Question about solar charge controllers

[RogueIT]

Looking at gopower solar kits and the GP-PSK-200 comes with a 30 amp, single bank, charge controller wile the GP-PSK-130 comes with a 10 amp charge controller.
Since we will be charging a single battery on a scamp, what does the 30 amp give me that the 10 amp doesn’t. Warning. My electricity knowledge is limited.

[Jim Bennett]

There is no real advantage to charge capability with a higher amperage solar controller. 30A for 200W is overkill, but will not be a problem. If you have an one board solar controller like many do with mounted systems, ensuring the amperage is adequate for the permanent and any portable added using it is necessary.

I have 240W of solar on my roof and carry a 100W portable. I installed a 30A MPPT controller to handle a full load and more. The thing is, a total of 340W at 18V is only 19A, and that is an optimal rating, something I never get near achieving due to the fixed panels getting nowhere near maximum solar reception. Ready for adding more portable, though that is very unlikely.

[thrifty bill]

Having extra capacity allows you to add a second panel at a lower cost in the future. I have a 20A controller on my 100W portable panel, which is overkill for sure. But I like that I can add a second panel without another controller.

[patrick crawford]

with regard to solar controllers i like to use the redundancy approach. i employ 2 100w panels, one on the roof of the casita and one on the roof of my truck's topper. each go to a dedicated 20a controller. my thinking is if one controller gives up i still have solar with the remaining controller. excess? well, yes, but the controllers are fairly inexpensive and it adds confidence that i can perhaps stay longer in the event of a failure.

p@

[gordon2]

10 amps is roughly 120 (120-137) watts.
30 amps is roughly 360 (360-410) watts.
The charge controller must be rated high enough for the panel or panels you plan to use it with. A higher rating is OK, a lower one is not. And there should be some fudge factor. So in practice I would limit a 10 amp controller to 100 watts in PV panel(s), and I would use a 30 amp controller with no more than about 320 watts of PV.

I have a portable 10 amp controller that I use with a single 100 watt panel. I have a 30 amp controller in the camper for two or even three 100 watt panels.

[thrifty bill]

Originally Posted by patrick crawford

with regard to solar controllers i like to use the redundancy approach. i employ 2 100w panels, one on the roof of the casita and one on the roof of my truck's topper. each go to a dedicated 20a controller. my thinking is if one controller gives up i still have solar with the remaining controller. excess? well, yes, but the controllers are fairly inexpensive and it adds confidence that i can perhaps stay longer in the event of a failure.

p@

I’ve thought a lot about doing this. Do you have a separate RV battery in your truck bed?

[patrick crawford]

I’ve thought a lot about doing this. Do you have a separate RV battery in your truck bed?

i do not have a separate battery in the truck's bed but while i'm underway i put the truck's panel to work powering a go sun cooler which lives back there. my house batteries are 2 6v agm golf cart batteries installed under the bed of my 16'sd (those are big batteries).

p@

[Natalie21]

I knew that a solar charger controller is a solar electrical component which primarily controls the amount of power sourced from solar panel to a power bank. But how to it work?

[Raspy]

Natalie,

A typical solar panel might produce 17 volts and varying amps throughout the day. Then at night it can become a load on the battery.

It needs to be matched to the battery, which should be charged up to just over 14 volts, and then held at just over 13 volts while standing by.

That is what the solar charger does. It manages the charging of the battery by matching the output of the panel to the needs of the battery.


There are two types of controllers. One is called a PWM, pulse width modulation controller and the other is an MPPT, Maximum Power Point Tracking controller. The PWM is very common, and inexpensive, but the MPPT better matches the solar to the battery and is more efficient overall, at an higher initial cost.

You could just hook the solar panel up directly to the battery, but it is not a direct match and will not work as well as it does with a controller.

[Natalie21]

Originally Posted by Raspy

Natalie,

A typical solar panel might produce 17 volts and varying amps throughout the day. Then at night it can become a load on the battery.

It needs to be matched to the battery, which should be charged up to just over 14 volts, and then held at just over 13 volts while standing by.

That is what the solar charger does. It manages the charging of the battery by matching the output of the panel to the needs of the battery.


