Using car's battery for yurt power?

[Captain Goddammit]

I have LED rope light on my Mutant Vehicle, running through an inverter. It didn't work with "any old inverter"... I had cheap "modified sine wave" inverters, an 800-watt and a 1200-watt unit. These are the ones you see everywhere and they are OK for some things, won't work for others. The problem is the waveform of the AC output. With a so-called modified sine wave unit, you get a choppy transition between + and - as it phases through the AC cycle, not a smooth one like the true sine wave power you have at home (or that you get from a good generator like the Honda EU2000 that everyone loves).

When I tried to run my LEDs on the modified sine wave inverter, they had a very eye-irritating high-speed (60Hz) flicker, and only got about half brightness.
The solution was a true, pure sine wave inverter. Which, of course, wasn't cheap.

You can avoid the expense of a good inverter by using 12VDC LED rope light. If you get a sine wave inverter, don't buy one of the ultra-cheap Chinese ones. You'll regret wasting your money!

[robrob]

We're going to build a hexayurt this year, and even though I have an eu2000, I'd like to keep it's use strictly to charging stuff.

I've never used a deep cycle marine battery before, so i have a couple questions.

first, if it's the solid color LED strips with red and black wires, can I just splice those onto a male cigarette lighter plug, and plug that straight into a female ciggarette plug that is clipped directly to the battery?

As far as the load goes, I'm thinking 2x of 5meter 5M Non-Waterproof 3528 strips (in a fashionable pink), and one endless breeze 12v fan. My simple math says Fan: 3A Led: 20W/roll. @12v, this is 1.6 A (round up to 2) = 4A for two rolls, for a total of 7A for this setup. A pal thinks a typical Warehouse store battery will drive that load for approx 16 hours.

As for charging... can I leave a charger hooked up to the battery fulltime, while it's carrying a load, and just run the genny a couple hours a day to top everything off? thanks in advance for any help. i've dug around and it all *seems* pretty straightforward, I've just never dealt with charging a battery like this before.

[GreyCoyote]

first, if it's the solid color LED strips with red and black wires, can I just splice those onto a male cigarette lighter plug, and plug that straight into a female ciggarette plug that is clipped directly to the battery?

As far as the load goes, I'm thinking 2x of 5meter 5M Non-Waterproof 3528 strips (in a fashionable pink), and one endless breeze 12v fan. My simple math says Fan: 3A Led: 20W/roll. @12v, this is 1.6 A (round up to 2) = 4A for two rolls, for a total of 7A for this setup. A pal thinks a typical Warehouse store battery will drive that load for approx 16 hours. [/quote]

7 amps at 16 hours is 112 amp/hours. The average deep cycle battery is 110-120 ah, and this means you'll be cycling it all the way down to zero capacity. This is hard (very hard) on batteries. Most of the time you don't want to take these batteries down more than half of their rated AH capacity, or about 60 AH. So I would suggest either shedding some load or recharging more often.

As for charging... can I leave a charger hooked up to the battery fulltime, while it's carrying a load, and just run the genny a couple hours a day to top everything off?

Yes, but it will depend on the charger and will require a "smart" charger that will shut-off automatically when a full charge has been delivered. Remember that if you have a 7 amp light/fan load, and a 10 amp charger, then you are only putting about 3 amps into the battery, so plan charging times accordingly. DONT use the 12v output of the Honda to charge a battery and expect it to taper-off when the battery is charged. It WONT, and you'll suffer an overcharge unless you disconnect the battery when it's full.

Honestly, since an EU2000 is almost inaudible over the background noise of BM, I would just hook-up the genny to the battery with a good charger at dusk and run it to exhaustion with a smart charger. You will get the battery charged and support the light/fan loads at the same time. No muss / no fuss. Yank the cord and walk away from it. When it quits, the battery will be charged, it'll be 4 AM, and you'll be ready to sleep while your blinkies and fan run off the battery.

[Captain Goddammit]

I interpreted what he asked to be whether he can just leave the charger hooked up, then run the generator as needed. The charger would be connected full-time but only charging while the generator is running.
If that's the correct interpretation, then sure.

Technically, charging batteries at a slow rate is supposed to be best for them, but charging at a high rate will reduce your generator running time. If you can scrape up a BIG battery charger, one of those things you see at auto shops with wheels and a handle that charge at around 40 amps, you'll cut your run time.
Don't let the labels fool you. Most small car battery chargers will say something like "10-20-100amp engine start". They will not produce 100 amps of charging power. I'm not sure exactly what formula of bullshit they are using, but a real 40+ amp charger probably has wheels on it. The slightly higher "engine start" function on most chargers is only temporary anyway and sets off the overheat protection within a minute or so.
Let's say you have the typical 110 aH deep cycle battery and a typical 10-amp charger. That's theoretically about ten hours of charging time, assuming a full 10-amp charge rate, which you probably won't get. That means running the generator all day. Batteries can take much higher charge rates. Those batteries typically go in vehicles with alternators that charge them at 30-40 amps or more when they are really low.

