Need some advice from the ZS Solar gurus.

[Patient Zer0]

My wife and I have become increasingly unhappy living the rat race and, after discovering this website: http://cheaprvliving.com/index.html , have decided to take a vacation from it in 2014. We are going to go "off the grid" and become Stealth RV'ers for a year+. To this end, I am in the process of converting a rehabbed 14' box truck into a 112 sq. ft. efficiency apartment on wheels. We decided to go with a solar panel/ battery bank for our lighting, heating, and power needs. Minor drawback, I know virtually nothing about what we would need to make this sort of thing work. I know I will need at least 2 deep cycle marine batteries, but no idea what kind. The work load of the batteries would be limited. 12v space heater in the winter, computer, monitor, speakers, and to recharge equipment. Just really looking for a brain to pick since I lack skills in this area.

[congochris]

viewtopic.php?f=45&t=87595

That should give you a few decent ideas, or at least a comparison of what you want vs what he has.

[raptor]

This link should give you a lot of information.

viewtopic.php?f=6&t=79742


Basically the solar panel and battery bank should be sized together.

You will want one or two Group 31, 4D or 8D deep cycle batteries.

A battery can only supply about 50% of it's capacity before it is effectively depleted.

Ignore CCA and look for amp hours.

A group 31 battery will have about 105 amps (so about 50 amps usable), a 4D battery will supply about 175 amps (or about 85 amps) and an 8D will hold about 225 amps (110 amps usable).

If your battery bank has 225 amps then you will want a solar panel that can replace 110 amps in about 10 hours so that means a 120 watt or bigger array. 120 watts /12 volts = 10 amps (@ max output).

A smaller panel would also work since you can recharge the battery bank when you drive the vehicle.


BTW the site your referenced has a lot of good info.
http://cheaprvliving.com/howtohaveelectricity.html

[TacAir]

I would suggest that a 12VDC heater is a lost option for such a large space.
Look into "Direct vent" kerosene heaters and a CO alarm.

Good luck!

[Tater Raider]

Look into... a CO alarm.

Cannot stress that one enough.

[Patient Zer0]

The 12v heater is just for the bunk. The stove and a small radiant heater will keep the rest warm during the day. I also plan to insulate the box.

[Tater Raider]

The 12v heater is just for the bunk. The stove and a small radiant heater will keep the rest warm during the day. I also plan to insulate the box.

I stand by my earlier statement. We've had friends of the family die of carbon monoxide poisoning whilst camping in their RV. Ounce of prevention and all that.

[TacAir]

The 12v heater is just for the bunk. The stove and a small radiant heater will keep the rest warm during the day. I also plan to insulate the box.

I stand by my earlier statement. We've had friends of the family die of carbon monoxide poisoning whilst camping in their RV. Ounce of prevention and all that.

I'll second that as well. We have a propane alarm, a CO and smoke alarm set as well. A small expense to allow you to wake up.

Also, if you are retrofitting a 'box' truck, don't forget a second way out in case of a fire. Don't turn your vacation from the rat race into something permanent....

Good luck.

[Patient Zer0]

The 12v heater is just for the bunk. The stove and a small radiant heater will keep the rest warm during the day. I also plan to insulate the box.

I stand by my earlier statement. We've had friends of the family die of carbon monoxide poisoning whilst camping in their RV. Ounce of prevention and all that.

Dually noted. It was something I hadn't thought of. I really didn't plan on propane for anything more than cooking though.

[Tater Raider]

Dually noted. It was something I hadn't thought of. I really didn't plan on propane for anything more than cooking though.

Go with the safety gear TacAir suggested then, please. Think of it as an insurance assurance policy.

[Blacksmith]

It will likely be impossible for your solar panels to generate enough electricity to run a heater. Most RVs and motor homes use propane or butane to run a micro furnace. The propane is often used to run the fridge and oven as well.

[Patient Zer0]

I was thinking this type of heater for the box area.

http://www.nextag.com/Roadpro-RPSL-681- ... rices-html

[solarguy]

The heater will drain your battery pretty fast. Even a "small" heater. Unless you are buying big expensive panels to totally cover the roof, and one wall, and a huge 10 or 12 battery bank of big deep cycle batteries, you can't heat with pv panels in any meaningful way. That heater you mention uses 15 amps of 12 volts = 180 watts. If you run it for one hour, that's 15 amphours. You could run that heater for 95*AH/15 = 6 hours before your pair of trojan golf cart batteries start killing themselves. That's assuming you don't run anything else. Also keep in mind, that's less heat than what comes off (2) 100 watt light bulbs.

