HAMA 2100mAh power bank teardown - doubling battery capacity with second cell in parallel [part 2]
I've done this before with a 6-cell laptop battery. They were wired in pairs, so the total voltage was 10.8V 4400mAh. I rewired them to be all in parallel, so it became ~3.6V 13200mAh, charged at 500mA 5V and discharged at 1A 5V, through USB.
With this small power bank, which is not enough to fully charge a smartphone battery, I just doubled the capacity, so if the specs on the bottom are accurate, it should output 5V 2x2100mAh ... mostly OK for a full recharge of a 2000-3000mAh smartphone battery.
NOTE: what I noticed, when starting to charge the thing, is that the electronics were relatively hot in the beginning of the charge, but cooled down after a while, as it put less energy into the batteries. Make sure it's in a heat resistant case while in use.
NOTE2: don't try this at home if you don't know what you're doing. NEVER short out, puncture or heat up battery cells. Only connect them parallel if their measured voltage is similar, otherwise discharge the higher voltage one until they are more or less equal.
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