Solar Panel battery charging

[Marsh]

Firstly we should know the basics of the solar. So to know the basics of the solar check out this guide which provides complete information.

[Sbrinson]

Kuba122- (GaryG - Kirkb),
Thanks for the great information. Having the numbers is very useful for the folks who'll use them. As you pointed out, having higher-wattage panels or multiple lower wattage panels improves the potential for successful off-grid use.

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Lengthy off-grid camping obviously involves minimizing battery power consumption. As mentioned earlier, the furnace blower was the prime power hog in cold weather. I usually set the night-time thermostat to its lowest setting, and used a cold-weather sleeping bag. I warmed things up for a short while in the morning when getting up and getting dressed and eating breakfast. Then I put the thermostat back down to minimum for the rest of the day to keep anything from freezing.

Note to GaryG. I've just replaced the controller board in my Atwood AFMD 25121-A furnace with a Dinosaur Model "FAN 50 Plus Pins" board. This has a blower control circuit that shuts the blower down after only 2 minutes if it detects a burner ignition failure. That would eliminate concerns about having a blower run for a lengthy time if TT battery power dropped too low to fire the burner.

Hotwater heater, refrigerator and stove are all propane powered, except for 12 volt auto-ignition. The 7-pin trailer connectors on the batteries facilitate easily disconnecting a low battery and juicing it up via the pickup's alternator while driving around.

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All of the lights in my older Coachman trailer were incandescent. To avoid the power penalty of using those things I acquired a bunch of battery-powered (AAA x3) LED puck lights that were used for night time illumination. They were/are also handy to mount inside various cabinets and pantry. They've continued to be handy in minimizing TT battery drain in the Starcraft even though all of the trailer's lighting is LED. I also acquired a 12-volt 19" flatscreen TV, which was also handy one time when an RV Park's power was interrupted by a storm. I also added several additional 12V outlets in the bedroom and kitchen areas, for cell phone charging and other uses.

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Kuba122 said : My system, now, is 200W and 20A MPPT with two batteries and a 300 Watt inverter for 110V.
What 110V items do you use in an off-grid mode? I have a 400 Watt inverter that I occasionally will use in the vehicle, not often in the trailer...and it is a hungry little critter, especially when the cooling fan kicks on.

A third 20-watt panel with a variable controller can be used to augment the mounted panels at 12 volts, or can be dialed-down to recharge 6 volt batteries for my game cameras, or further down to use it's USB port.

[kuba122]

My first system was 100W with a 20A MPPT controller feeding a single Marine Battery. The furnace draws 12 Amps (150 Watts at 12V). Depending how often and for how long it runs, You could have a significant hurdle to overcome. You could easily expend 300 Watt hours in one cool night for one furnace. My Marine Battery is 625 Watt Hours, so you see where this is going.

A 15 Watt Solar charger on it's longest, brightest, day will supply approximately 60 to 100 Watt Hours. Automatically you are in a deficit. In reality, though, one can assume 50% wattage replacement consistently, assuming you won't always have the panels pointed directly at the sun, and you will have cloudy days to deal with. So, 60 to 100 Watt Hours, just became 30 to 50 Watt Hours. Nowhere near enough to stay off grid long term. No more than a couple days running the furnace and your battery is cooked ....

If you are only powering LED Lights, you'll be fine for a longer term outing with 15 Watt System

There are several reasons to make sure the solar is disconnected from the trailer when towing, like has been stated, already. There is reason to have solar disconnected when shore power is connected (110V and 12V Ground is common and things can happen to cause problems with the solar, the trailer charger, or both. I have a DPDT (Double pole double throw switch wired in, along with a reminder light to prod me to disconnect.

My system, now, is 200W and 20A MPPT with two batteries and a 300 Watt inverter for 110V.

From the 2015 Starcraft owners manual:

120 Volt System
Air Conditioner 18 AMPS
Coffee Maker 6-12 AMPS
Converter (each) 8 AMPS
Curling Iron or Hair Dryer 10-14 AMPS
DVD System 3 AMPS
Microwave 12 AMPS
Refrigerator 6 AMPS
Satellite Receiver 2 AMPS
TV 2-4 AMPS
Vacuum Cleaner 8 AMPS
Washer/Dryer 12 AMPS
Water Heater 12 AMPS

