Modular 12v Power system - Easy enough for newbs

[Dr awkwarD]

Hey guys-

I just wanted to share the power system that I rigged up over the last burn so that maybe others can learn from/improve/steal the idea without credit.

I used:

• a 12v Costco Deep Cycle Marine Battery
• a 5 amp fuse (for safety) (Amazon Link)
• an array of car cigarette lighter adapters. (Amazon Link)
• a spool of 12 gauge wire
• battery clips
• a switch (if you're feeling fancy)

Directions:
Learn how to connect wire. Splice it, solder it, shrink tube it, whatever. Find a way that works for you. Wire the battery clips to a string of wire. Splice in the fuse socket and drop in your 5 amp fuse. Splice in the cigarette lighter array. It should go like this:

(-) Battery Terminal Clip -> (optional switch) -> Fuse -> Sockets -> (+) Battery Terminal Clip

You now have two modular 12v sockets. You can add additional splitters if you need. Investigate online and at truckstops and you can find all kinds of useful 12v stuff. I found some 12v car christmas lights and used those to light my yurt. Also, you can find 12v fans (for personal cooling or swamp coolers) pretty easily. This setup lasted me all week on one battery. I was running lights (continuously), a Figjam cooler and a fan. Be mindful of turning off stuff when you're not using it (which is where the switch comes in). They also sell battery boxes at automotive stores. This is a good investment for when you stumble home and don't want to worry about knocking the clips off your battery.

Word of caution: DON'T GO NUTS. You've only got 5 amps on here. Yes, they sell 12v refrigerators and cook-surfaces. No, you probably don't need them. Look on the back of the boxes for your power draw. Keep in mind that your total shouldn't exceed 5 amps. This should be more than enough.

Hope this is useful.

Cheers,
Jeremy

[Canoe]

Anything to ensure you don't deplete the battery below six volts?

[Dr awkwarD]

Anything to ensure you don't deplete the battery below six volts?

I don't have anything on there currently, but that's a good idea. Any suggestions?

[Canoe]

http://www.hobbyking.com/hobbyking/stor ... 150C_.html

Hobby King Voltage & Temperature Monitor 2-6S.jpg

Set the voltage for the alarm to go off. The alarm isn't that loud, but the blue LED is quite bright.
Have it controlled by the switch, just because, as it does consume a tiny bit of power.
Thermal probe isn't needed for this use, but it's amusing.

I got mine three years ago. There may be better available now.

[FIGJAM]

6 volts is crazy low.

Scroll down about 2/3rds of the way down this page and the chart shows 12.05 volts being 50% discharged.

http://www.marxrv.com/12volt/12volt.htm

[BBadger]

Yeah, if it's six volts, the battery is probably leaking or shorted out inside it or something.

[oscillator]

Generally speaking, you do not want to discharge a 12VDC battery much below 11 volts.

Discharge to 10 volts can incur damage, depending on the quality of the battery.

You can pickup an inexpensive voltmeter to check the battery. I use this one for playa duty (and leave the expensive FLUKE in Defaultia):

http://www.jameco.com/webapp/wcs/stores ... _355207_-1

-Osc

[Dr awkwarD]

One more tip that might help the uneducated:

Before I started building my power system (which, granted, is still pretty simple), I didn't really understand how amps worked. I'd read the "water-pipes = current" metaphor a million times, but the one thing that was never made clear is this:

Your devices pull amperage, your battery doesn't push it. Amperage is a measure of how much power your devices draw. I was worried that my battery was going to fry the 120mA fan I was running. I kept trying to figure out how to "step down amps." Until an electrician laughed at me, and then explained how it works, it wasn't really clear. Since this seems to be a common misconception (none of my friends knew this either), I thought I'd share it.

[Canoe]

6 volts is crazy low.
Scroll down about 2/3rds of the way down this page and the chart shows 12.05 volts being 50% discharged.

