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Old 04-14-2019, 09:22 AM   #1
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How to keep batteries charged while dry-camping

I have a 28' Thor Chateau. During last February's month-long snowbird dry-camping trip to Key West, I was not able to keep my battery charged for any significant length of time. My on-board generator provided power when in use but it was not practical to continuously run this noisy, gas-guzzler, and without this generator running, the battery would quickly run down so much that sometimes I couldn't again re-start the generator. Since then I have added a second battery, in parallel, and have replaced my bulbs with LED, but this won't solve the basic problem.
I am now looking for a solution to keep my batteries charged during extended dry-camping trips in the future. One option is to purchase a 200 watt suitcase solar panel system, that I would have to ground-mount, but this is rather expensive and is unwieldy. I am wondering if perhaps I might attach my quiet, fuel-efficient little 1800 watt Honda portable generator to the output leads of my big noisy on-board generator, and run it during low-electrical use periods to power my low-draw lights and such, as well as to keep my batteries charged.
If this is feasible, could I alligator-clip my portable generator directly onto the on-board generator output leads, without first disconnecting and isolating the on-board generator? Or would I need to install a junction box so as to isolate the on-board generator from the attachment of my portable generator to the output leads?
Is there a better solution to keep my batteries charged during extended dry-camping trips? All advice and suggestions will be appreciated. Thanks, Gordy, US Navy Retired
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Old 04-14-2019, 09:34 AM   #2
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I use my small generator to charge my batteries with a battery charger. works great.
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Old 04-14-2019, 09:43 AM   #3
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Why not install solar panels on the roof? It's a one time expense and then it just works. No noise, no schlepping fuel for a generator, no maintenance, charges from dawn to dusk.
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Old 04-14-2019, 09:45 AM   #4
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  • What appliances are you trying to power ? Just lights and maybe a TV/computer ? A good set of batteries should last a day. If you are going to run any more, you are going to need a larger battery bank. Buy 12VDC appliances (fan, maybe coffee maker). They are more efficient than running an inverter and the running regular household appliances.
  • If the only 120VAC appliance you want run are a TV/computer/phone charger, all you need is a 300W inverter. Spend the extra and get a Pure Sine Wave (PSW) inverter.
  • At a MINIMUM I would have TWO 6V golf cart batteries maybe even FOUR.
  • If you want solar charging, you probably need about 1,000 watts of solar panels and a GOOD solar charge controller. Yes, $$$$ !
  • The 12V outlet on any generator is really NOT meant for charging batteries. PERIOD ! Yes, it will run 12V appliance. A small, about 2000W, inverter generator will be much quieter and sip fuel.
  • You need a GOOD 120VAC multistage battery charger.
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Old 04-14-2019, 10:41 AM   #5
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1,000 watts seems like overkill unless you have a huge battery bank - rule of thumb seems to be about 1 watt per amp hour of battery capacity. So for a typical battery setup of about 200 amp hours 200 watts of solar should do the trick.
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Old 04-14-2019, 10:59 AM   #6
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Quote:
Originally Posted by Budhumph View Post
I have a 28' Thor Chateau. During last February's month-long snowbird dry-camping trip to Key West, I was not able to keep my battery charged for any significant length of time. My on-board generator provided power when in use but it was not practical to continuously run this noisy, gas-guzzler, and without this generator running, the battery would quickly run down so much that sometimes I couldn't again re-start the generator. Since then I have added a second battery, in parallel, and have replaced my bulbs with LED, but this won't solve the basic problem.
I am now looking for a solution to keep my batteries charged during extended dry-camping trips in the future. One option is to purchase a 200 watt suitcase solar panel system, that I would have to ground-mount, but this is rather expensive and is unwieldy. I am wondering if perhaps I might attach my quiet, fuel-efficient little 1800 watt Honda portable generator to the output leads of my big noisy on-board generator, and run it during low-electrical use periods to power my low-draw lights and such, as well as to keep my batteries charged.
If this is feasible, could I alligator-clip my portable generator directly onto the on-board generator output leads, without first disconnecting and isolating the on-board generator? Or would I need to install a junction box so as to isolate the on-board generator from the attachment of my portable generator to the output leads?
Is there a better solution to keep my batteries charged during extended dry-camping trips? All advice and suggestions will be appreciated. Thanks, Gordy, US Navy Retired
Verify the battery(s) condition. The original seems like it's done or close to done, if it fails or can't keep up with your load, while being charged from the generator.