There are two types of controllers. One is called a PWM, pulse width modulation controller and the other is an MPPT, Maximum Power Point Tracking controller. The PWM is very common, and inexpensive, but the MPPT better matches the solar to the battery and is more efficient overall, at an higher initial cost.

You could just hook the solar panel up directly to the battery, but it is not a direct match and will not work as well as it does with a controller.

Yes, I read in here: https://www.vogeltalksrving.com/mppt...ight-decision/ . MPPT is better than PWM but it quites more expensive than PWM a lots. Is that right? :bối rối:

[Raspy]

Roemer's law: Demand will always rise to meet supply.

Whenever we are putting a solar system together we have to factor in the available space we have for the collectors, the cost of the collectors, the angle they will be mounted at relative to the sun, the loads we want to be able to run, the storage capacity of the batteries, etc. If you really want to run more stuff, or may want to in the future. Or if the available space on the roof is limiting your capacity, or the weather is often marginal, you may want to get the maximum efficiency from your system. We already accept a loss in performance from roof mounted panels lying flat, or cheap lead acid batteries that charge inefficiently. So, it is a good idea to build in another loss in efficiency, by using a lower cost controller? Or is it better to pay a bit more and maximize the system that already has other weaknesses, as we try to get enough power to run the loads we have, and the loads we might want to add later?

You can probably count on getting to the maximum your system will produce eventually, and then wanting a bit more power. So, you decide. Is the higher cost of a better controller worth it, or not. More collectors would also be expensive, and there may not be room for more.

Example: I am thrilled with being able to run my lights and keep my batteries charged for days and days without running a generator. Then I want to run the propane heater some. Fine. Then I want to watch a movie in the evening. Fine. Then I want to charge my laptop, my wife's laptop, and our phones. OK. Then I want to charge my electric bike. Problem. Not enough power.

Then I discovered the most ridiculous use of all: Electric coffee maker! Sheesh! Extravagant usage! But wait, is it? It minimizes water use for cleanup, it is very convenient, it uses no propane. And it makes excellent coffee. 650 watts usage for 6 minutes to produce a pot of coffee. OK, fit that into the solar budget. A use I never expected to have, but one that followed Roemer's law. And one I'm glad to have.

My MPPT controller is so efficient that my system still charges, just a bit, while parked under the carport! A friend on mine reports he parks under a street light and gets some charging at night. Just a bit, but every bit helps.

I'm very happy I went for the MPPT controller.

[Raspy]

Originally Posted by Jim Bennett

There is no real advantage to charge capability with a higher amperage solar controller. 30A for 200W is overkill, but will not be a problem. If you have an one board solar controller like many do with mounted systems, ensuring the amperage is adequate for the permanent and any portable added using it is necessary.

A very good point.

I was concerned that a larger than necessary controller would be less efficient. But it is not.

I now have a 300 watt system that actually produces just over 15 amps to the batteries, or about 212 watts at near peak. I plan to add 300 more watts eventually, but want to get used to this system for a while first. My 50 amp MPPT controller will handle any upgrades, while still being efficient at very low light conditions.

[zack sc]

Can a good MPPT controller help you to charge in the shade or in partial shadow from a tree branch or something? What is an example of a good MPPT controller in the 20 amp range? Do I need an MPPT type controller, rather than a PWM, to make sure that my excellent Trojan deep cycle battery is properly taken care of?

[redbarron55]

For me there are tow issues to consider.
One is the charging current from the solar panels and to me is is less important.
The other is if you use the controller to track power usage going to the trailer.
I have a DC power meter, but I decided to use the MPPT controller to go to the DC buss in the PD4045. I separated the charging from the buss and connected it to the battery and then the battery already goes to the MPPT. I then took the output from the MPPT to the buss of the PD power distribution DC buss. Now I can see on one panel the power being produced the current going into or out of the battery and the output power to the trailer DC.
I find it interesting looking at the voltage and current coming from the solar panels at perhaps .5 amps at 60 volts and the charge current to the battery / trailer as a good bit more current at the nominal 12 volts. MPPT at work!
My MPPT is rated 40 amps, but the 300 watts of solar panels would never put that out, but the battery could!
This is the reason for a higher rating is nice for the controller if hooked up that way.