That would certainly explain why mine doesn't go blow 12 VDC for the week.
I could have sworn you PMed me six volts a few years ago.

[FIGJAM]

If I told you that, I was wrong.

[atomicray]

Cool thoughts here!

I own a marine support/repair/installations company here in Corpus Christi...been dealing with 12vDC systems my entire adult life...48 a couple weeks ago.

6vDC will make your battery invisible to most chargers, especially trickle chargers!

If you drain one that far down, rarely do I find a functional battery below 9vDC, then you can trick a trickle charger by putting the dead battery inline with a charged battery or one with more than 10vDC...the trickle charger will see the good battery and begin charging...because the dead battery is so low it will cause the trickle to boost the effort and they both charge.



In a playa situation you can tie two batteries together in parallel or simply put Neg/Black to Neg/Black and then Pos/Red to Pos/Red.

(picture...left is 12vDC batteries in parallel and the right are 6vDC batteries in series)



This arrangement will allow you to share the load...in series the voltage adds and the amperage stays constant...in parallel the voltage stays constant and the amperage adds.

So your marine battery with 12vDC (group 24 or 27 is most common) and 90-110amps...two of these in series would give you 24vDC and 90-110 amps...two of these in parallel would give you 12vDC and 180-220amps.

The water in pipes theory is a great one.

The amount of water that can pass a wheel inline with a given water pipe is the voltage, or potential to turn the wheel...bigger wheel you need more voltage...the speed and thus the pressure of this water is the amperage, or endurance to turn the wheel in time...the longer you need to turn it the more amps your battery will need to have.

Two marine 12vDC batteries in parallel will provide the 12vDC desired with the added bonus of two horses to pull the sled...pulling it at the same speed but only working half as hard.

All that and a solar trickle charger can keep up with a smaller load for each battery rather than a larger load for one...has to do with heat and effort within the charging system.

[Elorrum]

This was a simple thing for me this year. cheap charge controller, 12 dollars on ebay, wire up the panel battery and "load" (one of those 12V cigarette lighter splitters w/ 2 usb and 2 12V cigarette lighter outlets) I hope it prevented overcharge, although I only have a 15 watt panel. I followed the pictures, bim bam boom.

[Canoe]

If I told you that, I was wrong.

Damn. It was me!
Again!
You originally told me about the 50% charge for lead acid deep cycle and provided that same link. I still get it wrong. I know all about the min/max for various lithium cells, but for some reason I've got a mental block for lead acid plate that says 50% charge = 6 VDC (striking that out because it's wrong).
This is the second, possibly third time I've done that. And set my voltage alarm wrong...
I don't see an emoticon for kicking me in the butt.

[Zhust]

Not to get too far into it, but a couple suggestions:

Do get a cheap charge controller with a switched "load" circuit. You don't need to actually connect solar panels, but if you did, even a small controller will be plenty for any panels you'd bring to the playa (e.g. a 5-amp controller will handle 60 watts of solar which is like a square that's a yard|meter on a side, so pretty big.) The "load" circuit switches off if the battery goes below some safe threshold. You'll always want a deep-cycle battery: starting batteries (i.e. regular car batteries) would barely recharge after just one 50% discharge while deep-cycles are designed for it. That said, a "dead" car battery often has enough juice to run some LED lights for quite some time — although it does get rather heavy. (I said I would not go too far, but consider that branded D-sized alkaline batteries are 10 amp-hour, so 8 of those is 12V at 10 amp-hours, or equivalent to a lead-acid brick; not rechargeable, but 120 watt-hours would run 2 watts of LED lights for 7 nights. The drawback is you can realistically get about 1/4 amp out of them, so it's 4 watts maximum.)

Second, a rule-of-thumb is that 11.50V is a dead battery (0% charge) and every 0.1 V above that is another 10%, so 12.00V is 50% charged and 12.50V is 100% charged. The voltage reading is done without anything connected, although you can get by drawing less than half an amp or so; the voltage sags more with more current, and you're likely to see something like 10V while starting a car. That's just an estimating technique; read about lead acid batteries if you want to know more than you care to.

