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Re: Portable Power

Subject: Re: Portable Power
From: Walter Knapp <>
Date: Sat, 05 Mar 2005 11:44:12 -0500
From: "Rich Peet" <>


> ok, want a slow charger for a 12 volt nimh pack then use a dash board 
> light bulb in series.
> 
> For slower yet at any voltage then go to little watt 1 cent resistors 
> in series with the supply and use ohm's law to calculate the resister 
> for the current you want to supply at a given voltage. That is what 
> the old slow chargers used and nothing more advanced. A transformer 
> slightly over voltage, a couple diodes to convert to DC and a 
> resistor.  Nothing rocket science here.

That's exactly the point, if you intend to do it cheap, you have a price 
to pay. Cheap and safe is done slowly but is easily workable. You just 
have to tolerate 10-14 hour recharge times. With reasonable care you 
won't kill batteries that way.

NIMH are much more sensitive than nicad to overcharge, but even nicad 
was sensitive to overcharge.

Personally, I'll pay for the controlled charger. I don't have to have 
the fastest charger on the block, but would like faster than half a day. 
The price of the good chargers has been coming down if you don't go for 
the latest superfast models. The previous generation was safe for your 
batteries and typically took 3-4 hours to charge them.

Walt






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