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WATTS = VOLTS X AMPS ????

2FORCEFULL

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WATTS = VOLTS x AMPS...…..VOLTS = WATTS DIVIDED BY AMPS,...……..AMPS = WATTS DIVIDE BY VOLTS..….CORRECT????

SO HERE'S THE DEAL.,... I'm BUILDING a stealth camper van,,.. bout' done really...it has a fridge, micro, tv, and a coleman cub 9020 btu roof A/C...It's set up with 30 amp shore power... a 300 watt 24v roof solar... with a 30amp controller and a 3000 watt pure sine wave inverter powered from a 200 amphour gel battery...

so.... knowing what I know about solar and battery power loads... I did the basic , I wanna run the A/C off batterys… so here's where I think I went wrong, well, haven't yet because the a/c is still on the way.... but I have the hole cut in the roof and power ran to the hole,... My Idea here is...lets say I wanna run to so cal..with the van,... it has front and rear engine A/C... it'll freeze you out....but lets say I just get to barstow….I can pull into a RV park and hook up... most every one has showers and shitters...and run the roof ac... the bed is 72'' x 75'' so super comfy

so in all of this I started thinking.....the A/C is 11.7 amps runs about 1270 watts... 1550 watts in high desert heat,my inverter is 3000, with 6000 watt surge...should run it no problem, right???the battery is 200 ah … another should work.... right.......here's where I say wrong, won't work...


the running watts of 1550 is @ 120 volts....but,... I think if you are getting the power from 12v then inverting it to 120 volts you have to start there....????

so...1550 watts div by12 V = about 130 amps!!!!! a 200 amp hr batt will only give up 100 amp
 
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Minimatt

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Top line is correct, except the last item should be Amps = Watts divided by Volts

I believe your conclusion is correct: with the A/C unit drawing 11.7 amps at 120 volts, you will be somewhere around 130 amps at 12 volts through the inverter. The 200 amp-hour battery will not be adequate.
 

BasilHayden

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I would add 3 more panels, 3 more batteries and run the inverters off 24v if possible. In short you are short panels and batteries if you want it run for any period of time at all.
 

2FORCEFULL

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Top line is correct, except the last item should be Amps = Watts divided by Volts

I believe your conclusion is correct: with the A/C unit drawing 11.7 amps at 120 volts, you will be somewhere around 130 amps at 12 volts through the inverter. The 200 amp-hour battery will not be adequate.
thanks for posting, fix'd the first post...
 

2FORCEFULL

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I would add 3 more panels, 3 more batteries and run the inverters off 24v if possible. In short you are short panels and batteries if you want it run for any period of time at all.
One 300 watt 24v panel took up the whole roof
 

Shlbyntro

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Top line is correct, except the last item should be Amps = Watts divided by Volts

I believe your conclusion is correct: with the A/C unit drawing 11.7 amps at 120 volts, you will be somewhere around 130 amps at 12 volts through the inverter. The 200 amp-hour battery will not be adequate.
Agreed. And keep in mind that your calculations are based on a 100% efficiency through the inverter which does not exist. Some are better than others but a basic safe rule of thumb is to calculate for a 30% loss through the inverter. This is a high number but the one you want to use when you're trying to determine how large your battery bank needs to be.
 

DaveH

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you are missing the inefficiency losses of both the inverter converting from DC to AC and the inherent losses the battery suffers with temp and age.

sure when everything is new and run in 70' weather.....with two batteries i would be suprised if you could run the AC for more then 45 minutes.

put it in a hot environment, older batteries......you will be lucky to get 15 minutes out of it.

save yourself all the headaches and run your AC of a generator.
 

spectracular

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save yourself all the headaches and run your AC of a generator.
This. Your idea will work, but you’d need monster battery reserves to run for anything more than 30-45 minutes, even with that panel replenishing the batts. I’ve been told that panel ratings are theoretic maximums and are atypical of what you will experience after you account for losses due to atmosphere, angle of sun, etc...in short, they are rated as if they are in space and pointed directly at the sun.
 

