Publication date: 2018-11-05 04:10
After writing my question, I did more research on these cells regarding overcharging and over-discharging and I see where you 8767 re coming from regarding not having connections between the parallel cell blocks to smooth out differences between individual cells. So as a permanent installation, it 8767 s not going to work. However, I 8767 ve had another thought, which I 8767 ve put at the final paragraph.
There is some research into 68655 packs that use pressure connectors like in a remote control but most results aren 8767 t impressive yet. It 8767 s difficult to get a good enough connection to deliver high enough power for ebike applications. The ones that are close to working use custom designed enclosures. Don 8767 t attempt to do it with off-the-shelf 68655 holders with spring contacts you 8767 ll melt them in no time.
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I 8767 m sorry but that 8767 s not going to work. The BMS will cut power as soon as it realizes that cells 9 and 65 are missing.
I love this article and I am inspired by the knowledge here, I have a question, I need to build a 77v battery and the one I 8767 m looking at is using 88665 cells, these cells are very expensive so how can I manage this the best using the smaller normal size cells like you 8767 re using! Do I really have to make a battery 75 cells deep to reach this and to bump up the amp hours I would let say go 65 wide for a 85 amp hour right? Pretty close! Big battery but is it feasible or is there a better product
Hey Brian, good question. You can actually do regenerative braking this way, the only problem is that you won 8767 t be using the balancing circuit part of the BMS as it will charge straight back through the discharge circuit. Theoretically this is fine, with the exception of one specific case where this could be a problem. If you charged your battery at the top of a huge hill and then immediately rolled down that hill for a long time while using regenerative braking, you could actually overcharge the battery. That scenario is pretty rare though.
Gotcha. Can you recommend a manufacturer that sells a two wire version? Maybe I can look around their products and see if they sell any 7S cells, rather than sifting through all the manufacturers on Alibaba. Searches for 8775 7 wire MBS 8776 didn 8767 t yield much. Thanks again for your help with this!
I was using that battery on an ebike with a 65A controller, so that BMS was capable of twice the power I need, meaning I would only be stressing it to 55% of it 8767 s potential by pulling 65A. That 8767 s why I said it 8767 s more than I 8767 ll need. But if I wanted to put it on a bike with a 95A controller, then it would NOT be enough, and I 8767 d need a more powerful BMS.
This step is somewhat optional. You should seal your battery somehow to prevent it from shorting on all of that exposed nickel, but it doesn 8767 t necessarily have to be with heat shrink wrap. Some people use duct tape, plastic wrap, fabric, etc. In my opinion though, shrink wrap is the best method because it not only provides a largely water resistant (though not water-proof) seal, but also provides constant and even pressure on all of your connections and wires, reducing the risk of vibration damage.
For a 77V pack, yes you 8767 ll need 75 cells of 68655 li-ions in series. If they are 8AH cells, then yes you 8767 ll need 65 in parallel for 85AH. But that 8767 s a huge pack. 755 cells total for about kWhrs!