circuit design for 12v DC supplied battery-charger for 9.6v NiCD batteries?
Hello,
I would like to charge the 9.6v NiCd batteries of my Makita electric drill direct from the 12vDC supply on board my boat. Can anybody point me to a circuit design? Using a 12v/240v inverter and the existing 240v charger is not an option as the old charger is broken. |
Ric wrote: Hello, I would like to charge the 9.6v NiCd batteries of my Makita electric drill direct from the 12vDC supply on board my boat. Can anybody point me to a circuit design? Using a 12v/240v inverter and the existing 240v charger is not an option as the old charger is broken. This page is a decent explanation of how to do it-observing battery C rating: http://www.web-ee.com/Schematics/Bat...er/charger.gif You can replace that D6 by something like an ordinary green LED (cathode to Q2 emitter) and a resistor from the D6 cathode-Q2 emitter junction to ground for a 10ma bias -something like R=(13-2)/10=120 ohms. The Iout equation is then Iout=(Vled+Vbe)/R1 or about 2.7/R1- not super-critical. Replace the full-wave bridge with a single series diode for reverse hook-up protection. The MOSFET is heatsinked for a maximum power dissipation of (Vin,max-Vnicad,min) x Iout. Add a fast blow, agc type, fuse in series with the output driving NiCad (+) with rating of 1.5 x Iout. |
Fred Bloggs wrote: Ric wrote: Hello, I would like to charge the 9.6v NiCd batteries of my Makita electric drill direct from the 12vDC supply on board my boat. Can anybody point me to a circuit design? Using a 12v/240v inverter and the existing 240v charger is not an option as the old charger is broken. This page is a decent explanation of how to do it-observing battery C rating: http://www.web-ee.com/Schematics/Bat...er/charger.gif You can replace that D6 by something like an ordinary green LED (cathode to Q2 emitter) and a resistor from the D6 cathode-Q2 emitter junction to ground for a 10ma bias -something like R=(13-2)/10=120 ohms. ^^^^^ MAKE THAT 1.2K Ohms |
That circuit is a voltage controlled circuit. Panasonic recommends
against using this type of circuit: http://www.panasonic.com/industrial/...rgeMethods.pdf A better, albeit more complex, circuit that uses an approved method (voltage drop) can be found at: http://homepages.paradise.net.nz/bhabbott/charger.html Tom |
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