Need RV Charging System Advice (1 Viewer)

[1973Guppie]

Hi All,

I own a small pop up tent trailer. Right now it has one deep cycle battery powering it. I am planning on installing a larger inverter, a water pump, and a 2nd deep cycle battery into it. I would like to be able to camp for about a week and not worry about the batteries going dead.

Initially I looked at generators and solar panels but am now thinking that I might be able to recharge the batteries using an engine mounted hi amp alternator.

I am planning on purchasing a 220amp alternator for my 1996 landcruiser 80 series. I plan to wire it up to have 2 batteries in the vehicle but will probably have some type of disconect to only route power TO the trailer batteries when I need to charge them.

Question is though, how long would it really take to charge 2 dual batteries from a 220amp alternator and at what rpm's?? I do have an engine rpm controlled knob in the cab and can set my engine rpm to any setting I want during idle. I am guessing there has got to be some way to calculate a general time frame that it would take to charge 2 deep cycle marine batteries from an alternator at X idle. Anyone have some type of math formula?

hopefully somebody smarter than me will look at this and be able to help!

Thanks,

Noah

 

[rusty_tlc]

The problem with fast charging is deep cycle batteries like to be charged the same way they discharge, slowly. If you try to pump a lot of current into them fast they won't last long.

If you plan to camp in one spot for a week get one of these;

Honda Power Equipment - EU1000I

They are Uber quiet, I can talk in normal tones when standing right over mine. I can easily lift it with one hand. The MSRP shown on that site is pretty high, I'm sure you can find one new or used for a lot less.

When we had the big RV I would usually run the generator for an hour or so each morning to recharge from running the forced air heat overnight. If it was warm I would only run it every couple of days. A couple of times I forgot it was running and it ran for quite a while. One tank of gas would last us for at least a week.

 

[1973Guppie]

thanks, I was worried someone would say I should just get a generator,

in order to charge my DC batteries directly though wouldn't I need to hook up a standard shop battery charger to this though?

 

[e9999]

you want to get a *very* rough idea of how long, you just take the AmpHours capacity of the batteries and divide by the estimated current output in Amps of the alternator. That will give you an idea. (Yea yea, I know, there are non-linearities etc...)


and yes, you can use the DC output from a Honda generator and connect that directly to your batteries. Note that this is only like 10A or so, IIRC, or 140W, so it would take something like 10 hrs to recharge a typical truck battery.

Or you could indeed use a regular 120V charger and use more of the generator capacity. Should be faster then if it's a high amp charger, but those are usually considered bad for the battery.


I bought a desulfating smart trickle charger that I hope will keep my batteries in good shape. I just lost one on my trailer cuz I failed to disconnect it and it got discharged too deep and shorted.

 

[greentruck]

I think your alternator has plenty of omph needed to charge the RV battery, in fact maybe way more than is needed for that. You can charge a battery only so fast before it causes problems.

Effectively, you don't need to bump up the hand throttle while charging with your alternator, because you'll be able to supply all the juice needed at idle more likely to charge the RV battery. So your engine will be running for some time, in part to avoid overcharging, which is going to burn a lot of fuel, relatively speaking, for a small amount of power into the battery.

I believe at least some of the small Honda generators have a 12 VDC outputs specifically for use in such applications as charging batteries. Thus probably no need for a separate charger, even if the generator itself is another piece of gear you have to find space for. However, it will be vastly more efficient in use of fuel vs charge rate.

Another possibility is solar, which I only bring up because you're out West where the sun is much more reliable than places I typically go. It's the most expensive, but also lowest maintenance, quietest, and requires no additional gear as most are set-up to charge 12 VDC batteries.

EDIT: One more thing...

If you do commit to taking a small generator, then you can use it directly for some of your highest demand tasks, then rely on the RV battery less for those tasks, saving it for low demand tasks like lighting, small electronics, etc. That way it'll last longer and require less charging, which you may be able to do simultaneously when the generator is already running for high demand tasks.

 

[Atoyot1031]

I have a small popup as well and tend to camp in teh back country. I love the Honda generators, but couldn't justify $700 for a 1,000w generator. I bought one of the cheap 1,000w two-stroke generators from SMG for ~$100. It's louder for sure, but plenty reasonable for my needs if it put it at the end of a 25' extension cord. Then I carry a simple 2 amp charger for the camper. Anything more, and the deep cycle battery doesn't charge well.

Good luck!

 

[e9999]

I'll throw in something else for those contemplating using solar cells to recharge their battery: The capacity of PV cells to produce power is vastly overrated by the general public. Some outfits out there will sell you a little strip of cells to put on your dash supposedly to recharge the battery. As in plug it into the cig lighter. Well, first of course, one had better make sure the lighter is connected with the key out. But more importantly, these little strips put out a paltry amount of power. As in a couple of watts for your $30 "charger". Well, 3W at 12V is 0.25A. So assuming say 100Ah for a battery, it would take 400h to replenish your battery. That is if there isn't any significant permanent drain from your clock, computer etc, which sucks anything close to 3W. IOW, forget it. Funny how people think PV cells are powerfull. They're not... One needs a large area (read $) to get any significant amounts of power. [End of soapbox...]

 

[1973Guppie]

I have thought about going the solar route using 2 of these mounted to the top of my pop up tent trailer:

Sunforce Products Inc - Sunforce 15-Watt Solar Battery Charger Kit - RV Solar Power - Camping World

what are peoples thoughts on these? This would be my first choice but I am worried that as others have mentioned above that the solar avenue would leave me flat on a rainy or cloudy day while camping OR when camping with trees overhead, etc? has anyone run these succesfully?

I like the idea of solar but a generator is sure more dependable......

Noah

 

[1973Guppie]

just saw this on the description:

Works in all weather conditions.

is that true?

 

[rusty_tlc]

thanks, I was worried someone would say I should just get a generator,

in order to charge my DC batteries directly though wouldn't I need to hook up a standard shop battery charger to this though?

Most trailers have an internal DC charger that maintains the batteries when hooked to "shore" power.

I've looked into other sources of power than generators, so far I haven't found a better way that is cost effective. Right now I'm looking at wind, since we have plenty of that in Nevada, still not viable as far as I can tell.

Watch CL and E-bay, low hour generators come up for sale fairly often. Most times we move every day and the truck charges the trailer on the road. If we plan to be in one camp for a while I bring the generator.

 

[e9999]

here is what that site says:

"Amorphous solar cell panel produces 735 watts/49 amps per week. "

anybody who writes anything that nonsensical has evidently little understanding of power and energy concepts.


"Works in all weather conditions."
well, yes, they will likely "work" in all weather conditions if properly waterproofed etc.
Will they produce 15W in all weather conditions? Of course not...

sheesh...



OK so now, what can you do with 15W? well, run one light bulb, or power a fully charged netbook, or recharge a phone or run a little radio, something like that. Recharge your battery? Well, at 1A it would take something like 100 hrs / 2 weeks if you're lucky.

If you're thinking generator, think Honda EU series. Best way to go.

 

[1973Guppie]

thx for your help everyone, I think I am going to go the route of a generator for sure now, just easier, and more dependable overall, plus I won't have to really add another battery as I will have a way to recharge the existing battery anyhow......