Question about amp draw

Battery specs are not very linear and you can bet the spec of 914hrs at 25A is about as good as it gets and you can't extrapolate that to other draws very well.

solarix wrote: »

Battery specs are not very linear and you can bet the spec of 914hrs at 25A is about as good as it gets and you can't extrapolate that to other draws very well.

Think that the "914 hrs" is a TYPO. Reserve time is in MJNUTES @ 25 A ... FWIW.

doghouse, you might want to consider a "quiet" diesel generator. That would be lighter, realize that the noise of even a quiet genset might drive one batty when trying to sleep.

You are thinking about powering a fairly heavy load. And seems to me that you will not have enough PV to recharge the battery on many/most days, even at 10 hours of discharge on the batteries, and so on.

Just a drive-by post, FWIW Good Luck, Vic

Ok, now the doghouse name makes sense. Have you considered a 24V system, and / or a DC Air Conditioning system. The 2nd being a way to substantially cut your power requirements. Just might be a good time to anyalize what is out there, that can keep you comfortable and use less power.

Here is a company that makes a lot of different units, this particular one might do the job.. http://www.dcairco.com/product/truck...ir-conditioner.

A little video advertisement - entertaining. http://www.youtube.com/watch?v=xa4g2...ature=youtu.be

Power Consumption 100% duty cycle
720 Watt

Power Consumption 50% duty cycle
360 Watt

Voltage VDC
12 - 24 -74 Vdc (other voltages on request)

A couple of other considerations, the efficiency of the panels 8 years ago may be quite a bit less than those available today, the same goes for the solar controller possibly. It might be worth reviewing that. Obviously you spend a fair amount of time on the road, as well, so there is a chance to fully charge the batteries. How has the system held up on it's own charging your configuration presently.

I actually think your pretty close, I would plan on letting the batteries go to 50% when needed, you will have charging pretty quick and reliable from the truck engine with the solar more as back up. Most of this depends on the duty cycle of the A/C which will be difficult to figure out since ambient temps will vary so much. Also a big factor is how long since and how much heat will come from the engine cooling off.

I ran a window unit pretty much the same as what you're looking at on 4 - 6 volt golf cat batteries, they lasted 5 years 4 summers running an A/C in a well insulated cabin 10 x 16 built in the shade. I think with such a small space you will have a no more than a 50% duty cycle so figure 280 watts an hour with the inverter and minor loads. You will draw slightly above the 1/20th the battery capacity is rated. I don't deal the discharge ah crap, but most L-16s start at about 340 amp hour capacity so 4 in parallel and series should give you @700 ah 12 volt battery bank. figure a 280 watt load would be 280watts / 12 volts = 23.5 amps used each hour. The actual peak load will be 500+ watts(42+ amps) which will bring the batteries down faster than the amp hour rating which is done at 1/20th capacity.

doghouse wrote: »

Yeah Doghouse, I love these cabovers.
I'm building another one from the ground up with a larger sleeper/w a slideout. Lots of room to add more panels and get more power.

I looked into that 12/24 volt unit a few years ago, and the price being $1,800 to $4,000 depending on the dealer makes me shy away from a unit like that, also where to get it repaired. When a unit costs that much it scares me away. There is no reason for it to be that expensive. I have spent (wasted) a bunch of $$$ over the years on this project, and when it comes to high dollar stuff like this unit, I worry about how well it will work.

The system I'm using now has 6 -12v deep cycle group 24 batteries from Walmart. It will run my A/C unit for 5 hours before the bank draws down to 11.5 volts, at which point I break out the Honda genny and run the A/C and a battery charger. The next day I flip the switch on my dash and transfer the amps from my truck alt. (76 amps) to give the bank a good charge to top them off (until the light on my blue sky controller starts blinking at 14.5 volts) and then repeat the process as needed. So far the batteries have lasted 1 year (last summer was hot and they held up pretty well) and look like they might make it through this summer, but time will tell when I get to Tucson in August. Good thing is I just go to Walmart and get 6 new ones in one day and start off fresh for $400.

I'd like to go the 6 L-16 route, since the system was designed to charge that amount of lead, but I need to make sure that an investment that large will last a few years.

Just some food for thought here..

As far as servicing goes, I would inquire at a dealer. AC service should consist of cleaning, testing and possibly charging, any AC outfit should be able to handle that. It doesn't seem like there should be much servicing involved. I know expensive stuff can be scary, but my experience has been you truly get what you pay for. That is particularly true with stuff you want to last for a while. You can't expect to pay walmart prices, and end up with something designed to last a long time. That's not saying you can't get decent stuff at walmart, it just is not where I would be shopping for batteries for a system like this. Say 1800.00 on the low end for a unit you can get 10 years out of cost you 180.00 a year. A small price to pay if it is (and I am not claiming it is) for comfort and efficiency. Especially if you are not having to piece together additional equipment like inverters and more storage to power it. Just some thoughts for your consideration. When pricing it out, figure the expected lifespan.

Sometimes the reason things are more expensive is that more engineering, and better quality parts go into it, and the cost is higher as a result. Sometimes there is a rediculous mark up. Try to analyze it based on your actual needs, as well as the quality of the gear first, then worry about the price, and finding the best deal on it.

You will pay more for nice batteries, but if you use them right, and feed them right, they should last a while. Here are some decent batteries worth having a look at.. http://www.fullriverdcbattery.com/battery/DC400-6 The documentation for good batteries or lack of it, should give you an indication of who deserves your hard earned dollars. If a company has done the R&D and gives you good data to make decisions with, that is where I prefer to spend the money. Say you buy 4 sets of your 400 dollar batteries, which don't last long, or 10 years out of a decent set, which are more efficient and do a better job. The money comes out the same, but you've saved a lot of hassle.

If you were able to build the system on 24V for example, and run it that way, that will substantially reduce the amperage, and the size of the wire required. Some of the gurus here probably would have ideas on how to marry the two if it were worth considering before final decisions are made.

I've spend some time in years past in a few cabovers. Are you running a HAM or CB? I know anything that goes on a rig needs to be top notch stuff, as everything will take a beating beyond the comprehension of someone who hasn't spent time around a truck.

Hey Doghouse,
I was just reading this thread... if this is installed on a semi truck and 12v then why why why would you charge with solar? Just charge it off the main alternator. You will want to regulate the charge a bit so the alternator doesn't get overloaded, but even a trickle charge would be so much faster than a solar panel. It sounds like you drive right after sleeping. A setup like this would be virtually maintenance free and recharge you faster. And it won't affect gas mileage in any noticeable way.

Well if it's fun I can't argue that Good luck.