Replacement NP-FS11 Li-Ion Battery Pack: Plan B

Slitting the case
Slitting the case

Just for curiosity’s sake, I applied a slitting saw to the oldest defunct generic NP-FS11 battery pack, cutting carefully along the bonded joint between the two parts.

No coolant, 1000 rpm, 200 mm/min, the saw is 22 mm diameter. Much slower than you’d use if you were in production, but I’m not.

First cut all the way around at 0.5 mm inside the case, then another pass at 1.0 mm. The second cut went ting as it passed the tabs at the base of the cells, so I knew the halves were released.

Inside we find a pair of 14430 Li-Ion cells, wired in parallel, with a little protection circuit board just jam-packed with teeny parts. One may reasonably assume the circuit controls over-charge and over-discharge, as well as current limiting.

Pack opened
Pack opened

So a reasonable (or, perhaps, amusing) thing to do would be to buy raw cells from a nominally reputable supplier, do a heart transplant, and see if that improves the situation.

Protection Circuit - Outboard
Protection Circuit - Outboard

Photos of the protection PCB, showing the cell connections. Positive end of the cells is toward the PCB. I think there’s enough clearance in the camera’s battery compartment to allow a wrap of tape around the case in lieu of re-bonding the plastic together.

Protection circuit - inboard
Protection circuit - inboard

9 thoughts on “Replacement NP-FS11 Li-Ion Battery Pack: Plan B

  1. Ed,

    In my Sony PC100 camera battery, the board inside is the charger is like yours. My son misplaced the charger so I charge it by providing 6-7V at 500mA constant current from a bench supply. I stick a couple of screws into where the camera contacts go and then you clips. The board does the rest.

    Happy Easter

    1. The board does the rest

      Sounds good to me, although lithium cells are so fussy that you should probably charge the thing in an ashtray just to make sure it doesn’t burn a hole in your desk if things go wrong.

      1. Some of the Li_Ion cells I have played with had a thermal fuse of some sort. The packs suddenly go open circuit.

        1. I managed to short that battery when it was fully charged, at which point it went open-circuit. After quite some time, I put it back in the charger: the light cycled on-and-off once, then the battery was perfectly happy again.

          I don’t know if the charger told it to relax or if simply applying an external voltage would stroke its feathers the right way…

    1. I did some discharge tests that show the results can be nearly anything. IIRC, the original Sony packs were somewhere around 1100 mAh, but I can’t find any of them now.

      Search here for “np-fs11” to get more details than you probably want to know…

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