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Old 03-16-2014, 08:19 PM   #21
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Re: Armageddon: the smell of airborne rust

Quote:
Originally Posted by Redbear
Quote:
Originally Posted by jazty
The power supply actually had a knob for adjusting the voltage +/- 4v so I turned it right up. Why not
27.9 volts will be fine with hydrate (wet cell) batteries if you check periodically to keep the distilled water and acid level up. If you are using any kind of sealed batteries, check with the manufacturer's specification for charging instructions. That much voltage will cook most gel-cells once they are fully charged. If they out-gas through the safety vents, there is no topping them back up to replace the lost storage capacity. Somewhere around 27.0 volts 0.3 volts might be better in a 24-volt system.

But I suspect you knew that. I just don't want to see anyone else destroy an expensive battery bank by over-charging.

Nice build, by the way. I just caught up with it again to see all the progress.
Thanks for the concern Redbear. This information holds true for charging in general and especially PWM charge controllers. The beauty of the MPPT chargers, however, is that they will take a high voltage (relatively speaking. My model will accept up to 100 volts) and bring it down to a voltage that is appropriate for charging the battery bank. It's hard to see from the photos, but the power supply is pumping ~27 volts into the charge controller's solar panel connection ports and the controller is then bringing the voltage down to ~15 volts which is an appropriate temperature compensated voltage for my 12v battery bank.

Actually, ~15v might be a tad much, but the charge controller can be programmed to charge at a lower voltage. But then again, it is -1000 degrees here so perhaps 15v is just right...
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Old 03-17-2014, 12:41 AM   #22
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Re: Armageddon: the smell of airborne rust

I misunderstood. I thought you had a 24-volt battery bank (more common in coaches), and had the converter connected to the batteries in parallel with the output of the MPPT controller. I thought the meter was reading battery voltage. I did not realize that you were running the converter through the solar controller to step down the voltage. I wondered why you did that, and then realized it was probably a way to use available or bargain equipment.

So divide my numbers in half. Most of the sealed batteries I work with want 13.20 to 13.60 as a charging voltage, ambient temperature. That's where the 27.0 volt figure came from.

Since whatever you set the converter for will be throttled by the MPPT controller, carry on . . .
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Old 03-17-2014, 08:53 AM   #23
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Re: Armageddon: the smell of airborne rust

Quote:
Originally Posted by Redbear
I wondered why you did that, and then realized it was probably a way to use available or bargain equipment.
Bingo ;) I looked at installing a decent 120vac to 12vdc smart battery charger, but couldn't find anything within a reasonable price range that I'd be happy with. Then it dawned on me: I already have a "smart" charger which can accept 12-100vdc and is already connected to the batteries with 2 gauge wire, it just needs some input power to play with. 27 dollars later the system is charging the batteries. As I mentioned before, the MPPT charge controller also takes into account the temperature when charging the batteries. Few smart charges that I looked at were offering that feature, which up here is important. This is supposed to be spring, yet it's still -21C (-5.8F)!
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Old 04-16-2014, 12:55 PM   #24
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Re: Armageddon: the smell of airborne rust

Fun adventure the other day...

About 2 weeks ago I picked up my new house batteries: three US Batteries 12v XC2 155Ah http://www.usbattery.com/usb_us12vxc.html. Real nice. I was quite pleased. I went with three of these because they provided the amount of amp hours I was looking for while fitting very nicely in my battery bay.

Anyway, they sat around for the past 2 weeks as I got the electrical system to a point where I could get some use out of them; the last thing being setting up my inverter. Nothing fancy, just a used 1000w modified sine wave inverter I picked up for $60. I had done a couple modifications to it to make the power switch and display a remote unit, but it ran fine.

I went to plug it in to one of the new batteries the other day and *BAM*! Sparks and smoke. Oh #@$&! What the hell did I screw up?!?! Wiring looked fine. I even used my multimeter to test the wiring. Opened up the inverter and the fuses (soldered to the circuit board.. grr..) were all blown as well as a couple resistors.

