Changing from 12v to 6v Batteries - Page 2 - Montana Owners Club

bigmurf · 10-02-2009, 02:57 PM

Yep sounds like a engineer. zzzzz

firetrucker · 10-02-2009, 06:24 PM

Guys, you're mixing things up, and I'm not going to try to explain it all here. But here are a few points to consider:

1. Power is the rate of energy use (called work), and you get billed by how much energy you use (watt-hours), not how fast you use it. 1000 W for one hour equals 500 W for two hours, and your bill is the same.

2. Amp-hours is one way to rate the capacity of a battery, but it doesn't mean, for example, that you can get 225 amps for one hour or 22.5 amps for 10 hours or 2.25 amps for 100 hours. In fact, the higher the current draw, the less capacity your battery has due to losses in the battery. The battery capacity (C) is usually measured at some small current draw, often C/20 for automotive batteries, C/10 for RV/Marine, and C/6 for golf cart, but manufacturers play with this figure, so this isn't necessarily the best way to compare batteries.

3. Plan on getting less energy out than the rating of the battery, and putting more in than you used in order to get the battery back to full charge. AND, capacity decreases as batteries get colder, losing as much as 50%, and capacity goes up, but life gets shorter as the temperature rises above 77 deg F.

4. You can get more out of a deep cycle battery than an auto battery, or even an RV/Marine battery, because of the internal design. The auto or Marine battery is designed to give large currents for short times and normally shouldn't be discharged more than 50%. A true deep cycle industrial battery can be discharged 80% (down to the 20% level) regularly.

5. Don't forget the losses in the inverter and the wiring. Anything that ends up as unused heat means decreased capacity.

6. Try these links for more, if sometimes wordy, information on batteries, and, as pbahlin says, measure the energy that all your appliances use. Try to stagger their use so you get less loss in the battery, too.

Phred's poop sheets
Magnacharge website more concise description

There are solar system retailers that have some good information on documenting your energy usage and computing your battery requirments, but I don't have them at hand. Maybe Robbie or Dave or one of the dozens of others that are using solar systems can give you more info.

Bob

pbahlin · 10-03-2009, 10:51 AM

One minor nit...

People often use the terms energy and power interchangeably. To a physicist this is like scraping fingernails on a blackboard. We do the same thing with heat and temperature. Very, very cold objects contain heat energy but most people would argue that cold things do not have heat. There's not a whole lot of harm done in throwing these terms around incorrectly as long as everybody makes the same misconception.

Here's a non-physicist way of thinking about it. If you take a rock to the top of a mountain you have increased its energy. If you let it fall on the flatlanders, that energy is expended as work. So work and energy are opposite sides of the same coin. They both have the same units of measurement. One (energy) describes the capacity to perform the other (work).

Power, on the other hand is a measure of how long the work persists. When you turn on a 100 watt light bulb it consumes 100 watts of energy every second that it's on. If you think about it a bit you'll realize that your utility doesn't really care that you turned on a 100 watt light bulb. They only care about how long you leave it on. Watt-hours! If you leave it on for 24 hours you've consumed 2400 watt-hours of power that is being delivered at 100 watts every second.

BTW please don't let my DW know that I'm still 'splainin'. She may stop feeding me to get even!

pbahlin · 10-03-2009, 11:06 AM

This is the best detail on Solar that I've found. It's not a how to at all but it will provide a huge amount of background to anyone contemplating going off grid.

Handy Bob does not pull his punches. Refreshing!

Dave Anderson · 10-03-2009, 12:16 PM

Phalin & bob; I'm sure bothe of you guys REALLY know what your talking about, but to us"challanged" flatlanders, working with Amps is a whole lot easier. We know our Amp. hour capacity,We have METERS that tell in AmpS hOW many Amps we are taking out of our batts.We can tell how many Amps or % of amps any particular device is drawing and what % of amperage remains in our Batteries. It all seems simple to a simplton like me, Amps in VS. amps out. and yes our meters tell us when our Batts. are at 50% so we can start our gensets to recharge. I must I liked your explainations..........Dave

firetrucker · 10-03-2009, 04:35 PM

Thanks, Dave. And you're absolutely right, Paul. That statement about work should have come right after the word energy (slight attack of CRS). But, as Dave says, we need to talk the language he's using, while remaining consistent in its usage.

