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James Corbin
11/07/05 15:07
Read: 988 times
Dallas
USA


 
#103398 - Unexplaintable Battery Phenomenon
I have a circuit that contains a lithium ion battery pack (12.6 volt cell phone battery). I use a external charger designed for charging this particular battery (constant current constant voltage phases).

This external charger, during charge phases, also supplies the LPC932 and it's load. So again, the load consists of a 3-cell Li-Ion battery, firmware circuit that uses about 20mA, and a LONG piece of wire that is floating (about 3 meters).

The external charger isn't really designed to power a load AND charge the battery so the result is that the charger cuts off early and I don't get a FULL 12.6 volt charge. This isn't a problem for me. The result for me is a FULl charge is about 12.3 volts.

During discharge phase and when the external charger detects that the battery has dipped below 12.0 volts, it begins to charge again.

The problem is that when the charger decides to turn back on, I see a short voltage spike of about 14 volts. To me, it seems like this shouldn't happen since our LONG wire (inductor) isn't charged. What might cause this?

Seems like this circuit kinda represents what occurs when I switch from discharge to charge phase. Note that L1 in circuit is actually connected through a FET, but it isn't fully off. Current through L1 is about 40uA.

Is 40uA through a long winded wire enough to cause the battery voltage to see 14.x volts when the charger comes on?:



List of 7 messages in thread
TopicAuthorDate
Unexplaintable Battery Phenomenon      James Corbin      11/07/05 15:07      
   Charger issue only?      Kai Klaas      11/08/05 07:06      
      Out of circut, no spikes      James Corbin      11/08/05 08:45      
         Is it the cap?      Kai Klaas      11/08/05 09:26      
   I don't think so      James Corbin      11/08/05 11:27      
      the cap does not need to be defective      Erik Malund      11/08/05 11:38      
         The problem...      James Corbin      11/08/05 20:42      

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