I'm guessing he runs the the AC during the heat of the day then recharges.
AC off batteries
- Thread starter Billy The Impaler
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danthewolf00
Veteran Expediter
The ac takes to much power......you need a generator.
Those batterys are going to die very soon.
Those batterys are going to die very soon.
The guy in the video said 8-9 hours after it gets cooled off and switches to low.
Correct. 12-volt air conditioning is for short term usage, like in the cab of a farm tractor. The LiFePO4 batteries will last longer than a wet cell or AGM lead acid battery, but a 95 amp draw even for an hour or two will rapidly decrease the lifespan of the battery.
On paper he's right. In the real world, not a chance. No matter how well insulated the van might be, sitting there parked in an iron box on a black asphalt lot on a sunny day can make inside the van 120 or 130 degrees inside. A rooftop AC will not cool that down in an hour or two, and then maintain the temp on a Low setting. It'll take 3-4 hours at max amp draw of 95 amps (Peukert Corrected Amps = 123.73), leaving at most after 3 hours in the 540 Ah battery bank of 168.81 amp hours (already well below the 50% discharge threshold). Then the AC will draw about 25 Ah for a while, with about an hour or two of those 9 hours drawing a maintenance draw of 15 Ah. After the 8 or 9 hours the battery will be depleted and must be recharged.
At first the alternator might put about 30 amps per hour back into the bank, but that will quickly drop down to 15 or so after a couple of hours, then down to 8-10 amps. If you can average 15 amps from the alternator, it'll take 540 / 15 = 36 hours to recharge the bank. Now you are sitting in Laredo for 3 days and after 8 or 9 hours your battery will barely run the roof vent fan. It gets worse from that point on.
If you get a fancy charge controller you can put far more amps into the battery off the alternator, but it's not going to be much more than 60 or 70 for a few hours. But discharging and recharging even a lithium battery at those rates will realistically cause the battery to lose at least 1% of capacity per month.
Those batteries are $5000 a pair. Aside from the fact that the AC is about $4500, I'd have a hard time justifying paying $5000 for batteries just to then intentionally murder them.
Another note, what works is what you see as the norm on the road. You don't see battery powered AC units very often, but you do see inverter generator powered AC units, like all the time.
What if he runs the engine and main AC long enough to get the temp down inside so all the roof top has to do is maintain it?
danthewolf00
Veteran Expediter
No just no.....you ever sit in southern Texas or Phoenix, az
So you're considering using a $15,000 generator instead of a $2,000 generator?
Seriously, your line of thinking isn't wrong, I and others have tried it out crunched the numbers with experts (off the grid RV and boat people), it's just that many others have tried to do the same thing, and it just doesn't work. One former member here went all-in uh the 12 volt rooftop AC and had four 4 volt L16 batteries (780 Ah). It worked great short term and temporarily, but it didn't take long to discover it's just to many amps from not enough batteries.
A 12 volt fridge is efficient enough to run off batteries, because of its duty cycle. The things that just won't work long term off batteries is resistive heat (electric heater) and air conditioning. People who live of the grid full time do not try to run electric stoves, clothes dryers, AC, etc., off solar and batteries, they run those off a generator.
I had an aunt that lived outside of Tucson off the grid. Solar panels and a massive battery bank. The batteries were Rolls Surrette 2-volt batteries, 1837 Ah eaxh, 200 pounds each, about $900 each. She had 36 of them (about $30,000 worth, and 5500 Ah) wired in series/parallel for a 48 volt system. She ran the clothes dryer and other stuff like that off a diesel generator.
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so many of us wish this could work. it sure sounds quieter than having a generator that burns fuel and needs oil changes just seems counter productive. but so does melting in the hot sun
I heard from the guy again yesterday, and he again said that with 4 lithiums, I could run rooftop AC.
Has your guy ever expedited? You are getting real world advice from experienced expediters who have tried many systems to beat the heat and the cold while living in a van. Their information is based on the real world that you are going to work and live in. Listen to them, they will save you a lot of money and improve your life on the road. Good luck on your adventure.
danthewolf00
Veteran Expediter
Much like running a microwave oven the ac uses to much power to be run by batteries.