Cpaharley's thread on changing out his trailer battery reminded me of something I noticed on our trip back from Chilliwack.
I paid a lot of attention to our solar controller as I was interested in how the well the solar would work. In full October sun we would get 6 amps or so when in full October sun. I usually ran the frig on 12 volt on the road as I felt the Silverado's charging system and wiring to the trailer was pretty robust. Most of the time we arrived at our destination fully charged, but not always.
Later in our trip I noticed a large fluctuation in the voltmeter reading in the cab of the truck. Sometimes we would be charging at 15 volt or so and at other times only 12 something. Never quite made the correlation between that at the condition of the trailer batteries when we arrived at the end of the day.
In looking back, I think the difference is that the GM system varies voltage depending on conditions.
Looking up I found references in the owners manual and also info on the internet:
Voltmeter Fluctuation Condition:
Some customers may comment that the voltmeter is fluctuating between 12 and 14 volts on their full size pickup or utility vehicle. Starting with the 2005 model year, light duty full size pickups and utilities are equipped with a new Regulated Voltage Control (RVC) system. This system reduces the targeted output of the generator to 12.6-13.1 volts when in "Fuel Economy Mode" to improve fuel economy. The generator may exit "Fuel Economy Mode" if additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems that usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted.
Camper/Trailer Battery Charging Concerns:
Some customers may comment that when towing or hauling a camper/trailer, the auxiliary battery for the camper/trailer will not stay charged. In most cases, this concern is blamed on the new RVC system. While the RVC system does reduce the generator's targeted output voltage to 12.6-13.1 volts when in "Fuel Economy Mode", this feature is bypassed if the tow/haul feature is enabled. With the tow/haul feature enabled, the RVC system will stay in "Charge Mode" and the targeted generator output voltage will be 13.9-15.5 volts, depending on the battery state of charge and the estimated battery temperature. To keep the generator in the "Charge Mode", use either of the following two methods.
The first method is to use the tow/haul mode when towing or hauling a camper or trailer.
The second method is to turn on the headlights, which will increase the generator's targeted output voltage to 13.9-14.5 volts.
I ran mostly in tow/haul mode but not always. On some very flat terrain I sometimes ran in regular mode. So if you want your trailer battery to get the full shot you should run in tow/haul or turn on your lights.
This season I will monitor the system and see how the solar interacts with the alternator system. Thinking strongly of getting the Zamp Battery Check. Cpaharley, please keep us informed on how yours is working out!