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MP3 hack problem PLEASE HELP! Answered

I am replacing an old mp3 rechgargeable battery rated 3.7 volts with another one that is also "rated" 3.7 BUT when measured with the Vmeter the little bugger gives an output of 4.2, (too high) is there anyway we could add a led or some resistors to lower the voltage without draining the battery when the device is off? Thanks for any suggestions Cheers!

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VIRON
VIRON

13 years ago

Be careful, it sounds like you maybe replacing a NiCd or NiMH with a Li-ion. (Charging a Li-Ion with a NiCd or NiMH charger may be a fire hazard)

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dejabox
dejabox

Reply 13 years ago

Oh thanks for the warning but,oh, no not at all , both are Li polymer, and I verified they were as close as possible but the 4.2 volt thing does worry me. The old battery did provide correct readings (3.7) when it was new. Oh man I do not wanna fry the device...

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VIRON
VIRON

Reply 13 years ago

The peak charging voltage for Li-ion is Normally 4.2 volts, and when a proper Li-ion charger detects that voltage in the cell, it automatically Reduces the Charging voltage to 3.7V. But, that doesn't always mean the battery is Full. It continues charging at 3.7 Volts for some time after it reaches 4.2 volts. The hazard is that a NiXX charger will continue raising the voltage of a Li-ion to 4.3V and beyond, possibly causing a fire. So... a 4.2V Li-ion battery is at least "almost full". It sounds OK to me.

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thejrb
thejrb

13 years ago

This is most likely because your testing the battery with no load.

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Goodhart
Goodhart

Reply 13 years ago

I concur: the rating should refer to the voltage under normal load conditions.

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NachoMahma
NachoMahma

13 years ago

. If both batteries are labeled as 3.7V, then it should work. As dbc1218 and thejrb pointed out, battery voltage ratings are not exact (I think they are called nominal (a measurement that is a designation or theoretical size that may vary from the actual. www.sgia.org/glossary/Nn.cfm) values) and you are testing without a load. . Verify that it is the correct replacement battery and go for it.

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Doug Costlow
Doug Costlow

13 years ago

Most rechargeable batteries have higher voltages than what there rated at. I have four rechargeable AA's that when connected in series read over five volts with the Vmeter but it should be 4.8v