Using drill chargers to charge nimh/nicd

[NickF23]

Seems to be a shortage of companies making nimh chargers with temperature cutouts. The only one I know of being the chinese 'highpower' type chargers. I've had mixed results these, some have died, some not. I wondered if drill chargers might work ok for charging nimh so I tried an experiment to see if an old bosch charger I had would work for my nimh packs.

Much to my surprise it was very straightforward. The Bosch batteries use the same thermistor (10K ohms) that came with my nimh packs so it was simply a matter of connecting 3 wire cable to the charger (see pics below). This charger only charges at 1 amp but the temp cutout works fine and the packs fully charger each time. Nice thing is its quite robust as its designed to be kicked around a building site. I've not experemented with anymore drill chargers yet but there's quite a few available for cheapish prices for example this 5 amp charger might make a nice charger for a 48 volt pack (2 x 24v)

http://cgi.ebay.co.uk/Bosch-30-min-Dual-Bay-Battery-Charger-BC230-bluecore_W0QQitemZ130129624837QQihZ003QQcategoryZ20794QQssPageNameZWDVWQQrdZ1QQcmdZViewItem



Hilti also do a 36 volt charger which occasionally show up on ebay, plus there quite a few more by makita, dewalt etc, most of them charge at 24 volt and up to 8 amps. The other nice thing is they generally charge at a variety of voltages so you can make up packs with non standard numbers of cells.

 

[Rebel with a cause]

you're brilliant! I've got a few 12v NiCd packs I've been contemplating how to charge up, i've been eyeing my dewalt charger, but how to interface with the recessed connector had me scratching my head, but running an external connector from inside the charger is a very elegant solution. Keep up the good work

 

[kefa]

hey nick,

i've got a bosch charger and wondering if i can use it to charge my ryobi batteries. the ryobi batteries also has 3 connectors, the 3rd i presume is also for the thermistor. can i just do something similar and hook up all the connections to the ryobi batteries? or do the thermistors need to match up?

thanks,
kefa

 

[NickF23]

Hi Kefa,

Had totally forgotten about this one

Yeah, the thermistors need to match up. You can test the resistance by using a multimeter, the ones for the bosch chargers and also many ebike nimh packs are 10kohm at room temperature if you then warm up the thermistors by warming your hand you should get 7kohm ish. If not you can order 10kohm thermistors from many places including www.ebikes.ca.