Appliance vs. 4d battery with one Kyocera solar panel

dowgars · 11-03-2010, 01:57 PM

I need a little electrical question answered. Will the above single house battery and one panel, in daylight, maintain a 3.8 amp (at 110v) appliance? I know the formula's but practically not very good at these things. Thanks for any answers. RD

mjeffrey · 11-03-2010, 02:09 PM

Watts = Amps * Volts

Your panel is rated at 135W, I presume (the common Kyocera panel used on our vans).

Your appliance:
Watts = 3.8 * 110
Watts = 418

At 12V, those 418 watts equal 35A, which is a HUGE draw. Your 4D battery has 220Ah, I believe, and is useful down to, say, 50% - that gives you 110Ah to work with. Your appliance would draw it down in 3 hours. Your panel, in full sunlight, could probably put about 7A back into the battery per hour - 21A in that 3 hour period, giving you another half hour or so.

There are inefficiencies in your inverter, too, that would rob you of power and cut down the available time.

Anyone feel free to correct my math!

Cheers,
Mike.

dowgars · 11-03-2010, 02:28 PM

Thanks mjeffery: that really helps me. What if I leave the Van running say 4 hours? I know the panel isn't charging then but at that draw do you think the batteries could support the appliance and stay above 50%???

mjeffrey · 11-03-2010, 03:21 PM

I'm afraid I don't know much about alternators - eg. how much current they're capable of providing. I've heard of high output alternators for our vans that I think are rated to 200A, but I'm not sure if that's put out at idle or not (I'd guess not; some vans have a 'high idle' setting, though, that would help in this case). 200A would be enough to put some current back into your battery while also powering the appliance.

As a side note, the panel's current is still available when current is also coming from elsewhere. It all depends on your wiring, of course, but in general these power sources can be used in tandem.

Cheers,
Mike.

jage · 11-03-2010, 03:33 PM

Don't forget we're talking full direct sunlight vs. reality too. I guess the next thing to consider might be what is the 3.8 amp appliance, and why does it need to run all day?

dowgars · 11-03-2010, 03:37 PM

I do have a 200 amp. alternator. If I could get 3-4 hours even with the motor running and not draw my battery down below 50% I would be happy.
I suppose it would be of interest to explain what I'm researching. As some of you know I like to take my dog with me. Also I'm buying a off-road teardrop trailer. I've been laboring a long time to fiquire out how to keep the van cool in 100 degree heat. Well it will be a lot easier to cool the tierdrop. I'm having a 2500 btu dog kennel heater/air conditioner installed. It draws 3.8 amp/hr. I have a honda generator that will run it but I'm thinking I may be able to run it off the inverter awhile also. Comments appreciated. RD

jage · 11-03-2010, 03:49 PM

Look into K-9 units, although the equipment may be made to run with the vehicle running, at least it will designed for an automotive use- something that is designed for 12v will be more efficient, I believe, even without considering the inverter side of things.

Also, I have the chilly-dog system, designed to start the vehicle at a designated time or temperature. If you design the system with controls that fire the AC when the temperature reaches a point, then you don't have to design for 100% usage to consume down to a 50% battery. Even if the kennel cooler has a thermostat, the inverter still has to be on 100% of the time, and that's a huge draw even if not running.

Combine this with lower draw cooling solutions, like a fantastic fan, and you might get a longer system life. On the flip side, consider that you won't likely be driving enough everyday to recharge the batteries- if you're out hiking for 9 hours, the battery may be down to 50% when you return, but it will still be at 50% the next morning, and that's not even considering other use.

dowgars · 11-03-2010, 03:59 PM

I appreciate the discussion. I too have the chilly dog system. The problem is the van air with the van stationary and running is very inadequate in my van with a voyager top in 100 degree heat.
I don't intend to use it more than max a few hours at a time. Probably only 1 hr. at a time. Thanks

billwilson · 11-03-2010, 05:57 PM

Dowgars

fill us in on the trailer, and of course i would be remiss if i did not request PICTURES

Ford_6L_E350 · 11-03-2010, 06:32 PM

In all likelyhood, running the Honda generator will be a better idea. It uses less fuel, is quiet and there is no risk of damaging the van by running it unattended for a few hours. Even if you wear out or kill the Honda, it is cheaper to replace than the van engine.

As Mike said above, you can get 1-2 hours of AC from you 4D battery, but then you have recharge it. It is a good application of the Honda generator.

Mike