First Ever Top Balance of 3.2V 25Ah Prismatic Cells

[Lionking45]

I bought 48 of these 3.2V 25ah Prismatic Cells and connected them in parallel in batches of 16. The first 16 had an average voltage 3.428V with a standard deviation of about 50mV. These top balanced to a resting voltage of 3.592V. I set my PS voltage to 3.62V. I was able to top balance in a few hours with a standard CV power supply.

The next 16 I broke up into two banks of 8 as the first 8 averaged higher than the 2nd eight. The first 8, I connected in parallel had an average of 3.41V and had a couple of outliers at 3.3V and 3.33V but I was still able to top balance to 3.6V in a few hours.

The second 8 had an average of 3.29V with very small variation (4mV - which I guess is good) but is taking a very long time with a CV PS. I have seen in a few threads that below 3.4 volts, it is to be expected. My current input with the PS set at 3.62V is running at around 2A while the batteries measure at 3.327V.

Would I benefit from a higher current PS to speed up the process - say a PS that can go up to 10A at constant 3.62V.

Thanks for any input.

 

[John Frum]

I bought 48 of these 3.2V 25ah Prismatic Cells and connected them in parallel in batches of 16. The first 16 had an average voltage 3.428V with a standard deviation of about 50mV. These top balanced to a resting voltage of 3.592V. I set my PS voltage to 3.62V. I was able to top balance in a few hours with a standard CV power supply.

The next 16 I broke up into two banks of 8 as the first 8 averaged higher than the 2nd eight. The first 8, I connected in parallel had an average of 3.41V and had a couple of outliers at 3.3V and 3.33V but I was still able to top balance to 3.6V in a few hours.

The second 8 had an average of 3.29V with very small variation (4mV - which I guess is good) but is taking a very long time with a CV PS. I have seen in a few threads that below 3.4 volts, it is to be expected. My current input with the PS set at 3.62V is running at around 2A while the batteries measure at 3.327V.

Would I benefit from a higher current PS to speed up the process - say a PS that can go up to 10A at constant 3.62V.

Thanks for any input.

Please provide a product link to the psu.
What awg are the charge leads?

 

[Ampster]

Would I benefit from a higher current PS to speed up the process - say a PS that can go up to 10A at constant 3.62V

Yes that would be faster. The Ah capacity of 16 of those 25 Ah batteries is 400 Ah. So if they are at 50% that could be 200 hours at 2 Amps.

 

[Lionking45]

The power supply is just a 12V 25amp CV supply made by Alinco used to power 100W radios. I have a CV/CC supply on order recommended by Will Prowse (30V/10A adjustable) but that has not yet arrived. The AWG is 12gage but the cells are connected via 1/8" thick 5/8" wide bus bars in parallel (all + and all -).

 

[John Frum]

The power supply is just a 12V 25amp CV supply made by Alinco used to power 100W radios.

If its not a constant current power supply it will hiccup if you draw its rated power.
That usually also lets the magic smoke out fairly quickly.

The AWG is 12gage but the cells are connected via 1/8" thick 5/8" wide bus bars in parallel (all + and all -).

How long are the leads?

 

[Lionking45]

If its not a constant current power supply it will hiccup if you draw its rated power.
That usually also lets the magic smoke out fairly quickly.


How long are the leads?

around 12 inches

 

[John Frum]

around 12 inches

Strange.
You should be getting more current flowing.
Is the joinery clean, flat and tight?
Hope you are not using alligator clips.
Ring terminals on both ends are preferred.

 

[MisterSandals]

Can you provide a pic of your charging setup, one that shows the wiring?

 

[Lionking45]

Strange.
You should be getting more current flowing.
Is the joinery clean, flat and tight?
Hope you are not using alligator clips.
Ring terminals on both ends are preferred.

I simplified the connection between the power supply (eliminating fuses on both pos and neg). I checked the tightness. And yes I also used ring terminals on both ends. Now I am getting 12 amps.

 

[Lionking45]

Can you provide a pic of your charging setup, one that shows the wiring?

The PS is measured at 3.527 under load. The clamp meter reads 12.9A and the measured voltage on the bus bar is 3.35V.

 

[MisterSandals]

So you have this parallel pack wired incorrectly. Its not a balanced charge if both + and - are on the same end of the pack.

This may help your charging amps because you'll be charging all the cells evenly.

 

[Lionking45]

So you have this parallel pack wired incorrectly. Its not a balanced charge if both + and - are on the same end of the pack.

This may help your charging amps because you'll be charging all the cells evenly.

So I should place the positive end of the charge input on the far side. I tried it and the current increased to 16A. Thanks for the input.