2FORCEFULL

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here's the thing that got me thinking, and wondering how they do it... they say these will run a A/C 8 hrs off a 100 ah battery.... they have what called under hood gens,... 260 amp alt.. when the batter level drops the engine starts...



 

spectracular

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What about a remote start module from a car alm? Many have a low voltage auto start feature. Seems you could use something like that to start either the vehicle of a small generator.
 

2FORCEFULL

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you are missing the inefficiency losses of both the inverter converting from DC to AC and the inherent losses the battery suffers with temp and age.

sure when everything is new and run in 70' weather.....with two batteries i would be suprised if you could run the AC for more then 45 minutes.

put it in a hot environment, older batteries......you will be lucky to get 15 minutes out of it.

save yourself all the headaches and run your AC of a generator.
I have 30 amp shore power.... the idea for me was to go and plug in...most all the time it cools off at night,... so not needed... that and 2 a/c's for running down the road.. my battery bank power is to watch tv, and run the little fridge and micro wave..I have a float trickle charge to keep the battery topped off in the garage, and the solar to top off the battery's...this will be a cool little camper rig,... I have a king size bed rv with full wall slide out..... this is the one step up van down by the river..
 

2FORCEFULL

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What about a remote start module from a car alm? Many have a low voltage auto start feature. Seems you could use something like that to start either the vehicle of a small generator.
I don't really need the ac to run,... just the little fridge...but at the same time, how are the new class B's doing it... I went a tried one... ac started and kept going off 1 100 amp hour gel battery....
 

2FORCEFULL

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the way I set my van up , the inverter power and shore are separate.... I ran a twist lock 30 thru the wall, to a 30 amp plug in the van...my 120v power panel is 30 amp with three breakers...that panel has a male 30amp plug.... I hard wired a 30 amp pig tail out of the in verter… so when on shore power, I plug into the shore power plug,... then when going down the road... I plug into the 30 amp inverter pig tail...
 

spectracular

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I don't really need the ac to run,... just the little fridge...but at the same time, how are the new class B's doing it... I went a tried one... ac started and kept going off 1 100 amp hour gel battery....
A batt will run it...but for how long? The math is straight forward. You just need the amp draw on the new AC units.
 

2FORCEFULL

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A batt will run it...but for how long? The math is straight forward. You just need the amp draw on the new AC units.
the amp draw is 11.7 @ 115 v -------1270 watts... some how I don't think the conversion is right...the pulling 105 amps out of the battery..

I have a clamp on to check amps...we'll see... I know on the ram van class b's, they come with 100 amp hr battery's and it's an up grade to get the 200
 

2FORCEFULL

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the inverter says it will handle a constant 15 amp draw... it's 3000 watts, with 6000 surge..pure sine wave...
 

Blue

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What's a baller like you doing with gel batteries? If you plan on keeping this more that the normal 48ish hours get lithium batteries and don't look back. They pay for themselves several times over
 

DaveH

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as someone who has been around electricity for a while here is my tip to maximize your batteries.........

run AS FEW DEVICES as possible of AC power.

why? because ANYTIME you "convert" there are huge losses built in. as an example........a TV that doesnt draw much power on AC uses a ton of power when you run it through your inverter to your DC system.

find as many lights, TV's, fridges, other appliances that run DC natively.

when plugged into shore power, you would have a charger to keep your batteries topped off. GOOD inverters have this ability built in and go "both ways".

the only AC device in your van should be the air conditioner.
 

braindead

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here's the thing that got me thinking, and wondering how they do it... they say these will run a A/C 8 hrs off a 100 ah battery.... they have what called under hood gens,... 260 amp alt.. when the batter level drops the engine starts...




They can say what they want, but can it keep up with the temp you'd like inside and the temp it will be outside for that length of time is the question.

I'm sure that thing will run for 72 hrs in Alaska in January.
 

Taboma

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If this chart is correct ( If, being the key here), then something is off with your load measurements. It shows the starting load for a 10K BTU RV AC @ 2,000 watts
but the running load at 700 W. ??

