I made a power pack using 18650 batteries from an old laptop. All batteries tested individually are good. 4 batteries in 2S format. I used a cheap 2S 3Amp rated protection board I got on Ebay from China. I correctly connected all the terminals and properly soldered, B+/B- to the +/- of the final ends of batteries and BM to the middle.
The voltage measured directly at the battery terminals (at B+/B-) is 8.34 volts but at P+/P- (the input/output terminals of the board) it measures 7.7V.
So, I tried charging. I used a Sony camera charger, 110volt input, DC output 8.4V 1.7amp and measures at 8.45V. I have successfully used this charger to charge the camera batteries that are rated 7.4V but actually measure at 8.3V when fully charged. So I know the charger is working. But charging this DIY with that charger actually drained the pack. After 15 minutes of this charger the pack had drained to 5 Volt. Is there an explanation?
Then I used 12V lead-acid battery, reduced to 8.4V with a step down, to charge this pack. Within 30 minutes, it was charged to 7.74 volt. I continued to charge to see if it would charge to 8.4. After another hour instead of going up it dropped to 7.5. I continued to charge it further, and it topped out at 7.74. The voltage at B+/B- (+/- of the battery) terminals at this point was 8.2. Any Explanation and solutions?
Does this mean this protection board is not working correctly or is there some thing else wrong?
Thanks for the help.
The voltage measured directly at the battery terminals (at B+/B-) is 8.34 volts but at P+/P- (the input/output terminals of the board) it measures 7.7V.
So, I tried charging. I used a Sony camera charger, 110volt input, DC output 8.4V 1.7amp and measures at 8.45V. I have successfully used this charger to charge the camera batteries that are rated 7.4V but actually measure at 8.3V when fully charged. So I know the charger is working. But charging this DIY with that charger actually drained the pack. After 15 minutes of this charger the pack had drained to 5 Volt. Is there an explanation?
Then I used 12V lead-acid battery, reduced to 8.4V with a step down, to charge this pack. Within 30 minutes, it was charged to 7.74 volt. I continued to charge to see if it would charge to 8.4. After another hour instead of going up it dropped to 7.5. I continued to charge it further, and it topped out at 7.74. The voltage at B+/B- (+/- of the battery) terminals at this point was 8.2. Any Explanation and solutions?
Does this mean this protection board is not working correctly or is there some thing else wrong?
Thanks for the help.