I need help with a battery and charging system

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I need help with a battery and charging system

Postby tsyj » Mon Feb 13, 2017 8:59 am

I've read just about all the threads here, but I can't find the exact answer I am looking for, maybe someone can help.

I have a cargo trailer conversion that spends 90% of it's life at campgrounds with shore power. It is wired 110v, 30 standard. I have 2 trips planned that are primitive sites with no power available. I want to mount a battery box on my trailer with a deep cycle battery, and probably a 1,200 watt converter so I can run a couple lights (LED) and fans at night if it gets hot. I know that the sites are in the shade, so a solar recharging system is out. Is there some device that I can install on my Wrangler that I can hook up to with a quick disconnect and charge the battery if needed? I've read it's not optimal to charge a deep cycle like that, and it reduces it's lifespan?

Basically, I want to open the battery box, pull out 2 cables, open the hood of my Wrangler and hook the cables up with no tools and turn on the Wrangler to charge the battery. Is there such a device, short of just jumper cables

Thanks!
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Re: I need help with a battery and charging system

Postby Socal Tom » Mon Feb 13, 2017 9:09 am

You can find a 7 wire harness on amazon . Mine was about $60. If you hook it up, and wire te trailer as well it well charge while driving, and would charge while idling. The other option is jumper cables.
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Re: I need help with a battery and charging system

Postby Padilen » Mon Feb 13, 2017 9:11 am

If I understand your question your going to be using - your trailer battery and using your Jeep battery to recharge it.
I think your Jeep will be running a long time. There has got to be a better way/solution. Even a small cheap generator would be a better option to me.
But if you have a 7 pin wiring connection one pin is for charging.


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Re: I need help with a battery and charging system

Postby tsyj » Mon Feb 13, 2017 9:21 am

I'll be honest in my 40 years on earth, I've never dealt with the 12v RV world.

I want to take a 12v car sized battery and a converter and stick them in either a plastic tool box, or battery box as a package unit I can throw in the trailer when I know I have to camp somewhere without shore power.
Is there any type of system I can buy, or build that would allow me to hook that box up to my Wrangler and charge it with my alternator? Does the battery even have to be a deep cycle? I am realistically running a LED light on the exterior, and a box fan on the inside if needed (swamp cooler, etc), that's about it. I just need something that would run a fan for 8 hours for when it gets warmer here in Florida.

Thanks!
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Re: I need help with a battery and charging system

Postby Socal Tom » Mon Feb 13, 2017 9:53 am

Ahh when you put it that way look at these systems at goal zero http://www.goalzero.com/power-packs. You could build something yourself that would work in a similar fashion. Also, some of the "emergency power stations" like this https://www.amazon.com/Stanley-PPRH5-Professional-Power-Station/dp/B0051SO7JQ/ref=sr_1_2?s=automotive&ie=UTF8&qid=1486998477&sr=1-2&keywords=emergency+power+station might suit your needs. Home depot offers some, as well as a large selection on amazon.
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Re: I need help with a battery and charging system

Postby Dale M. » Mon Feb 13, 2017 10:11 am

Its already been answered ... Any battery can do what you want, it all depended on the amp-hour rating of battery...
That value (amp-hour rate) you need will be determined by the sum of all the loads (LED's, inverter, fan, etc:).
As for charging, small generator with 12 VDC output or "jumper" cables to tow vehicle or some sort of "plugin" connector as 7 pin or Anderson power pole connectors (in essence "charge while towing") ...Its about as simple as it gets about the only "magic" device to fit your need is what SOCAL Tom mentions.... Only thing I find with these do all magic boxes, is they do a lot of things, but not anything really well....Only other option is Solar, and yes they will charge "somewhat" in shady area or overcast day...

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Last edited by Dale M. on Tue Feb 14, 2017 9:47 am, edited 1 time in total.
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Re: I need help with a battery and charging system

Postby MtnDon » Mon Feb 13, 2017 10:31 am

tsyj wrote: I want to mount a battery box on my trailer with a deep cycle battery, and probably a 1,200 watt converter so I can run a couple lights (LED) and fans at night if it gets hot.


If the goal is to make 120 VAC from the battery , that is an inverter.


Charging from the Jeep engine will be slow. That could be shortened if you have a hand throttle so you can rev the engine higher than idle. Noisy too,=.
Our 6x12 deep vee nose cargo trailer camper conversion... viewtopic.php?f=42&t=58336

We have a small off grid cabin we built ourselves in the NM mountains; small PV solar system; 624 watts PV, Outback CC & inverter/charger ... http://countryplans.com/smf/index.php?topic=2335.0
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Re: I need help with a battery and charging system

Postby Socal Tom » Mon Feb 13, 2017 10:59 am

Assuming you mean a typical 115V box fan. From what I found on line they used about 77 watts per hour, at 12V that will take about 50 amps over 8 hours. ( not counting the efficiency lost converting to 115V) that would suggest you would want a battery with about 100 amp. hour capacity ( going below 50% lowers battery life expectancy). And you would need to recharge it everyday ( idling the engine for 6 to 8 hours assuming charging at 10 to 15 amps per hour).

Alternatively you could use something like this 200MM case fan
https://www.amazon.com/Cooler-Master-Me ... m+case+fan
it uses less than 1/2 amp per hour, so the same battery could run it ( or a couple of them) for several days before you would need to recharge, and at 120CFM per minute each they should provide a good air flow if directed properly. 2 of these would exchange the air flow about once per minute and be fairly quiet ( assuming 250Cubic feet of trailer)
Tom

FWIW a strong box fan moves about 2500CFM per minute on high, in a small trailer that would exchange the volume about 10 times per minute ( could feel like a wind tunnel and be pretty loud) In a 2500 sq ft house one box fan would exchange the air about once per minute.
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Re: I need help with a battery and charging system

Postby lfhoward » Mon Feb 13, 2017 11:25 am

On my trailer I haven't installed my solar panel yet, so I think I have a system that is sort of like what you're envisioning.

