Charging booster:

Many model craft are powered by 12 V rechargeable batteries. Often, it would be a godsend if these batteries could be charged by a lead-acid (12 V) car battery. However, that is not possible, since the car battery voltage is just sufficient to charge an eight-cell (9 V) battery. One solution to this problem is, therefore, to raise the car battery voltage and this is what the booster presented in this article does. In conjunction with the car battery, it enables 12 series-connected cells to be charged at charging currents of up to 4 amperes.