Are there any RELIABLE, low, light, Roof, electric AC's/heaters on the market

[tx2sturgis]

A 420 a li-ion (dedicated house) battery fully  charged should supply more than a couple of man-shift-weeks (or 10 ea, 8 hr shifts) of ac no problem.

Wow...either that's 'creative' math or wishful thinking. 

I think you have moved a decimal point one digit too far in your calculations. 

In standard AGM powered engine-off anti-idle APU HVAC systems for OTR trucks, a 400 ah battery bank drawn down to 20% remaining, the bank is rated for one night of power, not 2 weeks. Then the recharge time is ALL day the next day, with a heavy duty (over 200 amp) alternator putting out most of that capacity for many hours. 

Please understand we are not trying to throw a wet blanket on your ideas, but only pointing out the practical limitations. 
At any rate, if you can make it work as you say, please post a full report. I'd love to read it.

 

[John61CT]

Take away the emotional stance to lead and the math imprecision, add a **lot** of infrastructure investment, at least $4k and yes it can be done.

Run mostly off solar when sunny don't use that for charging.

200A actual DC genny (alt) output needs to run at 25-30% of the time the aircon does, so it does buy you some time-shifting.

The bigger the LFP bank the longer (in hours) you can delay burning the dino juice.

The key question is how many watts running how many hours per day?

How large a fuel tank, dollar costs per month also need looking at.

 

[John61CT]

400 ah battery bank drawn down to 20% remaining, the bank is rated for one night of power, not 2 weeks. Then the recharge time is ALL day the next day, with a heavy duty (over 200 amp) alternator putting out most of that capacity for many hours. 

No need for LFP to get full, no declining acceptance.

A 400AH bank could be put together for around $3-4K, a HO DC genny for maybe $1,500

Lots of DIY a bit less money.

So 80AH per night, if actually 160A going into the LFP bank, will be accepted in 30 minutes. So at that rate maybe 2 hours runtime per 24 hours?

Seems optimistic to me, but smaller more efficient aircon maybe.

 

[tx2sturgis]

Keep in mind the ratings and equipment I mentioned are rated for commercial service, real world, amortized cost, and include declining performance (and depreciation) over the lifecycle of the equipment. 

The specs also include all hotel loads, and assume very hot or very cold ambient conditions when the system MUST perform well. 

And sure, LFP and LI might be more tolerant of higher charge rates and lower top-off values, but the batteries are very expensive and involve some financial risk. And group 31 AGM batteries are drop-in replacements if one goes bad, and available everywhere. 

But having said all of that, for systems that include about 400 ah, they do not claim the AC will run for 14 nights, they are sized for one high demand, 10 hour sleeper berth period, where the driver might run the heat or AC, maybe a fan or blower, and other hotel loads, like microwave oven, TV, laptop, phone charger, bunk heating pad, etc.

I think we can assume that if the weather was mild and the loads were lightly applied, the system might last 2 or 3 nights, but I doubt it would be good for even 7 nights with no charging input.

Yes, it's all very doable, no doubt about that, as I stated earlier. But you run into the practicality of cost vs benefits. 

In the trucking world, the practicality issue gets a nudge due to anti-idling laws for heavy vehicles, not to mention HOS regulations, so they are forced to figure out a way to do it, no matter the cost.

But, everything is a trade-off. As in this case, as I stated earlier, all it takes to make it happen, is determination, and a big, fat, open wallet.

 

[jimindenver]

There are lots of formulas, figures, rates, and theories but in reality they are nothing but a jumping off point. It says it will work but until you build it and push the button, they are just scribbles on paper. So I will be interested in seeing how this unfolds.

 

[John61CT]

I was not giving any credence to the idea of multiple days without charging.

I think it came out to the high-amp DC genny / charger needing to run at a 1:3 ratio to the aircon?

There are alts that can put out 350A continuously, so that ratio can be reduced, but if running aircon say half the hours in a 24 hour period, you're definitely burning dino juice a few hours per day every day even with a larger LFP bank.

At that point the solar panels pretty much become extraneous decoration.

 

[tx2sturgis]

At that point the solar panels pretty much become extraneous decoration.

Unless you have a lot of moving horizontal (or vertical) real estate!

 

[John61CT]

It's exceptions that help prove the rule



Happy New Year everyone

 

[Technomad]

There was a lot of back and forth here. Ignoring AC (it’s just a load) and focusing purely on generation, if you would be driving 1 hour every day at highway speeds anyway, am I correct in understanding you guys are saying a portable generator is a better choice than a second alternator?

Effectively the second alternator has only the cost of the decreased mpg from its load on the engine, while the portable generator burns has directly.

Assume a perfect battery / large bank that can absorb 200A of power continuously.

It seems you’re saying alternators (which are really just generators) attaches to a vehicle engine only work for 15 minute and produce much less of their rated load after that.

So why do the inverter generator generators not have the same problem? Or why don’t we attach one of those generators to a vehicle engine?

I actually think that both use the same generator and the only difference is a small engine be a big engine driving them.


Sent from my iPhone using Tapatalk

 

[John61CT]

The issue is if you are stationary boondocking, running your big propulsion engine just for aircon or battery charging is wastefully expensive, both in fuel and engine wear & tear.

Plus it takes a lot of expensive specialized engineering to get alternators to deliver enough current to run an external aircon or to deliver the proper staged charging required to take proper care of an expensive deep cycling bank.

Since you'll have a quality mains charger that already is designed for that, a suitable sized quiet efficient generator is often the best complement for a solar setup.

Finally, many modern fuel-efficient vehicles won't even allow the necessary alternator additions or modifications.

 

[user 13531]

I've seen a couple of rigs with residential mini-split systems, condenser is usually mounted on the tongue or rear bumper. Residential units are designed to operate with a much larger temperature range. Down side is even with the smaller btu systems they suck a lot of juice. Samsung, Fujitsu and Mitsubishi all make very dependable systems..

Here's a couple links for cold weather tests and more discussion...

https://www.buildinggreen.com/blog/cold-weather-tests-limits-our-mini-split-heat-pump

http://www.fiberglassrv.com/forums/f56/using-a-mini-split-a-c-heat-pump-on-your-unit-58009.html

 

[breeze]

Yes, those certainly seem like a good deal if you have the room for the equipment. I am just going to economize w/alternator/solar/li-charging and concentrate on minimizing room/space by eliminating Lead-acid batteries, generators, and out-door compressors. It really is cheaper, but requires an investment and a minor risk of Present Value of Cash.

With my pick up truck ergonomic style cab of my Nissan NV, it kind of made me do the right thing (like Buddha), since most of you have 3 to 4 more feed of cargo length in your high-roof vans.