Can Both A 100 Watt And 120 Watt Solar Panel System Be Connected To The Same Trailer Battery

Updated 02/17/2026 | Published 06/25/2024

Question:

I have a 100 watt solar panel on my trailer roof with a 12volt 10 amp controller. I have one Battery on the trailer. the battery start dropping after two days. I also have a solar plug in directly into the battery. Can I plug my 120 watt portable solar panel into this plug with its own 10 amp controller top help keep battery charged? I assume when battery is charged the controller would cut off and not charged but not sure.

asked by: Tom G

Expert Reply:

Hey Tom,

A 100 watt panel is good for about 5 amps per hour in peak conditions so you wouldn't really be getting enough power to charge the battery unless you were just using this as a maintenance charge while in storage. You can definitely run a separate solar panel system directly to the battery. The solar charge controllers should be reading the battery charge level and adjusting the charge sent to the battery accordingly, so there's no issue there. You just won't want to tie two panels together with different wattage ratings.

If you did then the higher wattage panel would be limited to the rating of the lower capacity panel. In your case instead of getting 220 watts you'd get 200 watts. You'd could also run into issues with the charge controller's capacity if you add too many panels to one system.

If you ever want to add in more permanent mount panels to the system then I recommend checking out our solar calculator (linked below) to see what your energy usage adds up to and what system would be right for your needs.

expert reply by: Kevin C

Robin H.

2/17/2026

Hey Tom, how did things go when you added the 120-watt portable panel to your trailer setup? Did the two controllers keep the battery topped off like you were hoping? Your update could make it easier for others trying to balance multiple solar panels.