If the battery(s) check out OK, what loads are you running that pull them down that fast? Maybe look into swapping in some lithium iron phosphate replacements if the loads are that big.


Add solar up top, as someone else suggested, 1w/Ah of battery capacity, especially in Key West should be enough, but this one sounds like too much load for the battery bank, so no guarantees.
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Old 04-14-2019, 07:08 PM   #7
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Quote:
Originally Posted by Budhumph View Post
t it was not practical to continuously run this noisy, gas-guzzler,
Something else to look at is what kind of charge rate your converter is supplying to the batteries. At the rate I deplete the batteries during the course of a 24 hour period I only need to run my genset 2 hours or less a day. Basically an hour in the morning and an hour in the evening, which is the same time we use the more power hungry appliances. Of course battery capacity comes into play but if your converter is only charging at a trickle rate, it won't matter how big or small, or how long you run whatever generator you're using.

Mark B.
Albuquerque, NM
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Old 04-14-2019, 08:42 PM   #8
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Thanks to all six responders

Johninsd: The roof would be nice for solar panels but I don't have the room due to vents, etc., so I'd have to ground-mount. We agree that 200 watt panels in a sunny place like Key West should keep the batteries charged.
The old wizard: "Batteries lasting one day" is my problem. When dry-camped for a month, I need something that will re-charge them on a daily basis. I'm not looking for 120 volt power....my on-board generator provides that for the little time we use it for microwave, hairdryer, etc. I only need a daily charge to my batteries....limited use of the on-board generator isn't doing the job.
Winterbegual: Right.....I have added a second new battery, in parallel, but not even a second battery will stay charged as long as I need them charged, without daily re-charging.
Dom: From what I have read, it is not advisable to run a charge directly into batteries without first passing it thru a charge controller.
Mark K5LXP: You make a very good point. From what I have read, a modern charge controller can make a lot of difference. I will get one of these if I end up with solar, but as you suggested, replacing an antiquated one that the on-board generator uses might also be in order.
For All: I'm still looking for an answer as to whether it is electrically okay to hook my small portable Honda generator directly onto the on-board generator output leads, or whether I need to isolate the on-board generator from my portable generator/output lead connection. Thanks again to all..Gordy
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Old 04-14-2019, 08:47 PM   #9
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Quote:
Originally Posted by Budhumph View Post
For All: I'm still looking for an answer as to whether it is electrically okay to hook my small portable Honda generator directly onto the on-board generator output leads, or whether I need to isolate the on-board generator from my portable generator/output lead connection.
I answered that. NO ! You can not properly charge batteries from the 12V outlet of any generator.

It might be "okay" as in not blowing anything up, but you will never put a proper charge on the batteries.
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Old 04-14-2019, 09:50 PM   #10
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Quote:
Originally Posted by Budhumph View Post
I have a 28' Thor Chateau. Since then I have added a second battery, in parallel, All advice and suggestions will be appreciated. Thanks, Gordy, US Navy Retired
Did you replace the batteries as a matched set or simply add a second battery?
If the later your original could still be the culprit with a weak or failed cell. I have always heard "keep battery sets identical for size (amps) and age" for best results.

I have a pair of 12v deep cycle in my Chateau that I top off charge with a briefcase set of 105 watt panels (3-35w). The charging is only truly required after very cold nights with furnace running regularly.


