Top Balance Question

[Rossman]

Sweet, thanks. Do I need to balance it to sync with the other cells at 3.4V?

It should drop back to resting voltage like your other cells?

 

[jmsol]

It should drop back to resting voltage like your other cells?

Then it would be fine to connect them in series with BMS ready to use?

 

[Rossman]

Then it would be fine to connect them in series with BMS ready to use?

Yeah, assuming you brought them all individually up to ~3.65, they should all drop back to roughly the same resting voltage, and they are ready to go!

 

[jmsol]

Yeah, assuming you brought them all individually up to ~3.65, they should all drop back to roughly the same resting voltage, and they are ready to go!

How much should they be expected to drop to resting voltage?

 

[Rossman]

How much should they be expected to drop to resting voltage?

Not sure, think they fall back to around 3.4 or so? Someone else might know better.

 

[Bossrox]

Okay, so I've started top balancing my batteries about a week ago and it's a 16S 48V Eve 230AH battery pack.

I have my bench power supply set to 3.65V (according to meter) and all the cells attached in parallel.

The past two days, the cells have been floating at 3.64V and won't go much higher, the amperage on the power supply has gone down, and little to nothing is happening with the cells, is this common?

Can I just leave them balanced at 3.64V if I am only going to use them up until 3.64V and what capacity would 3.64V be, 95%? What would be around 90% capacity and 10% capacity so I only use 10-90% capacity.

Thanks for reading!

They're 99.9% charged. Let it go at that & build your bank.

 

[jmsol]

When top balancing individual cell is it normal for the amps to first drop down and then start increasing?

Using a 10A 30V bench top power supply with a single 280Ah 3.2V cell.

Could the cell be damaged?

 

[TomC4306]

When top balancing individual cell is it normal for the amps to first drop down and then start increasing?

Using a 10A 30V bench top power supply with a single 280Ah 3.2V cell.

Could the cell be damaged?

You can't balance an individual cell. you can charge it but not balance it to balance requires more than one.
Did you adjust the voltage setting on the power supply after connecting it to the battery cell?

 

[jmsol]

You can't balance an individual cell. you can charge it but not balance it to balance requires more than one.
Did you adjust the voltage setting on the power supply after connecting it to the battery cell?

Thanks for your reply.

I was careful not to touch the voltage. Everything looked ok and it dropped down to about 8.3 amps, but then slowly started rising to 8.6. I got worried so I turned the power supply off. Not sure what to do now, if it's damaged or not?

 

[sunshine_eggo]

Thanks for your reply.

I was careful not to touch the voltage. Everything looked ok and it dropped down to about 8.3 amps, but then slowly started rising to 8.6. I got worried so I turned the power supply off. Not sure what to do now, if it's damaged or not?

I wouldn't be concerned. I would be concerned that you're using the stock leads with the alligator clips. Too much resistance. Consult the top balancing guide for new lead fabrication recommendation.

 

[jmsol]

I wouldn't be concerned. I would be concerned that you're using the stock leads with the alligator clips. Too much resistance. Consult the top balancing guide for new lead fabrication recommendation.

Thanks, that feels reassuring.

I did make my own wires. But I will inspect them to see if they have become faulty somehow.

 

[sunshine_eggo]

Thanks, that feels reassuring.

I did make my own wires. But I will inspect them to see if they have become faulty somehow.

Hmm... unless you're near 3.65V, improved leads will usually sustain the full 10A.

 

[jmsol]

Hmm... unless you're near 3.65V, improved leads will usually sustain the full 10A.

It was the leads. I crimped on more proper lugs for better connection and now it works as it should. Just goes to show how important a good connection is