some time ago I was going through internet and looking for li-ion cells to make new battery for my EMTB
I was using lipos so far, but this is not a good source of power and I can clearly say that to EVERY PERSON that will try to use them to power high-drain builds: “this is crap”.
They supposed to be 10C constant and 10Ah but reality was a bit different. Voltage sagging, puffing cells, unbalanced cells, etc.
I decided to go with li-ions and then I found THIS:
Volkswagen’s E-Up! electric car li-ion cells. 12 cells in a pack, configured as 6s2p, but that can be changed easily to 12s1p. 1 cell 3,7V, 25Ah, 5C constant, 10C peak, 147mm x 90mm x 25mm, +/-700grams each.
They are quite big, but that is not a problem with mountainboard.
I once came across a lithium-titanate battery pack in a similar form factor on eBay going cheap. Believe it was taken from a forklift or something. Discharge and charge rates were pretty awesome (like 150a charge!), but that was the only good thing about it. Energy density was low, the pack weighed 6kg, and the nominal voltage of each cell was 2.7v or thereabouts.
might be a bit off topic, but i assume you used the hobbyking multistar batteries because of the 10c. they really are crap and not at all 10C, more lik 2 to 3c. This is why nobody will recommend them to you. I know of some people that the 20-30C Zippys work fine and i’m personally using 12Ah 15C Graphene cells without any problems.
Maybe just a heads up for future lipo purchases.
On the other hand the VW cells look really awesome and i can’t wait to see how they perform
Sorry to hear about your negative experience, but any lipo that is a true 30C or higher at 8000mah will blow away most Li-Ion setups when it comes to amp delivery (in my case 2S2P). The majority of amp hungry mountain boarders use Lipo.
@Acido, even cheaper actually, I paid 250$ for 12 cells
@Der6FingerJo@telnoi I get your point guys, I used crappy lipos, so I got crappy results, but I think it is worth to try those VW’s packs anyway. Then, maybe, I will be back to lipos, who knows
ok, I did a short test (weather in my city is horrible now)
I took my board for a ride, I did (according to google maps, forgot to switch on endomondo…) 17,5km = around 10miles.
+battery was loaded yesterday
+start-up voltage was 49,1V
+temperature outside 7 degrees Celsius, 44 Fahrenheit
+setup: EMTB, 2x6374 190Kv, 2xFOCBOX, motors set to 50A max, batt max 15A (just for safety, I am going to change it back to 65A and 25A)
+hills, hills and once again hills, some of them pretty steep (wheels were spinning)
+heavy and oversize load board is around 20kg and mine “waaaaay over” 90kg
After that, when my face was frozen I came back home, battery voltage was 45,0V.
I was completely shocked during that ride, voltage sagging during full acceleration was around 0,7 Volts! I am currently waiting for BT module so I will be able to upload some charts from BLDC app.
O checked each cell and they are balanced quite good: LV: 3,71V, HV: 3,75V. << NO BMS so far
this board is ridiculously fast in that setup …or maybe it is just too fast for me, anyway, going over 40km/h on EMTB is a bit different than 40km/h on a longboard
@Der6FingerJo I found info that VW is actualy resigning their contracts with Sanyo for those 25Ah cells. They will use Samsung’s 37Ah cells which are THE SAME SIZE THAT 25Ah…that means that maybe in a future I will be able to change my battery for even bigger without changing box
@Acido yes, they are big, I thought that I will be able to use them in original enclosure, but no way…I designed a simple box that will make that 12s look like 2x6s lying on their side, that will make them a bit higher (which I dont care) but deifinitely less wide and it currently printing
…or maybe it is just too fast for me, anyway, going over 40km/h on EMTB is a bit different than 40km/h on a longboard