Recent content by GijsW

I just thought of a possible mitigation method, one could design the cell holders so that the cells are supported on the edges (so not in the middle of the terminals, that way all the force is on the cylinder on the outside, which shouldn't pose any issue

Hi everyone, I've got a question regarding how much force one could apply to a cylindrical lithium cell (LiFePo4 in this case). My plan was to build blocks of 32700 cells and clamp them together (plus to minus to get series connections). However, this would mean that quite a lot of force would...

Hi everyone, I'd like to discuss the need for fusing individual cells within a pack. The idea behind fusing cells is that when one cell fails (shorts), the fuse burns, the failed cell is isolated, and the rest of the pack continues to function. Tesla does this by using small wires to connect...

Your comments were very helpful, thanks! I found a vendor on alibaba (Sichuan Lingxiang Technology) who can supply me with 2 chargers which I can parallel when using a simple combining circuit supplied by them. Thanks again!

Hi everyone, Does anyone know whether or not it's possible to charge a single lithium (LiFePo4 in my case) with two parallel chargers? The reason I'd like to do this, is that for my application (an electric boat) sometimes I'm constrained by a 6A circuit breaker, while other times I could go up...

Thanks! I learned a lot! I didn't think about the bms balancing voltage. My bms isn't programmable, and the specifications list: "Balance detect voltage=3.5V" "Balance release voltage=3.5V" So maybe using a 84 V charger isn't a great idea. Or I could buy a cheap tiny 87.6V charger (1A or so)...

Hi everyone! I'm building a 24S LiFePo4 pack. The chargers for these packs have a cutoff at 87.6V. Could I also use a 20S regular lithium charger for my pack? It should work, right? As far as I know, they're both CCCV chargers. The only thing is that the 20S charger has an end voltage of 84V...

Ok we went with LiFePo4 after all :D . Bought a little spot welder and a bunch of 32700 LiFePo4 6Ah cells. Going to assemble a 24S5P pack first. The idea is to make multiple packs, but if the LFP turns out to be too heavy we could opt to switch to NCA/NMC for our next pack. That will depend...

Thanks for the suggestions guys! We wanted to use lifepo4 since they are fire-safe, cheap, have insane lifetimes, are quite tolerant to higher operating temps and are easy to assemble (large 90ah cells). However, we just decided to go with 'regular' 18650 lithium cells in order to achieve...

Thanks for the replies! The intended use is indeed low speed cruising in canals, though it should be able to do around 9-10 km/h with headwind and 8 people on board for shorter periods of time. The reason I care so much about efficiency is that the batteries are to be charged at home, meaning...

Oh, one more question. I was under the impression that brushed dc motors were quite inefficient (around 60-70%) Now I'm seeing some PM brushed DC motors with 90% peak efficiency (motenergy for example). Would these be a good option as well? And what efficiency would forklift motors roughly...

Thanks for the replies! The simulator is incredibly helpful. It appears the efficiency is proportional to the torque (it does go down a bit for lower voltages). When throttling the motor, the max efficiency goes down, and the max efficiency point is found for lower torques. We are probably...

Hi everyone! Together with a couple of friends I am converting a small 18ft canal boat (about 750 kgs unloaded) to electric. We hope you can provide us with some help in the motor selection. The required motor power is roughly 1.5 kW constant, with peaks up to 3 kW. The propeller shaft...