Solar setup question

[Burro]

Need some guidance about a solar setup.

I only run a fridge off my deep cycle battery and would like to extend my use some.
I have a small fridge that pulls 1.4 amps when its running and 6.3 amps when starting up. I run it off a group 27 battery and an inverter. It will run for two days before the battery stops. I’d like to extend the duration of how much time I can stay off shore power. So, I was going to add a 100 watt solar panel.

It looks like I might be able to put about 5amp hours an hour back into the battery (given optimal conditions). Does this sound about right with a 100 watt panel?

Some side questions. Has anyone glued a flexible solar panel to their teardrop? Just curious how this would work? If I could avoid putting holes in my aluminum that would be my preference.
Also, anyone on here wire up their camper to their alternator for charging down the road? I was thinking if using some 6 gauge old jumper cables to run a large gauge line from the alternator to the trailer battery with a relay to turn off when the truck is not running. The 7 pin 12volt line is worthless for charging the battery. I could drive across the country and never charge the battery.

Thanks for any advice or links to previous posts!

[tony.latham]

Also, anyone on here wire up their camper to their alternator for charging down the road?

My Tacoma charging system works well (with its 130 amp alternator) through the trailer connector. I think 6 gauge wire would be gross overkill –-10 gauge is fine. You might check your alternator and see what the rated output is.

If you end up installing a flexible solar panel, avoid the cheap PET panels and get an ETFE panel such as a Renogy. PET panels are notorious for dying after a year or two.

It will run for two days before the battery stops.

How far are you dragging it down? Below 12 volts?

Tony

[Burro]

I also have a tacoma with the tow package. So, I think it has the 130 amp alternator. I pull the battery down until it stops.... But I’ve have the same deep cycle for about 4 years with no problems. I plan to replace it this spring when I upgrade the solar charging system.
I know it takes a day to charge using my 15 amp deep cycle battery charger once I run the battery down. I’d like to limit this, and decrease the zap on the battery.
Thanks for the tips. I might add another battery to get a few more amp hours of stored energy.

[Chasein70]

Don't count on 100 watts from a 100 watt panel unless you're going to sit on top of your trailer continuously adjusting your panels to point at the sun. I have 360 watts on top of my trailer and on a sunny day the most I've seen is 220.

[edgeau]

I have a 100w flexible panel. It rarely gets 5amps going. 4 is common in full sun but unless you are chasing the sun all day you won't get it constantly. It is for this reason I have avoided permanent attachment to the Teardrop. I like to park in the shade and run a cable out to a sunny spot for the panel. The flexibile one is nice and light but not as robust as the glass and aluminum ones.

Sent from my Pixel using Tapatalk

[Chasein70]

Lol....Guess we posted the same time thinking the same thing

[Cosmo]

My trailer charges when plugged into the car. It works great. I charge while driving. Charges the battery very quickly -

What is the amp hour rating of your battery? Mine is 115 amp hours.
I can get 36 hours of battery powering the fridge (and everything else (drawing down to 10.5 volts) with no power input to the battery. After that its solar or start the car motor or shore power to recharge. I have been doing this for 2 years and survived the clouds. Your usage is probably different than mine so no guarantees! The reward is unlimited off grid with refrigeration and no noise.

I am in the North East where trees which I love are providing shade and clouds provide rain and skimpy solar. Treeless sand states probably have an easier solar situation.

For my type of situation (mixture of conditions) I use (2) 100 watt panels free standing so you can point them towards the sun. i am using this system with a Dometic CFX-35 fridge. For constant deep woods with clouds I would consider a third panel. If your controller is adequate you can build out as you learn. Crawl, walk, run. Another way is to use one Flexcharge PV7 Controller on each 100 watt panel and build as you go. They will all turn on and off at the same voltages. I have done this also. Lots of options available.

I need the 200 watts for days when its cloudy. Under trees is tough too. If mine were roof mounted I would get much less sun than free standing panels.

If the sun is shining and I can get it on my panels - 200 watts will have me fully charged by 10 or 11AM. I then charge the laptop and other devices with the spare capacity during the day and I go into the night with the house battery fully charged along with everything else.

