Dry camping, batteries and slide out

You probably have about 200AH of batteries. 100AH is usable.
You started at 2/3s full, or about 135AH. That leaves you 35 usable AH.
During your drive, you may have added 30AH (depending on your charger). that leaves you 65 usable AH.
Your coach drains AH with various systems that are always running (propane detector, dummy lights, etc). Best case is 1AH/hour or 48AH over a weekend (My coach sucks about 48AH/day - we have A LOT of dummy lights). That leaves you about 20 usable AH.
You have a 20W solar panel - it probably gives you about 5AH/day, 10AH over a weekend. So you have 30 usable AH over the 48 hours.

It will help you a lot to start with full batteries. The 66AH you didn't have would have gotten you through the weekend unless you used the furnace a lot.

When we had a tt and no solar, if we ran out of battery we hooked up to the truck and ran the engine for about 15 minutes, then did the slides with the engine on. It worked for us. If you want to go longer than a weekend, you will need either more batteries, more solar, or a generator. The tt power suck will drain your batteries otherwise.

Start with an energy audit.

Create a battery bank that is 3 to 5 times the rate of daily consumption.

The larger the battery bank the smaller the wattage needed per 100 amp hours so long as the system stays above 60 watts per 100.

There is not much point in having more than 150 watts per 100 amp-hours because above 85% state of charge that is above the charge acceptance rate.

If you wish the RV to behave as if it were plugged into shore power with the ability to run the roof air conditioner then move to a 48 volt battery bank with 2400 watts of panels.

rbadger28 wrote:
What watt solar panel is required to be totally free of of shore power?

rbadger28 wrote:
What watt solar panel is required to be totally free of of shore power?

You need 110% of your daily usage to break even on battery usage.

Example:
As weekend camper, you might use 100AH per trip. Let's say that on a weekly basis, we have split the week into 3days camping/usage and 4days storage/charging.

To keep the battery at the optimal 50% or better state of charge(SOC), you want to begin the trip with a fully charged 200AH battery bank. Now to be ready for the next week, you need to replace that 100AH with 110AH of charging. The 110AH can be spread over 4days, or 110/4=27.5AH per day.

With solar, you must first know how much solar insolation, or power, is available in your storage location. Suppose your location is rated a 5. This means that you have an effective annual rating of5hours per day; 27.5AH/5H=5.5Amps. That is a panel rated at 5.5A.

There is one more adjustment needed to adjust for flat v.s. tilted panels. A tilted panel always faces directly at the Sun. There is a seasonal rating to account for flat panels being less able to harvest insolation into Amps. Using 70% will give a good estimate of your effectiveness; 5.5/.7=7.8A.

A panel rated at 7.8A Isc is needed to recharge the battery bank.

Now, what if it rains during the 4day charge period? :)

HTH;
John

I got an estimate for Solar. $3700.

I don't think I need it that much. I will only be running the lights, pump etc and the tv to watch a movie at night.

I purchased a Go Power! GP-PSK-120 120W Portable Folding Solar Kit with 10 Amp Solar Controller by Go Power. Amazon

It's keeping the batteries up even on the cloudy days in the driveway. I even turned on the fan for 2 days trying to drain the batteries a little bit. It has a 4 stage battery charger.

You need a lot of solar if you use a lot of 12 power . Boondockers have about 200 watts , sometimes more .

I installed toggle switches on my tv, radio system and detectors. I flip things on when I want to, that saves a lot of 12v power.

Being that I park in the shade or it rains whenever I go anywhere, I got rid of my solar system and use my Honda 2000 to recharge . For me, its the better bang for the buck. I can run 4-5 days w/o recharging. I have 2 grp 31 AGM's 12v. @ 105 amps per battery.

check out the first post below......this is where your power is going.

http://www.rv.net/forums/index.cfm/fuseaction/thread/tid/21135413.cfm

What watt solar panel is required to be totally free of of shore power?

I discovered two issues with my camper that were affecting my battery life. First my domestic refrigerator has a heating cable around the door gasket that runs off 12 volts continuously. It's supposed to prevent condensation around the door, but it consumes a lot of power. Second my WFCO converter will not go into boost mode no matter how discharged my battery gets. It always remains in adsorption mode which takes a very long time to recharge a depleted battery. If you have a WFCO converter you may have this problem too and therefore your batteries may not be fully charged at the beginning of your trip. I solved the first problem by disabling the heater cable. I solved the second by monitoring my battery voltage with a digital voltmeter and using an inexpensive stand alone charger you can buy in any auto supply store.

battery monitor at 2/3 means you were already at a low point, propably about 11.7-2v Your tow should have charged them up in an hours pull, so chack that you have connection between tow and towed. its easy to blow the tow fuse if the power demand from the the tow battery surpasses what the tow fuse and wiring to the rig can give.
Dont depend on your monitor. Like waste tank level monitors, they are not dependable.
A$5 multimeter will show you battery voltage state, . A $50 dc clamp ammeter will help you learn your load, thus how long you can run at load to 50% discharge

20 watts is barely a maintainer. You need to plug in and charge those batteries 48 hours when you return from draining them. If you are going much below 12.0 volts you might be over discharging them.

Need 60 to 100 watts to do an actual recharge and even then you need a battery cut-off switch to prevent parasitic draws. For camping 100w to 200w per battery is a general rule of thumb.

The 12 Volt Side of Life

Thanks so much for this great feedback.
I use NO inverter.

I am guessing my issue is the fact I did not fully charge the batteries prior to he weekend.

I use fridge (on propane). I use limited LED lighting. Water pump has been off most of the weekend except for some limited dish cleaning.

So based on the feedback I see here where people are dry camping for a week I can only deduce I had low battery at start of trip. Although I must say that the monitor in my room said batteries were two thirds full.

In terms of the soul a question I only have a 20 W panel. What do you think I need to put anything in this to add in terms of wattage ?