Best in your dry-camping adventures.
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Old 04-15-2019, 12:35 PM   #11
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Quote:
Originally Posted by Budhumph View Post
I am wondering if perhaps I might attach my quiet, fuel-efficient little 1800 watt Honda portable generator to the output leads of my big noisy on-board generator,
Didn't see the most obvious answer to this question, and that would be to plug your shore power connection into your inverter genset. By doing so you would either through mechanical or electrical means isolate the onboard generator. 1800W would easily have enough power to charge batteries and run most anything in the trailer except A/C. My inverter unit does not have a 30A plug but I just use an adapter. The downside I see to this idea is it's one more thing to schelp around, drag out, fire up, carry gas for and maintain. I've been thinking about going to an even smaller inverter unit like a 1kW or so, with the idea it's half the size and weight and still would be plenty to top off the batteries and run most loads in the RV.

I agree with the other posts that using the 12VDC port of a genset to charge the house batteries isn't a good way to go. The charge rate is low and the voltage probably not high enough to do a complete charge. One option that I've used is to connect a separate converter directly to the batteries and plug it into the genset 120V. That gives you way more charge current and the correct charge profile inherent to the converter. But it's more equipment and connections and doesn't give you any AC inside the RV. My vote would be to connect the genset to the shore power connection and use the RV's converter.

Quote:
Is there a better solution to keep my batteries charged during extended dry-camping trips?
As you mentioned, portable solar is "unwieldy". I call it a PITA. You have to drag it out, set it out somewhere it gets sun or keep moving it around to keep it in the sun, hope no one steals it then pack it all up and put it away when you're done. "Load management" is what I pay attention to so I have power when I want and need it. Any watt saved is about 1.25 less you have to generate. Seems simple enough but when you're used to living in a regular home or apartment with kilowatts available at your fingertips, saving watts here and there isn't instinctive - at first. If you don't already have one, a battery monitor that not only shows battery state of charge but also watts being delivered from the system is a big help in knowing where your battery is at and what you could be doing to minimize draw, or maximize charge. You may discover a number of phantom loads like idle cell phone and laptop chargers you've got plugged in doing nothing, maybe some other 12V accessories that "sleep" but still draw power. My TV inverter has an idle current so that gets turned off when the TV is off. Doesn't sound like those small loads would make much difference but over the course of a 24 hour period they add up. Watching power draw during a typical day will reveal your major power users.

Knowing your actual battery capacity is a key variable. You can't go by just what the battery is rated for, you have to put a load on it and actually measure it. If you have more than one battery, test each one separately. I do this at least once a year, sometimes more on every rechargeable battery I have. This can reveal a weak battery and also issues in insufficient charging. Without an independent capacity test, you have no idea if a shortfall of power is due to user habits, insufficient charging, a weak battery or a combination of all of those. After the capacity test I would then monitor whatever charger/converter unit is in place to see at what rate it is capable of restoring a charge to 100%. Just as with the batteries you can't go by what it's spec'd for because there may be issues with the installation that's affecting the charge cycle. The converter that came with my RV was a single stage set at float voltage. Pretty much only good for maintaining the batteries when connected to shore power all the time and nearly useless for restoring a charge in any reasonable amount of time from the genset. So modifying the converter was one of the first things I did.

I am quite comfortable in the design and operation of solar/battery systems and I thought about putting more panels on my RV but ultimately dismissed the idea as not practical for my situation. Even though nearly all of my outings are dry camping situations I would rather park my RV in the shade than a sunny spot just to make the panels happy, then have to run my genset anyway to keep the A/C going. By watching my battery monitor I can tell exactly where I'm at and know I won't wake up to a cold dead RV in the morning. After a while monitoring the system and getting comfortable with knowing where you're at will become intuitive but you have to start with known good batteries and a known charge rate. From there you can determine what if any system changes need to happen (more batteries, more solar, different converter) to accommodate your power usage requirement.

