Manually recharging batteries

Last modified on July 24, 2026 • 1 min read • 195 words I have a old-fashioned battery charger from Varta (type 57 037 091 101) that doesn’t switch off the current when the batteries are fully charged. Unfortunately this is the only charger I have e.g for D size batteries (also called mono batteries). The charger lists the necessary charging times for different types of batteries on its back side. If you assume 100% efficiency, the necessary charging time is given by the following formula: charging time (h) = battery capacity (in mAh) / charging current (in mA) The times given in Varta’s table exceed these theoretical times by 24-65%. Mostly they are around 40% longer than the calculated. This agrees with the data given in the usage instructions of my Hama charger that claim that charging time (h) = battery capacity (in mAh) x 1.4 / charging current (in mA) However, I have read on several web sites (e.g. gaiam  ) that the factor for charging losses is 1.25 and not 1.4; consequently I still don’t know exactly how long to charge when I need to charge manually. Especially I am wondering whether there are differences in the charging inefficiency between e.g. NiCd and NiMH batteries.