Battery Charge Requirements

Padlin wrote:
Looking into a solar setup for my new trailer, first off is figuring out what I need for controller output to correctly charge my batteries. I'm planning on eventually having a pair of either 100w or 130w panels, that's all the space I have.

Batteries are 2 6v Interstate GC2-XHD, 232Ah.
Specs show per 6v
Bulk 7.2v
Absorption 7.75v
Float 6.6v
Equalization 7.8v

Do I read this right I need a 12v controller that will put out double these figures? Very few do, and those are user configurable to get to those levels (Blue Sky Solar Boost 3000i MPPT or Sun Chaser PWM, among a couple others).

My pair of GC2-XHDs are quite happy with a single 130w panel and a Solar30 PWM controller. The controller is set to 14.8v for daily operation. You could use a second 130w panel in the winter when demand is higher and solar day is shorter.

Expected max amps with a 130w panel is 8.2a (panel Isc) and you might see a few more amps at times so use a 15a controller for one panel or a 30a for a pair. Roof mounted flat you might get 50-60AH day from one on a really good day, so your daily usage determines if you need the second panel. IMO try it with one panel and a 30a controller (in case you get a second panel)

You only need to go into the 15s for voltage once in a while for your 100% SOC "overcharge" and with solar you don't need to have a fancy controller that can be set that high, you can just disconnect/by-pass the controller and go "panel direct" That is the same drill as doing an equalization with a manual charger--you have to be there and make sure voltage does not climb too high, take your SGs to see when SG stops rising and you are done. Also disconnect batts from rig to not let the fridge DC voltage go over its 15.4v limit.

Then go back to normal operation with the controller in the mix.