Mark B.
Albuquerque, NM
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Old 04-16-2019, 08:00 PM   #12
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Hi Budhumph,

I can relate to your problem as we have the same challenge. Doing the following has greatly improved life living on RV-12V.

1) converted all house lighting to LED
2) charge the batteries direct with a stand-alone 4-10-20-40 battery charger instead of relying on the lesser-powered on-board charger
3) changed from two 12V batteries, to two 6V-AGM batteries
4) installed a simple volt meter in a location where I always see it
5) shut down the whole house inverter until 110V is needed

Now the details on each.

1) Converting all the house lighting from florescent to LED made a noticeable improvement on battery health. I converted the original florescent fixtures rather than replacing them. CLICK HERE to read my write-up with many pictures. The conversion was extremely cheap.
LED lighting power consumption can vary a lot. My particular conversion decreased power consumption by 55% or 66% pending the quantity of LEDs I activated for each application in our rig.

2) I bought a Black & Decker battery charger from Walmart 11 years ago that has 4-amp 10-amp 20-amp and 40-amp settings. The few times I have shore power available, I charge slowly over-night at the 4-amp or 10-amp setting pending what is running through the night. The majority of the time I need to maximize our Onan generator run times so I set the charger to the full 40-amp setting to speed things up. I clip the charger directly on the battery terminals, not anywhere else. At the 40-amp setting, pending the condition of the batteries, I need to run the generator daily for 1 to 2 hours before getting a near-complete charge. That is a long time, but is required. Apparently we are power hogs.

3) This made the biggest improvement by far. CLICK HERE to read specifics and also some pictures. Our 12V batteries (2 different sets) wired "properly" in parallel never worked well together. They drained and recharged at their own individual rates which worked poorly over-all. Each set also provided only 2 good years of use. Our 6V AGM batteries wired in series drain and recharge together uniformly. They behave much more like huge a single battery than the pair of 12V batteries did. We are starting year #5 with the 6V-AGMs and they are still very healthy.

4) I installed a volt meter in a location where I can see it all the time. It helps me quickly identify a situation requiring action. I got fancy with mine. CLICK HERE to read about it and see some pictures of the project.

5) Our on-board whole house Tripp-Lite converter/inverter unit turned on but doing nothing is a serious power hog. With minimal 110V being used like the microwave clock and TV in stand-by mode, it consumes 12-amp hours of power. So we turn the unit off until we need 110V. And then, most often we run the generator for those short bursts of high power usage. We primarily utilize the inverter at night watching DVDs before bedtime.

I glanced over the other replies and also your comments so some of my input is redundant. I just wanted to provide you with all my personal experience in one reply rather than commenting in agreement to so many replies.

Ron Dittmer
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Old 04-16-2019, 09:36 PM   #13
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Boondocking (dry camping) becomes a issue with all of us on a class c, now first off is to check the rating on your 110v to 12v converter, if it has 3 stage charging then I would get a small 1800 inverter generator and let it run, or let the on board onan do its thing, i have a 4k microlite, and it is not a "gas hog " only burns less than .2 of a gal/hr with a_c running I burn .5gal/hr the main thing is to see how powerful your onboarding charger is
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Old 04-17-2019, 08:12 AM   #14
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http://www.irv2.com/forums/f87/how-to-keep-batteries-charged-while-dry-camping

Quote:
Originally Posted by DbleDutch View Post
Did you replace the batteries as a matched set or simply add a second battery?
If the later your original could still be the culprit with a weak or failed cell. I have always heard "keep battery sets identical for size (amps) and age" for best results.

I have a pair of 12v deep cycle in my Chateau that I top off charge with a briefcase set of 105 watt panels (3-35w). The charging is only truly required after very cold nights with furnace running regularly.


Best in your dry-camping adventures.
I am totally in the dark here-forgive the pun, but the portable option seems doable to me. However not knowing anything about them my question is - How exactly do the portable solar panels work, ie how do you connect them to your rv so that the batteries get charged.
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