When I purchased my RV from Camping World they never told me anything about the solar panel on the roof and the inverter. I know now that the residential refrigerator runs off the two batteries that are charged from the solar panel or shore power, but the inverter is in the off position and has to be turned on manually, I assume. I would think that if we lost shore power it would automatically switch on the inverter. I’m trying to understand the solar system and the RV, and if I should upgrade the 100 W panel to a bigger panel. I heard that there’s a 300 W or 350 W panel available now. —Joseph, Cedar Creek 38ftk 43’
I cannot find the model you have listed. However, it seems that Forest River uses a 1000W inverter in most of their larger 5th wheel units. Typically these units have a 12-volt cable coming from the battery to the inverter and an automatic transfer relay that determines if you are plugged into a 120-volt source such as the campground pedestal or generator. When 120-volt power is present, the transfer switch goes into pass-through mode and allows the 120-volt power to pass through to the appliances that the manufacturer has determined need AC power while boondocking. Typically this is a residential refrigerator and a few outlets such as the TV. Some manufacturers are now running the line to the bedroom for outlets for CPAP machines.
When there is no 120-volt power being supplied to the inverter, the relay switches and draws 12-volt DC power from your batteries and inverts it to 120-volt AC power to supply those chosen outlets. And, yes, it does have to be turned on. You would want to always leave the inverter on so it can switch, as you indicated, except during storage.
Size of solar panels
Let’s take a look at your other question about the size of your solar panels. You state there is a 100W panel on the roof and two house batteries. The first question is, what size batteries and what condition are they in? If they are lead acid or AGM batteries, you will only be able to draw 50% of the listed amp hours. So if you have two 100 AH batteries connected parallel, which is positive to positive and negative to negative, you will have 200 AH but can only use 100 AH. If you have two 6-volt batteries connected in series, which is positive to negative, it will give you a 12-volt bank but does not double the amp hours. So you would only have 100 AH and can only use 50%.
I know it’s confusing and nobody told you that there would be math required. Well, we are not done yet! If you have two lithium-ion batteries, then you would have 200 AH and can use almost all of the available amp hours.
How long will you run unit with just batteries?
The answer to the original question depends on several factors, starting with how long do you estimate needing to run the unit with just the batteries? Keep in mind when the power goes off or you are dry camping, you will be using other 12-volt components, so you need to calculate what will be used and for how long. This is not a perfect science as it is difficult to guess what might be running and for how long. Go Power! has a good calculator sheet that will at least help to identify these components and calculate what size solar panel system as well as battery power you need. Download a copy here.
If you have two 12-volt lead acid batteries, you will not be able to run the refrigerator very long, and the 100-watt solar panels will not be enough to keep up for very long. If it’s just overnight, it might be fine, depending on the condition of your batteries due to sulfation.
According to the Zamp Solar website, they do offer a Forest River 100-watt kit, which seems to be what you have on your rig. You can add a second 100-watt panel or go bigger. However, I would also suggest looking at adding a portable model. This would allow you to park the rig in the shade. That helps keep the rig cooler during hot temperatures, and you can put the panel out in the sun to provide a charge. Both Zamp and Go Power! have the permanently mounted panels as well as portables. They are both owned now by Dometic.
You might also enjoy this from Dave
Why aren’t my solar panels charging the house batteries?
I have solar panels to help charge the house batteries while boondocking, but after a couple of days the house batteries are dying. I turn on the engine to recharge the house batteries, but often it won’t charge them, even if I let the engine run for 15 minutes or more. Sometimes it charges as soon as I start the engine. What’s going on? —Brian, 2017 Leisure Travel Van (Unity)
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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