Multiply Amps by 120 to get 120V system watts


12 Volt System
Aisle Lights 1.0 AMP
Baggage Compartment Lights 1.4 AMPS
Decorative Wall Lights 1.5 AMPS
Dinette Light 4.5 AMPS
Exterior Entertainment Center 5-7 AMPS
Fantastic Fan 1.5 AMPS
Fluorescent Double Lights -12” 2.0 AMPS
Fluorescent Double Lights -18” 2.5 AMPS
Furnace 12.0 AMPS
Generator Start 95.0 AMPS*
Halogen Light 1.7 AMPS
Illuminated Switch .125 AMP
Inverter variable
Leveling System 95.0 AMPS*
LP Detector .125 AMP
Map Light 1.5 AMPS
Porch Light 1.5 AMPS
Power Awning 10.0 AMPS
Power Vent 5.0 AMPS
Refrigerator 3.0 AMPS
Shower Light 1.4 AMPS
Step Cover 10.0 AMPS
TV Plate/Antenna Booster 1.0 AMP
Vanity Light 4.2 AMPS
Water Heater 6.0 AMPS
Water Pump 7.0 AMPS

Multiply Amps by 12 to get 12 Volt System watts - always round up!

LED Lights are typically less than 1W each. 10 fixtures = 10 watts is a good rule of thumb.

So, if you run all 10 lights (10Watts) for three hours you use 30 watt hours.

Don't forget your TV current, if you plan to watch, off grid.

[Sbrinson]

Gary, I probably should have been more specific about "breakaway brakes" in my initial post. Sorry for any confusion.

[Sbrinson]

Gary G said
Thanks for your response to my solar panel post. I appreciate the added info about the furnace running at night. I will watch this carefully. I am a bit confused as to why, when hooking up the trailer to the tow vehicle that you would be worried about sufficient power for the electric brakes? Does the trailer's brakes not get their power from the tow vehicle's battery and not the trailer's batteries? I would not have the tow vehicle hooked up to my trailer when boondocking either.

Hi Gary,
Keep in mind that the trailer's emergency breakaway brake system is powered by the trailer's on-board battery system. When working with
alternative charging systems (solar panels) and incorporating a shut-off switch or battery-selector switch, it is important to ensure that the battery
power to the breakaway break system has not been interrupted....especially before heading out on the road. The best surprise is no surprise.

[GaryG]

Hi Guys, I started using solar panels to top up batteries several years ago when I started using a travel trailer at our hunting camp, which is way off the grid. I mounted two 15 watt solar panels & controller on a frame made from 3/4" PVC pipe. The frame can be manually moved, and the angle of the panels can be adjusted for maximum sun exposure. At the time my Coachmen trailer did not have a battery shut-off switch, and I eventually discovered that the propane detector put a constant load on the battery that was sufficient to pull the battery down over a couple of weeks. I installed a marine-type battery selector/shutoff switch and used it to select which of two deep-cycle batteries would be powering the trailer and which would be charged by the solar panels....and to disconnect both from the trailer whenever it was sitting unused. You may already know this, but it is important to recognize that batteries connected in parallel (+ to +, - to -) will equalize so that they both have the same potential. This means having a fully-charged battery connected to a weak battery will result in the weak battery draining the strong battery. Consequently it is a good idea to have some method of separating them. Both batteries are in cases, and each one is connected to the switch with a 4ft. long pigtail utilizing a 7-pin trailer-type connector. This arrangement lets me put a depleted battery in the back of my pickup and connect it to the vehicle's trailer connector to re-charge it off the vehicle's alternator when I'm driving around. I moved the whole shebang over to my Starcraft Launch 24RLS when I upgraded trailers. The Launch does have the external connection for the solar system input, but this still requires having a controller metering the charging. Starcraft also included a shut-off switch, which is located in the front pass-through storage compartment.

For off-the-grid survival, your 12-volt furnace blower is probably going to be your most serious power consumer. If you are in extremely cold weather, low battery power will result in the blower starting-up... but the furnace's safety system will not allow ignition of the burner. If you are already asleep, the blower may run all night, causing further depletion of the battery. Important notice: As you experiment with whatever solar hookup you eventually decide to use, make certain before towing that power to the trailer's electric brakes has not been compromised. A small Volt-Ohm meter is a great item to include in your trailer toolkit.

Thanks for your response to my solar panel post. I appreciate the added info about the furnace running at night. I will watch this carefully. I am a bit confused as to why, when hooking up the trailer to the tow vehicle that you would be worried about sufficient power for the electric brakes? Does the trailer's brakes not get their power from the tow vehicle's battery and not the trailer's batteries? I would not have the tow vehicle hooked up to my trailer when boondocking either.

