So i have been down the rabbit hole but want to be sure i understand what I have absorbed… I have a new RV that has two 200 watt solar panels. Reportedly these put out 18-20 volts which should be 10-11 ish amps. They are in parallel, so Volts doubles but amps stays the same…I think. Or is it volts stay the same but amps double?
It has a gopower solar controller and I want to change to a victron. Sizing I am thinking 100/30. I will not be adding more solar to the roof/solar controller. Can/should I add a mountable display to look at the marvels of the soalr controller process or is the app adequate?
There is no PV isolator in this system, yes, comes that way, and I want to add one. Is there a preferred cutoff device? I am going to mount this between PV and controller.
I am getting rid of the 100 aH wet battery and going in with a 230aH lithium.
Finally, should I leave the panels as parallel or should I go in series. I believe the controller at 100/30 should handle either. I understand parallel is less efficient than serieal for hours available to charge, parallel has to match the charge voltage before charging takes place where serial will charge when any light is available and the MPPT should manage the voltage.
Is there anything grossly wrong with my thoughts on this? Any further advice or considerations? I don’t forsee more solar on the roof, there maybe a solar suitcase of 100watts with separate controller, plugged directly to battery, haven’t decided that. Thanks everyone in advance! Scott
The 100/50 is exactly the same size as the 100/30 and not much more expensive. If you voltage match the ground mount with the roof array, you could parallel them as well. As soon as you set up a solar system, the first thing you want is more solar and a larger battery.
The panels in parallel work fine - the voltage stays the same and the current doubles. If you want to disconnect the solar, you’ll need a DC breaker. Something like a Noark, and it needs to be rated for 1.4 x the solar current. So if you have 20A of solar, you’ll need a breaker rated for 1.4 x 20 = 28A. A 32A breaker will work for this example - Noark 32A 360VDC 2 Pole MCB Ex9BN - N84453.
Parallel is best for shading conditions. If you series connect panels and one gets even a little shade, the output will drop to match the shaded panel. In parallel, the shaded panel might drop to say 2A while the unshaded panel still produces the full 10A - so the total into the controller will be 12A instead of being limited by the weakest panel.
Thank you Owen, Great information. Unfortunately threre isn’t an “easy way” in the premade rv to get the suitcase in parallel to the system so if I want it will be someother solution. We are looking for being able to be off-grid for only a couple of days at a time. SO i think this will be more than adequate for fridge, a few lights, slides, and a water pump. Shade is an issue and I understand parallel is better for that. Thanks again!
As for the choice between series and parallel it’s important (besides the shading) that the MPPT will only start working once the panels reach battery V + 5. So if your battery V is around 13V, the panels need to produce at least 18V to start charging the batteries.
If shading is not a big factor (e.g. you expect that both panels gets shade at the same time), I would choose series.
You can add a screen, but that means an extra investment to get a Ekrano GX (or Cerbo Gx plus screen). The alternative route is a raspberry Pi plus screen. If you get a Smartsolar MPPT you can connect easily with Bluetooth to see the fancy stats as well.
Be carefull with replacing a lead acid or AGM battery with Lifepo. The alternator will overload when charging without the Orion DC-DC charger in between. the Lifepo 230Ah Will probably want to charge with full capacity of 200Ah or more while the alternator can only deliver less than half.
Huib, I have heard mixed stories on this. How do I block my alternator from charging my lithium battery? I do have a ford F350 but no idea what sized alternator it has. thanks for any info you can offer. S
The best solution is buying an victron Orion Dc-Dc charger and put it between the starter battery and the lithium battery. Very easy setup and you can manage the voltage and the current for charging the lithium battery. This also prevents the starter battery from being discharged by the lithium battery
