NiCad Battery bank Balance circuit (1.2v 32Ah x 20 cells)

[ronsimpson]

Thanks for the data sheet. So which type of battery do you have? There are three in the data.
KPM?KPL?KPH? Then there are numbers to indicate size like 100?

 

[TJP]

You can do, it will speed up the overall process.

Morning

PSU set to 17.95 v

Row 1 - 10 cells total voltage - 16.64v - draws 1.5(3) amps

1.665, 1.666, 1.666, 1.663, 1.666, 1.658, 1.660, 1.668, 1.662, 1.664v

Row 2 - 10 cells total voltage - 16.59v - draws 1.5(7) amps

1.658, 1.672, 1.652, 1.658, 1.654, 1.661, 1.658, 1.665, 1.655, 1.660v

Will all cells eventually be the same?

Cells are boiling nicely.

I am not sure if row 2 is already saturated?

Your feed back welcomed

TP

 

[TJP]

Thanks for the data sheet. So which type of battery do you have? There are three in the data.
KPM?KPL?KPH? Then there are numbers to indicate size like 100?

Morning Ron

Is KPM32P - cell where MNF in 2009 but never used.

So need to get the cells up to the same performance !

According to sources these are diehard's - so I am hoping the will all come back to good potential. I don't think there is any damage for standing this long none of them are dead.

TP

 

[rjenkinsgb]

Row 1 - 10 cells total voltage - 16.64v - draws 1.5(3) amps

1.665, 1.666, 1.666, 1.663, 1.666, 1.658, 1.660, 1.668, 1.662, 1.664v

Row 2 - 10 cells total voltage - 16.59v - draws 1.5(7) amps

1.658, 1.672, 1.652, 1.658, 1.654, 1.661, 1.658, 1.665, 1.655, 1.660v

I'd reduce the current (PSU setting) somewhat, the cells should not be rising to that voltage if they are in good condition.

The metal in the plates may have crystallised from being unused for years, meaning the cell internal resistance may be rather higher than it should be.

Under normal working conditions the "active" metal is amorphous, which makes it more reactive with the electrolyte. If left unused, the metal gradually crystallises (the same way that galvanised steel develops crystal pattern in the zinc coating over time), which changes how the cells react.

The cure in normal NiCDs is to deep discharge each cell individually to a fraction of a volt, then recharge.
As long as the loads are connected directly to each cell rather than an overall battery, there is no possibility of voltage reversal and it does no harm, just allows the plates to slowly react at their own rates rather than being forced.

 

[TJP]

I'd reduce the current (PSU setting) somewhat, the cells should not be rising to that voltage if they are in good condition.

The metal in the plates may have crystallised from being unused for years, meaning the cell internal resistance may be rather higher than it should be.

Under normal working conditions the "active" metal is amorphous, which makes it more reactive with the electrolyte. If left unused, the metal gradually crystallises (the same way that galvanised steel develops crystal pattern in the zinc coating over time), which changes how the cells react.

The cure in normal NiCDs is to deep discharge each cell individually to a fraction of a volt, then recharge.
As long as the loads are connected directly to each cell rather than an overall battery, there is no possibility of voltage reversal and it does no harm, just allows the plates to slowly react at their own rates rather than being forced.

Thanks bro

So what you suggest is drop on the PSU voltage but keep the rows still charging IE at n lower amperage?

The equalization V on these cell are 1.54 - 1.69 v/cell?

What PSU voltage would you recommend?


TP

 

[ronsimpson]

1.665, 1.666, 1.666, 1.663, 1.666, 1.658, 1.660, 1.668, 1.662, 1.664v

It looks like you do not need a balance circuit.

for those that don't want to dig through the datasheet.

 

[TJP]

It looks like you do not need a balance circuit.

for those that don't want to dig through the datasheet.
View attachment 134392

morning Ron

This show the cell volts from 1.7v per cell, which is the equalizing voltage per cell. I don't really understand this chart. As I see it you will never get these cells to full capacity? especially if they are charged at for example 1.45v ?

Why is it not necessary to balance the cells?

Thanks for your replies

TP

 

[rjenkinsgb]

Why is it not necessary to balance the cells?

NiCd (and many other rechargeables) "leak" a small amount of current, especially when at or near full charge, so all cells in a battery pack chain get a steady trickle charge which automatically equalises them.

Lithium battery types are an exception, as they have near zero leakage so no self-equalisation.

It looks like those particular cells have a higher full charge voltage than the ones I found data on at the start of this thread, so the approx. 1.66V per cell is fine, and they have already balanced to +/-20mV of their average voltage.

 

[TJP]

NiCd (and many other rechargeables) "leak" a small amount of current, especially when at or near full charge, so all cells in a battery pack chain get a steady trickle charge which automatically equalises them.

Lithium battery types are an exception, as they have near zero leakage so no self-equalisation.

It looks like those particular cells have a higher full charge voltage than the ones I found data on at the start of this thread, so the approx. 1.66V per cell is fine, and they have already balanced to +/-20mV of their average voltage.

Thanks for all your help guys.

Am busy with the 2nd row - just to get them all as close as possible.

Really appreciate al your time and input in this thread.

Will let you know how they turn out.

Thank you TP