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I've replaced the cells of a nimh battery pack, just to discover that now the charger signal an error and doesn't recharge it. Most probably some data was erased in the battery pack IC when I disconnected the old cells and now the smart battery IC doesn't start the charger. Is it possible to find out which data was erased and reprogram the IC connecting something like an arduino to the serial pins of the battery?

oppure
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  • serial pins of the battery? what's the battery model? – dandavis Mar 25 '17 at 23:58
  • it's an electrolux 24 volts battery pack made of 20 1.2v nimh cells, the pack has 5 pins: +24v, gorund and +3.3v SCL SDA for the serial interface, the pcb has a single texas instrument IC with 10 pins and marked something like "25 BRPI" plus 2 smaller IC with 5 pins and marked "OCFQ". After replacing the cells the pack supply normally, but when charger is plugged charging doesn't start and a led indicating an error is lit. – oppure Mar 26 '17 at 06:13
  • interesting. such an IC shouldn't be using volatile memory, and "OCFQ" is just an opamp. i would check the internal resistances and voltages of both the old and new stack; there's only so many electrical properties that can change that would "freak it out". maybe the old cells weren't worn out after all. maybe a (temporary) mix of old and new would allow it to boot. just guessing tbh, that's unusual... – dandavis Mar 26 '17 at 11:43
  • thanks dandavis. if you understood exactly the IC model can you let me know so I can have a look at the datasheet. The various IC tha TI makes for Smart Battery Bus seem all much more complex than this one. There is definitely some exchange when I plug the charger, the led is initially green it becomes red after a few seconds, so it must be the battery which tells the charger not to start charging. The original cells were 1300 mAh the new one sare 1600mAh I tought such a small difference wouldn't make any difference, may be I was wrong.. – oppure Mar 26 '17 at 13:36
  • unfortunately the old cells were binned long time ago so I can't make a comparison – oppure Mar 26 '17 at 13:38
  • last guess: i noticed that a couple of [TI's battery gauge ICs](http://www.ti.com/lsds/ti/power-management/battery-fuel-gauge-products.page#p199=I2C&p338=NiMH) max out at 29000mah, and yours is now 32000 – dandavis Mar 26 '17 at 15:34
  • thanks, may be I can try some resistors in parallel with the stack to see if it starts the charger. – oppure Mar 27 '17 at 14:41

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