This is an excellent resource for anything alternative energy related:

http://www.fieldlines.com/

You will have to do a little math to estimate your power needs.

If you use one amp, for one hour, that = 1 amphour. This has nothing to do with cold cranking amps. CCA is for starting batteries for cars. If they even mention CCA, that automatically means the battery is inappropriate for deep cycle use. Golf cart batteries are usually the best bang for the buck if you don't need them to last more than 4-5 years. A starting battery will not make it one year.

So, figure out how much your devices use, there's usually a nameplate rating somewhere. Or get a Kill-a-watt meter, like so:

http://www.amazon.com/P3-International- ... B00009MDBU

That will measure watts or amps, but only of AC.

You can use a multimeter or VoltOhmMeter (VOM) to measure the dc use if it's under 10 amps.

It's handy to know that Volts x amps = watts also.

Then you can make a little spread sheet for how many amphours per day, you need to run your actual stuff. Let's say you need 20 amphours. That means you need to run a total number of amps of 4, and run it for 5 hours. Or 10 amps for 2 hours. See the relationship?

*A t105 trojan golf cart battery is rated for 195 amphours. BUT, you can only discharge it about 50% and expect to get good life out of them, so let's say 95 amp hours. And that (like almost all golf cart batteries) is 6 volt, so you would need a pair of them to make your 12 volts. If you put them in series (like we just did) that has no effect on your amphour rating. If you put them in parallel, then you double your amp hour ratings, but now you'd need two sets of batteries (4 total). each pair makes your 12 volts, and you run the two pairs in parallel to get double the amphours.

http://www.trojanbattery.com/Products/T-1056V.aspx

Each of those puppies weighs 66 pounds, and you would need at least two, four or eight would give you much deeper capacity and allow you to go double or quadruple the days without charging up.

You'll need some kind of overcharge protection, that's called a charge controller. And keep in mind, when they are charging, they make hydrogen gas, the most flammable gas there is. It's better if they are in a dedicated sealed box that's vented to the great outdoors.

that should get you started.

Are you trying to do a strictly 12 dc system? Or do you want some ac available as well? All depends on what you want to run.

For every watt you burn, you need to produce 1.2 to 1.5 watts to replace it, since batteries and wiring and inverters, etc, are not 100% efficient.

HTH,

troy

[raptor]

Solarguy has some good advice and he posted before I did.

That said:
http://www.sonicelectronix.com/item_236 ... L-681.html

Product Specifications

Voltage: 12-13.8 volt DC
Heat Current: 22-25 amp
Cool Current: 0.45 amp
Pulse Start Current: <28 amp
Fuse Type: 15 amp x 2

I cannot opine upon the heat out put. But here is the electrical math.

The thing uses about 25 amps for every hour you run it.

24 hours of running will require 600 amps @12 volts so you will need a battery bank of at least 1,200 amps to run it for 24 hours. 1,200 amps would require about 6 8-D sized batteries.

Another way to look at it is that you need one 8-D size battery (even a cheap one is about $250) for every 4.5 hours of run time before it needs charging.

A battery bank of 1,200 amps needs about 200 amps of recharging capability to keep it topped up.

BTW on my boat I have two battery banks totaling about 900 amps and have two 150 amp alternators one to charge to charge each bank. If I run the engine at about 65% of rated continuous power, it takes about 6 hours of running to fully recharge the battery bank if I let it get to the 50% level. This is because you risk boiling off the electrolyte if you put in too much power at once.

IMO you are better off using a vented propane heater and use the 12 volt heater only when the engine is running and developing enough power to get maximum power out of the alternator.

[Patient Zer0]

Solarguy and Raptor, thank you. I am heading out the door right now, but I have specific questions. I am completely new to solar power. I have much to learn about electrical work in general, let aloone solar power.

[Dutch3]

I cannot opine upon the heat out put. But here is the electrical math.

The thing uses about 25 amps for every hour you run it.

