Battery charger

[jha07]

Does anyone know where I might be able to get a nimh charger that's capable of charging 36-48V battery packs at 2 or 3A? The chargers I've seen all have fixed voltages and I'd like to get something that's somewhat flexible.

 

[flecc]

I doubt if such a thing exists. There are many flexible chargers for smaller numbers of cells, but the largest I've seen is one for 16 to 20 cells.

Generic NiMh chargers need not only thermistor cut-off, but voltage limiting as well for safety. The auto detection to enable that needs to be unconditionally safe at high voltages and current, not too easy to provide at reasonable cost.

With US prices very low at present for NiMh chargers for those voltages, you could buy two, and the postage for the pair wouldn't be too dear.

Have a look at Powerstream, choose battery chargers at the left, then NiMh chargers and scroll down to these:

PST 3PN 9560-48

PST 3PN 9545-36

both at about £28 each after currency conversion. I know these chargers and they are very reliable.

Change the postage from the premium one shown at checkout to USPS Express or Standard for a quick low cost service.
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[jha07]

Thanks. The 48V charger there, PST 3PN 9560-48, has a 3 pin connector for the use of a thermister. I've never had a charger with a thermister before. Are they supplied with the charger?

 

[flecc]

They both use thermistor control via the third pin. The thermistor isn't supplied, but you can get suitable ones cheaply.

Any 10 kOhm thermistor with a beta value of around 3950 is ok. Here's a suitable one:

Radiospares RS 151-237. The characteristics are R = 10k, B = 3914.

from RS Components

They will also operate with a 10k resistor in place of a thermistor, but then the cut-off would be done by those charger's safety limiting.
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