You should use li batteries in series ONLY when you need a bigger voltage, and a DC/DC step-up converter can't be used.
1. If you connect batteries in series you will need a special charger, that will charge every battery separately (search on a RC forum for Li-po chargers for examples). You battery pack will have +,- and (n-1) aditional wires, where n=number of batteries. You must connect in series ONLY batteries of the same type and capacity!!!
2. If you connect them in parallel:
- you can use a simple charger to charge the pack;
- you must use ONLY batteries of the same type (Li-ion or Li-po);
- charge batteries to the same voltage before connect them in parallel !!! if one is charged, and other empty, the emply one will absorb a very big current at the connection time;
- I would give-up the protection circuit from phone batteries if current bigger than 500mA is necessary.Posted on: June 19, 2010, 08:44:18 20:44 - Automerged
Have you tried it?
I just examine an opened cellphone battery protection pcb, it is based on DW01 protection IC and S8205 dual n-ch mosfet. Google gave the datasheet, here is the typical application circuit.
I wonder, will it work in series or parallel connection, in both direction charging and discharging?
Put them in series, and connect the pack to a charger. When first battery will be charged, the OC MOSFET will break the circuit, blocking all other batteries to charge.
Parallel connection is the best option. This way you can use the protection circuit from every battery.