View Full Version : large battery banks
07-16-2006, 09:22 PM
It's been awhile since I discussed my project- a camper on the chassis of a fairly large commercial truck, so I may have to back up at some point to explain my rationale for this idea- but, other than size and weight- any thoughts as to the drawbacks of using a large bank- say, 6 or so- of deep cycle batteries instead of a larger on-board generator?
Right now, I have a Honda 1000i. For the same money, I probably would have been better off with the less-refined, noiser, and heavier Coleman model (2 or 2.5k, I think) but it's what I'm stuck with now. It has an 8a 12v output, so I woudn't mind running it 4 hrs a day or more if I could be charging a battery bank instead of just say, a radio, a few lightbulbs and
the occasional power tool.
Having a good sized battery bank might make a small windmill worth the expese and storage space.
07-16-2006, 11:12 PM
That is what EarthRoamer does, and I am impressed. They generate ~30+ amps of solar power and run a around 300 ah of battery power. No generator
The Honda 1000 is a great little generator and would be a perfect compliment to that type of system.
IMHO, you are on the right track!
07-17-2006, 01:21 AM
Hinoranger, your idea to go battery power is a good one, but I would certainly try to avoid running a gas generator for half the day to charge them!
If I were you I'd forget the wind generator idea and go with photovoltaic panels. Wind generators of a size you could transport are very low in output at anything below a real blow. PV panels are totally reliable and have no moving parts. With 300 or 400 watts of PV power, plus engine generator charging while on the road, you should be in good shape. You'll need a charge controller for the panels to avoid overcharging and reverse current flow through the panels at night.
If you're going to install a battery bank, multiple six-volt batteries wired in series are generally more efficient than 12-volt batteries. At our house (which is off the grid), we use 12 Trojan T105 six-volt batteries wired for 12 volts, and a 2500-watt inverter. With around 1,000 watts of PV panels we have plenty of power; I run our backup generator maybe twice a year. You wouldn't need nearly that for even a big camper.
We also have a 600 (theoretical) watt wind generator, and while it's nice to generate power at night and on cloudy days, it really only augments the panels slightly. with a normal breeze it puts out maybe 75 watts at 12 volts.
07-17-2006, 06:02 AM
I agree with the idea of using batteries and photovoltaic panels. With a large truck you should have plenty of room on the roof for mulitple panels. The sizing of the bateries and panels will depend on your load and there are a lot of "system power calclators" out there to help you determine proper sizing of the system.
07-17-2006, 02:36 PM
thanks for the feedback.
One "problem" I have is that my truck is actually sprung to carry a lot more weight (somewhere around 13,000 pounds) than I'll ever need to, unless I add a jaccuzi or start a really large coin collection. I bought the truck for commercial purposes and needed the capacity at the time. Also, the most powerful motor was only available in the heaviest chassis, so that was a consideration, too.
Ideally, it would be nice to trade the box I'm building onto a lighter vehicle, but you know how hard it can be to actually get any equity out of a vehicle by trading down. Also, 4wd versions of this truck do exist in other markets and it might be somewhat feasable to retrofit the front drive axle.
Someone in Wyoming claims to be doing exactly that with a very similar truck, a Mitsubishi.
-so the good thing about that is that an extra 500 lbs of ballast wouldn't hurt much.
Havn't done any homework here at all, but I have around 100 sq. feet of roof area available, or maybe a little more if I really need it. Can someone throw out some ballpark figures as to how much output for what kind of cost I'd be looking at?
07-17-2006, 02:59 PM
here's a the only pic I could find easily (new HINOs have a conventional cab).
Mine has the same cab but an 18' van box in front of a 5' flatbed and is the 33,000 lb GVW.
and here's the guy who's doing somthing similar with a Mitsubishi.
I'm sure that's going to be out of my price range for awhile.
07-18-2006, 02:11 PM
Mitsubishi 110-watt panels are 25 by 56 inches and list for about $680 each in my current catalog. Sharp 175-watt panels are 32 by 62 inches and run $1,000 each. Weight is 25 and 37 pounds, respectively. You wouldn't need nearly all your 100 square feet to get enough charge capacity. Just enough money!
07-18-2006, 04:42 PM
One idea I've been thinking about is an awning made of a fabric base plus a flexible thin film solar panel. Here's a web page illustrating the idea
If you're deploying a tent or awning in camp, it may as well contribute some solar power. This would only supplement a roof-mounted system, since you'd need to recharge your batteries while driving during the day.
For more conventional rigid panels, Sharp, Kyocera and BP all make 170 watt panels with 25 year warranty.
07-18-2006, 04:51 PM
Your idea is a great one, and Iowa Thin Film already does similar with their military line.
Regarding the while driving comment. No issue there, as the alternator charges the batteries while driving.
Oh, and I use the Power Film panels and love them. I just need to buy more as I am a gadget freak and need more power ;)
07-18-2006, 05:43 PM
"You wouldn't need nearly all your 100 square feet to get enough charge capacity. Just enough money!"
maybe if I plant soybeans on my roof, I'll have my own portable source of biodiesel, too.:sunflower
Seriously, I'm going to do what I can with solar but for the cost of two solar panels I can buy enough fuel to run my Honda year and have enough left over to buy a new generator when I wear this one out!
