rickyjar
Member level 2
User “pier” describes a modification of his Ferm driver. The battery and charger are a total misunderstanding.
The battery (14.4V) has supposedly the capacity of 1.2Ah but it cannot even be 0.6Ah, and there is no control over charging, if it comes to charging, so there was a need to do something with that.
A used laptop battery li-ion 10.8V 6.6Ah was bought online. It turned out that the battery is in good working order. It was dismantle into nine single cells (18650 size) and they were connected together in twos in parallel, and then three such packages were connected in series. This way, the 10.8V 4.4Ah battery was built, after charging 12.6V. It is a bit smaller battery than the original one, but there is no difference in revolutions, this is surely because in the case of the original one voltage was going very low.
As it is know, li-ion batteries have to be charged with a charger that will not let battery voltage be exceeded, which is 4.2V per cell. Additionally such packages have to be charged with a balancer that controls the voltage of the particular cells in a package.
A simple charger on LM317 and balancer from this Link are used.
Summing up, the modification turned out to be very satisfying. The battery holds really long.
Link to original thread - Przeróbka zasilania taniej wkrętarki