Moding a cheap Li-ion charger

Posted by crimsonpisang on   0 comments   0 trackback

I was browsing on ebay for spare batteries for my Motorola Milestone and I came across a seller selling 2 batteries and a universal charger for about USD 11. Since the charger was crap anyways so I though I could modify it to something less crappy and much safer.

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As expected, FR-2 PCB and the cheapest components they could get.

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A 1ohm 1W current limiting resistor was used instead of a fuse. There were no noise filtering passives on the AC line. The switching design was pretty much generic and I'm assuming that the SOT-23 device labeled Q1 is a TL431 shunt regulator. The li-ion charge controller is a Hotchip HT3582D. Datasheet was in Chinese so I can't give any further info.

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Does not seem like there is enough of creepage distance between the AC and the DC side.

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I had a MCP73831 PCB charger lying around in my junk bin. This controller charges batteries at 500mA max. I've tough of using a 1A charge controller but it seems that 500mA offers flexibility to charge batteries that has capacity lesser than 1Ah. I've also reused the LED portion from the old PCB.
The charger board was able to fit in snugly. I've used some hot glue as standoff for the board.

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Charger put back together, works like a charm and much safer too.

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I've add a connector that taps directly to the battery. I could hook up an external charger or a discharger/capacity analyzer.

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