using 8Ah graphene 75c
starting with lg cells and samsung 35e
0.2 nickel
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Whereâd ya get em? I bet Mooch would be curious.
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to get better experience at battery building (before i start to locally build some packs) i have been given a bunch of old scooter/ euc/ onewheel packs which need to be fixed up
got a bunch of high quality chargers for them and im gonna be charging and discharging all of them to sort into groups before welding
was about to send @Battery_Mooch a message asking how this can be done safely
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A few are around.
But IMO there are many more fakes than genuine ones being sold if weâre talking HG2âs.
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âSafelyâ is never a word we can use. 
We can try to lower some of the risks though.
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all cells i get are from fogstar wholesale
love it when you make those comments.
what things can i do to lower the risk enough that i can use those packs without wetting myself every time i do
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Youâll be testing and using the packs as is?
Or will you be salvaging the cells, testing the cells, and making new packs?
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yes this
all of the packs have some issue (some its just a bms that needs replacing other loose connections etcâŚ
if there is no easy fix i will be salvaging the cells
creating very cheap packs which are functional but not for heavy use
WaitâŚso you will be testing and possibly using these packs?
Letâs start overâŚdo you want to minimize the risk of testing packs or individual cells?
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individual cells
if those cells are in good condition i will be using to build packs
those packs will be basically just given away with a warning saying they were made with old cells and may have low capacity and power output
Okay, thanks.
Take all necessary safety precautions when disassembling the packs. I will leave that to you to research. If you donât find enough to feel comfortable doing it then do not do it.
For each cell it can be good to check their DC internal resistance and then their capacity. This will take fâŚoâŚrâŚeâŚvâŚeâŚr. You can then sort them into p-groups. Thereâs info online on this.
You will need a good charger to do this though and a good mounting jig if using a hobby LiPo charger. If using a standard round cell charger then press up against the bottom contact consistently every time you measure IR to help make good contact. These chargers have lousy consistency and accuracy otherwise. I donât have a round cell charger to recommend.
Test the accuracy of your charger before committing to this testing. Insert and remove a cell three times for each slot, measuring the IR each time. If you cannot get results all within a milliohm or so then you will have a tough time sorting cells.
Try testing the capacity of the same cell at least once for each slot. Are the results pretty consistent? If not you will have trouble sorting them.
Do everything on a non-flammable surface and only when you are around and awake. Have a large metal container to push a cell into in case it doesnât like being charged or tested. Do not use a container that seals tightly as you will just create a bomb as the gases expand inside if the cell goes into thermal runaway.
Check how hot the cells are getting during charging as this is where trouble can start. Youâre adding energy to the cells and damaged ones can overheat. Any cell noticeably warmer than the others should be recycled.
A self-discharge test is great to do too. Charge all the cells fully and then let them sit for a day. Measure the voltage of each and then let them sit for at least a week. One month is much better. Then re-measure the voltage of each. A change of more than a few millivolts means that cell is self-discharging too quickly and will force that p-group to be balanced more and can limit the performance of your pack. It will also be the cell that ages the fastest, forcing you to replace it sooner.
When not testing the cells, or storing them for the self-discharge test, be sure to place them somewhere they cannot start a fire anywhere if one goes into thermal runaway and starts lighting up the others. These things can zoom around like frakkinâ model rocket engines so donât store them in a linen closet.
IMO, donât use any cells that have dropped to under 80% of the rated capacity and donât use any cells that have a much higher IR than the rest. The tighter the spread of capacities and IR for all the cells the better the pack will perform. But this means you will be rejecting more cells. You have to decide what your priority is.
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wow lots of info and its all super helpful
i think i have all the kit you mentioned above and will def take necessary precautions before doing anything with the cells
for the cell chargers i was given a dragon vp4 plus xtar and a yc6000 youshiko
i dont really know if these are any good but was gonna do some more research on them
for sorting cells into groups to be made into packs what requirements do they have to have (all within how many mAh and millivolts and IR?)
thanks so much and will read through your post a couple more times before doing anything
hopefully all works out well
thanks again
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Itâs up to you. The tighter the grouping of capacities and IR the better the pack can perform. You could check online to see what others do and even use www.repackr.com to help group the packs.
Good luck!
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nice thanks
what is an acceptable number for capacities and IR?
dont really know a starting point of what is normal
Where in Canada are you? If youâre in the Toronto area I would do your spot welds for u NP. I have a Kweld.
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No way!!! Yes please!
Ya no worries man. DM me.
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Honestly, there are no âacceptableâ numbers except those which we choose. Some people will have very firm ideas of the numbers to use and others will just say pick what works best for the cells you have.
I know you just want a starting point, something to make getting going on this easier. I donât have it for you, it doesnât exist. I donât say this to be a hard ass. I say it because thatâs the situation you are in.
Use your Google-fu, check around, see what others have done. But using someone elseâs numbers without even knowing why those numbers were used wonât do you much good.
How about just choosing your own numbers and seeing how many cells meet those numbers? If you have enough that pass testing then you could tighten up the numbers or just go with what you have. If only a few cells meet your numbers then you can decide whether the cells are not worth using or whether to loosen up your numbers.
This is why there is no âacceptableâ or âcorrectâ numbersâŚit all depends on what you have and what youâre willing to accept. Wanting to salvage cells and build your own packs means you have elected to take on the task of learning about and setting these numbers.
Letâs try it nowâŚ
What is the rated capacity of the cells you have?
What is their rated internal resistance (IR)?
We need to know this to know if any of them are too badly degraded when you start testing.
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im mainly using samsung 35e
you rated them at 3500mAh and claimed they have a high internal resistance (trying to find a spesific number)
will look a bit more into salvaged cells and what is an acceptable difference in those numbers
above everything i want to make sure these packs are safe. i have no interest in creating packs which are dangerous and therefore safety is everything and i will keep the numbers tight