A cheap volt meter will get you by, but the accuracy might not be so hot — note that if the meter is off by 0.3V, that's 30% of your charge. Most meters are better than that, but it's something to keep in mind. Oddly, those cheap Harmer Fright meters seem to be pretty accurate.

[FossaFerox]

If you don't care about battery health, what % of a battery's listed AH capacity can you expect to get out of it?

I'm in the earliest stages of brainstorming what I believe is a first-of-its-kind interactive element for my camp next year, and while I can build the installation piece for like $450-500 (well within our camp's budget) powering it is going to be tricky. I'm looking at somewhere between 330 to 660 mA draw on the center piece, plus additional current draw for some LED lights for nighttime use. I plan on including an on/off switch so people can flip it off when not in use, but knowing the state of mind most burners get in, I completely expect to have to power it 22 hours a day.

Call it 12-17 AH a day of power consumption with the 12V batteries I'm seeing listed having ~35 AH. This means things are looking grim. If I can suck them dry I'm looking at 4 batteries minimum which is heavy and super wasteful. But the cost of renting a generator (never mind the added transport and gas costs to run it) cost more than the additional batteries. I could add 4 batteries for the cost of recharging the first two...

I'm drifting from my own post at this rate.

Back to my original question. Is it realistic to expect to get 35 AH out of a battery with 35 AH as the listed capacity?

Bonus side question, is there a better way to do this? Perhaps kidnapping a neighbor's beloved camp member and ransoming them back for a recharge from their generator?

[FIGJAM]

Costco sells a 115AH battery for $80.

[FossaFerox]

Costco sells a 115AH battery for $80.

I know this is like the eighth or ninth time I've said this, but you rock. I promise that if I'm ever forced to kidnap someone and ransom them back, you get a pass. As for the Costco battery, can I expect to actually get 115 AH out of it before it's a brick?

[FIGJAM]

Maybe not quite that much, but if you drain them to 50% and hook some jumper cables to them, you can Idle your car for an hour and get them back to 80%.

This will use about a gallon of gas.

[Captain Goddammit]

I'll elaborate on that a little bit. I use those batteries in my MV. How far down you can take them depends on what you are powering, if it's lights you're good to drain them quite a bit. I was powering a 2000-watt inverter and running a lot of stuff and had to keep them pretty far "up".
As for charging from your idling car: that does work, pretty well in fact, usually the limiting factor is the jumper cables themselves. Most these days are shitty, wimpy ones with really fat plastic insulation on them so the cables LOOK thick.
Get ones with thick wire, at least 2-gauge. Lowes sells a good set of those for amazingly cheap, I actually bought three sets just to cut off the clamps and use the 2-guage wire because it worked out to be the best deal.

The next good trick is to double up on the jumper cables. Hook up two sets at once. Three even. This also works when you're trying to jump-start a car who's battery is too dead to crank over even when you hook up a set of cables. (Years and years ago, I was the AAA guy). Your batteries will get more current and charge faster.

[unjonharley]

I shortened the jumper cables to about 18 inches.. Then put ends on to bolt the cable to the storage battery..Then clamp to the van battery.. I charge while driving.. I leave if hooked up so I will always have a hot jumper battery.. Or have it ready to run a drill or what not.. I also have an inverter wired to the battery with a switch.. Now I'm shopping for some good clamps.. Captain, what did you do with those cut off clamps??

[Captain Goddammit]

Now I'm shopping for some good clamps.. Captain, what did you do with those cut off clamps??

Uh... lets just say the First Mate is a very naughty girl...

[unjonharley]

Now I'm shopping for some good clamps.. Captain, what did you do with those cut off clamps??

Uh... lets just say the First Mate is a very naughty girl...

Ooooo K