they are shorter as @Athrx says. for my hummie i could have fitted it all in without routing any extra space, but it is super tight, so i decided to route about 8mm at one end to make cable management easier
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Show me how yours is doing so far lol
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heh, will do. am painting it at the mo 
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I do it often
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@Battery_Mooch I got some questions for you I’ve been wanting to ask you:
What would be the best way to meassure cell aging considering they are still assembled in a 12s4p pack. I understand I’ll need to measure IR, but what’s an acceptable range?
What would be the main cause of cell drifting? I know they tend to drift when p-group connections are poor and have high resistance, when the BMS goes bad or when you use a high current charger
I understand
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DC and AC IR don’t change much over the life a cell until it’s really worn out. IR is also state-of-charge and temperature dependent, making consistent testing tougher.
AC IR values are quite low, so differences are hard to see, but the test results are barely affected by lead and connection resistances. DC IR is higher, and easier to test, but the results are affected more by the resistance of the leads and connections. This isn’t an issue though if the resistance of the pack or cell is measured when new and changes to the resistance are measured over time.
The big manufacturers typically don’t spec IR change for determining end-of-life but, IIRC, I have seen a 15% increase mentioned. That is tiny and tough to measure.
Capacity loss over time can be easily measured though if a good tester is used. Most chargers that test capacity are very inaccurate but could be used if they are very consistent. Of the ones I have tested the SkyRC MC-3000 was pretty good for capacity checking and good for DC IR checking if you pressed against the bottom chargers contact while measuring.
You would also need to decide when a cell has reached “end of life”. That is, how much of a capacity or IR change do you accept before replacing the cell(s)? Most manufacturers spec cycle life out to a point where the capacity has dropped 20%. Though I have seen a couple cells spec’d out with a 40% loss before the cell is said to have reached end of life.
Most cells can be used far beyond this point but any damage to the cells is accumulating at the same time and that, without any data to help you decide, must be taken into account. This is why a conservative number like 20% loss is often used.
Differences in self-discharge rates will cause cell (or p-group) voltages to drift apart in series strings without a BMS. With a BMS they should all be the same voltage once balancing is done. But immediately after that they can start drifting again. This typically isn’t an issue unless the pack is being stored for a while.
Cells within p-groups will, of course, balance themselves out but that can take a bit of time if the charge rate was very high and/or the connections within the p-group are bad. Each p-group can settle at a different voltage though.
Higher charge and discharge rates accentuate the IR differences between p-groups and cells and will create temporary voltage differences, within and between the p-groups. These differences disappear once the current flow stops and the p-groups balance themselves internally. Voltage differences due to differing capacities between the p-groups however do not disappear when the current stops. The BMS must fix these but if the cells were top-balanced before then when they are recharged they should all end up balanced again without BMS intervention.
As mentioned earlier, the BMS must also compensate for the different self-discharge rates of each p-group too. Though that typically isn’t much of a concern unless the pack is being stored for a while.
If there is no BMS then balance charging needs to be done occasionally. There are no guidelines for how often. The p-group voltages will need to tested over time and a schedule determined from that. There are no guidelines for determining how much of a difference in p-group voltages is acceptable. It depends on how hard they are being used, what the low voltage cutoffs are, etc.
The bigger the differences though, the worse the pack performance will be. Safety, solely due to p-group voltage differences, shouldn’t be an issue as long as none of the cells ever drops below 2.5V. This is ignoring any safety issues due to internal cell damage, temperature abuse, over/under-discharge and charge, and any other misuse or mishandling.
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Anecdotal evidence does not offer proof, but I also use chargers in parallel occasionally and haven’t had any issues.
I’m looking to have the same battery and bustin board with Torqueboard DD motors. I’m around 175lbs and am wondering what type of ranges ill get on paved bike trails going 25-40kmh. You have any rough estimates? I was hoping to hit 35kms of range.
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Can get 647x NEW P42A direct from Moli Canada.
Shipping them to Germany is too expensive. “US$ 1,525 (duty, VAT, fees included)”
As they are from 2020 I get them for a special.
Maybe here in the forum with shipping domestic US someone is interested in these P42A ?
Interesting! Thanks for posting that.
That’s a great (and tiny) distribution IMHO.
About half of the cells are are in the lowest voltage set with none below that. This means all of the cells were self-discharging at the same rate as the main group or less…a good thing. This makes it easy to create packs with known self-discharge rates and that allows easier design of a BMS tailored to compensate for those known self-discharge rate differences.
(Edit) I agree with @Skyart too…that voltage spread is nothing.
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So 10mv is the largest difference? This is like nothing to worry about, less then nothing. In the thousands of cells ive gone through the largest difference to date is 11mv for me ever.
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Can anyone point me in the direction of a legit supplier of these cells? These are very expensive (or sold out) in Australia. Looks like the only place I can get them is Alibaba, but not many mentions of Alibaba in this forum. I guess they are much easier to source in the US.
Does this place look legit or no?
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Getting cells to Aus is expensive as fuck.
The only place to get them in Aus is Vapour Eyes or Vape Traders (their parent company).
If you buy from anywhere other than an authorised vendor, you risk buying duds.
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Thanks for the links. Figured it would be a crapshoot. Still, I’d be willing to test the waters on a few small test orders.
Have a test batch on the way. Anyone in Aus have the gear to load/capacity test these?
if y’all are still looking for some molicels down there in aussie land hmu 
Deleted two posts. Had weird IR on cells 1 and 12. Thought it was possibly fake cells. Turns out it was my unorthodox charging technique. @Stealther It’s a PITA to get cells down here for sure. I hope I’ve found a couple good suppliers, but it takes weeks to land them via slow boat from China.
We have an authorised molicel reseller here, it’s great.
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