Our Box Truck RV Conversion

[redman4556]

Sorry for the diversion in topic. My dad (ex-electrician) basically tore me a new one about using a generator as opposed to a deep cycle battery bank and solar panels. He also explained that even at the discounted price, I could put together a more efficient and easier to use battery bank system for around the same or slightly less cost. If anyone does need a long lasting good generator, those hondas are a steal at target's price!

Edit: I figure that with my dual batteries under the hood, if I run out of sun and stored power, I've always got an emergency back up charge with the engine running.

 

[java]

Dual barriers does not a house battery bank make..... You will not be able to run ac on a battery bank.

What all are you trying to run? Calculate your estimates usage and double for bank size.

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[redman4556]

Maximum load on at one time would be AC and a couple of LED lights. AC is a tiny 5000 BTU GE, super energy efficient window unit that takes up at absolute most 4 amps at any given time. I'm planning on connecting 4 marine deep cycles which ought to be wayyy more than needed for such an AC unit? In such a small space, I'm not planning on running the unit for more than a few minutes at a time either. And dual batteries have nada to do with the bank, I just figured I could safely disconnect my accessory battery and charge a deep cycle off the alternator in the case of an absolute necessary emergency charge in the boonies (say its been raining a few days straight). Having the dual batteries just makes it easier to charge a battery off the alternator as a deep cycle can't start a car (properly) so I'd want a regular car battery in the circuit as well for easier charging.

 

[java]

5000 btu is 1465 watts, 1465 watts at 12vdc is 122 amps. That's a ton of power....

It's doable, but will take a huge battery bank.... Realistically it's not doable.

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[redman4556]

I think we're on totally different pages. I know online calculators convert watts to btu's, but in the case of air conditioners these btu ratings don't make much sense. As I don't plan to at any time make the unit work hard enough to actually hit the rating it can in a test factory, the unit I'm looking at will use at most 550 watts per day even on the hottest of days. (Much less or none at all on cooler days, and this includes the spiked wattage at each start-up these things tend to use.) 550 watts between 4 deep cycles is chump change, no?

 

[java]

I think we're on totally different pages. I know online calculators convert watts to btu's, but in the case of air conditioners these btu ratings don't make much sense. As I don't plan to at any time make the unit work hard enough to actually hit the rating it can in a test factory, the unit I'm looking at will use at most 550 watts per day even on the hottest of days. (Much less or none at all on cooler days, and this includes the spiked wattage at each start-up these things tend to use.) 550 watts between 4 deep cycles is chump change, no?

Yes 550w is nothing. But I think your off on your wattage calc.... What is the actual spec 12v or 120v on the ac unit?

FWIW my fridge draws 4.5 amps running, the heat is about 6 amps when running, the maxxfans is 2.8 amps on high. It adds up in a hurry. I draw about 10% of a 500AH bank a day running fridge and lights and a little heat.

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[redman4556]

Yes 550w is nothing. But I think your off on your wattage calc.... What is the actual spec 12v or 120v on the ac unit?

FWIW my fridge draws 4.5 amps running, the heat is about 6 amps when running, the maxxfans is 2.8 amps on high. It adds up in a hurry. I draw about 10% of a 500AH bank a day running fridge and lights and a little heat.

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Unless I'm crazy, I'm pretty sure my estimates are accurate. Max draw on the 120v unit is 4amps and it really will only be on in short bursts. The 5k btu rated unit is WAYYY more cooling power than I will ever need.

EDIT: I should mention that my estimates have accounted for power lost to the inverter.

 

[java]

Yea but 4 amps at 120v is 122 at 12v. Plus inefficiency from conversion.

I'd say it will run what, 2 hours a day? That's still 240 ah. My bank. Is 500 total, that's all my useable staying above 50%SOC

My main interior lights are 33w when they are on and they are all led.

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[redman4556]

Yea but 4 amps at 120v is 122 at 12v. Plus inefficiency from conversion.