I'll think about it, though.
07-18-2006, 08:31 PM
Solar panels are perfectly quiet and utterly reliable, never wear out (25-year-old panels are still producing power), and don't pollute or use fossil fuels!
07-18-2006, 08:56 PM
Seriously, I'm going to do what I can with solar but for the cost of two solar panels........
Take a good look at used solar panels. New would be ideal but as Johnathan mentioned they seem to last forever so there is a used market out there for them.
I picked up three 50w panels for $20 each one time, they would have been $400 each. Granted they were a little brown in spots and therefore most likely not 100% efficient but according to my voltmeter and the way they treated my battery bank they were plenty useful!
Here's an angle you should look into --- Notice the solar panels on the road construction equipment? Most of the lighted signs and the big arrows telling you to turn or merge are battery powwered and have 35-100 watts of solar panels on top of them. I'm not sure but it may be a requirement for this equipment to be updated for maintenance every few years if they need it or not. There may be a way to buy these used panels.
Onother source would be government auction.
And if your going to have a system that bit you may also want to consider a battery monitor.
07-19-2006, 01:55 AM
good points. I do have a small collection of new surplus panels from some kind of commercial application- not road construction, but somthing along those lines- which might be good for 50 or 100w. A good start, anyway.
Other that, I've always been pretty good about commuting by bike or bus for many years now. I might not loose much sleep over using an extra couple of gallons of fuel a week to keep the lights on and my food cold.
07-19-2006, 02:43 AM
Here are a couple of comments on a previous thread that may interest you:
1. From el coyote
We do a fair number of panel set ups for our trailers. When it comes to the output of panels we only count on 70% performance because rated outputs are based upon full sun and accurate placement of the panel towards the sun. It is good to know how to apply Ohms' law to your power requirements to evaluate your needs: Amps x Volts = Watts
Lets say you decide to hook up a 20 watt panel to your battery bank and you live in AZ where you can count on an average 6 hours of full sun daily. Here's what you could reasonably expect on the low end:
((20watts x .70 efficiency)/12 volts)) x 6hrs= 7 amps.
On the high end;
20w /12v x 6hrs = 10 amps
Remember that your battery is essentially a fuel tank that has a maximum capacity rated in Amps. Hooking up a solar panel to a fully charged battery without a charge controller could cause overcharging of the battery that will shorten it's life.
A very good book has been written on RV electrical systems and covers solar panels. It is written in lay person's terms and is an easy read. I got mine from Amazon.
RV Electrical Systems by Bill & Jan Moeller
2. From me:
We have a Kyocera 120 and a K60 (space limitations) on the roof of our ATRV with a RV Power Products Model 2000E Charger Controller/Booster. During our entire trip to the Arctic Circle last August/Sep I never had to use the genset to re-charge the five (yes, [i]five[i]) deep-cycle batteries on the trailer.
This is overkill, but I like to err on the positive side. When we set up our solar system on the house in Baja six [now seven] years ago we determined what our 'needs' would be, figured out the number of pv panels/batteries and doubled it.
Mario gives excellent advice above. I have that book he mentions and I do recommend reviewing or purchasing a copy.
If you're wanting to only maintain your vehicle battery over several (many?) days of non-engine charging, a small pv panel/charge controller is all that's required. If, however, you have a 12v fridge, a blender for you margueritas, a couple of exterior 12v lights (flourescent or LED of course) for the campsite, then you'll have to increase your pv wattage. That book is an excellent guide.
08-07-2006, 09:27 PM
For re-charging at higher rates than solar can manage, and without the noise of a generator, consider a fuel cell, of the type used on boats etc.
08-12-2006, 04:08 AM
At our house (which is off the grid), we use 12 Trojan T105 six-volt batteries wired for 12 volts, and a 2500-watt inverter. With around 1,000 watts of PV panels we have plenty of power
You power your entire house off of 12 six-volt batteries? I don't know much about Solar Power, but I find it fascnating. How many amps can that setup handle, and howmuch stuff do you typically power?
08-13-2006, 04:56 AM
Todd, we have more than enough power. With a 2500-watt inverter (which produces better sine-wave AC current than the power company) I can run a table saw or any of my other power tools. Right now we live in a small cottage; once our mansion (1,000 square feet) is built I'll probably add a couple more PV panels. If I get really power hungry we could step up to a 4,000-watt inverter and add a few batteries.
No problem running computers, lights, evaporative cooler, etc. Once a good solar setup is in place you really don't even notice it, except when your friends call you during storms to tell you their power is out.
08-17-2006, 03:37 AM
We run entirely on solar (about 350 watts of panels on our roof) and alternator power. For our usage (fridge, computer, lights, radio, etc) we have boundless power in the summer. Winter we end up needing to drive or idle for an hour or two every couple weeks if it has been cloudy (or frequent snow on the panels). 425ah of battery storage in the house bank.
We decided to forgo a generator because we could use the engine alternator if necessary, a generator would take more space, potentially a different source of fuel (hard to find small diesel generators), noise, exhaust, etc.
The largest improvement we made to our power system was installing a battery monitor and tracking down where all the power went (lead to extra fridge insulation, switches on the electronics that drew power even when off, etc). With these cheap changes we more than halfed our daily consumption with no impact on our lifestyle.
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