24 hours of running will require 600 amps @12 volts so you will need a battery bank of at least 1,200 amps to run it for 24 hours. 1,200 amps would require about 6 8-D sized batteries.

Amps (amperes) are a measure of current flow rather than capacity. So in reality, if rated at 25 amps, the thing is pulling 25 amps every second you run it. Ampere-hour or amp-hour (ah) is a more convenient unit for describing capacity. A battery rated 100ah would theoretically deliver 100 amps for an hour or 25 amps for four hours. Efficiency will suffer due to wire resistance, parasitic losses and temperature, so the actual runtime will be somewhat less in the real world.

The rate of discharge also affects capacity. Looking at a pair of Trojan T-105 batteries (rated 225ah) wired in series to produce 12VDC, we see the capacity in minutes @25 amps is 447. About 7 1/2 hours, which is less than the 9 hours we would calculate simply using the ah rating/current in amps.

http://www.trojanbattery.com/Products/T-105Plus6V.aspx

[raptor]

The rate of discharge also affects capacity. Looking at a pair of Trojan T-105 batteries (rated 225ah) wired in series to produce 12VDC, we see the capacity in minutes @25 amps is 447. About 7 1/2 hours, which is less than the 9 hours we would calculate simply using the ah rating/current in amps.

You omitted the fact that as batteries age and are discharged deeply they lose capacity. Thus even the factory ratings are assuming a new battery in peak condition. The actual results will generally vary and almost always be less than desired. A three year old battery will generally have a measurably lower capacity than a factory new battery.

[Tater Raider]

Honestly if you are going to do the solar thing the place to start is with basic electrical knowledge. Check amazon.com or the local book store for a self-help book on it and study the hell outta it.

[Patient Zer0]

Honestly if you are going to do the solar thing the place to start is with basic electrical knowledge. Check amazon.com or the local book store for a self-help book on it and study the hell outta it.

Please point me towards a book that will not scare off a newb. I want to do this, I just don't know how.

[raptor]

Look for a book titled "12 volt bible".

[Evan the Diplomat]

You might want to check Expedition Portal for how some of the remote overlanders set up their vehicle. This couple has a solar rig, but they don't have your electrical requirements. http://www.dinoevo.de

[Tater Raider]

Handbook of Basic Electricity (Rea)
Electronics For Dummies

Both got good reviews on Amazon.com as basic books. Rules for electronics apply to electrical stuff too (ohms is ohms) and might give you a few ideas on fun stuff you'd like to try as well.

[JohnE]

My wife and I have become increasingly unhappy living the rat race and, after discovering this website: http://cheaprvliving.com/index.html , have decided to take a vacation from it in 2014. We are going to go "off the grid" and become Stealth RV'ers for a year+. To this end, I am in the process of converting a rehabbed 14' box truck into a 112 sq. ft. efficiency apartment on wheels. We decided to go with a solar panel/ battery bank for our lighting, heating, and power needs. Minor drawback, I know virtually nothing about what we would need to make this sort of thing work. I know I will need at least 2 deep cycle marine batteries, but no idea what kind. The work load of the batteries would be limited. 12v space heater in the winter, computer, monitor, speakers, and to recharge equipment. Just really looking for a brain to pick since I lack skills in this area.

You've already gotten some very good advice, I'll simply add that an "efficiency apartment on wheels" means you don't have to live where it's cold unless you want to. Your plans for Insulation combined with some low power draw electric blankets might be an alternative to consider as well. I recently bought an an emergency re-warming blanket originally designed for treating hypothermia patients that can be recharged with wall power as well as with a 12v source. It runs for hours on a battery pack.

[LBB]

The 12v heater is just for the bunk. The stove and a small radiant heater will keep the rest warm during the day. I also plan to insulate the box.

I stand by my earlier statement. We've had friends of the family die of carbon monoxide poisoning whilst camping in their RV. Ounce of prevention and all that.

I'll second that as well. We have a propane alarm, a CO and smoke alarm set as well. A small expense to allow you to wake up.

Also, if you are retrofitting a 'box' truck, don't forget a second way out in case of a fire. Don't turn your vacation from the rat race into something permanent....

Good luck.

I don't know how far you are with this, but in the armed forces we had two extra exists out of the box in the back. Some had even one exit in the floor in case the vehicle was on it's side. And it's quite a good exit when someone is at the "front" door.