Originally Posted by Summer2Go
I'm not expecting air conditioning, just enough power to run fans, lights, and water pump, ...maybe a TV for movie length of time. We will drink tea instead of coffee, and not use the microwave, or toaster oven. I want to know more about the Zamp outlet on the new Roo. Does it automatically charge the battery when the panels are plugged in? Does the camper's inverter handle everything? Would it help to get bigger panels? I'm thinking bigger panels will certainly create more charge, and charge faster. So maybe an 80 watt Zamp panel set, instead of 40 watt. 100 or more watts might be overkill for our usage?
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Ok - good that you are not trying to run air conditioner.
Fans, lights, water pump and entertainment system run on 12v. You could calculate their draw based upon their specs and your expected usage.
TV is 110v so you would need an 12v-110v inverter to use it.
Keep in mind that the trailer's "converter" takes 110v and converts it to 12v to power all the trailer's 12v draws and also to charge the batteries - when you are plugged in to 110v or a generator. It does not supply 110v back out to anything unless it is being powered itself by 110v.
To use a 110v appliance when you do not have 110v coming into the trailer, you need a 12v to 110v "inverter". Your trailer does not come with one as a default. An inverter needs to be matched to the draws you plan on placing on it, your battery bank's capacity and the required wave form of whatever you are planning on running from it. Some will work with a modified sine wave, others may require a pure sine wave.
I know all of this sounds complicated - because it is - at least until you get your head wrapped around it.
As for panel size, battery capacity, inverter size, etc, there are two ways of getting to an actionable answer.
One is to measure and calculate your usage/needs add a fudge factor and buy accordingly. This is the smart, right (and hard) way to do it.
The other way is to make some estimates, listen to what others are doing and make a WAG as to what you should do - and then buy accordingly. You may end up buying more or less then you need, so keep that in mind.
Here is what we run:
1 group 31 12v Interstate marine battery (called a deep cycle but marine batteries are not true deep cycle)
1 group 27 Interstate marine battery (carried as a spare)
200w of Renogy flex solar panels into a 30A PWM controller
1 400w Pure Sine Wave inverter to power the TV (LED TV is very low power)
We also have a generator that we sometimes bring and will be switching over to dual 6v deep cycle batteries when these marine batteries wear out.
On sunny days with our current set up, we typically have fully recharged our batteries by early afternoon. This is with moderate overnight use of the furnace (the biggest user of 12v power), heavier use of the water pump (typically 3 showers + dishes etc). Fans and lights. We are used to saving resources (as we moved up from a PUP) but are not energy misers.
So this set up works well for us in our typical usage. I've even stopped carrying a generator for most trips.However, last weekend we got caught in bad/cold weather and could not use our solar, and ended up draining both batteries and borrowing a generator for a few hours as a result.
But to answer one of your questions directly - yes bigger is almost always better when it comes to battery and solar capacity. I wouldn't bother with anything under 100w. The savings aren't there and you'll likely want to add more (probably matching) panels in the future. I would rather have 3 panels to get to 300w rather than 8x 40w - as an example.
Hope that helps some.