I’m in trouble

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Stoopid_Sparkie

Joined Mar 31, 2021
1
Hi there fellas.

I am in a spot of bother. My wife and I are new parents and as such have been buying all crap, sorry essential items for our new arrival. One truly essential item is a breast pump. This little pocket rocket was great until I plugged in the wrong charger. It’s is a 9v 1.4a dc charger juicing up a 7.4v 900mah battery. I have plugged in a 12v 2a dc charger. It appears now that the unit will work when the right charger is plugged in but the battery isn’t charging. I assumed I had damaged the cells in the battery so I sourced a new one but it is behaving the same way. When you plug the charger in the battery indicator reads full but as soon as you remove the charger, it dies. Having opened it up I’ve found a little chip which reads 7.4v suggesting I’ve cooked that and that’s the end of it. I’d welcome any feedback
 

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DickCappels

Joined Aug 21, 2008
7,147
With the charger disconnected from the unit see if you can sense and voltage across the battery leads -use a voltmeter, not your tongue :- ) This may tell you whether a fuse internal to the battery pack has opened. If. you can see battery voltage then the problem is somewhere on the board.
 

Yaakov

Joined Jan 27, 2019
2,341
With the charger disconnected from the unit see if you can sense and voltage across the battery leads -use a voltmeter, not your tongue :- ) This may tell you whether a fuse internal to the battery pack has opened. If. you can see battery voltage then the problem is somewhere on the board.
He said he replaced the battery. It seems that something in the BMS/power management system on the board sacrificed itself. I am a bit surprised there was no overvoltage protection. I can't really tell from the photos exactly where to look.
 

DickCappels

Joined Aug 21, 2008
7,147
I missed the part about changing the battery.

Don't feel bad about plugging into the wrong charger. A rechargeable 120 volt shave of mine did not do well when I absentmindedly plugged it into 240. I guess we all do it.

How are you at tracing signals? You could poke around the power input side of the PCB and try to work your way to the battery, noting where the signal stopped. Its a long shot, particularly without the schematic but it might work.
 
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