The reserve wattage is for poor sun days when the panels may output 1/4 of the wattage. I posted a couple of videos about this setup on Youtube.

=Cosmo

[Burro]

Awesome! Thanks for the ideas. I had never considered using the inverter built into my truck while I’m driving. I think I’ll do that. I also think I’ll start with a free standing panel and see how much power I get back into the battery and then build out the system from there.

I’d love to get a battery tray that hangs under the camper near the axel and put in 2 of 3 batteries. I haven’t seen a rugged tray that could hold that weight yet. I’d ultimately like to be able to be free from shore power and a generator for up to 4 or 5 days if possible.

[troubleScottie]

Actually, the other poster (Cosmo) suggested running 12VDC from the tow vehicle (TV) to the trailer, not using the inverter.

One could run your battery charger. However there are lots of power loses go from DC to AC back to DC.

For a direct 12VDC connection, the general plan is an appropriate fuse, an always open solenoid (switched on to allow charging of trailer battery), an long run of wire to end of TV for the plus wire; just a long run of wire for the common; then a connection (Anderson connector pairs?), then two wires on/over the trailer to the battery. Think big audio amplifier in trunk. 6AWG sounds good.

The major draw back is the alternator is not quite the same as a multi-stage charger. So the battery may not completely charge. Of course depends on length of charge time, state of battery, etc.

Some solar MPPT allow connection from TV, so you can get a staged charge. However, you are then limited by the amperage of the MPPT unit. Some are small.

[absolutsnwbrdr]

We attached two 120w flexible panels to the roof of our little Scotty project, using VHB tape. Works like a charm! If I recall, in direct sun we can pull about 12-14 amps. The nice thing is we don't have to worry about them walking away if we leave camp, so they are collecting sunlight from sunrise to sunset. With that said, I do plan on picking up a smaller 'portable' 80w panel that I can move around and put in direct sunlight for an extra boost if ever needed. There are pros and cons to both 'permanent' and 'portable'.

20180511_155701.jpg (323.43 KiB) Viewed 1151 times

EDIT: just realized I posted our solar info here: viewtopic.php?p=1237055#p1237055

[Burro]

Thanks again for the clarifications. I have an extra set of old jumper cables that have never been used. I was planning to use them as the 12V line from the TV battery or alternator in order to reduce loss of power. My truck is 18 feet long and the teardrop is 14 feet long. So, I have 32 feet of span to get back to my battery in the camper.

I actually have an old fuse setup from years ago doing stereos (90’s) that I thought I’d never use. So, it will be great to re-purpose that stuff. I think I might lean towards starting with one flexible panel and see if that gets the job done. If not, since I can double sided tape it on, I can remove it and add another.

Great suggestions.

Since my alternator is 130 amps, would that mean that I could possibly put 100amps an hour back into the camper batter cruising down that highway if I wasn’t running a bunch of electrical stuff in the truck? Is that thinking correct? 130amp alternator = 130amps an hour? If so, wouldn’t I be able to bring the camper battery mostly back to full charge in about an hour to hour and a half, and then the solar charger could top the battery off?

[Burro]

Actually, the other poster (Cosmo) suggested running 12VDC from the tow vehicle (TV) to the trailer, not using the inverter.

One could run your battery charger. However there are lots of power loses go from DC to AC back to DC.

For a direct 12VDC connection, the general plan is an appropriate fuse, an always open solenoid (switched on to allow charging of trailer battery), an long run of wire to end of TV for the plus wire; just a long run of wire for the common; then a connection (Anderson connector pairs?), then two wires on/over the trailer to the battery. Think big audio amplifier in trunk. 6AWG sounds good.

The major draw back is the alternator is not quite the same as a multi-stage charger. So the battery may not completely charge. Of course depends on length of charge time, state of battery, etc.

Some solar MPPT allow connection from TV, so you can get a staged charge. However, you are then limited by the amperage of the MPPT unit. Some are small.

So, is this the setup I would need:

Attach 6 gauge connector to alternator and run line back to Anderson connector (positive), have a fuse near the alternator. Also attach a solenoid near alternator.

