Feedback request Xuba battery build (HS senior project)

[thisisnew]

I do not remember the amps that were pushing through yesterday but I never saw it higher than 10 or 11 that I recall. Also, I only have 8 fuel cells, not 16. They do not balance very evenly across the fuel cells and I have switched sides a few times to manually even it out. My understanding is that it will do that itself but I was a bit nervous and wanted to even it up.

I think I had set the charger incorrectly yesterday as the volts would keep increasing as it would charge. Somehow I had the amps constant. I set it to 3.5 last night when I went to bed and the volts per the charger was 3.63 when I woke up. I reread the manual and figured out how to keep the volts constant, other than some small variation up and down. Right now it seems to be pushing .30 amps only. The cell that has the charger reads 3.622 and the cell at the opposite end is 3.546.

My Overkill BMS and the capacity testers arrive this evening so hopefully I can get all charged and then hooked up and test it tomorrow or Sunday.

 

[newbostonconst]

Having different voltages at one end then the other means the wire isn't big enough or there is a bad connection. It will even out eventually just need more time.

You should take your voltage reading when it is not charging and batteries disconnected from each other to be the most accurate. You can do it if it is barely charging but you can see with your uneven voltages that you are not charging evenly and your results are skewed. To be the most accurate the cell should also sit for a couple hours to get the absolute best measurement but that likely isn't needed for what you are doing.

I would just call them cells and not fuel cells. It is kind of miss leading saying fuel cell. Your cells are 280ah right?

 

[thisisnew]

That is correct, the cells are the EVE 280ah ones from XUBA. They are all connected using the busbars sent with the cells.

I have been taking the reading with all hooked up and in the process of charging. It varies often but it seems the amps are down to .2 now, so it still seems to be going ok. Thanks for the help/feedback.

 

[lmwilco1]

Connect the positive wire from the power supply to one end of the parallel string of batteries and the negative to the other end. That will keep all of the battery voltages the same. Let them sit until the current goes to 0 and you should have all of them at the same voltage and balanced. How about a photo of your charging setup?

 

[Ampster]

I have been taking the reading with all hooked up and in the process of charging. It varies often but it seems the amps are down to .2 now, so it still seems to be going ok. Thanks for the help/feedback

What is the voltage? If you are 3.6-3.65 you should be top balanced at less than an Amp of current.

 

[thisisnew]

I now have the wires at opposite ends as you suggested. Here is the photo:

 

[newbostonconst]

Do you have a good volt meter to measure what the voltage is with charger disconnected?

 

[thisisnew]

I have a Klein CL380. I hope it is decent? I just unhooked all and checked the voltage at both ends, one was 3.602, the other end was 3.527, so presumably still a ways to go. BMS and capacity testers are here so should be able to get to everything this weekend.

 

[newbostonconst]

You are surprisingly pretty close unless there is surface charge(you would have to let it sit to tell that)..... To get from 3.5 to 3.65 is a small amount of charge (guessing a couple percent) to get from 3.3 to 3.45 is about half the battery charge or more....

 

[Gazoo]

I now have the wires at opposite ends as you suggested. Here is the photo:

Nice job on your box. Yup....you are extremely close to having the cells top balanced. Keep a close eye on things. Looking good....

 

[lmwilco1]

I am surprised you are reading a different voltage across your pack, 3.602 to 3.527. How long after moving the wires to opposite ends of the pack did you measure that? I would let it site until all cells are at the exact same voltage, that will give you the best balance.

 

[thisisnew]

I just checked the ones on the ends again and they have not increased at all? Perhaps the ones in the middle of the pack are drawing from them, not sure. I will keep the charger going and keep an eye on them but turn it off tonight but leave them in parallel and see what it reads after sitting overnight. Maybe I did not get a great reading the last time I checked...

I am not in a rush as I have been looking at the Overkill BMS and am confused as to how to hook it up. Does anyone have a youtube video or a diagram to link to that I could examine? Looks a bit daunting. I intended to mirror Will's video on the hand cart system and he used the Electrodacus but I did not want to keep waiting so went with the Overkill which seems like a great BMS, just not sure I have the know-how to wire it vs Will's video on the Electrodacus. I will spend some more time trying to sort it out, maybe reach out to Steve from Overkill.

 

[Gazoo]

I believe the instructions and all are on his website.

Support/Downloads

User Manual User Manual: Download Manual (6.5mb PDF) Simplified 4 Cell Assembly Ultra simple view of a complete 4 cell battery assembly. – Click for full resolution. Bluetooth Mobile Apps iPh…

overkillsolar.com

 

[thisisnew]

I believe the instructions and all are on his website.

Support/Downloads

User Manual User Manual: Download Manual (6.5mb PDF) Simplified 4 Cell Assembly Ultra simple view of a complete 4 cell battery assembly. – Click for full resolution. Bluetooth Mobile Apps iPh…

overkillsolar.com

Thanks very much for this link. I googled for a youtube video but could not find one and was looking at the wiring instructions included in the package and am confused with tying in the BMS heavy gauge wires to my positive terminal. I will review the links you sent.

 

[lmwilco1]

you might be able to get an idea from my battery pictures, https://diysolarforum.com/threads/my-190ah-battery-build.10161/ the BMS is kind of hidden but the balane lead blac goes to he battery negative, then connect each white in order to the next buss bar on your build. Finally the red wire goes on the final plus terminal. Before you plug the balance lead connector into the BMS use a voltmeter measuring from the black to each white wire and finally the red wire in turn to make sure that each new wires goes up by your cell voltage. If one does not g up at all or goes up by 2x the cell voltage then you made a wiring error. The instruction that come with the BMS and the instructions that are linked above are pretty bullet proof. Don't forget the fuse on the positive terminal of your assembled battery. When you are ready to attach an inverter remember that you need a pre charge resister to charge the capacitors in the inverter, if you don't it will likely put your BMS into over current shutdown mode.

 

[thisisnew]

I have one cell on the left end that was at 3.5 and the others were all a bit above 3.6. I disconnected and will manually charge this cell for a few hours to see what happens. I think I will try to leave all under compression and see if I can individually charge each cell to 3.65 today.

 

[thisisnew]

It only took about 15-20 mins to get that cell to 3.648. I will do each one separately. It should not take too long.

 

[thisisnew]

So I am almost finished getting all the cells to 3.64+. I went back and checked the voltage on the first cell that I charged to 3.648 this morning and it now reads 3.628. Is it due to potential imprecision of my multimeter or is it natural for it to do this? It seems some of the other cells have started to slightly ease down too. I had not been recording the voltages but just started.

 

[Gazoo]

I think you are close enough. The cells will ease down to their resting voltage of around 3.3 volts. This is normal.

 

[thisisnew]

So I decided to capacity test one cell only the first time round. I will either recharge the one cell, connect the BMS, then capacity test the battery or continue on and capacity test one-by-one.

In hooking up the capacity tester I had a tough time setting the low charge disconnect. The cell drained very quickly from its initial 3.6 volts down to where it has now been operating for some time at 2.85 volts. I had to reset the device after about a minute or two of it running so the capacity will not be entirely accurate but pretty close I guess.