Originally Posted by bangkaboat
For the solar panel controller, if the panel is 105W, or less, a Sunforce 7A charge controller will do the job. I think that mine was less than $25usd, in Los Angeles. It works, don't know if it's going to fail prematurely.
Please be careful with "cheap" shunting controllers. These devices begin switching on/off once the bank hits absorption voltage and can really cut your time to FULL by days not minutes..
In the case of some of the Sunforce units they switch OFF at 14.2 volts and they do not switch back on again until 13.0V. This may be fine for off grid where you often have a load that sucks the bank back to 13.0V very quickly, but, with a boat on a mooring
, with no loads, it can take a healthy bank a LONG time to drop the surface charge back to 13.0V. I have some customers banks of AGM
& deep cycle wet cells that will hang out at over 13.0V for over an hour. That is an hour of lost
charging time waiting for a cheap
shunting controller to switch back on and provide maybe 60 seconds of charging before raising the bank ti 14.2V and then shutting off again. Sometimes these controllers will never restore the bank to full.
Below is a video of one of the "better quality" shunting controllers, a Flex Charge PV-7. It goes OFF at 14.2v and comes back on at about 13.6v. This is showing the "current" but you can see it turn on and off. I applied a load of 0.1A just so it would go to -0.1A when OFF for the video. When you get close to full your OFF time can be as much as 10-20+ times longer than your on time with some cheap controllers.
In this case the "ON" time is about 5-6 seconds and the OFF time close to a minute to get the bank back down to 13.6v before it can turn back on again. This bank still had 20 Ah's to go and it would take 5-7+ days for this bank to eventually get "full" from an 80-85% state of charge with 5-6 seconds on and 60 seconds off, remove the 0.1A load and it would likely make this even longer..
Contrast that Flex Charge controller, or a Sunforce, with a quality PWM or MPPT
like the Genasun's and the difference in the last 15% of charge, and the time it takes, can be DRAMATIC.
I just replaced both a Sunforce and a Flex Charge shunting controller in the last month with Genasun MPPT
controllers. On one boat "FULL" was cut from averaging 7-8 days to about 2 days and on the other boat "FULL" was cut from roughly 5-6 days to about 1.5 days. Same boat, panels
, batteries just a much better quality controller that does not turn ON/OFF like a cheap shunter will.
If you stick with Morningstar, Blue Sky, Genasun and a couple other REPUTABLE controller manufacturers, you'll be doing well. The eBay stuff is very often a scam.
I have replaced a number of eBay so called MPPT controllers that were NOT MPPT at all but rather simple shunting controllers. MPPT controllers do not shut off for long periods of time....
The Genasun MPPT's are a very good value for smaller for panels
. Under 150W, that is pretty much all I am installing these days.
Please be careful with "cheap" controllers as you often get what you pay for.