Hello everyone!
I have been doing a lot of research and learning in the buildup to building my own high-capacity pack for my Boosted Rev. I have nailed down most of the details but one of the final decisions I need to make is the cell. I’ll be upgrading from the stock 12s3p configuration to 12s5p so out of the gate I will have plenty of reserve capacity. But I don’t want to have to rebuild the pack from cell degradation after a few hundred miles.
I am hoping to keep at least 12 miles of range on the pack at the top 25mph speed, long term. Currently I am getting about 7 miles on the stock pack, which is probably around 7-8000mAh in its current state (3p LG HG2 with ~100 cycles). That translates to a desired long-term pack capacity of ~12-13.7 Ah. If I fudge the numbers a little, let’s just nail down my goal as keeping a cell capacity of 13/5=2.6Ah over 500 cycles.
So, 2.6Ah after 500 cycles is a pretty high bar that from my reading most cells won’t be able to do. So I looked for cells that are reputed to have a long cycle life and what I came up with is the Samsung 30Q and the Molicel M35a. Various sources I’ve seen say that Molicel cells have especially good cycle life, and the nominal 3500mAh capacity seems to give some reserve capacity. But they are only 10A continuous current cells, unlike the Samsungs that are 15A continuous…
The two Rev motors total 1500W. If that figure is at peak voltage and scales downwards linearly as the battery voltage decreases, then that would mean the cell current would be 1500/44.2/5=6.8A. If it doesn’t scale linearly, the peak cell amperage could be higher. 6.8A is up into the range of what would reduce the Molicels’ cycle life, but since the Rev speed limits to 25mph that 6.8A would not be continuous. So maybe I have nothing to worry about? Please share your thoughts here.
Overall, I’m leaning towards the Molicel but it’s a very hard call. But since I’m being pretty ambitious with my cycle life expectation, I would like to make the best decision possible.
tl;dr Which cell would be more likely to have at least 2600 mAh of capacity after 500 cycles supposing somewhere in the realm of 4-7A of continuous cell current?
Thank you!
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I found a PDF with some graphs from Samsung showing the current-gen 30Q having 2579 mAh of capacity after 250 cycles at 10A. My use will be a lot less demanding than 10A continuous and I will not be fully discharging nor fully charging the cell, but since the 15A cycle results are nearly identical to the 15A results maybe the cycle conditions are less important for the 30Q. I’m not sure if I can draw any relevant conclusion from this data. SAMSUNG-30Q_Introduction_of_30Q6_comparison-20191216.pdf (1.1 MB)
@BatteryMooch should assist you. He knows batteries. If you want a faster response time, I would suggest the other forum since you’ll have a much quicker answer than here. Pm me if interested on that. I am limited on battery knowledge and only know about making packs. The math here looks fine, however, you want to know if its possible to have the cells longer as time passes by limiting your amp uses. This is out of my limits. You can however, modify the pack and put it in the rev. It has been done and unfortunately failed and was swapped from the original stuff within the rev:
If you’re trying to modify your rev, do note that boosted has been stingy in that department. You have to change the esc and the bms as well in order for this to work.
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There’s not enough data out there to help you with this decision. I’ve seen verrrry long cycle life with both of those cells in testing but have not directly compared them or done testing that would allow you to estimate which might be better for your setup.
Those 30Q graphs really can’t be used for your setup. Especially with 4A/cell charging.
The cell manufacturers would tell you to test them for your application but that would take a couple of months and isn’t very convenient to do. 
A data point to consider is that some pack builders are not happy with recent 30Q cycle life. This can be due to the BMS or the cells or both. I wanted to mention it though.
Bottom line though…we don’t know.
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Thanks both of you! It seems like going with the Molicels is at least probably not a big risk so I will stop agonizing over it and choose them. You will probably see a pack build post from me sometime in the next couple months 
I’ve been researching that heavily and I haven’t been able to reach a satisfying conclusion. The BMS will go into a fault mode (“red light of death”) if it detects an issue and the mode has to be reset by wiping a memory chip or by sending a command over CAN. It doesn’t seem like he ever attempted to do that reset. My current plan is to transplant the BMS electronics from a dead battery I bought off ebay and then attempt to clear the fault mode using CAN. If that fails… there is always the stormcore option.
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Good decision making you have there. Hope to see how well this goes. Hope to see some photos of your stuff.
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