Can I just run a single positive line back to the Anderson connector and ground the connector out on the frame or receiver on the truck, and on the camper run the ground to the camper frame near the battery?

[Louisd75]

Need some guidance about a solar setup.

I only run a fridge off my deep cycle battery and would like to extend my use some.
I have a small fridge that pulls 1.4 amps when its running and 6.3 amps when starting up. I run it off a group 27 battery and an inverter. It will run for two days before the battery stops. I’d like to extend the duration of how much time I can stay off shore power. So, I was going to add a 100 watt solar panel.

It looks like I might be able to put about 5amp hours an hour back into the battery (given optimal conditions). Does this sound about right with a 100 watt panel?

Some side questions. Has anyone glued a flexible solar panel to their teardrop? Just curious how this would work? If I could avoid putting holes in my aluminum that would be my preference.
Also, anyone on here wire up their camper to their alternator for charging down the road? I was thinking if using some 6 gauge old jumper cables to run a large gauge line from the alternator to the trailer battery with a relay to turn off when the truck is not running. The 7 pin 12volt line is worthless for charging the battery. I could drive across the country and never charge the battery.

Thanks for any advice or links to previous posts!

I've gone back and forth a few times now on adding a solar setup to my trailer. My biggest consumer is a 12v fridge. I weighed the pros and cons of putting the fridge in the galley of the trailer when I was building it and wound up deciding to keep the fridge in the truck. My reasoning is that, even when camping, I still drive the truck around to go places and see things. Keeping it in the truck means that we never have to remember to pack a snack. It does mean a little bit more walking between the bed of the truck and the trailer galley area, but in reality it hasn't been a big deal.

It's strange that your 12v line off the 7 pin connector isn't enough to charge. I haven't had any issues with mine charging the battery. It might be worth throwing a volt meter on the connection to make sure that you're getting a full 12v out of it. Here's an idea if you want to go with a separate charging line. On my truck I ran a leftover section of 8ga wire from the battery to the bedside storage cubby on the diver's side. It's protected by a fuse right after the battery. I made a little mount to install a Blue Sea fuse block in the cubby, like so:



I can now easily come off that fuse block (which is always hot) and run a circuit to a connector for the trailer should I so desire. In my setup, I have three circuits in use, one for the canopy dome light, one for the 12v outlet that I plug my fridge into and one for a dual USB charger installed right below the 12v outlet. The plugs are on the passenger side just forward of the tailgate:



Regardless of which direction you decide to go, I would HIGHLY recommend that you have some sort of undervoltage protection in place to prevent running your starting battery down. I'm currently relying on the voltage protection that its built into the fridge, but I have plans for an additional low voltage disconnect mounted in the cubby that would shut off power to the fuse block if need be.

[cheaterparts]

Just wondering do the guys charging off there tow units alternator do you use a Dc - Dc charger if not you wont be fully charging your trailer battery - first a car alternator just don't fully charge any battery
then you have a voltage drop over the distance from the Alt to the trailer battery - running a good Dc - Dc charger will increase the voltage to correct charge rates

I use a C tek D250SA https://www.ctek.com/products/on-board/d250sa and there are other brands out there - these will lift the voltage to 14.8 v which is needed to charge a AGM deep cycle battery

and worse still are the later cars with smart alternators - they just don't charge a battery on your trailer without assistance of a Dc - Dc charger

the C tek also has a MPPT solar controller built in and will handle 300 watt of solar panel and they are a 5 stage smart charger
of cause the other advantage is when the trailer battery/batteries are full these send power to the cars battery to top that up as well

something like this is probably worth looking at if you dont use one

[tony.latham]

Just wondering do the guys charging off there tow units alternator do you use a Dc - Dc charger...

No. But I'm not running an AGM so the system charges it just fine.

On the pending build, I'll install an AGM. I'll have a cutoff switch from the tow vehicle and will generally just charge off the 100-watt panel to get the battery fully charged. When we're on the move and the AGM is way down, then I'll allow the vehicle to bring it up but I'll let the solar controller top it off.

That's my plan.

Tony