Boondocking Battery Charging Question

[bfisher003]

Background: My wife and I have a new 23' TT. It currently has one 80 Amp-Hour battery. I recently installed an 1100W inverter to run the TV and a couple of other things when we boondock. At this time I don't have any solar power installed, so the only way I have to charge the battery would be when I hook the TT up to the Grand Cherokee and start the engine--I believe this will charge the battery, but somehow seems kind of inefficient with the relatively small wire.

My question: Would it be more efficient, burn less gas and re-charge the deep cycle battery faster on the trailer if I hooked up a set of jumper cables from the GC directly to the trailer battery and started the Hemi?

Thanks for your help.

[tbbg II]

This is a tough one. You may be able to charge a bit quicker, but you do have a pretty small electrical system on the TT. At least the battery capacity is small. The alternator/voltage regulator on the Jeep is designed to keep the starting battery charged and run whatever other elecrical devices in the car. It really isn't designed to charge a deep cycle battery, especially at idle speed. If you plugged a bigger device to 120VAC, you could drain the battery very quickly.


You may not be looking to spend a bunch of money, but a couple golf cart batteries would be a good thing coupled a solar set and/or a small generator. I assume you have a charger (some call it a converter) in the TT which charges the battery when plugged into shore power. The solar set up would connect directly to the battery whle the generator would connect to the shore power cord.


Camping is a wonderful thing. All the stuff from civilization gets in the way sometimes, though.

[DAN L]

bfisher003
harbor freight has inexpensive gennys and solar. i have not used either so I cannot speak about their effectiveness.
do a forum search for more info.

[bfisher003]

Originally Posted by tbbg II

This is a tough one. You may be able to charge a bit quicker, but you do have a pretty small electrical system on the TT. At least the battery capacity is small. The alternator/voltage regulator on the Jeep is designed to keep the starting battery charged and run whatever other elecrical devices in the car. It really isn't designed to charge a deep cycle battery, especially at idle speed. If you plugged a bigger device to 120VAC, you could drain the battery very quickly.


You may not be looking to spend a bunch of money, but a couple golf cart batteries would be a good thing coupled a solar set and/or a small generator. I assume you have a charger (some call it a converter) in the TT which charges the battery when plugged into shore power. The solar set up would connect directly to the battery whle the generator would connect to the shore power cord.


Camping is a wonderful thing. All the stuff from civilization gets in the way sometimes, though.

Yes, our trailer has a converter that charges the battery when we plug the shore power in and it also charges from the GC when driving down the road. I do plan to install another battery or two 6v batteries and at least a couple hundred watts of solar to charge the battery/batteries, but that's a few months down the road at this point. In four days we are leaving for a month-long trip out West (Colorado, Yellowstone, Grand Teton, etc.) so right now I'm just trying to come up with a somewhat efficient way to charge the TT battery when we are camped for a few consecutive days. I realize that charging the battery by running a 5.7 liter Hemi isn't the most economical way to do it, but since that's what I'm stuck with I'm just trying to figure out if it would be better to do with with jumper cables vs. using the trailer to GC wiring.

[simonsrf]

Originally Posted by bfisher003

Yes, our trailer has a converter that charges the battery when we plug the shore power in and it also charges from the GC when driving down the road. I do plan to install another battery or two 6v batteries and at least a couple hundred watts of solar to charge the battery/batteries, but that's a few months down the road at this point. In four days we are leaving for a month-long trip out West (Colorado, Yellowstone, Grand Teton, etc.) so right now I'm just trying to come up with a somewhat efficient way to charge the TT battery when we are camped for a few consecutive days. I realize that charging the battery by running a 5.7 liter Hemi isn't the most economical way to do it, but since that's what I'm stuck with I'm just trying to figure out if it would be better to do with with jumper cables vs. using the trailer to GC wiring.

I'm all about solar, but in your case, I'd suggest a generator for your needs. It could be running and charging you batterie(s) while you're using your electrical devices at the same time.

