Charger
Here I am using a current clamp meter. It indicates that the batteries are receiving 10.6 Amps.
I built the battery charger myself, using some plans I found online: http://www.austinev.org/evalbum/tech/bonn_charger.html
This is Lee Hart's design of a bad boy charger. My charger is very similar. The key component is the inductor. I took apart a microwave oven and rewound the transformer and made some taps at the halfway mark. So now I have a low and high setting, by using the entire coil or just half. I also have a super high setting when I take the coil completely out of the circuit.
The charger converts the 120V AC (from a wall socket) into DC. It does this by the use of a diode bridge. The bridge flips the negative portion of the voltage to be positive. This way the cycles are all positive. Then the capacitor reduces the ripple. The reason you get more than 120 Volts is because the actual peak to peak voltage of AC is 171volts.
The batteries can be charged in the super high setting at 150 volts, which is about 2.5 volts per cell. I usually use this setting when the batteries can take it without blowing circuit breakers (when the batteries are discharged they have a lower internal resistance, which causes higher amperage).
Using Ohm's Law, we see that if the circuit is using the low setting, the charger is using 15 Amps, and 120 Volts. The internal resistance is 8 Ohms. However, when the charger is putting out 150 Volts and 10 Amps, the internal resistance is 15 Ohms. Sometimes the internal resistance will get as low as 5 Ohms. So when I plug the charger in, the circuit pulls 20 Amps and the circuit breaker will trip. To prevent this, I check the amperage with a clamp meter. I can decrease the amperage more by using a longer extension cord to the outlet.
They are battery chargers designed for electric vehicles. These cost at least $1,000 and are only made by a few manufacturers. The nice thing about them is that they regulate the current as the voltage increases.
I also charge my original 12 volt battery with a charger that accepts the 120Volts DC from the batteries and converts it to 12 Volts DC. This is usually called a DC-DC converter. However, I am now using an Iota battery charger that is designed for 120Volts AC, which by chance also works on DC. Having the 12Volt battery continues to power the signal lights, the high beams, and the heater fan.