How much solar power needed for?

[icanon]

Hey everyone! I do a lot of astronomy and planning to go on the four day 'off grid' trip. I'm wondering how much solar power do I need? Basically just need to keep my 12V RV battery charged. I just need the battery to keep the propane fridge, water heater running and water pump to shower with (no microwave, a/c, or TV). So how much of a solar power kit do I need?

Thanks. 🙂

[icanon]

Thanks everyone who replied. As soon as I do I will get back and let you know how things worked out.

[CA_Traveler]

smkettner wrote:
I would go with the free 40w and an extra battery. See how you do.
I doubt you need a controller needed in use.

Good suggestion.

If you are going to leave it connected at night then add a diode so that the panel doesn't draw power from the batteries.

[time2roll]

I would go with the free 40w and an extra battery. See how you do.
I doubt you need a controller while in use.

[2oldman]

icanon wrote:
Can I solar charge a battery while the battery is in use?

Of course, it's no different from any other kind of charging.

[icanon]

Fishbreath wrote:

If you are in Canada, this might not work, especially this late in the year.
A 40 watt panel will probably not be enough.......
Let us know what you decide.

I do live in Canada. I try setting up last week in a fairly dark area but was able to get electricity in which it got me thinking I wanted completely dark preserved area and found some in my future travel next summer so I preparing for it. I don't want to prepare in the last minute, I want to get everything installed and working. I have a celestron Schmidt-Cassegrain telescope with two power packs.

[icanon]

Love some of the suggestions you guys gave.

For example turn off hot water until needed, trying a dry run in driveway. I don't need lighting in TT at night as I'm doing my astronomy and want to keep my eyes adjusted to the dark, also I have rechargeable led lantern, in which they will be fully charged and good for serveral hours but don't require them remember want to keep the area as dark as possible so I can keep my eyes adapted to the dark. Also never thought about the detectors and how much and how many amps it requires.

I guess adding another panel would be helpful? Can I solar charge a battery while the battery is in use?
Again thanks you guys have been so helpful.

[CA_Traveler]

Don't put 12V batteries in series as you then have 24V. Parallel is OK and the connection can be switched or not. If switched then you know that you have a fully charged battery on standby.

[wbwood]

Get some portable battery or solar lamps/lanterns to use inside at night as needed. Keep hot water and water pump off until needed. If you keep the hot water heater on, it will use electricity to spark the ignitor to try and keep hot water. How water will remain in your HW tank for hours when you turn it off. Just turn the the HW tank and pump on when you need to. You can avoid the fridge issue also if you just take a cooler. Matter of fact, hit your battery disconnect when not using anything in the trailer. It will turn off your detectors as well. But you won't need them if you don't have the propane running or using electricity. More or less, you will just be in the trailer like it's in storage. I would definitely add a second battery, it will extend your time. But if you can limit yourself to camp down to more barebones and turn things off when not needed, then it will help.

Otherwise, carry a generator or get at least 100watts of solar. 40 watts, might top off your battery in a day if you don't have anything pullign power while you are doing it, but you would probably need to not less than at 70-80%. A generator can have them charged back up full in an hour or so, depending on how low you drain them.

We are rather new to the dry camping thing and have been reluctant at doing it, but we are doing it more and more and realizing what it takes and what we can do to make it better.

[Fishbreath]

I'm all for having the solar panel as a portable. That way you can optimize the amps by moving it to face the sun.
For several years I used a 185 watt panel to keep my batteries up in a 28 foot toy hauler. (No TV, Microwave) I camped for weeks and the batteries were charged up every afternoon. I never camped north of Oregon in the summer though.
If you are in Canada, this might not work, especially this late in the year.
A 40 watt panel will probably not be enough.......
Let us know what you decide.

[JiminDenver]

40w isn't much, then again with your usage it might be enough to make it through the four days without having to recharge. Maybe try some driveway camping to see what happens. Very nice of your neighbor.

Do you have LED lighting? They can be had for a few bucks each and one or two in the most used lights would make a huge difference.

[Muddydogs]

icanon wrote:
Now I'm a little confused. Some say ok others are saying the opposite.
Remember it's just to keep the propane fridge, propane water heater and for the water pump for the shower. No lights, microwave, a/c and no furnace just the bare minimun.

Another question: do I put the batteries in series or hook up the battery to the TT one at a time?

Thanks

You are also powering the co and propane detector and while not a lot most people figure it takes 15 to 25 amp's a day to power a trailer just to run the detectors and fridge. Propane water heater is very minor power usage.

So I assume you probably have a group 24 deep cycle battery which at best has 80 amp hours of juice. To get the best battery life you should only run the battery down 1/2 way so your looking at 40 amp hours of battery life. If you figure it takes 20 amps a day to keep your trailer alive you have 2 days on one battery with no water pump or lights and 4 days with 2 batteries and no water pump or lights. Now you might say well I will just run the battery until its dead and recharge it, well that's fine but once you get below 12.0 volts some things start to wig out in the trailer and you just might be awaken in the middle of the night to your propane or CO detector going off due to low voltage.

The 40 watt panel will help and if you have good sun might just get you through the 4 days but in the reality of things 40 watts of solar isn't much.

[icanon]

Now I'm a little confused. Some say ok others are saying the opposite.
Remember it's just to keep the propane fridge, propane water heater and for the water pump for the shower. No lights, microwave, a/c and no furnace just the bare minimun.

Another question: do I put the batteries in series or hook up the battery to the TT one at a time?

Thanks

[garyhaupt]

Your sig ays somewhere north of the border....does that mean you are in Churchill, Manitoba? If so...you are hooped. On the other paw...if you mean you in someplace warm and sunny? Go do it. Just keep the panel alingned to the sun. And switch out batteries...4 hours for one, four hours the other. And don't use the furnace..open the oven door and light'r up. Or a top burner. That furnace fan is killer.


Gary Haupt

[2oldman]

Barely