Question

What components are needed to charge a 6s 12V 5Ah LiPo battery from another a 36V 10s 10Ah battery. Please explain.

Answer 1

First of all please note that you should know how a battery is charged. Then only you can understand the correct requirements and components to charge a battery.

A battery gives us DC voltages and DC currents and to charge a battery we also need a DC source of voltage but the condition is that the source voltage should be greater than the voltage of the battery that is to be charged because if it is not so then current will try to flow from your battery to the source(This is not what you want!). Also, this condition satisfies the fact that current always flows from higher potential to a lower potential.

Now, this DC source that we are talking about maybe another battery but its voltage should be higher than the voltage of the battery. But this is all that is needed to charge a battery theoretically, this is theoretical because theoretically, an ideal battery can handle any amount of current to charge itself but in practice, this is not what actually happens because we know that batteries have different current handling capability. Therefore we need a Resistor to limit the charging current so that it doesn't damage the battery.

In your case, you are trying to charge a battery 12V 5Ah from a Battery 36V 10Ah. It's fine and you can surely charge your 12V battery without any issue but you should keep in mind all the points that I discussed so far.

Your 12V has current rating of 5A so if you charge it will a current greater than 5A then your battery may get damaged so please add a resistor between the two batteries as shown in the following figure. You can buy the resistors from electronics shop. Use a resistor of value greater than 4.8 ohms so that current remains smaller than 5A.