I have a battery box on the tongue. In my case I have 3 deep cycle batteries in it, wired in parallel.
I have a battery charger that is mounted inside of an electrical cabinet in the trailer. When I plug into shore power, it automatically charges the batteries and keeps them topped off.
I have an inverter that makes 120V AC household current out of 12V DC from the batteries for when I'm not plugged into shore power.
(I also have a 12 volt DC system for lights and fan, but will ignore that for this discussion and I will assume your lights and fan run on 120V AC household current.)

To see how long you can run your equipment, you'll need to figure out how many watt hours you're going to use in a 24 hour period, and do some math. A single Group 24 deep cycle battery has 12 volts x 80 amp hours = 960 watt hours in it. Since you won't want to drain it down past 50% to maximize battery life, then 480 of those watt hours are useable. Since your inverter is only 90% efficient, you get 432 watt hours from this battery before having to recharge. Less if it's cold outside.

The question is, how many hours can you run your 120V AC equipment on that?
LED light bulb = 15 watts (60 watt incandescent equivalent) or 25 watts (100 watt incandescent equivalent)
Box Fan = 105 watts on high, 77 watts on medium, 56 watts on low
Total usage = 71 watts with the fan on low and with the more efficient light bulb
(A simple 200-watt inverter would get the job done. No need for the more expensive 1200 watt unit you mentioned.)
432 watt hours / 71 watts = 6 hours of electricity with everything constantly on.

Whether or not that suits your needs depends on how long during a day or night you'd be running your fan and lights, and how many days you'll be camping off the grid. Perhaps you'll want to choose a larger deep cycle battery with more capacity, or wire 2 or 3 batteries together in parallel. Three group 24 batteries wired in parallel would get you 1296 usable watt hours, which would run your lights and fan for 18 hours total (2 nights of 9 hours each). I think the simplest solution would be to have a battery system that would give you enough juice for your boondocking trip, and just recharge it when you get home.
My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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Re: I need help with a battery and charging system

Postby lfhoward » Mon Feb 13, 2017 11:35 am

I agree with Socal Tom about the box fan being a pretty inefficient use of power. Your batteries would last longer if you ran those cooling fans he suggested and an led light off off a 12 Volt DC circuit, so that you didn't need to go through an inverter. You'd need to wire up a simple 12 volt circuit with a fuse to make that work, but it would probably be worth it.
My off-road camper build on an M116A3 military chassis:
http://www.tnttt.com/viewtopic.php?f=50&t=62581
Tow vehicle: 2008 Jeep Liberty with a 4 inch lift.
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Re: I need help with a battery and charging system

Postby tsyj » Mon Feb 13, 2017 4:40 pm

Wow. Thanks everyone for all the info. Like I said, I've never dealt with 12V RV systems, and their intricacies...

I did some reading based on all the responses, and I think I am going to go with DC lighting and fan and skip the inverter. I can take a piece of ceiling trim down to access enough of the walls to wire a DC light (the one that came in the trailer is a good candidate). The old cooler filled with ice and a 12v fan blowing air through it will be fine for our comfort needs (I think). Everything else we can live with lanterns, and propane stoves, just like tent camping. :D
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Re: I need help with a battery and charging system

Postby aggie79 » Mon Feb 13, 2017 5:58 pm

I have one of these:

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https://www.ryobitools.com/power-tools/products/details/18v-one-plus-portable-fan

It works really well. The version I have is battery only but you can get one that works off of battery or shore power.
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Re: I need help with a battery and charging system

Postby Shadow Catcher » Mon Feb 13, 2017 9:44 pm

I can think of three possible solutions. High voltage solar panels meant for a grid tie system, mine puts out 74V no load full sun and ~36V load in shade, required a MPPT controller. We spent 8 days on the North shore of Lake Superior in a camp site with maybe one hour of full sun no shade, and at the end of the eight days we were at 64% state of charge. Our big load is a 12 refrigerator.
A solar panel that can be set out in the sun, I have a 135W high voltage.
I have a set of jumper cables with 150A Anderson PowerPoles with are connected to the tear battery and another set of connectors on the tow vehicle battery. Our Subaru uses .34 GPH at idle.
I used computer case fans which work well and use less current and of course LED lights.
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Re: I need help with a battery and charging system

Postby tsyj » Tue Feb 14, 2017 12:29 pm

Shadow Catcher wrote:I can think of three possible solutions. High voltage solar panels meant for a grid tie system, mine puts out 74V no load full sun and ~36V load in shade, required a MPPT controller. We spent 8 days on the North shore of Lake Superior in a camp site with maybe one hour of full sun no shade, and at the end of the eight days we were at 64% state of charge. Our big load is a 12 refrigerator.
A solar panel that can be set out in the sun, I have a 135W high voltage.
I have a set of jumper cables with 150A Anderson PowerPoles with are connected to the tear battery and another set of connectors on the tow vehicle battery. Our Subaru uses .34 GPH at idle.
I used computer case fans which work well and use less current and of course LED lights.


Great info, thanks. I have some more reading to do!
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Re: I need help with a battery and charging system

Postby Graniterich » Tue Feb 14, 2017 4:58 pm

Most sites I have been to are in the shade! I move the panel to a sunny spot, I have extension cables to go up to sixty plus feet, works great
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