[robrob]

Hmm.

so, assuming I would be using a mainstream/$50 battery charger and not a wheeled one from an autoshop, is this plan even worth it? I suppose I could lower the load, and only hang one run of lights, and use the fan on medium to get down to around 4 amps... but at that point it alsmost just seems like a better plan to buy a $99 AC unit and an an extra 6 gallon gas tank :/ dang it.

I was hoping I might have found a good sweet spot. sounds like i'm not quite there yet.

[robrob]

grey coyote: would something like this qualify as a decent /smart charger? (ie: something to leave running every day)

[GreyCoyote]

Rob: that should work, but I have never used that particular charger. I have its big brother on my 4-battery bank and it works well.

Take the DC cables for your EU2000 along as a backup just in case. It wont be automatic, but it will work fine as a manual, back-up charger.

[Captain Goddammit]

That should be fine.
You just have to figure that your actual average charging rate will be maybe 10 amps or less, and figure on running the generator however long it takes to replace the amp-hours you used from the battery.
Running the Honda isn't the worst thing in the world though. You could get an AC! Or a microwave... microwaves rock at BRC. Most of the time when you're hungry there you just want food ASAP and easy. Microwaves also allow you to cook inside without heating up your space.
And there's popcorn!
And you can bring a vacuum cleaner... Oh, and coffee maker! That REALLY rocks in BRC!

[--Ever--]

Hah Captain, I dig your style.

LED rope, A/C, hotplate, espresso machine and burr grinder.

[GreyCoyote]

Epic yurt! Now THAT is glamping!

[--Ever--]

Yeah baby.

Man, I've done the back of a Suburban, a tent, a painter's van + geodome, an RV, an Airstream... Yurt is by far the best value.

Our mats for the eu2000i tank extender arrived. Just need to get my battery situation on lock and we should be good. I think my old inverter might be dying though.

[Captain Goddammit]

That is indeed an epic yurt!! Luxuries of home seem ten times more luxurious in BRC!

[robrob]

holy smokes that yurt is amazing!

yeah, i think the new plan is- ditch the $70 endless breeze and buy a $99 AC.
Just run LED lights off the battery at night. Top off battery and run AC on the eu2000 during Day.

[mozburrn]

To answer OP's question.

The short answer is it's not a great idea to using a starting battery for playa power, but not necessarily a terrible idea.

But, how deeply you discharge makes a difference. Here's another site's general estimates on the number of discharges possible with the two types of lead batteries -

Starter battery:
100% Discharge: 12–15 cycles
50% Discharge: 100–120 cycles
30% Discharge: 130–150 cycles

Deep cycle battery:
100% Discharge: 150–200 cycles
50% Discharge: 400–500 cycles
30% Discharge: 1,000 and more cycles

(source: http://batteryuniversity.com/learn/arti ... _lead_acid)

Using a starting battery to power your yurt is more reasonable if you do shallower discharges, though it's still better to use deep discharge batteries.

[--Ever--]

Should we not have time to get a "smart" charger, we'll be left to simply charging it manually.

Obviously there's lots of variances, but does anyone have any rules of thumb for how long it would take to manuall charge:

• A normal car battery from 20% to 100%
• A deep cycle from 20% to 100%

This would be off an eu2000i. Recommendations for which charge port to use would be helpful too.

[mozburrn]

Should we not have time to get a "smart" charger, we'll be left to simply charging it manually.

Obviously there's lots of variances, but does anyone have any rules of thumb for how long it would take to manuall charge:

• A normal car battery from 20% to 100%
• A deep cycle from 20% to 100%

This would be off an eu2000i. Recommendations for which charge port to use would be helpful too.

Charging a starting battery and a deep cycle battery are done in the same manner. Since starting batteries aren't meant to be deeply discharged and instead just need to be topped off, you'd normally use a trickle charger with them, which keeps them healthy but which would take forever to charge from a low charge state (although this would be safe and good for the battery). A marine/rv charger assumes deep discharge, and varies the amount of charge going in because lead acids can take safely take higher charge flows earlier in the charge process when the battery is still pretty empty.

A popular battery is the Everstart Maxx, which has about 125 Ah. Until the battery reaches about 80% of its capacity, you can put in lots of current. So bringing it from 20% to 80% charged (~75 Ah worth of charge), with one of those 50A wheeled chargers, will happen in a couple hours. With a popular $30 Schumacher charger that does 12A, longer - maybe 7 hr or so. Beyond that, the charging circuitry lowers voltage (and therefore current) to prevent overcharging, so it'll take longer to do that last 20%, but I'm not sure how individual chargers handle this - you'd probably want to find out from the manufacturer.

The same chemical reactions that make it undesirable to charge rapidly above 80% are exacerbated by heat. So in the playa heat, charging from 80-100%, should take even longer if you're doing it right. I'm not sure if chargers are usually temperature-sensing, or if they just assume a high temperature to be conservative, and base their charge algorithm on that.

It sounds like you're considering charging your battery of the EU2000i's 12V port. You'll find from searching about this that it's not ideal, as it doesn't have a smart charging circuit. You'll be charging less than you should be able to when the battery is deeply discharged, and overcharging it once it's near full. You could do better than that with a $200 solar setup. Considering you're using a $900 generator, I'd consider spending $30-$100 on a proper charger to plug into the 120V output to take full advantage of it. Amazon prime it for 2-day shipping?