Teardown of a Vivitar Rapid battery charger

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Kerry Wong did a teardown of a Vivitar rapid battery charger for the NP-FW50 lithium-ion battery pack used in Sony A6000 digital camera:

The circuit board itself though looks surprisingly clean and well designed. It does not use any dedicated lithium ion battery charging ICs however. Rather a MC34063A buck/boost DC-DC converter chip is used to provide the current limited 8.4V constant voltage. This arrangement is less ideal then the typical lithium ion battery charging technique. Typically, the charging current is held constant until the voltage reaches a certain threshold and then the charger switches to constant voltage mode. Once the charging current drops under a predetermined threshold the charging is done. The charging current under constant voltage charging however, monotonically decreases from the get go so it usually takes much longer to obtain a full charge. But the good news here is that overcharging is unlikely as the charging voltage is fixed to the correct battery terminal voltage.

More details at Kerry Wong’s blog.

Check out the video after the break.

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1 Comment

  1. Dang, sounds like a really cheap charger… poor form of Vivitar to slap their brand on it, but well, I suppose the price is a dead giveaway. Really reminds me of cheap NiCd and NiMH chargers, the kind that come free with a set of batteries… I never used those rubbish chargers.

    I suppose Vivitar is not worried about precision here. I’m curious, so what does it mean for cell balancing in NP-FW50 battery packs? Does the battery pack have protection and/or cell balancing so it is safe from overvoltages? Do clone battery packs have the same kind of protection circuits (presumably) like authentic battery packs? Makes me wonder about the safety features of NP-FW50 battery packs…

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