 

2FORCEFULL

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so,... my in line fuse came ,.. so I was able to hook up to battery power..here's what happened...tv on.. clamp on tester on positive battery cable..3.02 amps...turn on fridge... jumped to 9.7 amps,... turned on micro wave (700watts) went to 22.6 amps... now with every thing off but the tv, put the clamp on on the ac out cord..... .01 amp.. ran my big shop vac... no problem... I can go back and check at the breaker box to the hot coming in and get a better reading.... but any ways... does what I want......
 

2FORCEFULL

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What's a baller like you doing with gel batteries? If you plan on keeping this more that the normal 48ish hours get lithium batteries and don't look back. They pay for themselves several times over
these have a 3 year warranty and good for 12 years.. cost 400 vs 1200, i'll be 80 when they go bad..
 

Flying_Lavey

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I saw one of the RV A/C companies (Dometic I think?) Now has inverter A/C's for RV's (same technology thats used in mini-split systems). An Inverter system will draw substantially less power. Specially in the situation you describe. The compressor and fan motors speed up and slow down based on the load so once the coach reaches its set point, it RARELY will run 100%. I'm sure they are a pricey little bastard, but, would be a trick set-up on your little van.

Sent from my SM-G973U using Tapatalk
 

Boat 405

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Get a honda 2200 generator and put a soft start kit on your roof top ac and be done.
 

Havasu Catman

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I don't think you will be able to run ac on solar. Go to amsolar.com They have some great information about solar.
 

rrrr

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the amp draw is 11.7 @ 115 v -------1270 watts... some how I don't think the conversion is right...the pulling 105 amps out of the battery..
How do you get 1,270 watts out of multiplying 11.7 X 115? That's 1,345.5 on my calculator. If you're running 120 volts, the current drops to 11.2 amps.
 

2FORCEFULL

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I don't think you will be able to run ac on solar. Go to amsolar.com They have some great information about solar.
you wouldn't run it off solar... it would run off the battery bank... the problem would be how to re charge the battery...
 

Sleek-Jet

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so...1550 watts div by12 V = about 130 amps!!!!! a 200 amp hr batt will only give up 100 amp
You are correct, watts is watts.

Since the DC system is running the inverter you need to start there on your math.

It'd be easier to hide a small genset somewhere on the RV.
 

DILLIGAF

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I am far from an expert but that doesnt seem like it is going to work in real life conditions Steve. When plugged into shore power sure but lacking on batttery and solar capacities.

i am ready to pull the trigger to outfit my 5th wheel with 1500W (maybe 1875 if i can get one more panel on top) of solar and between 6-12 battle borne lithium batteries so I can be off grid majority of the time as I travel around the USA. The lithiums can (I have been told) drop down to pretty much 0 capacity and be recharged.

at least get a couple of lithiums but the solar panel will be nothing more than a trickle charge and if the AC is running I have no idea how long it would stay on for. Not running AC i think that would work great for ya. Somebody mentioned a soft switch for the AC...yep

by the way...these lithium batteries only weigh 29 lbs
 

WhatExit?

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When's the rv for sale? Towing capacity? That's a nice rig
This is 2FF's best "For Sale" thread yet. Talk about a "Stealth Camper Van" this thread is the best stealth for sale dealio he's done yet 😁 😁 😁
 

2FORCEFULL

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I am far from an expert but that doesnt seem like it is going to work in real life conditions Steve. When plugged into shore power sure but lacking on batttery and solar capacities.

i am ready to pull the trigger to outfit my 5th wheel with 1500W (maybe 1875 if i can get one more panel on top) of solar and between 6-12 battle borne lithium batteries so I can be off grid majority of the time as I travel around the USA. The lithiums can (I have been told) drop down to pretty much 0 capacity and be recharged.

