Need info on charging deep cycle battery with solar panel

[Oddball]

Mods please move this if I posted in the wrong forum, I'm looking into solar power to charge my camper battery. Its a deep cycle 140 minute reserve Napa battery. I have two small lights and possibly the fridge and maybe the furnace i want to run off the battery, not more than an hour at night. My plan is to use the battery at night and then charge it back up during the day. My question is what is the minimum watt solar panel I need to charge the battery? Will a battery tender work or do I need enough watts for a full on charge? Basically I want to keep the battery charged enough to last 5 days or so. Ive tried searching but im not finding what I need. Thanks
Robert

 

[Argonaut20]

The refrigerator takes a bunch of power on 12V. Run it on propane unless it is an Engle. Most of the folks here go 85W to 120W from what I have seen. Do a search for the solar installs and you will get the complete story. You might also look at the amps spreadsheet for guidance in size of panel. I went with a 40W because I don't use a lot of power but your needs may vary.

 

[Barko1]

As Argonaut said the fridge will kill you very quickly and that furnace will also draw plenty. A battery tender isn't up to the job, takes forever especially the last 20% to charge. I'd think about adding another battery. The cheapest solar panels are probably Harbor Freight and they seem to be OK. You can get 45w of charging for as low as $149. I wired those into a controller I had for another panel from Northern Tool and now have a total of 75w w/2 batteries. I didn't really need the last 15w panel but it helped my roof with lifters stay closed when I pulled it down I'm paranoid about draining the batteries so I swapped the regular furnace for a Wave 3 which uses no DC and also swapped the 3 way fridge for a Coleman Stirling that like the Engel uses very little. Now I am always fully charged , but this week I am heading to the very cloudy Maritime provinces and figured that extra 15w panel may help keep everything running. Like I said I'm paranoid so I also carry a real automotive battery charger so if I do run low I can find some AC and get fully charged. Out East I will likely be around electric so I'll be fine, out West on a long remote trip I have taken a small generator so I can charge that way if need be.

 

[Oddball]

It looks like I'm going to have to do more research, I can run the fridge off propane, the furnace is propane but needs power to trip the thermostat. I probably wont use the furnace anyways. Thanks for the reply's

Robert

 

[Hittheroad]

Robert, I have much the same objectives as you do. The fridge and furnace will easily go 5 days on propane. For us the big issue has been how long we stay up reading. It is never all that important as you can run the truck for 30 minutes and restore the battery. Yet it would be nice not to have to do that. What is impossible to know is how much sun you are going to have when you need it. My estimate is that a 80 watt system should cover most of what we need when there is good sun and when there isn't nothing is going to help (except running the truck.) Get at a 30 amp charge controller and you can add more panels if you find that would help.
All this advice is from someone who has yet to try anything but has given it some thought.
Most of the time we have been able to get by without running the truck just to charge the system. When we have had problems it is usually because we left the fridge on DC when we should have switched it to propane. A better brain would probably remove all need for solar.

 

[Oddball]

Yeah it sounds like were trying to do the same thing. I found a decent deal on a 45 watt set up, so I might buy two and maybe it will be good enough, but that might be enough to power the whole camper. Unfortunately I don't know much about solar but I'm trying to learn as much as I can

 

[Argonaut20]

Check ebay, Amazon, etc. for solar panels and controllers. The furnace draws power for the fan. Be careful about how you use it and you can run for several days without worrying about the battery too much unless it is pretty cold where you are camping. Put in LED for lights and the power consumption for reading, etc. goes way low. My $.02 worth is to try the 45 watt set up. See if it will do the job.

FYI, my approach is to leave the panel mobile so I can set it in the sun when I want to camp in the shade. I intend mounting the panel between the overhang on the camper and the truck cab roof in a mount that allows me to slide the panel out for charging while on the truck or to remove the panel completely so it can be set in the sun if the truck is in the shade. I bought connectors from here:
http://www.solarseller.com/low_voltage_dc_pumps__lvm__teel__accessories__plugs_and_extensions.htm
using D and F from that page and 14 gauge cord to make a 15 foot extension cord. I mounted the 'roof connector' where I could get at it from the front turnbuckle access panel near the battery. I can then plug the cord in and place the panel wherever I want. Until I finish the mount, I will carry the panel loose behind the seat in the truck or in the camper.
Some posts that may be of use:
http://www.wanderthewest.com/forum/index.php?/topic/3303/
and for a roof mount:
http://www.wanderthewest.com/forum/index.php?/topic/2063/

 

[griz]

Amp hours is the key. Need to know the amps an item draws then its all down hill from there. The bigger the draw the bigger the s/panel will be to recharge the battery quicker.
The fan in the furnace is the killer. Nothing else should be a problem unless your packing a hair dryer.