[ZekenSpider]

This is my experience with my new TM 3326. The TV is a 2004 Suburban with a 10 gauge wire to the TM tow receptacle. It has 30 Amp fuses at both the TV and TM battery buss end. As I get ready to tow, I set the refrigerator to 12 Volts DC (and refrig. fan on) with shore power still on. Then I connect the TV with engine running. The TV voltmeter sits at 14.7 volts. The TM battery voltage is 14.6. I disconnect shore power and see no change. The TV voltmeter stays at 14.7 volts for the length of the tow (so far, only 200 miles) and the TM battery remains at 14.6 volts whenever I stop, as long as the TV generator is running.

Unless you have a battery isolator (to isolate your TM from your TV) the two batteries (the TM and the TV) will be in parallel and will receive the same charging voltage from the TV generator. That voltage will be controlled by the TV generator regulator which is set to around 14.7 volts. The TV generator will jamb as much current into each battery as they each will accept based on their individual internal voltage levels and the voltage drop encountered in the wire length and size of each charging circuit. The maximum current into the TM battery will be limited by the TV or TM battery circuit fuse (or circuit breaker).

In practice, this means the TV generator(while running) will be a constant source of DC current at 14.7 volts into the TM DC buss. That buss will be providing continual current to your TM equipment (usually just the refrigerator) and to the TM battery up to the limit of the fuses. That will force the TM battery internal voltage to rise to 14.7 volts.

By the same analysis, when on shore power, the TM and TV battery will be charged by the TM inverter (if the TM and TV are still plugged into each other and the TV is not running). In addition, if you have a solar power system on the TM, the solar power regulator will charge the TM battery at a fixed 14.3 (adjustable) voltage.

The TM battery voltage always rises to the solar regulator set point. The only time I see the TM inverter 3 level control come into play is when parked in storage at night with no loads turned on.

I have wondered about using AGM batteries. Let me know if you think they will be durable. So far, in my application, I do not go very far into discharge cycle.

Jerry Miller