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Small Cabin Forum / Off-Grid Living / Recommendations for a solar charge controller upgrade
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# Posted: 27 Jun 2016 09:12

Hi all...I want to swap out my solar charge controller for something a little nicer. My solar generator came with a cheap Chinese one (model CMTP02) that works okay except there's an issue I have sometimes. When my batteries are fully charged from my solar panels, the inverter sometimes won't turn on and it sounds an alarm which I assume is an over-charge warning. In order for me to get the inverter to turn on, I have to remove the solar panel wire going into the charge controller. Once I do that, the inverter turns on fine, and I can return the solar panel wire into the charge controller.

Now I don't know exactly if this is more of an inverter issue or charge controller issue but I want a charge controller with more function anyway, such as a digital readout of battery voltage. I'm Hopi g with an "upgrade" such as this that the issue I'm having will be cured. It's a pain to have to keep unscrewing the screw that holds my solar panel wire into the charge controller.

My system components are this...

(2) 150 watt solar panels
(3) 100ah AGM batteries
1500 watt PSW inverter
30 amp solar charge controller (model CMTP02)

Can anyone recommend a new solar charge controller more feature-rich than the one I have, for under $100?

# Posted: 27 Jun 2016 17:01

I would want to look further into what is causing the problem before throwing more money at the system.

Q? What is the battery voltage when this occurs?

If the inverter is sounding an alarm there should be an indication as to whether or not the voltage is too high, too low, or whatever. One of mine sounds a low voltage alarm whenever I place a heavy load on it. It has a over-volt alarm but I've never heard it. So, I would check that battery voltage and check the specs on the inverter high limit.

As for a better charge controller, for a PWM I like the Midnite Solar Brat. I have one on the trailer. For MPPT I can't recommend anything in the under $100 range. Any I would consider myself are over $200, most over $300, which is why I selected the Brat for the small system on the trailer.

# Posted: 28 Jun 2016 10:53

Rugercpl: Are you running your load through the charge controller terminal (wire points under the lightbulb icon) or off the battery terminals? If you are running it off the Charge Controller, try hooking directly into the battery terminal and see if you are still getting the issue when fully charged. That way you can isolate if it truly is the charge controller or if your inverter is the problem.

As for a cheap MPPT - You get what you pay for - but with only 300 watts of solar and 300 AMP hours of battery, you may find luck with one of these: Tracer 4210RN MPPT. I use this one in my small cabin (100 amp hour agm, 210 Watt 24 volt panel) and it works great. I went with the 40 AMP charger as I plan to install my second 210 watt panel and a second 100 amp AGM. It has been working exceptionally well for two years now. I run all my loads off the battery post - not through the charge controller. This allows me to turn off the loads circuits when I leave to prevent any accidental phantom draw but still get have the batteries charging.

# Posted: 28 Jun 2016 12:34

Quoting: offgridjunkie
Are you running your load through the charge controller terminal (wire points under the lightbulb icon) or off the battery terminals? If you are running it off the Charge Controller,

Darn good point!! NEVER run an inverter off the load terminals. The load (on those charge controllers that have that) are meant for smaller loads than a 1500 watt inverter.

# Posted: 23 Jul 2016 04:50

I don't use the load terminals on the charge controller. My inverter is connected to the battery bank.

I got a new charge controller...another El Cheapo from China. It's working just fine and it has controls to prevent overcharge as well as a readout of its functions. No more alarm from the inverter warning of overcharging since I can control the power from the solar panels to turn off once the batteries reach a certain voltage. My former CC charged my batteries higher than the inverter liked (14.2V). I have it set to 14V now with no issues.

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