Another Solar Controller question

tensch wrote:
I have a 100w Renogy solar panel that is used to keep the two 6 volt batteries (flooded) charged while dry camping. The controller that came with the trailer when I bought it was one of the cheap generic chinese models (blue) that sell on amazon for $15 or $20. The usb ports broke and I am looking to replace. My thought is that a PWM is fine for my needs. What amp size controller is recommended? And what are the optimum float, high voltage and low voltage disconnect settings, and load on setting for this setup? Thanks

First look up the charging voltage specs for those 6v batteries. Typically 14.8v absorption with 13.6 float at 77F, but higher with lower temps and lower with higher temps. If you get a temperature compensated controller, then just set for 77F and leave it.

100w at 6.2 amps Isc (which is what you see with PWM) is not much for keeping up a pair of 6s unless you hardly use any 12v and it is always sunny.

So in case you get more solar, go for more amps size of a controller with adjustable voltage settings ( even if you don't get more panel watts.)

The Grape 40 amper is often recommended here (Home Depot ISTR) for not much money.

One hundred solar watts isn’t much. Standard is one solar watt per battery amp hour plus times 1.25 to 1.50 watts in the great Northwest.

“I bought it was one of the cheap generic chinese models (blue) that sell on amazon for $15 or $20”

Then you get a cheap generic charge. I’m all for saving money but I want my controller to work everyday correctly. BATTERIES cost a bundle. Penny wise, pound foolish.

100 solar watts is at best 5.50 amps per hour. Times, at best, five hours per day...27.5 amp hours to the batteries. Peanuts. Solar panels aren’t that expensive.

Lwiddis wrote:
100 solar watts is at best 5.50 amps per hour. Times, at best, five hours per day...27.5 amp hours to the batteries. Peanuts. Solar panels aren’t that expensive.

X2

Get another solarpanel and spring for an MPPT. They aren't much more money and totally worth it.

If you want a good charge controller that is pwm, it is hard to beat the Grape 40 amp unit. It is fully featured with a temperature sensor.

https://www.homedepot.com/p/Grape-Solar-COMET-12-24-Volt-40-Amp-Solar-Charge-Controller-GS-PWM-COMET-40/305498558

http://www.grapesolar.com/docs/GS-PWM-COMET-40%20large%20print%20manual.pdf

I have to agree that 100 watts is on the low side--depending on the time of year and the location.