ducktapeguy
Adventurer
This may be a basic question but I did a quick search of this forum but couldn't seem to find the answer. Can I run a solar controller off the main battery/alternator with a solar panel and have it charge my aux battery? Not at the same time, but if they were wired in with a switch is that going to cause an issue?
Background. I have an DIY aux battery pack to run my fridge. It's stored in the rear cargo area next to the fridge. It's connected through a relay box to the main battery cable so it charges whenever the car is started. I've recently added a 100W solar panel with 10A renology controller to charge the battery. The panel is mounted to the roof and the wires run into the engine compartment. What I'd like to do is switch between solar and alternator whenever the car is parked/driven., What I would like to do put the solar charge controller near the battery in the rear cargo area, however, I only have one set of 10ga wires leading the the rear cargo area so it would have to use that for both the battery and panel.
When the car is parked, the panel wires connect through the relay to the charge controller to the battery. All is fine on that end and it works as designed. But, when the engine is running, the alternator output would be connected to the input side of the charge controller. I'm assuming power is power, whether it comes from the alternator or solar panel, the charge controller shouldn't know the difference. But in reality is there going to be a problem using the charge controller in this manner? The alternator voltage doesn't get much higher than 14V, where as the panel can output 20V. Not sure if there is a certain voltage threshold or delta the controller needs before it starts charging, and I don't know if this might cause problems with the alternator charging circuit. Right now i've got the relay disabled so it's only being used for solar, but I'd like to have them switch automatically.
The alternative is to locate the controller in the engine compartment and have the relay switch between the output/battery side of the controller instead of the input. Eventually I may do it that way when I relocate the battery but for now it's going in the cargo area.
Background. I have an DIY aux battery pack to run my fridge. It's stored in the rear cargo area next to the fridge. It's connected through a relay box to the main battery cable so it charges whenever the car is started. I've recently added a 100W solar panel with 10A renology controller to charge the battery. The panel is mounted to the roof and the wires run into the engine compartment. What I'd like to do is switch between solar and alternator whenever the car is parked/driven., What I would like to do put the solar charge controller near the battery in the rear cargo area, however, I only have one set of 10ga wires leading the the rear cargo area so it would have to use that for both the battery and panel.
When the car is parked, the panel wires connect through the relay to the charge controller to the battery. All is fine on that end and it works as designed. But, when the engine is running, the alternator output would be connected to the input side of the charge controller. I'm assuming power is power, whether it comes from the alternator or solar panel, the charge controller shouldn't know the difference. But in reality is there going to be a problem using the charge controller in this manner? The alternator voltage doesn't get much higher than 14V, where as the panel can output 20V. Not sure if there is a certain voltage threshold or delta the controller needs before it starts charging, and I don't know if this might cause problems with the alternator charging circuit. Right now i've got the relay disabled so it's only being used for solar, but I'd like to have them switch automatically.
The alternative is to locate the controller in the engine compartment and have the relay switch between the output/battery side of the controller instead of the input. Eventually I may do it that way when I relocate the battery but for now it's going in the cargo area.
Last edited: