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I am trying to replace the battery in a handheld recorder (m-audio microtrack). I am following this guide. The guide instructs to use a 3.7V battery, and this value is the same as written on the original battery which I pulled out of the device. I am trying to turn the device on with a Li-Ion battery that I took from a mobile phone - the battery is also rated 3.7V, is fully charged and functional - the mobile phone works OK and indicates a fully charged battery. However, the device is not turned on (polarity is correct).

I measured the output voltage of both batteries, and the original reads 4.15V with open terminals, and about 4V with load (the device connected and turned on). On the other hand, the mobile phone battery reads 3.8V.

Can this voltage difference be the reason the device is not turned on with the replacement battery? Is there another possible reason? It is weird especially because the info written on the original battery also says 3.7V.

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  • \$\begingroup\$ Should work. A fully charged LiIon battery should be > 3.8V. May be LiFePo4 - but should still work. How did you charge it? 3.7V is the average discharge voltage for LiIon 0 usually considred to be 3.6V. Vfull +` 4.2V. Vdischarged ~~= 3.0V. \$\endgroup\$ – Russell McMahon Mar 14 '12 at 10:21
  • \$\begingroup\$ For more info on LiIon battery voltages look here: batteryuniversity.com/learn/article/… \$\endgroup\$ – Stefan Paul Noack Mar 14 '12 at 12:54
  • \$\begingroup\$ I charged it while inside the mobile phone, when it was connected to a PC with USB cable - that's the 'regular' way to charge. \$\endgroup\$ – Itamar Katz Mar 14 '12 at 15:18
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A typical Li-Ion battery will be 3.7V nominal. This voltage corresponds to a state of almost full discharge. A fully charged Li-Ion battery will typically reach 4.2V.

It may be the case that the specific battery you're trying to use as a replacement has additional protective circuitry preventing it from delivering current to your recorder. All those extra terminals may be expecting to 'see' the mobile phone they're designed for.

Perhaps you have accidentally damaged the pcb of your device. To verify that, you can attach ~4V to the contacts of the recorder and see if it's broken or not.

If you're certain your recorder is not the source of the problem, you could try a different battery. Or, at your own risk, try to open up the li-ion battery and try to power the recorder directly from the li-ion cells hidden inside, omitting the protection circuitry (which I do not recommend).

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  • \$\begingroup\$ The recorder is ok, that I am sure of. Using another battery is possibly what I will try. thanks. \$\endgroup\$ – Itamar Katz Sep 3 '12 at 17:42
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Every Li-Ion battery has got a protection circuit and some time it is smart, There may be another 1 are 2 terminal extra, for temp sense and smart application bateery charge vel etc. Try to change with battery circuit, be care full while doing and avoid short circuit.

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