your cars alternator is around 13.8-14.4 vdc so even if you install the 2 volt battery, you wont be able to get maximum performance....because the batteries get the vdc from the alternator. you will always be at 14 volts...you have to change the regulating diode inside the alternator to charge them to 16 volts.....good luck finding a place that can do that in bangkok.... it can be done, but most places will say that it can not be done because they do not know how to do it. you also have to be careful not to overload your cars oem electronics, this can be done easily by using diodes with the proper amperage rating, 1 diode will drop voltage by approximately 0.6 volt to do it properly you need to get atleast 17.5 vdc from your alternator.