out what size charge controller for solar panels.??

[carl2591]

I was gifted a couple of 335 watt solar panels the produce 46.3V Voc, 37.9V Vmp, 8.8A Imp, 9.36A Isc.

I have a 20 amp MPPT controller that might work but not sure as the info show 12 or 24 v operation. Is this considered a 24 v system??

This is going on camper shell to provide extra power when needed or if RV parked in shady spot. I was going to mount this spare MPPT and take some wires out to a connector so i can plug in large panel to put power to mppt controller to help charge up 2-6 v batteries. (12V)

there will be several 12v panels of about 360 watts total which could be wire in series to make 24v system but do to shading issues my stay parallel. '

Not sure the best way to go on this system.

I have checked voltage and with full sun it at like 46 volts DC (not hooked up to any thing just the leads)

[CA_Traveler]

CA Traveler wrote:
Serial is actually better for shading if that is a concern for you.

Click for more information on this prior post.

[CA_Traveler]

The panels in the pic are referred to as 24V panels. They are the very large 72 cell 36V panels. You will need a MPPT controller that can handle 1 or 2 in either parallel or serial. Serial is actually better for shading if that is a concern for you.

For your parallel 12V panels (36 cell) be sure they are all within about 0.5V output. For this setup a PWM controller is the best option.

This may help you: The PWM controller uses the panel amps to charge the battery. The MPPT controller is designed to take the higher 24V panel voltage and it's amps and convert it to the lower battery voltage with higher amps.

[MEXICOWANDERER]

According to weather reports, North Carolina and North Pole are almost neighbors. Recalculate for borderline cryogenic operation.

[BFL13]

This is all for a pair of 6s????

You can run the three 12s rated 360 total on your existing 20 amper in parallel so it won't go over the Voc limit, and that is plenty of solar for two 6s. It should be a 30 amper, but it is bought and paid for.

To take advantage of your new big panels, first you need a scenario/usage daily AH requirement, etc. If same old, sell those extra panels. If new scenario, what is it exactly? How many batteries? How many AH per day do you need to replace? How long on battery with no solar do you have to allow for in the scenario? (ie does it get overcast often and for how long before the sun comes back out?)

[MrWizard]

NO picture

[carl2591]

ok after some more looking and reading I am getting a bit more handle on this issue.. more like refreshsing my knowledge base of which you guys have helped a lot. 🙂

I seems like i need a 45 amp PWm like a tri star CC for the 360 watts of smaller panels. They are three panels in a 2-100 watt and 1-160 watt panel which will be mounted on airstream.

for the larger higher voltage 335 watt 40 volt panel I need an additional 30 or maybe a 40 amp mppt controller when when i use that panel.

I was looking at the bogart 2030 charge controller but it only go to 30 amps which would not be a problem now but woiuld be limiting in the future if i decided to add another panel or two. ( according to mornngstar String Calculator the 45 amp can do up to 800 watts)

the Mppt I am looking at is on amazon EPEVER 40A MPPT with remote and temp sensor cable. I can get it will wireless dongle to help set it up..

[pianotuna]

Hi,

Only if the battery bank were changed to 24 volts would a 24 v dc to 12 v dc converter be needed.

I would not do that in your shoes.

I would get a much larger fully featured MPPT controller.

carl2591 wrote:
while i do have two panels i as planning on only using one of them and it sounds like that is all the MPPT can handle. and using a 12 v volt system. In reading the article posted it appear I might need a DC to DC convertor to lower voltage?

[MrWizard]

No DC to DC converter is needed, thats what the mppt charge controller does
connect to the battery first, when the controller sees it is on a 12v system
it will use thee correct 14v charging, some older controllers need you manually select the settings via switches,

a 12v battery is not 12v, it is over 13v at full charge and 12v is 50%
that is the improvement of 100+ years of battery technology

you don't charge a battery at 12v, it takes 14+v to do it right
thats 280w output, input must be greater
335w is about perfect for a 20amp controller

you will need different controllers for the different panels
the different operating voltage of panels is too great

the output side of the the separate controllers/panel systems
can go to the same battery bank
the panels will ever 'see' each other, never be connected together

the controllers need to have the same voltage settings for best operation
same charge voltage same float voltage

[carl2591]

That is what i am seeing. Looks like i need either two 30 amp cc or a 60 amp one.
If i go 30 which would be better mppt or pwm. The other panels equal 360 watts at like 19 volts and the 335 is 40 volts.

[Ed_Gee]

carl2591 wrote:
while i do have two panels i as planning on only using one of them and it sounds like that is all the MPPT can handle. and using a 12 v volt system. In reading the article posted it appear I might need a DC to DC convertor to lower voltage?

No. You certainly don’t want to clutter the system up with unnecessary items. You don’t need a DC Dc converter. A Solar charge controller IS essentially a DC DC converter. Do as most here have suggested and just get a decent MPPT solar controller than can handle the current on your panel! As already pointed out, the solar controller you already have can NOT handle the current from just one of your 350 Watt panels.

[carl2591]

while i do have two panels i as planning on only using one of them and it sounds like that is all the MPPT can handle. and using a 12 v volt system. In reading the article posted it appear I might need a DC to DC convertor to lower voltage?

carl2591 wrote:
I was gifted a couple of 335 watt solar panels the produce 46.3V Voc, 37.9V Vmp, 8.8A Imp, 9.36A Isc.

I have a 20 amp MPPT controller that might work but not sure as the info show 12 or 24 v operation. Is this considered a 24 v system??

This is going on camper shell to provide extra power when needed or if RV parked in shady spot. I was going to mount this spare MPPT and take some wires out to a connector so i can plug in large panel to put power to mppt controller to help charge up 2-6 v batteries. (12V)

there will be several 12v panels of about 360 watts total which could be wire in series to make 24v system but do to shading issues my stay parallel. '

Not sure the best way to go on this system.

I have checked voltage and with full sun it at like 46 volts DC (not hooked up to any thing just the leads)

[pianotuna]

carl2591,

Think of it this way. The existing controller can do 20 amps output at a nominal 12 volts. That is only 240 watts. The panels are simply too high a capacity to be efficiently used with such a controller.

If the RV battery bank were changed to 24 volts, then the controller could handle just one of the two panels.

Here is an article to perhaps help: https://freecampsites.net/adding-solar/

[MrWizard]

It's a 12v system
37v 8.x amps
CC to battery voltage 14.x,
Max output for (1) panel to battery approx 20 amps
For two of the panels you will need another controller either another 20 amp
Or a single larger controller

[Lwiddis]

“but do to shading issues my stay parallel.”

If you mean “might stay...”, real world RV camping has shade issues unless you never stray from NC deserts. lol Parallel is the better choice.

[Lwiddis]

My 30 amp WindyNation MPPT is limited to 400 solar watts 12 or 24 volts.