Mixing Poly and Mono panels.

[mikakuja]

I currently have 2 100w mono panels with an EPsolar 20amp mppt controller and MT50 display and 2 6v Trojan GC batteries mounted in my RV. (The solar controller is capable of 260w max with 12v panels).
I was poking around CL today and came across a great deal on 50w panels and thought that it would be nice to pick one up for that little extra power. The problem that I ran into is that the panels ended up being Poly......
Now my experience with solar is limited but from what I understand mono and poly panels react differently in heat and cold as well as low light situations. My question is, is there enough difference on a lower power system like mine that it would negatively affect the system? Or should I just stick to Mono panels?

Any advise would be great.
thanks

[Almot]

You're far from maxing it out. Unless you drive to some place high in the mountains, but in BC there isn't much need usually.

Get 4*6V if trailer tongue can carry it. You'll be getting less amps on cloudy/rainy days, bigger capacity will help.

[time2roll]

There is no poly and mono electricity. If the Vmp spec is close the MPPT will be fine.

[mikakuja]

Well, I couldn't leave well enough alone, just had to max out my controller @ 260w 12v.... Just ordered a new 60w mono panel, mounting hardware and mc4 connectors... Should be here some time next week... Now to make the decision on the possibilities of 4 6v's instead of two...
And yes, panels all wired in parallel...

[Almot]

RJsfishin wrote:
Any 20 amp controller will handle the reality of 250 watts

Duh :).

Wire gauge will be important then, 2*100+50 would have to be wired all in parallel.

[RJsfishin]

I would never connect the panel directly to the battery.
Any 20 amp controller will handle the reality of 250 watts, and probably even 300. I have never seen over 16 amps out of my 290 watts.

[Almot]

Yes, one could live with 200W on a sunny day. As long as you don't plug in all the wall chargers at the same time - you're right about that.

I wouldn't connect 50W panel directly. Batteries need to float at correct 13-something voltage. Yes, like Fred said, you can put a switch and shut this panel off when it goes into Float, - if this kind of pain is alright with you.

[christopherglen]

Like Golden_HVAC said, hook the 50 watt directly to the batteries. If the batteries are full, the controller on the 200 watts will throttle them down, and with the propane detector, radio memory, and who knows what other phantom loads the batteries will be fine. Ignore the voltage on the panels (as long as it is above ~15 volts) and go with the AMP rating. Being used assume ~80% of that rating as a max, likely less by the time you mount it to the roof and wire it.

[mikakuja]

I would agree that 50W is hardly worth the trouble. However, if I can acquire a panel cheap enough that extra 3ish amps makes a difference with limited optimal hours of sun. If I was certain that I could get away with it I would go for another 100w panel... My luck I would fry the controller and end up having to buy a new one... Actually, the 200W system doesn't do a bad job keeping things topped up (if my wife and kids don't plug in everything that needs charging at night using the inverter). For me it's just knowing that I have the ability to squeeze a few more amps that makes it tempting to add a panel.

As for installing a second cheap controller and or no controller with a switch... Thanks, but no... I would rather upgrade my current controller. While this might work just fine, I wouldn't be happy with it.

[Almot]

When in parallel, mismatched currents of mono/poly are not important.

But I think 50W is not worth the trouble. Get some down blanket, run furnace less, and you'll recoup those extra 10-12 AH. Or use propane heater. Convert all lights to LED if you haven't done so.

If you are really energy-hungry with 200W (it's hard not to be, where you are), then get another 100W and replace controller with 30A. I wouldn't buy unknown controllers from Ebay or Chinese Amazon-type hubs like Ali.

[Golden_HVAC]

Why not buy a 20 amp PWM controller for $13 for the extra panel?

Or install it without a controller at all. It will only put out about 3 amps at 17 volts, so it should not overcharge the battery significantly. You can install a switch to shut off the 50 watt panel when you are not camping, or if the battery is full.

Your CO detector, propane leak detector and refrigerator will have a constant draw of about 1.2 amps, so if the 50 watt panel is putting out 2.5 amps (say noon and the battery is full for some reason) then the 50 watt panel will run the detectors and put only about 1 amp into the battery. That is not enough to even warm up the battery, or cause any water loss.

For reference your built in charger will still be putting about 1 amp into the battery once it is "Full" and it is resting at 13.5 volts.

I bought some 20 amp PWM controllers here. AliExpress.com Search for PWM 20 amp controller. Then search by price. Also check 'free shipping' if you like, it will probably give the best overall price. Some will sell a item for say $3.55 and then have $14.75 shipping to USA. While another seller might have the same item for say $9.55 with free shipping.

I bought a lot of LED lights there, and many other things, such as a dog collar that vibrates when the dog barks. Great training tool.

I also bought a dash cam, and a rear view dash cam combo with rear view mirror, it records both front and back cameras, displays the rear view in a 4" screen that is also a rear view mirror. $68 or so. It is a wired camera, the kind that I wanted for my RV. I extended the wires, and drilled a 1/4" hole to run the wire through the back sidewall, and then sealed with rubber roof sealant.

Good luck,

Fred.