at least get a couple of lithiums but the solar panel will be nothing more than a trickle charge and if the AC is running I have no idea how long it would stay on for. Not running AC i think that would work great for ya. Somebody mentioned a soft switch for the AC...yep

by the way...these lithium batteries only weigh 29 lbs
your deal is way different than mine...I go from vegas…. to bullhead, bout 100 miles... when I get there, I have a brand new house that has a garage with 50 amp power... so if I don't wanna go in the house, I can stay out in the van with ac on shore power..next, I go to havasu… there I have a house with an rv pad.. I have the house rented out... but not the rv pad, i'm building a new house next door to there, in fact, they are framing it while I type this.. when I go there to check on the build... I can plug the van in for a short stay.... or just go there in the big rv with 2 ac's...I have no intentions of getting into "it's a van life" and try'n to live in a match box,.. intentions are to be able to bring food from home...stop where ever I want and have lunch or dinner... take a nap, or sleep over nite...I added the micro wave as it was only 59 bucks, and it makes the build more complete.. yester day I ran it a couple minutes off the inverter..didn't seem to affect anything... but, probley never get used much... but there if needed..the bed is the big plus... almost king size, and I can sleep there with out dropping the table...or drop the table if my wife is with me and need more room..but.. we both have plenty of room with the table up,... the mother in law pole in the middle keeps everyone on their own side
 

2FORCEFULL

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This is 2FF's best "For Sale" thread yet. Talk about a "Stealth Camper Van" this thread is the best stealth for sale dealio he's done yet 😁 😁 😁
also,... I'm building a custom stealth 20' v nose camping/cargo trailer that hauls 2 rzr's and sleeps two...300 watts of solar 30 amp power...and a honda gennie...
 

2FORCEFULL

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I sold this rv cause it was too big and did too much
IMG_0817.jpg
 

2FORCEFULL

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Get a honda 2200 generator and put a soft start kit on your roof top ac and be done.
why not just put the key in the rv that has 5kw gen , two roof ac's, a king size bed, start it up and go ????
 

2FORCEFULL

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This is one of those deals where you start with not enough..spend a bunch of time and end up with very little...but it works for you , so cool...
 

DILLIGAF

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your deal is way different than mine...I go from vegas…. to bullhead, bout 100 miles... when I get there, I have a brand new house that has a garage with 50 amp power... so if I don't wanna go in the house, I can stay out in the van with ac on shore power..next, I go to havasu… there I have a house with an rv pad.. I have the house rented out... but not the rv pad, i'm building a new house next door to there, in fact, they are framing it while I type this.. when I go there to check on the build... I can plug the van in for a short stay.... or just go there in the big rv with 2 ac's...I have no intentions of getting into "it's a van life" and try'n to live in a match box,.. intentions are to be able to bring food from home...stop where ever I want and have lunch or dinner... take a nap, or sleep over nite...I added the micro wave as it was only 59 bucks, and it makes the build more complete.. yester day I ran it a couple minutes off the inverter..didn't seem to affect anything... but, probley never get used much... but there if needed..the bed is the big plus... almost king size, and I can sleep there with out dropping the table...or drop the table if my wife is with me and need more room..but.. we both have plenty of room with the table up,... the mother in law pole in the middle keeps everyone on their own side
You rent out the RV pad in Havasu? If so, PM me with some details......
 

2FORCEFULL

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and, nobody makes what I want that does what I wanna do...this van gets 18 mpg going to havasu from vegas and 17 mpg coming back,... tows 10k, has a 17k hitch 6.0 v8
 

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Micro-air Easy Start 360 is great. Just added 2nd 13K AC to my 27' class C, Put "Easy Start" on both units . Start up 11.1 amps / running 8.1 on high cool on 93 degree day. ( each) . Now I can run both AC's on 30 amp no problem. Both will also run on the 4k generator.. Tons of YouTubes videos n it.
 

2FORCEFULL

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Micro-air Easy Start 360 is great. Just added 2nd 13K AC to my 27' class C, Put "Easy Start" on both units . Start up 11.1 amps / running 8.1 on high cool on 93 degree day. ( each) . Now I can run both AC's on 30 amp no problem. Both will also run on the 4k generator.. Tons of YouTubes videos n it.
probley gonna do something like that on my class A so I could run 3 ac,s… it has 50 amp/5000 gen
 
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