Basic bare bones solar power controller?

[DaveM]

I have a very basic solar system set up I'm trying to build. A single 100w Rockpals foldable panel (18v 5.5 amp) charging a single 12v dc deep cycle marine battery. The battery will run to a BlueSea fuse box that connects to a couple of LED light strips in my trailer and a 12v socket to run a Dometic fridge. Closed system, not grounded to the trailer, no power in from the tow vehicle (for now).

I see a lot of basic 12v controller options on Amazon for under $40. But I have no idea what specs I'm looking for? Can somebody recommend a simple and reliable controller for my use case?

 

[jonyjoe101]

one of the 10 amp pwm controller should work with your panel, 100 watt maxes out at about 5 amps. You can find them for less then 15 dollars. The one on the picture I use as a backup and it works fine on my 240 watt panel but its better for the smaller panels. I like the ability to charge usb items also. No need to spend more then 20 dollars on a pwm controller.
Also for the smaller 100 watt panels mppt would do absolutely nothing to increase the amp output.

 

[Sneaks]

one of the 10 amp pwm controller should work with your panel, 100 watt maxes out at about 5 amps. You can find them for less then 15 dollars. The one on the picture I use as a backup and it works fine on my 240 watt panel but its better for the smaller panels. I like the ability to charge usb items also. No need to spend more then 20 dollars on a pwm controller.
Also for the smaller 100 watt panels mppt would do absolutely nothing to increase the amp output.

View attachment 615761

I have one of that controller's clones. Paid under $13 to use with a 100w panel.

 

[DaveM]

Thanks all, good to know. Renology definitely pops up a lot in my searches.

There seem to be different flavors of these for pos/neg grounding. My reading suggests this is irrelevant in my application and won't affect how the system is actually wired. Is that right?

 

[DaveM]

Ok, final question I think. Is it ok to stack ring terminals on the battery posts? I'll have a 10awg wire from pos & neg on the batt to a BlueSea fuse box (then on to the LEDs). The controller would also need to connect directly to the battery terminals. Or is there some other less obvious way this gets hooked up?

 

[vomhorizon]

I have a $19 Renogy 10A PWM (wanderer) that I use as a means to charge my in vehicle AGM and as a backup/secondary source to charge my LiFePO4 that has a dedicated MPPT charging it. I've had it for just a few days but it works though the CC won't accomodate 10 awg ferrules very easily. It has a lithium charge profile setting (adjustable) so ticked off all the boxes for my application. You can also add a seperate bluetooth module to it later if you want to monitor what is going on (though the cc comes with a screen which has all that information).

 

[burleyman]

One nice to have feature is amps display to monitor charge current. The blue-faced spare I have does not. I have ordered low-cost Renogy and HQST brands that do. Knowing typical charging amps, especially in full sun, discharged battery conditions can alert you to possible wiring/connection, dirty panel, panel orientation, or shading issues.

 

[broncobowsher]

Rock solid and super basic. Been running it for 8 years now. SunKeeper SK6.
Almost no dark current (night time battery draw). Just about the only charge controller that will actually publish a dark current number.
No displays, no alarms, no internal switching. It's just a battery charger for a solar panel. I got 7 years out of a battery in AZ (that is an extremely good number for around here) and I replaced the battery before it was gone. Lots of options with a lot more bells and whistles. But if you just want a simple and rock solid PWM charge controller, SK6. For higher amp systems, SK12 will handle 12A instead of the 6A.

 

[DaveM]

Follow up question, can these inexpensive controllers be used with smaller panels to keep batteries topped off during storage? Or does that risk overcharging the battery?

 

[vomhorizon]

Follow up question, can these inexpensive controllers be used with smaller panels to keep batteries topped off during storage? Or does that risk overcharging the battery?

As long as you match the charge controller to the battery chemistry, you will not overcharge it.

 

[broncobowsher]

Follow up question, can these inexpensive controllers be used with smaller panels to keep batteries topped off during storage? Or does that risk overcharging the battery?

Define a small panel.
The quick answer, the charge controllers are there to prevent overcharging the battery. Some of the really simple old school solar battery maintainer didn't have any controller to them. It was they were so tiny and so low power that there wasn't enough output to really cook a big battery. Those were little more than a glorified solar calculator cell and a diode to prevent discharge at night.
Get up to a panel that actually has a decent output and you need a charge controller. By decent output, that is anything actually usable.

 

[DaveM]

Define a small panel.
The quick answer, the charge controllers are there to prevent overcharging the battery. Some of the really simple old school solar battery maintainer didn't have any controller to them. It was they were so tiny and so low power that there wasn't enough output to really cook a big battery. Those were little more than a glorified solar calculator cell and a diode to prevent discharge at night.
Get up to a panel that actually has a decent output and you need a charge controller. By decent output, that is anything actually usable.

Not sure, whatever is enough to keep a 12v deep cycle charged up while in storage (months at a time unused). Need to look into this today, but I'd guess between 5 and 10 watts. The idea is to mount this panel to the top lid of the compartment over the batt and use it to maintain the batt in the offseason so I don't have to keep it plugged in all the time. In camp I'll use my 100w Rockpals panel to actually charge the batt.

Makes sense that the controllers would keep the batt from overcharging but I wasn't sure as I was also seeing "maintenance" controllers.

 

[DaveM]

Update: purchased Renology Wanderer last year sometime. Used with Interstate SRM-24 12v deep cycle and a 100w Rockpals panel. Seemed to be working ok at first but a few months ago I started getting an E10 error code on the SCC which indicates solar panel over voltage (?). I assumed I did something wrong in my setup but now I think the Renology just crapped out. Will be looking for something more robust this tine around.

 

[billiebob]

Update: purchased Renology Wanderer last year sometime. Used with Interstate SRM-24 12v deep cycle and a 100w Rockpals panel. Seemed to be working ok at first but a few months ago I started getting an E10 error code on the SCC which indicates solar panel over voltage (?). I assumed I did something wrong in my setup but now I think the Renology just crapped out. Will be looking for something more robust this tine around.

I too have the Renogy Controller. Power in, power out. No other connections. I all wanted was a closed solar system to run my fridge. The project now is collecting the bits to get it running, I'm sure I'll eventually add some lighting and power for the ipad, camera, phone etc. I mounted 200W on the roof so it can charge while I drive. I almost did the "set up the solar panels" at camp thing but most days I'm driving thru the peak solar charging hours so I mounted the panels permanent and now will have one less thing to set up or trip over.

I'm watching to see what your charging problem turns out to be..... best of luck with that.

This was my starting point

And mounted

 

[DaveM]

I'm looking at some of the Morningstar units as a replacement. They seem to be higher quality . When looking into the Renology Wanderer error code I'm getting it seems that a bunch of other owners ran into same issue and Renology replaced under warranty for units that seem to work for them. Guessing it was a QA issue, but I'm out of warranty I think and don't really want to use them anymore anyway. Cheap units.