I'd say it will run what, 2 hours a day? That's still 240 ah. My bank. Is 500 total, that's all my useable staying above 50%SOC

My main interior lights are 33w when they are on and they are all led.

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I'm sorry for the confusion, on the hottest of days here in California, for camping purposes that ac wouldn't run for even an hour a day. Couple of minutes here and there.

And my calculations of wattage were based on over an hour per day of use. 4amp isn't constant its maximum. How many batteries are in your bank? I have zero familiarity with deep cycles.

 

[pappawheely]

Excellent question, one you won't like the answer to one bit. Nobody will like the answer to this. Tripod jacks and concrete blocks! I'm hoping to buy a box already off the truck, but the trucks i'm looking at with boxes still on them don't have much to cut underneath. If the ubolts holding the box down are too difficult to remove with tools, that's the only thing I can forsee having to cut as nothing is welded down there. The more I look the more I'm feeling these wheelwell and sideskirt having boxes are mounted in much more difficult to remove ways than a standard cab/chassis style flat bottom box.

EDIT: I went back and looked at your box. It seems it was secured with welded on bracketry and other welds as opposed to the two frames simply being ubolted together?

There were parts that I cut off but the bolts that were holding the box to the frame (16) were seized up, would not budge with an impact or heat. I had to use the plasma and grinder.

 

[southpier]

sounds like the whole family has it together

 

[The Artisan]

Red you are going to need a 2k genset just to start that AC unit, let alone run it.
Kevin

 

[wagex]

Yea but 4 amps at 120v is 122 at 12v. Plus inefficiency from conversion.

I'd say it will run what, 2 hours a day? That's still 240 ah. My bank. Is 500 total, that's all my useable staying above 50%SOC

My main interior lights are 33w when they are on and they are all led.

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amps x volts = watts. 4ax120v= 480w 480w\12v= 40amps. not sure where the 3x multiple came in. but somehow the amp hour calc was right ¯\_(ツ)_/¯

120 amp hours per hour of the compressor running is correct.

if you run the AC 5 minutes per hour that would be about 10AH per hour which might be enough to keep it cool in there depending on insulation and outside temp. it feasable. so for an 8 hour day 80AH+ would be required. also need to calculate the roughly 20% loss of efficiency in the inverter.

 

[java]

amps x volts = watts. 4ax120v= 480w 480w\12v= 40amps. not sure where the 3x multiple came in. but somehow the amp hour calc was right ¯\_(ツ)_/¯

120 amp hours per hour of the compressor running is correct.

if you run the AC 5 minutes per hour that would be about 10AH per hour which might be enough to keep it cool in there depending on insulation and outside temp. it feasable. so for an 8 hour day 80AH+ would be required. also need to calculate the roughly 20% loss of efficiency in the inverter.

I went off the 5k btus. 5k btus = 1465W

I see your probably right though... Either way its still a huge drain on a battery.

 

[redman4556]

I went off the 5k btus. 5k btus = 1465W

I see your probably right though... Either way its still a huge drain on a battery.

I'm planning on a 400 ah bank. Though 100a+ for a hot days ac usage is a big drain, it's not near my capacity and I sincerely doubt even using it that much. Keep in mind the maximum electrical load at any one time would be this ac and a few led's.

Konakid - I don't think so? This is a tiny, super energy efficient window ac we are talking about. If I were using the Honda generator I shouldn't need nearly the full 2000w power of the generator to start and run the ac and some lights. For many reasons, I've chosen to go with a solar supplamented batter bank instead.

I'm getting ready to go look at yet another box. I've come to the realization that 10' boxes are much more elusive than 12' one's. I believe I can get away with a 12' box so long as I mount it real well and don't take the truck off road. Does anyone know whether the rails on the bottom of these flat bottom boxes are 3 inch or 4 inches thick? I saw a couple, but was too stupid to measure at the time. Does it vary? I'm just trying to figure out how tall of mounts and what size ubolts I need.