How much solar power is needed

Herg · July 2020

I am thinking about getting solar. How much do I need to run for a couple days without hooking up to electricity or the truck? I will most likely only run a few lights and the fridge. Thank you

pthomas745 · July 2020

You don't know what you need until you know what you want to use. The trailer is pretty easy on power in most cases, but the biggest draw will be the fridge. Do you have the 2 way or 3 way fridge?

I see you have another thread with your battery issue. The size of the battery is a factor, too.

Try this blog by an owner who worked out a lot of things about battery management and solar and it will help getting a handle on it.

Battery management

https://jenngrover.com/guilty-as-charged-rv-battery-use-management/

Solar

https://jenngrover.com/category/tb/solar/

Marceline · July 2020

To some extent it depends on the capacity of your battery. If you have sizeable battery capacity (more than 100ah) you might be able to get away with a 100w solar panel. But I would recommend getting a bigger panel (at least 160w) since you want to run your 2way fridge.

Herg · July 2020

What’s the difference between a two or three way fridge?

pthomas745 · July 2020

Fridges can run off of "shore power", 12V power, or propane. A three way fridge can run on Propane/Shore/or 12V. A two way fridge can run on 12V or shore power.

The 3 way fridges on 12V are not very efficient, (about 11 amps per hour?) and are normally run on propane.

The 2 way fridges on 12v are much more efficient (about 3 amps per hour). As Marceline points out, many owners use larger batteries and more powerful solar panels and the 2 way fridge on 12V works just fine that way.

AirBoss · July 2020

Two way fridge runs on 2 of the three possible power sources...12V (battery), 110V (shore power), and Propane. A 3-way runs off all of those.

AirBoss · July 2020

FYI, the factory installed Victron solar system puts out just under 200watts. There are several 200W solar "suitcases" out there that would likely be more than adequate for your purposes.

Herg · July 2020

How would I know what I have? Just got it a week ago

AirBoss · July 2020

Look for manufacturer and model number plate. A google search or perhaps someone on here can assist. It's likely a 12V/110V fridge that doesn't run on propane, but that's not a given.

Sharon_is_SAM · July 2020

@Herg, the clamshell TaBs only have 2 way refrigerators. You have a 2 way.

Check your battery to find your available amps. Did the previous owner upgrade the battery?

MarkAl · July 2020

The above are all good suggestions / answers. But it will mis-lead you to either spend too much money for your needs or put the money in the wrong place. Not to scare you but for every system you need to watch your energy bank account. Every trip starts with a full charge on your battery.
1- you drive to a campground and hook into their power - you maintained your bank account and have enough power
2- you drive to a sunny open campground and position your trailer or solar panel to receive the sunlight
a- Your bank account starts growing
b- Turn on the high current refrigerator, your computer with the monitor
c- Sun goes down, Your bank account is going down fast
d- By morning your bank account (battery) was large enough to withstand the night's withdrawal and you leave to go home and recharge your account
3a- You live in the Pacific Northwest where the moss grows heavy for a reason and setup your trailer and solar panel to catch any available light
a- Your bank account is savings only and doesn't grow
b- Turn on your high current refrigerator .... and
c- Next morning you're broke, the battery is dead and the breakfast meat is warm in the refrigerator
3b - You bought a Lithium battery!
a- You may have dodged the bullet today but it's a two day trip...
3c - You crank up the generator and supplement your account (battery) but you have to deal with the noise

There is no single answer. You need to know
1 - How much Energy (Amp * Hours) is available (stored) in your battery
2 - How much Energy you expect to use in 24 hours (1 day)
3 - How many days you need the above to last
4 - How do you replenish it or do you need to.

NOW you can ask about battery capacity, solar and or generator:

I - Solar is not an efficient way to replenish this energy but it's cheap (and quiet).
a - Every AMP*Hour you have as a deficient must be replenished before you hit your battery's storage capacity.
b - A 120 watt panel (for simplicity) produces 10 AMPS an hour but only when the sun is directly shining on it. If in one day your deficient is 20 AMP*Hours then 2 hours will replenish your account or at least limit the deficient.
c - The above may be enough if your trip is short or if the next day is much sunnier
II - Ultimately every dry camper must have a plan for their worst case trip
a - That could involve a generator, large battery or a second solar panel for more efficient energy production
b - Be aware of the current capacity and expected duration: battery monitor that includes a current "shunt". The monitor may be a meter (Victron BMV712 and others) or just the shunt but broadcasts to a smartphone the current energy accumulation (Victron Smartshunt).

Our "plan" is not in place yet as we are still learning but we expect a second portable array for spring / summer and move to a generator for winter and maybe fall use.

Sharon_is_SAM · July 2020

@Herg - @AirBoss has a 400, so the factory installed solar is 190 watts. The clamshells roof space is more limited and the factory installed solar is only 130 watts.

Start with looking at your battery and we can help you from there. You said you only need a couple of days. We need to know how much you plan to use your lights, water pump, Alde, fan, frig, etc. If you only plan on boondocking infrequently, you may be better off using other options such as: portable solar Lucci lights, a good cooler (can last multiple days), flushing the toilet with a jug of water, heating water to bathe, etc.

AirBoss · July 2020

@Sharon_is_SAM
Good point...I was approaching this as since it seems he doesn't have factory solar he'd likely be going with a suitcase and the reference to the wattage was a guide when he considers which one to purchase. Price is of course a driver but on some models the delta between 130W and 200W is nominal.

This forum is such an incredible resource. Even when posting in an effort to help others, one is also helped! That is a sign of a true forum family!

1991sb · July 2020

Where do I find the specs on the solar roof package installed on my new 2021 T@B 320s? Is that the 130W Sharon_is_SAM mentioned?

Sharon_is_SAM · July 2020

Yes.

ChanW · July 2020

@MarkAl,👍👍!! Does that work if I interface my solar with my online bank account? (If only...!)

Herg · July 2020

I will not be running the air as it should be cool enough not too. A few lights pump once in a while. Maybe stereo. Will take showers elsewhere

ontheroad · July 2020

@Herg...you wouldn't be able to use your a/c unless hooked up to electric ...your 2way fridge will be the hungriest of all your battery power...we have a portable system that we take with us that can be set up, all you need to do is connect to your battery, we have a solar port, easy connection. As others have posted Jenn Grover's battery management is a must read..see link above..

Sharon_is_SAM · July 2020

@Herg, you need a shorepower hookup or generator to run the air conditioner. Having said that, if you have the stock battery with only about 75 amps and you plan on running the frig, pump and lights on battery (Friday on propane), a lot of owners get away with a portable 100 watt panel as long as you have a lot of sunlight. You should take a look at the chart from jkjenn so you know what uses a lot of power - like the porch light, the light over the counter or the Fantastic fan at higher speeds. Do you have a way to monitor your battery besides the SeeLevel?

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