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Full Version: Battery 3.7v Vs 4.2v
OESF Portables Forum > Everything Else > Archived Forums > Distros, Development, and Model Specific Forums > Model Specific Forums > Sharp Zaurus > Cxx0 Hardware
My new C860 is having the notorious 'battery recharge problem' (I hope;).
Currently at 1.5V or something, I was thinking of charging it externally with a custom setup to full charge, and then reflash the voltage level in the DM menu.
Now, I've read in several posts that the reading of a fully charged battery should be 4.2V, while there's 3.7V indicated on the battery pack. 0.5V seems like quite a difference to me. Or am I mixing things up here? Anyone can clear this up for me?
This is normal. 3.7v is the "nominal" voltage -- this is the voltage your battery will spend most of its life at. 4.2v for an unloaded 3.7v battery is perfectly normal. (Just as a 12v car battery can be measured at 13v or more soon after being charged)

--Michael Spencer
mspencer is correct, 1.5volts sounds dangerously low... if you discharge batteries too deeply they may not recover. Be very careful charging the battery externally... if you don't know what you're doing you could fry your battery or reduce it's life...

My suggestion (take it at face value) is to use a 5v power supply and a 5ohm 3 watt resistor in series to charge the battery for 1 hour only. This will give you enough juice to set the menu options and let your battery charge in the Z properly. This will definitely not harm your battery using the value of resistor shown, and is cheap.
If you check some of the older battery threads, you will find that the "third" (center) terminal on the battery connects to an internal thermistor that is used by tje Z & external chargers to regulate the charging current and keep from frying the internal battery electronics.

This is NOT a simple battery like an "AA" cell! You have circuitry inside that can be damaged by overcharge, heat, reverse polarity & such. Proceed with reasonable caution.
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