phone battery contacts and charging question

paulr

Flashaholic
Joined
Mar 29, 2003
Messages
10,837
Phone batteries usually have 3 or 4 contacts but often only two of them do anything. But I notice that the Nokia BP-4L really has different voltages going to the contacts. The middle contact (when the cell is near empty) is at 3.3 volts but the outer one is only at 2.9 volts or so. Question: what do the three contacts do? I have one of those clamp-type universal chargers that has worked well with other phone batteries, but doesn't seem able to charge the BP-4L. Thanks.
 

csshih

Flashlight Enthusiast
Joined
Sep 21, 2008
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Location
San Jose, CA
there should be a protection circuit built in which also checks the temp, etc, of the cell.
 

Lynx_Arc

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Joined
Oct 1, 2004
Messages
11,213
Location
Tulsa,OK
Phone batteries usually have 3 or 4 contacts but often only two of them do anything. But I notice that the Nokia BP-4L really has different voltages going to the contacts. The middle contact (when the cell is near empty) is at 3.3 volts but the outer one is only at 2.9 volts or so. Question: what do the three contacts do? I have one of those clamp-type universal chargers that has worked well with other phone batteries, but doesn't seem able to charge the BP-4L. Thanks.

http://cpkb.org/wiki/Nokia_BP-4L_battery_pinout
 

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