I need to start with cells that can handle a good amount of current. The current plan was to harvest LG MH1 cells from a online reseller and then stick them in NESE modules.

I know it is good practice to at least cycle test them once before sticking them in a parallel pack together. Can anyone recommend a reliable set up for that? Looking at around 120 cells to start so it would be months to get through all of them at 4 at a time.
I support the rationale behind that good practice, but I personally don't think it makes sense to invest months into testing salvaged cells for what will always essentially be a disposable (or at least low-cost) pack. I'd charge 'em, check for accelerated self-discharge, store outside, always balance charge, and be happy with what you get out of it.

MorbidlyObeseKoala said:
Also had a silly noob question for way earlier in the process. If I put a balancing BMS on the pack, can I just find any old lithium charger at the correct voltage and charge through the BMS? Leaning toward something from Daly as those are pretty popular around the internet.
Absolutely not -- never rely on a BMS to prevent your house down from burning down.
 
Thanks for the feedback so far, I'll be sure to begin with a properly balanced pack and I plan to store outside whenever possible. I had assumed leaving outside during the bitter cold of the winter (several months from now) would cause more damage than getting to an appropriate SOC and monitoring once a month in a better temperature controlled area. Could be wrong.

As for the charger, I'd love some recommendations other than the Bentley of chargers (grin satiator). Looking at 60 or 72V currently. Again, still early stages of planning this build.
 
goatman said:
cant you equalize all the cells to the same voltage and just do a resistance test to each cell to sort them out, only take a couple hours to do the testing
With the increased price of new 18650 cells there will be even more DIYers harvesting used cells ... https://www.batteryclearinghouse.com/products/200-cells-200-lg-mh1-18605-3200mah-10a-cells-in-5-aluminum-cased-packs . Seems like a thread is needed on a KIS recommended/preferred practice for cell selection/harvesting from salvaged packs of questionable quality.

For example when doing an IR test at what cell voltage and more importantly what IR range would you consider acceptable (e.g. salvaged 18650 LG MH1 cells) that's still worth using in a DIY build for it's original intended purpose (10A Max Cont Rating) ? Are there a couple KIS ES threads you might recommend ?

With all your recent experimental ["desulfating"] tests what is your consensus for how best to possibly "regenerate" (extend) the life of salvaged 18650 cells that's applicable not only for a high energy cell like 30Q, but also other NMC 18650 cells like LG MH1 ?

Voltaplex lists both Samsung 30Q and LG MH1 as NMC chemistry ... https://voltaplex.com/lithium-ion-battery/18650-battery?s_chemabv=29 .
 
i dont know
was it 120 cells of mh1
same brand
dont you lose capacity to resistance
resistance is heat
my thinking is
same resistance should be same capacity for the same (mh1) cells
 
I just did this with "donated" batteries...

I purchased an opus BT-C3400 and xtar VP4 to test the cells. I had a nice little system going... Charge the cells at 1amp on the xtar while simultaneously running a cycle test on the Opus at 1amp. The charging takes considerably less time... so I quickly had a pile of of fully charged cells. Once I had liberated all the cells and fully charged them, I switched the xtar to cycle test as well.

The whole procedure is -> charge -> discharge -> charge. I thought I was very clever for starting with fully charged batteries and getting right on to the discharge -> charge part of the program. The total time was probably the same, but it felt faster and perception is reality.

I kept reminding myself that I am doing this as a hobby, and learning about electricity/batteries/electronics in a manner that is going to be fun. I can say that by doing everything myself, I have learned a TON. In the long run, it may not pan out to be worth the time / money tradeoff harvesting cells. I hope it is to be sure, but I haven't any experience to say one way or another. My build will be done by the end of July (hopefully sooner) and I will put it all to the test!
 
Thanks for the input everyone. eMark found the ones I was looking at. JehuGarcia on youtube has a series where he makes a power wall out of these so it seems like they are capable cells as long as the time is taken to confirm what has been purchased.

Seems like the consensus is begin all of the cells at the same state of charge, perform cycle testing to make sure there aren't any in dramatically worse shape than the others before assembling. Obviously supervise charging activity and keep distance from valuables as best as possible.

One main reason I gravitated to the NESE modules was the ease of replacing a bad cell or parallel group. So as long as I monitor the groups in some fashion, I should be ok to keep the cells well balanced.

The next part to research will be charging once these are put together.
 
I was thinking of using the NESE modules with salvaged cells as well. I got all the way to the assembly phase and realized that salvaged cells did not have uniform ends. This was due to removal of nickel strip. The removal always left small bits of nickel behind and deformed the ends of the can.

NESE rely on a friction fit that really needs flat and uniform battery contacts. I ended up selling my NESE modules and going with a spot welder for my harvested cells.
 
Yeah, I do realize that is part of the process for prepping the cells for the NESE. They will need to be as uniform as one can get them. I suppose they would need to be fairly uniform for spot welds too so that you are getting good contact across the full piece of nickel.

I'm going to start with some sandpaper, may move up a dremel if I get confident.

Ended up purchasing a XTAR VC8. It can charge 8 cells at once, it can read IR, it can do capacity tests on 4 slots at a time and it can do a "storage" charge if you aren't using the cells for a long time. It was reasonably priced at about $35 but you do have to supply a usb C power source which is a small drawback I guess.

I'll be interested to see how the IR readings come out. So far the handful that I have tested are reading close to each other at 40ish mOhms.
 
I have VC8 and VC4. VC4 is much better for cell harvesting. Only 4 of the slots on the VC8 can do the C/D/C, and they only discharge at 300mA.

VC4 can do 2AC/1AD/2AC cycle.

VC8 also only displays the discharge capacity, while on the VC4 it cycles between charge and discharge so you can spot discrepancies.

Only reason to get VC8 is if you really want an 8-slot charger.
 
I got an XTAR VC8 to speed up battery condition and capacity testing. I got it on amazon for around 45 bucks. It's going back because for what it does, it costs too much.

Comments

1) charges up to 8 batteries at once but limited to one amp.
2) discharge is quite slow as in hours
3) capacity seems accurate
4) discharge/capacity tests 4 batteries max at one time.
 
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