I'm looking to build a NiCd charger to charge 2 or 4 1.2V NiCd's
The only circuit I've come across is for a 9V battery
Has anyone tried to convert this to change 2 or 4 cells. Or can anyone point me to another free circuit.
Why not look at Microhip's website they have charger chips (NiCd and NiMh cell compatible) and application notes with example circuits.
Chris
As noted above, Microchip (and others - Maxim and TI spring to mind) make charge controllers for multiple battery chemistries, NiCd included.
Having once spent a while in the black hole of NiCd analysis, I would caution you to read carefully the charge permitted for the particular cells you wish to charge, for they are not all created equally. Some permit fast and rapid charge, others only permit standard charge (Standard is normally C/10 for ~14 hours, Fast C/3 for 4.5 hours, Rapid
2C for 1 hour although these vary among manufacturers).In addition, you should consider a charge conditioner to get around the memory effect (that manufacturers will tout as having been solved, but they really haven't) to maximise the life of the cells. Takes a little longer, but saves a lot in the long run.
Cheers PeteS
Assuming AA-size cells, you can buy these in the UK, with 4 LEDS, a Test/Discharge meter function and it optionally does AAA sizes, C sizes, 2 x
9V accumulators as well, with 4 AA-size NiCd cells for about £12. Why design one?
Why bother. Two and four cell chargers are very cheap.
If you are designing a product then perhaps you should think again and employ someone who knows what they are doing....
a) NiCads are being phased out because they are bad for the environment (See NiMH). b) Have you ever seen an abused NiCad explode ?
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