bme, replacement bme, and charge*sh are all mutually incompatible with eachother.

In the script, the line
i2cset -y -m 0xfc 2 0x6b 0x02 0x8c;

Sets charge voltage to 4.20V, replace 0x8c with other values:
4.20 = 8c
4.16 = 84
4.10 = 78
4.00 = 64
3.90 = 50

Note, the charge meter detects "full charge" roughly as: If voltage is higher than 4.x, and current lower than Y, then battery has reached fully charged state. I forget what x and y are, but if I had to guess, I'd say 4.04 and 50mA.

If you set charge voltage too low, hw battery meter no longer works as good as usual. Also, as long as charge voltage exceeds battery meter's threshold, it will jump to 100% even when charging battery to less than 100%. In that case, after a calibration cycle, it would show that the battery's capacity is less than it was before.

As a side-effect of the N900 power topology, if you're charging the battery when the power consumption is high, the battery ends up with less charge than when charging an idle N900.