[GaryG]

Hi Gary. It seems like we are both starting our new trailer adventures at the same time. I drive from Burbank CA to Phoenix on Wednesday to pick up my new 19BHS. Will be towing with a 2016 Toyota Highlander. Will be interested in hearing how the solar panel works out. I have a question though. My understanding is that there trailers are "solar ready". Why do you (we) need anything more than just the panel and the attachments that come with it?

Thanks for your response to my post. If you are referring to the controller as 'anything more' some solar panels do not come with a controller, that is the reason I had to purchase one, otherwise, without a controller or regulator, the solar panel can possibly damage your battery because the 15 watt solar panel can generate as much as 22-24 watts at peak sunlight and that, over an extended amount of time can overcharge and ruin your 12 volt battery or even worse, melt wires, etc.

I'm taking my solar panel and accessories down to where my trailer is stored as soon as I get a nice, warm sunny day to try it all out. It worked great here at the house, but I didn't have it hooked up to a batter of any kind.

Best to you with your new starcraft. I'm sure you will love it like we do ours. Love to see some photos of it.

[Sbrinson]

Hi Guys, I started using solar panels to top up batteries several years ago when I started using a travel trailer at our hunting camp, which is way off the grid. I mounted two 15 watt solar panels & controller on a frame made from 3/4" PVC pipe. The frame can be manually moved, and the angle of the panels can be adjusted for maximum sun exposure. At the time my Coachmen trailer did not have a battery shut-off switch, and I eventually discovered that the propane detector put a constant load on the battery that was sufficient to pull the battery down over a couple of weeks. I installed a marine-type battery selector/shutoff switch and used it to select which of two deep-cycle batteries would be powering the trailer and which would be charged by the solar panels....and to disconnect both from the trailer whenever it was sitting unused. You may already know this, but it is important to recognize that batteries connected in parallel (+ to +, - to -) will equalize so that they both have the same potential. This means having a fully-charged battery connected to a weak battery will result in the weak battery draining the strong battery. Consequently it is a good idea to have some method of separating them. Both batteries are in cases, and each one is connected to the switch with a 4ft. long pigtail utilizing a 7-pin trailer-type connector. This arrangement lets me put a depleted battery in the back of my pickup and connect it to the vehicle's trailer connector to re-charge it off the vehicle's alternator when I'm driving around. I moved the whole shebang over to my Starcraft Launch 24RLS when I upgraded trailers. The Launch does have the external connection for the solar system input, but this still requires having a controller metering the charging. Starcraft also included a shut-off switch, which is located in the front pass-through storage compartment.

For off-the-grid survival, your 12-volt furnace blower is probably going to be your most serious power consumer. If you are in extremely cold weather, low battery power will result in the blower starting-up... but the furnace's safety system will not allow ignition of the burner. If you are already asleep, the blower may run all night, causing further depletion of the battery. Important notice: As you experiment with whatever solar hookup you eventually decide to use, make certain before towing that power to the trailer's electric brakes has not been compromised. A small Volt-Ohm meter is a great item to include in your trailer toolkit.

[KirkB]

Hi Gary. It seems like we are both starting our new trailer adventures at the same time. I drive from Burbank CA to Phoenix on Wednesday to pick up my new 19BHS. Will be towing with a 2016 Toyota Highlander. Will be interested in hearing how the solar panel works out. I have a question though. My understanding is that there trailers are "solar ready". Why do you (we) need anything more than just the panel and the attachments that come with it?

[GaryG]

Just purchased a 15 watt Solar Charging panel (from Harbor Freight) to use while boon-docking. We are going to Antelope Island State Park close to Salt Lake City for 2 nites/3 days during Spring Break with no electric hook up. I'm sure we will need to use the furnace at night along with the typical lights, etc. I am hoping it will keep my two 24volt batteries charged up during the day. I read many reviews and talked with a few RV owners who have done the same thing. I'll let you know how it works. I tried it here at the house and the solar panel produced 15 watts @ 1amp. It has a controller and several connectors to fit what ever need you might have. If it keeps my batteries up to charge I will be one happy camper.

I have all LED lights in the trailer, so that will be a big help at night. Otherwise we will use the batter for the water pump, electric fan on the furnace, ceiling fan in the bathroom, and the electric ignition on the fridge, furnace and stove/oven and hot water heater.

If you have some solar experience I'd be glad to hear from any of you on the forum. Thanks in advance.

Here's the link if you might be interested in what I purchased: http://www.harborfreight.com/15-watt-12 ... 96418.html
I also purchased the additional controller as it did not come with one: http://www.harborfreight.com/7-amp-sola ... 96728.html