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Will a bigger alternator work? Power in the bed...


outomyelement

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Hey all,

I'm trying to figure out an inexpensive way to add batteries in a toolbox in the bed with an inverter for tools and an AC system for the bed. Can I either 1) divert some alternator power to charge a few deep cycle batteries in the bed, and if so, will I need a larger alternator, or 2) should I just get an inverter and charge the batteries while the car is running with a second inverter?

Thanks for your help!

Kevin
 


Will

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First, your alternator is large enough to work if you run the engine at a high enough rpm--maybe 2,000. A throttle lock would be nice. A quality deep-cyce can absorb about 40amps of current per 100AH. A pair of group 24s (about 65AH) would be easily serviced by your alternator drawing 50amps max. during charging.

Keep in mind that a cheap high-amp alternator is a piece of shit for doing what you are doing. I would not swap out a stock one for one of those. A marine alternator, like a Balmar, is meant for that. They don't sell one over about 130amps in the standard frame sizes that would be found in a car or truck. A 200amp Balmar would weigh 25# and cost a couple thousand.

Next thing is, it's a bad idea to discharge a deep-cycle battery below 50%, and a bad idea to discharge a starting battery below 10%. So for a deep cycle you need about twice the bank size that a calculation would give you. For instance, if you want to run a 5,000BTU window unit that draws about (a guess) 700watts while it's running, that would drain completely a single Group 24. So you would need 2 to keep one from going below 50%.

Another thing to consider is the inverter. An inverter isn't good with surge loads. A small 5,000BTU window unit runs at about 6amps (a guess) and whenever the compressor starts probably surges to 40amps. An inverter doesn't have a long surge capability like a generator--which can lug along for a while before popping it's breaker. I would get a huge, cheap inverter and hope for the best. Definately web search and see what exact combinations people have had success with. I decided against risking this with my bus conversion because a couple thousand bucks worth of batteries and inverter and maybe it would or maybe it wouldn't be able to start the AC. I ran a 5,000BTU off of my Yamaha EF1000--which is a very small generator. I would lug like hell then finally the AC would hum to life. I kept the AC on full blast and used the camper windows to keep it warm enough to not allow it to turn back off. You might consider 2,000Watt Honda or Yamaha instead of batteries. They are quiet, reliable, last more than 200 cycles (which is the expected life of a deep cycle flooded battery) and there is no risk in it not working.
 

Will

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And another thing--don't plug a battery charger into an inverter. Charge the battery with an alternator.

Also, don't use a battery isolator (which uses diodes) on your expensive deep-cycles. There is resistance in the isolator which keeps a battery bank from reaching a full charge--or can overcharge the other battery because the alternator field is only sensed on one bank. A better device is a battery combiner which connects the batteries together to charge them using solenoids instead of diodes.
 

COPPERHEAD85

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:word:

i run a battery store,plus will knows his stuff,i agree....if you want to run and have no problems....use a gen.
i just helped a guy do an install with 2 31 series AGM batteries with a 3200 watt inverter with a isolater to run a AC in his van,that way he could charge the batteries while he drove and run the air at night while he & his wife slept.
works ok but he would have been better of with a small honda gen.
the inverter craps out before the batteries do.after wire and batteries (at $239 each and a $300 inverter) a few more bucks and he could have got the gen.

the AGM batteries will smoke a wet but have to be charged to 13.2 volts.they are worth the money but you have to know how to maintain them.
 
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outomyelement

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Thanks for the feedback! I think i'm leaning towards a 1000W or 2000W super quiet Honda generator. You're right about it costing less after a little more research. I guess I'll reserve a compartment in my toolbox. I'll have to run a vent out the box, out of the bed...

Thanks again.
 

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This generator is cheap and extremely quiet. They are also reliable. You could get a Chinese one for $100 probably. I would take my Yamaha to war with me. And remember every 3 decibels is twice the sound pressure so look at that when shopping for one.

This is how my Yamaha was mounted on my Casita--I didn't do it, it was the work of a previous owner. There were vents in both sides and a large computer type fan screwed inside one of the vents blowing out the exhaust and heat. The fan plugged into one of the 120V recepticles and the other recepticle was used for the RV cord. It worked for my EF1000 but you might need more ventilation and a second fan for a 2000W. SOund deadening pads stuck inside the compartment would help deaden it even more.

 

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outomyelement

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Thanks for the photo!

I have an under-bed toolbox that fits well against (below) the rear cab window in the bed. I was thinking I would put the generator in that and either run a vent out of the side or down through the bottom. I have a camper shell, so I'm not worried about leaking.

Thoughts?
 

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Well, first and foremost you don't want to die of CO poisoning. Next, you need a fresh air intake and a foul air outake. You will see by running your generator that there are vents in the housing that will guide you in what needs to go in the toolbox to vent it. Maybe you can cut a hole in the front of your bed for the intake and through the floor for the outake. The big problem is that the exhaust pipe needs to be sealed until it gets outside the perimeter of the vehicle. Otherwise it will pool under the truck and slowly find its way through cracks and crevices in the bed. I was thinking a box like I had, mounted on maybe a hitch mount plate and stored in the back of the truck. When you stop, you can lock it to a front mounted receiver with a locking hitch pin and run a cord back. If needed, it could ride on the front. These are not heavy generators.
 

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