[tbbg II]

Originally Posted by bfisher003

Yes, our trailer has a converter that charges the battery when we plug the shore power in and it also charges from the GC when driving down the road. I do plan to install another battery or two 6v batteries and at least a couple hundred watts of solar to charge the battery/batteries, but that's a few months down the road at this point. In four days we are leaving for a month-long trip out West (Colorado, Yellowstone, Grand Teton, etc.) so right now I'm just trying to come up with a somewhat efficient way to charge the TT battery when we are camped for a few consecutive days. I realize that charging the battery by running a 5.7 liter Hemi isn't the most economical way to do it, but since that's what I'm stuck with I'm just trying to figure out if it would be better to do with with jumper cables vs. using the trailer to GC wiring.

Unfortunately, neither one is very good. I would hope the plug to the car is fused. If so, it must be a pretty small fuse because of the small wire that was not designed to recharge a depleated battery. Jumper cables are of larger gauge, but the fact that car alternators are speed dependent (low RMP, low output), to get any real charging you may need to sit in the car and depress the gas pedal a bit to increase the engine RPM's. But this may actually overcharge the TT battery, since this is also not designed to recharge a second depleated battery. Either way, depending on the amount of juice you use, you may be looking at hours of hemi running each day. Sorry to be a naysayer.

[Big Bear Local]

Get a small generator.

[nothermark]

The short answer is that they jumper cables are a bad idea. Batteries are not instant charge devices. They take time to absorb a charge via chemical changes in the battery. You would be a lot better off with a generator and a plan to run it for a few hours in the evening to both cover your peak load and charge the battery at the same time.

You are also over invertered or under batteried. The easy way to estimate current draw on an inverter is to multiply the 120 VAC load current by 10. That has a bit of error but the efficiency of the inverter eats the error. 1100 watts at 120 VAC is 1100/120=9.2 Amps. The 12 VDC side will draw ~92 Amps from your 85 AH battery that should not be discharged more than 50% of capacity. That would put you at less than 30 minutes run time before you are eating your battery plates.

Reality is that you probably do not need 1100 watts for the TV. Forget the coffee pot or hair dryer. I'd look at a 2000 watt generator and appropriate 3 stage charger/inverter to simulate shore power in the evening for 3 hours or so. Let the line from the tow vehicle do the 10% top off that takes a long time. That would also let you use the Microwave or A/C if needed for dinner.

[KerrTx]

Google Zamp Solar or look for it on Amazon. They make portable Solar for RV's in several configurations.

[parkerbill]

I appreciate all the responses, but again, I am aware of the current state of the single battery, over invertered, etc. , but guys one must start somewhere and I started with the inverter, next will be solar panels, as I said, and additional battery capability. I had a limited amount of time (and money), so I have what I have at this point in time and it will have to do for the next month, unless I just happen to pick up a generator along the way. LOL

[wingnut60]

Having been in this situation early in my camping days, I can tell you that trying to charge the battery with the TV is not going to make you happy. Once the battery goes down, not much but a 120volt charger run off a gen/shore power will properly recharge it. The TV is designed to keep the battery from running down when traveling, it will not do much more than that.
Having also been in the limited money situation several times, I found that actually spending for a gen (got a cheap/loud one) was better than being without battery power.
Hope it works out--if nothing else, I believe the battery will get more charge from using cables rather than the charging wire in the trailer harness connection.
Joe

[mavric65]

Look here
http://www.amazon.com/Renogy-Watts-M...le+solar+panel

Plug and play and can move it to be in the sun all day $280

[1bigmess]

Originally Posted by DAN L

bfisher003
harbor freight has inexpensive gennys and solar. i have not used either so I cannot speak about their effectiveness.
do a forum search for more info.

I have used their solar. If you know how to use solar efficiently and effectively, wait for their full kit to go on sale or coupon and buy two and a combiner (?). 90 watts of solar power max from two kits will charge OK and at good voltage. If you want more solar power, but the panel sets until you have enough, or downs the money on good PV tech and install and be pretty much done with it if you like/can afford it.

[1bigmess]

Originally Posted by Campingman

Get a small *QUIET* generator.

Just a little friendly reminder about gennie noise. It doesn't have to drive your neighbors crazy if it drives you crazy first.