Bob

scattershot · 10-10-2009, 12:48 PM

OK, guys, for us really stupid folks out here, (me), what kind of endurance can I expect from two 6V Trojan golf cart batteries running the furnace moderately at night like at Qsite), two reading lamps for a couple hours, and typical waterpump usage before I have to hook up the generator to recharge? One day? Two? No TV or radio, frugal usage.

Thanks

OntMont · 10-10-2009, 03:36 PM

We have that set-up, and I think that if you are frugal, you could certainly go for a couple of days, perhaps more, but what I find we do is to run the generator for some other purpose on a daily basis, and that tops up the batteries at the same time. I would be interested to hear how long people have got by on batteries alone, but a lot depends on temperature and wind conditions. I do know that we could run down our original 12v battery overnight if the furnace was running a lot.

scattershot · 10-10-2009, 04:54 PM

Thanks, OntMont. That's been my experience, as well, with the 12V system. Anyone else?

Trailer Trash 2 · 10-10-2009, 06:42 PM

I'm just courous, if helium gas is lighter than air and rises sound'nt ( ie: Hindenberg blimp ) the vent hose be at the top of the battery box and vent out the existing vent that the factory put in. I often wondered if the bottom hole was to allow fresh air to enter the battery box as a result of the chiminy efect of the gases going out the top vent.

Dave Anderson · 10-10-2009, 07:11 PM

Scattershot; what your hearing is about right, 2 days,maybe 3 if your frugal. You will have a blast in Q ,you will be able to replace those 3 amp reading lights with.2amp led's from the vendors. If your really going to get into boondocking, you may want to look at ceramic or bluflame heaters instead of that VERY ineffeceint furnace, get rid of that ,and you can add 2 days to your stay.........Dave

scattershot · 10-11-2009, 04:36 AM

Great info, Dave. I'll look into it. We boondocked at Qsite for 12 days a couple of years ago, but we had to run our Honda every morning. Be nice to know we don't have to.

Tell me more about these ceramic heaters. How are they powered?

Thanks,
Gene

Dave Anderson · 10-11-2009, 06:33 PM

Gene; bothe ceramic and bluefflame are tapped into your LP line at a point that works with the spot you want to place your heater. They are reasonably small and 99% efficiant, useing NO amps to run a fan----No fan! We've had bothe Blueflame(in our last monty) and ceramic in our present rig, It's a tossup for us If you can make the Q trip there will be several of us to show & tell with...............Dave

scattershot · 10-12-2009, 07:04 AM

We're planning on being in Qsite, and would love to see your setup. Do these need to be vented?

Our trip will be dependent on the weather here. Last year we were snowed in for the whole month of January. We got one break in the weather, but it was snowing and icy in Albuquerque, and we figured someone was trying to tell us something!

Thanks for the info.

simonsrf · 10-12-2009, 07:11 AM

Everything I have read and know about my solar system is in amp readings. Amps are the measure used to determine battery storage, controller readings and panel sizes. .02

Engineers would say that Watts are a more accurate measure, but they haven't talked to the marketing guys, or the solar manufacturers yet.

Check out the AMSOLAR Education Page.

Dave Anderson · 10-12-2009, 07:26 PM

Well said Robbie; you know how challanged I am with talking this Amp thing .We must drive the engeneers crazy!! got no Killowott class!!!! ...Dave

scattershot · 10-14-2009, 07:06 AM

Another question... Where are you guys getting your Trojans? Local dealers here get $120 - $130.00 each for them, and that seems a little pricey to me.

Thanks,
Gene

Tom S. · 10-14-2009, 09:37 AM

Quote:

quote:Originally posted by scattershot

Another question... Where are you guys getting your Trojans? Local dealers here get $120 - $130.00 each for them, and that seems a little pricey to me.

Thanks,
Gene

That doesn't seem bad to me. You can get them cheaper on the web, but by the time you pay for shipping, you'll be at or above that price.

OntMont · 10-14-2009, 10:05 AM

I bought mine from Continental Battery in Harlingen, TX. Continental have outlets throughout the Southeast. Price (about 3 years ago) was under $70 each for T-105.

scattershot · 10-14-2009, 04:25 PM

Thanks, guys. $70.00 or so seems a little more reasonable, if I can find them at that price!

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