Nice demonstration of how the LiFePO4 curve works in the middle of the flat area, and as a further demonstration it would be good to show how balancing should be done in the steep area of a LiFePO4 curve.
Good suggestion. I actually want to do that, and highlight the dangers of using an adjustable bench top power supply. I've seen so many horror stories of people slightly touching the knob, and overcharging their cells. This needs to be done with a charger, or power supply that you can digitally program the max voltage.
I don't think you could have set this up better to give you the results you wanted to see. You can't balance at mid level voltages for LiFeP04...doesn't everyone know this? That's why you set your balance voltage above 3.40 or 3.45 Doing the test between 3.20 and 3.30 isn't going to balance in capacity, just voltage...which means nothing. Take a fully charged cell and combine it with a cell at 75%. Or an empty cell with a cell at 50%.
How would anyone just know this? Most of us just want something lighter and with greater capacity than lead acid that we can charge and discharge thousands of times.
I did not set this up for a desired result. I set it up to be charged somewhere in the middle of the SOC which is how you usually receive cells. Some people are under the misconception you can receive cells, and just parallel them right out of the box and they will balance without a topping charge.
Thank you for making this video, because I have tried explaining it to people, and they are like, but I've seen it on RU-vid that you can, lol . Good news I just ordered two super beast batteries from battery Hook-up and am just waiting for them to get here. Any recommendations for a bench power supply. I plan on building a 4s 130p Headway battery bank to be able to start and power my bus
Awesome James glad to hear you finally have some batteries coming! I don't have a specific model suggestion, but I would find one that requires you to digitally set the voltage, I don't like the idea of a knob you can accidentally bump, and overvolt your cells.
Not what I expected. I'm pretty sure lead acid do. Pressurized cylinders do. So you would just assume that within a week they would balance. Minuteman prep kind of showed this when trying to add additional LiFePO4 batteries to a solar generator (Titan I think) - I think that particular one uses lithium-ion though.
BTW a complete battery in parallel with another will eventually balance when you reach either low, or high state of charge. So minuteman prep adding additional batteries would be fine. It's the cell level builds that needs to be balanced before assembling them in series.
If wiring them parallel doesn't balance them then would they balance after installing the bsm or balancer? And can i use a lithuim battery charger to charger my 96ah headway battery bank?
An active balancer will balance them at the top of charge. The BMS can too, but might take a super long time. "A lithium Battery Charger" is very vage, do you have a specific model?, and what voltage if your battery bank, or better yet how many cells are in series?
I'm not sure what you're trying to illustrate with this demonstration. When people put cells in parallel, the goal is to create an identical voltage level, and that is exactly what happened when you connected these cells together. You carefully chose cells at 25% and 50% SOC, knowing their voltage would be very close anyway. I think you already know it's a bad idea to put a cell at 3.2 volts in parallel with a cell at 2.6 volts...and you carefully avoided that scenario. The odd thing is, I think you were going for an "aha!" moment by showing that two LFP cells with an identical voltage do not equalize their state of charge, but that has never been the assertion. You put cells in parallel to balance the voltage, not the SOC. I would also point out that if you put 4 of those cells of equal voltage into series to create a 12v battery, then charged it using a decent BMS, the higher SOC cells would reach the absorption phase sooner, but otherwise the entire pack would complete charging at the same voltage AND the same state of charge percentage. In other words, you did a very good job of showing what batteries of this chemistry do, but I'm really confused about what point you were trying to make, if any?
I know this sounds crazy but a lot of people think you can balance the SOC of LiFePO4 cells by simply placing them in parallel (or even series) for a period of time. I've even had people commenting on my videos that this works. I made this video to educate the people that are under this misconception.
@@BradCagle OK, I didn't realize a lot of people misunderstood why you put cells in parallel before connecting them in series. Now it makes sense why you'd do this experiment.
@@karldingbat BTW they are not in parallel the whole time. There's a few spots where I'm doing the charging test in series as 2s to see which cell charges first. So if there is a specific spot where they actually are in parallel, yet I'm saying series please let me know what time so I can fix it. I watched the video again and don't see it, please let me know. Thanks
