When we bought our Airstream Flying Cloud 23FB last year, we had the dealer add the Airstream solar option. That was a single 80 watt (6.67 amps) solar panel mounted on the roof. It is really nice, and we want to increase it. I see that the solar controller is rated up to 25 amps. Since 3 panels (240 watts) at 12v is 20 amps, the controller should handle it.However, looking at the wiring diagram, it looks like the wire from the panels to the controller is 10g wire fused at 10 amps. The wire from the controller to the battery buss is 12g wire fused at 10 amps. If we go to 3 panels, the 20 amps of charge are way too much. Even if we only go to 2 panels, the 13.34 amps is too high.Can we bump our solar up? And if so, how high? We REALLY want 3 of those 80 watt solar panels on the roof.

You'll have to increase your wire size or go series and get a controller to handle the voltage.

Why is the panel-controller wiring fused @ 10 amps? Replace the fuse with a 30. On the controller-battery wire, replace it. It should be a short run, anyway.

An 80w panel normally has an Isc of about 5 amps, which is what you would expect to see with it aimed right at a high sun. 6.67 amps if that is what you are seeing at the battery, could mean you have an MPPT controller with the batts very low to get that many amps, or else your panel is more like 110w. with an 80w panel, you would normally have a simple PWM controller.Anyway, yes you can increase the solar. But first confirm which controller you have now by brand and model, and also if you can, which panel you have. Then we can spend all your money on suggested upgrades. :)

#10 wire? +1 for just increasing the fuse. Actually you can just delete the fuses as the panels will never generate enough to be an issue. 30 or 40 amp fuse near the battery is all you need.Increase wire size only if you find you are not getting the power you expect and it is due to voltage drop in the wire.

All of this information is coming from the Airstream schematics. The TT was pre-wired for solar like this. Now, replacing that 12g wire from the controller to the battery is doable. They are in the same, easily accessible, compartment.

Wanting to increase our solar | Good Sam Community

19 Replies

doughere
Explorer
Oct 31, 2018
You probably have a PWM controller; but check. If you have a PWM, the #10 from the panels to the controller is OK (not great). Change the 10 Amp fuse to the controller to a 30, but leave in as it is important to be able to disconnect the panels if you are working on the battery (it is important to connect the controller to the battery before the panel to the controller). Change the wire form the controller to battery to #8 if possible (#10 OK), leave the fuse in fused at 30 Amps.

Doug
2oldman
Explorer II
Oct 30, 2018
Bobbo wrote:
. I will talk to Airstream, and if they say it is doable, I will proceed.
AS won't know any more about ampacity than a chart.
Bobbo
Explorer III
Oct 30, 2018
MrWizard wrote:
yes you can goto 3 panels, 10ga will be fine for 18amps, 10ga is rated for 30amps
you will get more voltage drop from panels to controller than you would with larger wire, but larger wire would be excess wasted $$ unless you also changed the solar controller to MPPT

the panels put out 18-22v, but the controller charges at 14+

you do not need to change the controller and wire
you 'can' thats a -future- option, but it is not required
what you want to do (add 2 more panels) will work with out changing anything else

Thank you. Anything that helps is good. I realize that the wiring may not be optimal, but it will be better than what I have right now with only one panel.

Changing the 12g controller/battery wire is a piece of cake. Changing the 10g roof/controller is not. I will talk to Airstream, and if they say it is doable, I will proceed.
MrWizard
Moderator
Oct 30, 2018
yes you can goto 3 panels, 10ga will be fine for 18amps, 10ga is rated for 30amps
you will get more voltage drop from panels to controller than you would with larger wire, but larger wire would be excess wasted $$ unless you also changed the solar controller to MPPT

the panels put out 18-22v, but the controller charges at 14+

you do not need to change the controller and wire
you 'can' thats a -future- option, but it is not required
what you want to do (add 2 more panels) will work with out changing anything else
red31
Explorer
Oct 30, 2018
here's the specs of a low Vmp 80w solar panel
note that max power watts / Vmp = Imp
Max Power: 80 W
Open Circuit Voltage (Voc): 21.0V
Short Circuit Current (Isc): 5.36A
Optimum Operating Current (Imp): 4.65A
Optimum Operating Volatage (Vmp): 17.0V

Dimensions (inches): 39 x 20 x 1.33
BFL13
Explorer II
Oct 30, 2018
Bobbo wrote:
All of my information is from Airstream brochures. The brochure says the panel is an 80 watt panel, so I just divided 80 watts by 12v to get 6.67 amps. I don't currently know the brands of the panel or the controller. I am going to be in that compartment in a few weeks when I install a 200 amp latching disconnect relay between the battery and the inverter. (I am tired of going outside to use my Blue Sea disconnect.) When I am in there, I can get the controller information. I will have to grab a ladder and go up on the roof to find out what panel I have. It will be a few weeks before I am able to retrieve all of that information, so we can let this thread lie for a while. I will be studying in the meantime.

OK, now you know your way of getting the amps is wrong.

You can put your own eyes on what controller you have, and report that. You will not be able to see the panel label with its specs if it is mounted on the roof. You could get an idea of what it can do if you have an ammeter and are in full sun (as much as you can be with it flat and your latitude and time of year)

Thing is, the answer is still yes. You can have more solar. Just a matter of the details.
pianotuna
Nomad III
Oct 30, 2018
A fuse is a disconnect. But it is not a switch. It is unnecessary to fuse between the controller and the panels. Be sure to get a switch rated for 30 amps DC.

theoldwizard1 wrote:
pianotuna wrote:
I would replace the 10 amp fuse between the panel and controller with a dc rated disconnect switch.

By electrical standards, a fuse IS a disconnect !
theoldwizard1
Explorer II
Oct 30, 2018
pianotuna wrote:
I would replace the 10 amp fuse between the panel and controller with a disconnect switch.

By electrical standards, a fuse IS a disconnect !
Bobbo
Explorer III
Oct 30, 2018
All of my information is from Airstream brochures. The brochure says the panel is an 80 watt panel, so I just divided 80 watts by 12v to get 6.67 amps. I don't currently know the brands of the panel or the controller. I am going to be in that compartment in a few weeks when I install a 200 amp latching disconnect relay between the battery and the inverter. (I am tired of going outside to use my Blue Sea disconnect.) When I am in there, I can get the controller information. I will have to grab a ladder and go up on the roof to find out what panel I have. It will be a few weeks before I am able to retrieve all of that information, so we can let this thread lie for a while. I will be studying in the meantime.
Lwiddis
Explorer II
Oct 29, 2018
Does ANY RV manufacturer do solar correctly? Nope not even AS. Cheapout on wire size.