Join Date: Apr 2006
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Re: Nicro Day-Night 2000 solar vent repair
Very roughly? The picture looks like there are four cells in the package, which gives it a voltage of about 4 time 1/2 volt, or two volts total. A lithium battery typically is 3.7 volts and they tend to catch fire or explode when improperly charged, so aside from not having enough voltage to use one, you'd be safe having a plain NiMh or NiCad battery in there.
Tricks in a battery? Sure, measure voltage and current, match with battery size, add a blocking diode so the battery doesn't discharge into the solar cells at night. Use a battery holder if you can, so it is easy to change when it goes.