battery life while boondocking

[csp]

We are planning an off-road trip to Land Between the Lakes in southern Kentucky in a few weeks. My coach is a Monaco Dynasty. I have a solar panel charger set up on the roof. My question is how long will the batteries stay charged. I will be running the fridge on 12 volt gas, lights, and furnace on 12 volt gas. How often do I need to start the generator and how long should I let it run to charge the batteries. I do not want to go out for the day and come back to dead batteries or wake up in the morning with dead batteries.
Any other boondocking advice would be helpful. We have stayed places before without power but not for a long period of time.
Thank You Chris

[akadeadeye]

I am interested in responses here as well. We have an auto gen-start which can be set to start the generator when battery voltage gets to a pre-set level. I believe ours is factory set at 11v. However, we have never boondocked for a long enough period to test it. We have four 6v deep cycle house batteries. I do know I ran them completely down once by forgetting to turn off a couple of things while it was in the shop for service.

While overnight boondocking I have checked the voltage reading on my control panel and the next morning it was at 12.2v from about 13.4 the night before so I suppose we might have gone 2 days before a charge was necessary. But that is just a guess.

Don

[Gary RVRoamer]

The furnace fan is a battery killer - in chilly weather it will run the batteries down overnight for sure. As for the other stuff, it all depends on how many lights and how long they are on. And maybe the type of light too - halogens are much bigger power consumers than LEDs, for example. The fridge uses very little power, though.

I'd guess you will need to run the generator twice daily for a couple hours. Charge it up at night and re-charge again in the a.m., which also gives you full power for breakfast meals, coffee, etc. For maximum battery life, don't let them discharge more than 50%, which equates to about 11.9-12.0v.

[safari1]

We do a lot of boondocking in AZ mountains. I did have only 1 house battery and ran the gen. twice a day for an hour or more if I had to run furnace. I bought 2 Blue Top Optimas, much better. The drain is not as bad and they recharge faster. I now run the gen. maybe 45 min twice a day.
Last trip had fridge on, ran lights, ran furnace 2 times overnight, and radio on. Checked batteries before starting gen. they were at 12.4 volts. Before with 1 it was at 11.7 volts after 12 hours. I also have no solar panel.

[John Hilley]

If you have the typical 15 watt solar panel included in a lot of motor homes it won't do much for you. Conservation is the best way to extend time. Try not to have more than a couple of lights on at the same time. Some lamps have two bulbs in them, take one out, there will still be plenty of light. We run our generator first thing in the morning and usually at dinner time. We have one 130 watt solar panel that helps considerably. We run our TV and satellite receiver for probabably 6 hours each day. We have four 6 volt golf cart batteries.

[BryanL]

This is one of those questions you have to answer empirically through your own experience and adjustments.

For me, it'd probably be a week or more. For some of my friends, overnight - maybe.

The amount of electrical energy storage in an RV is extremely small compared to typical household use (less than 10 KwH compared to 30+ KwH/Day)

Your battery bank should last a weekend if sized right.

Solar is also rather puny. It is only the serious solar types that get into the kilowatt range and most can just muster a couple hundred watts of solar. That usually means about only 1 or 2 KwH per day of energy.

More than anything else, how long your portable electrical system will serve will depend upon your lifestyle. It is amazing how the small things can add up.

[Downsizer]

CSP.... look around your dash to see if you have an emergency start switch for your batteries so you can crank in the am?? I have a Monaco Windsor (2000) and I ran my chassis battery down. I used the emergency switch to get enough to crank and start. Your solar panel is probably a 90 watt one??? We just added 3 more 135's and now self sufficient!! We also have all LED's throughout and don't waste our free juice though.

[RJay]

I agree with Gary. You don't say how large your chassis battery bank is but I would suggest running your generator as long as you can at night and then again the first opportunity you have the next morning. After the first night you'll have a better idea of your batteries capacity for the nights to follow and any changes you may have to make, if any.

[csp]

We are now back from our boondocking off-road trip. We ran the generator about 2 hours in the morning and 2 hours in the evening. We ran the furnace, fridge, and lights at night. One night it got down to 37 degrees. I would not start the generator until about 8 AM in the morning and the battery was still at 3/4 charged at the time of start up. When I started it in the evening it showed full charge but I started it any way.
Electric is nice to have but we survived just fine without it.
Chris

[az bound]

Quote:

Originally Posted by akadeadeye I am interested in responses here as well. We have an auto gen-start which can be set to start the generator when battery voltage gets to a pre-set level. I believe ours is factory set at 11v. However, we have never boondocked for a long enough period to test it. We have four 6v deep cycle house batteries. I do know I ran them completely down once by forgetting to turn off a couple of things while it was in the shop for service. While overnight boondocking I have checked the voltage reading on my control panel and the next morning it was at 12.2v from about 13.4 the night before so I suppose we might have gone 2 days before a charge was necessary. But that is just a guess. Don

Your AGS system should handle things very well. We used ours for a whole month while boondocking in BC. That was in April and the weather was quite cool so the furnace ran considerably. One thing that I found was that if I started the genset manually for any reason I had to reset the AGS to auto or it would not function properly. Ours has 2-245AH AGM batteries and a residential refer.
Another nice feature of the AGS is that when the betteries are fully charged it will automaticaly shut down the genset and continue to monitor and restart as needed.

[LaserMark4]

Quote:

Originally Posted by Gary RVRoamer For maximum battery life, don't let them discharge more than 50%, which equates to about 11.9-12.0v.

I've have read this important "don't go lower than 12.0v discharge level" on several battery sites and I have manually been pretty faithful to not let my sets go below this level before I manually start my generator.

But my consternation is why would the fairly high end Magnum Energy Inverter/Charge and control module have the default auto generator start at 11.0 vDC? And there is no other setting higher than 11.0v start point that you can select. I'd would think these guys would know the ins and out of the batteries they intimately control and manage. So, I hate to use the AGS feature if this is going to damage the batteries, but to not have it when dry camping in cold weather with uncertain discharge rates is not reassuring either?

I'd love to use the AGS auto gen start feature and let it do the work for me, but again, will the 11.0 v start thresh hold be a killer to the batteries??

[Midniteoyl]

Because that inverter company thinks all batteries can be discharged to about 15-20% without harming them, which of course is wrong according to the battery manufacturers themselves. So no, they don't know the 'ins and outs'.

[az bound]

A fully charged 12v battery puts out 13.4 v. Minus 20% is 2.68v, which equates to 10.72v. So the 11v restart is within a safe range.

[Luv2go]

Here is a graph with a typical lead acid battery voltage vs state of charge (from This Wikipedia entry):



This is the "resting" battery voltage, i.e. minimal discharge current for a period of time and obviously not being charged (actually this article from "The 12V Side of Life" says 6 hours with no load or charge).

Also, these charts vary somewhat depending on battery type (flooded, AGM, Gel) and brand, so your battery chart may be different. For example, the chart from "The 12V Side of Life" is quite a bit different than the above graph.

IMHO, 11V is too low for good battery life. For example, with my batteries will last for 600 cycles with an 80% depth of discharge versus 2000 cycles with a 20% depth of discharge.

With my AGS I am lucky enough to be able to set the start voltage to whatever I want, 12V in this case, which translates to approx 50% depth of discharge. The voltage has to be at that level for a certain amount of time (20 minutes), that prevents starting with short-term heavy loads such as microwaves or hair dryers.

Still, I monitor battery level and try to make sure I don't get less than 20% depth of discharge to maximize my battery life (using a "Trimetric" battery monitor).