diy solar

diy solar

One cell always higher

Yes your right. I got to 3.6 in another hour.
Now can you please tell me the best settings for my BMS?
Here is only a few default settings.
Overvoltage = 6.3v I set this.
under voltage = 2.5v
Pack over voltage = 14.6
Pack under voltage = 10v
Balance turn on voltage = 3.2v
Balance precision = 0.03v
Single full voltage = 3.6v
Single cut off voltage = 2.8v
Self discharge rate 0.2%
 
Yes your right. I got to 3.6 in another hour.
Now can you please tell me the best settings for my BMS?
Here is only a few default settings.
Overvoltage = 6.3v I set this.
under voltage = 2.5v
Pack over voltage = 14.6
Pack under voltage = 10v
Balance turn on voltage = 3.2v
Balance precision = 0.03v
Single full voltage = 3.6v
Single cut off voltage = 2.8v
Self discharge rate 0.2%

Hopefully overvoltage is 3.6?

Balance turn on, set to 3.4v. Below that it is self defeating, you don't want it to come on until you get to the steep part of the curve. If you balance before then, you are actually UN-balancing your pack.
 
From 3.1 to 3.4 there should be such small variations between cells that balancing will not happen anyway.
Many seem to worry about active balancers in the same way. Balancing really shuts off in the middle voltages.
 
I finally got the cells balanced and hooked everything up. I started my engine and watched the current go from 100a to 0 in about 5 min. I then put my small 10A charger on and it ran for a few minuets before shutting off. Everything was working perfectly.
Then the problem, I had 2 small battery cables to B- and bought a bigger one and I swapped that out about 1/2 hour ago. Now the BMS has shut down. I get full voltage across B+ and B- but C- is about 2v. If I put the 10a charger on B+ and C- I get lights and the battery is charging again but If I remove the charger it shuts down. I tried disconnecting each cable and reconnecting them, no luck. I had the same problem yesterday when installing it but it suddenly came on. Now it wont. I do not see any problems with any cell or any parameters. Nothing should be shutting it down. All cells are within parameters and the total Voltage is also. The temp is 27c.
Any Ideas?
 
I am a little late here but I cannot tell if everybody is on the same page with the battery type.

4 lipo4 280a
“lipo4” is a gibberish cross between lipo (lithium polymer) and LiFePO4 (lithium iron phosphate). Pretty different battery types!

Are all the different voltages being thrown around because chemistries, equipment and settings are mixed/confused? The charger probably has different charge profiles for each.

I would have thought the Lipo charger/balancer
My guess would be that 280Ah cells (common) would be LiFePO4 but if OP really has a lipo BMS and lipo charger, it might explain some of these oddities.

Just a thought.
 
A before and after pic of the battery cable with the dual before and the larger after would be nice.

DOes the BMS keep track of cutoffs and type?

Do you have a charger and what are the settings. I found that an absorption of 3.45 volts per cell or slightly less works for my SCC and battery. For my Float, I set it to the 24 hour resting voltage of my battery.
==========
The exact type of battery is important. When I saw 4.1 and BMS attached earlier, I started thinking there was a Lithium Ion BMS installed, which has higher parameters than a LiFePO4.
 
The battery is charging through the C- terminal but it wont allow a load through it. It was earlier today working perfectly.
 
The exact type of battery is important. When I saw 4.1 and BMS attached earlier, I started thinking there was a Lithium Ion BMS installed, which has higher parameters than a LiFePO4.
Yea, those hobby chargers are usually really good with charging cells within their range when proper battery type selected and using balance leads.
The BMS looks compatible with different lithium types.

The BMS is 3 terminal B+, B-, C-,
Sounds like it’s wired properly. And the balance leads are connected too?

Happen to have pics of batt/BMS wiring (extra eyes find issue all the time here) and of your charger and BMS settings?

Something in those pics should explain how you got a cell to 4.1V.
 
the 4.1 was before I balanced them. Also before I set up the parameters.
I will take picts but again, I did NOTHING except change out 2 small wires n the B- for a larger one.
 
Individually top balancing my cells (without changing any settings) one cell ended up at 3.67, have I ruined it? Can I lower the voltage just slightly somehow and do a re-balance?

It's possible I may have let it charge a bit longer than the other cells at 3.4V. Talking minutes not hours.
 
Individually top balancing my cells (without changing any settings) one cell ended up at 3.67, have I ruined it? Can I lower the voltage just slightly somehow and do a re-balance?

It's possible I may have let it charge a bit longer than the other cells at 3.4V. Talking minutes not hours.
3.67 did not damage the cell. At least nothing you’ll notice. Not a mere .02 volts.

I bet if you did a voltage check now 7 hours after the incident, it would be less than 3.65 volts. When I charge my cells, there is some ”settling” that happens where the voltage decreases a couple of tenths as time goes By without a load And after a few hours, settles on something.

What I would do is take my capacity tester and run the cell so it drops below 3.45, and if its less than that now, run it down a tenth of a volt. A Light bulb or somethign else would work. I’d run it at the C20 rate. If you can’t do the C20 rate, just do less.

Then I would just finish the top balance to 365 volts and call the cell good. You could capacity test it.

I went over by more than .02 volts in my top balance and did the procedure I listed above. I hav the cells in an RV now for a year and they are fine. I don’t remember how much, but it was a few tenths volts more, and you only have a couple of hundredths.
 
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