After steaming for a while I thought, "Well crap.. That's disappointing. Ah well. Moving on, it's probably time to charge this battery". I plugged the charger to the terminals and the "Reverse Polarity" light lit up. I thought to myself, "What?! I'm usually extremely careful when connecting things." I took a close look.. Seemed fine. Dammit, now my charger must be broken, too! Tried it on another battery and it worked fine so back to the first battery. Still reverse polarity. Pulled out the multimeter, probed the terminals and sure enough. This battery was shipped from the factory REVERSED!!!

I'm not sure if anyone else has encountered this sort of thing, but it truly did blow my mind. I must have checked it 10 times before bringing it in for a refund. They quizzically listened to my story and after showing them the reverse polarity with my multimeter they happily gave me another. The nice fella said he'd see what he could do about paying for my burnt inverter as well, though I'm waiting to hear back about that.

Yowsers...
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Old 04-16-2014, 03:21 PM   #25
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Re: Armageddon: the smell of airborne rust

Wow, sorry to hear about the bad battery.

Nat
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Old 04-17-2014, 12:50 PM   #26
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Re: Armageddon: the smell of airborne rust

Yowzer Indeed! --- Yer lucky that rascal didn't blow up in your face! Never heard of a "reversed" battery making it that far out of the factory.
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Old 04-17-2014, 05:58 PM   #27
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Re: Armageddon: the smell of airborne rust

OUCH!

Good thing an electrical fire didn't start! THAT was close! Sad to hear about the inverter frying!

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Old 04-17-2014, 06:22 PM   #28
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Re: Armageddon: the smell of airborne rust

Yeh, it could have been MUCH worse. Imagine I had gotten so far as to have the batteries all connected together! 2 batteries properly in parallel then one connected reverse... And that's how we build an electrical bomb
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Old 05-06-2014, 11:30 AM   #29
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Re: Armageddon: the smell of airborne rust

Perhaps it's time to post some info about my electrical system. I don't imagine this will be an interesting read for most, but perhaps someone will care to analyze and comment on what I have going on here.

The system is 12v for most everything. Reason? 12vdc adapters and appliances are plentiful and cheap and a small, properly designed 12v system with short runs can stay below 1% loss. I installed a couple NEMA 5-15 outlets and have them connected to an inverter, but I honestly don't have much to run off of the 110vac system aside from some power tools and my coffee grinder. Practically all digital appliances use between 5vdc to 20vdc so it's not hard to find the proper adapter or connector to use them on a 12v system, though sometimes you'll have to make your own.

Power usage:
Worst case scenario - Summer:
  • Ceiling exhaust fans (on medium speed): 2x 2.5a = 5a. 10 hours a day = 50ah[/*:m:1kjvcd61]
  • Range hood fan: 4a. 1 hour a day = 4ah[/*:m:1kjvcd61]
  • Ceiling lights: 12x 0.33a = 4a. 6 hours a day: 24ah[/*:m:1kjvcd61]
  • Refrigerator: 1.1a average. 24 hours a day: 26.4ah[/*:m:1kjvcd61]
  • 12v laptop adapter: 3.5a max. 10 hours a day = 35ah[/*:m:1kjvcd61]
  • Water pump: 5.2a max. 2 hours a day = 10.4ah[/*:m:1kjvcd61]
  • Stereo: 8a max. 4 hours a day = 32ah[/*:m:1kjvcd61]
Total: 181.8ah

Worst case scenario - Winter:
  • Ceiling exhaust fans (on low speed): 1x 1a = 1a. 2 hours a day = 2ah[/*:m:1kjvcd61]
  • Range hood fan: 4a. 2 hours a day = 8ah[/*:m:1kjvcd61]
  • Ceiling lights: 12x 0.33a = 4a. 10 hours a day: 40ah[/*:m:1kjvcd61]
  • Refrigerator: 1.1a average. 24 hours a day: 26.4ah[/*:m:1kjvcd61]
  • 12v laptop adapter: 3.5a max. 10 hours a day = 35ah[/*:m:1kjvcd61]
  • Water pump: 5.2a max. 2 hours a day = 10.4ah[/*:m:1kjvcd61]
  • Stereo: 8a max. 4 hours a day = 32ah[/*:m:1kjvcd61]
Total: 153.8ah

As noted in the titles, these are worst case scenarios. I usually won't have the stereo blowing my ears out for 4 hours a day. Me and my lady won't typically be showering for a half hour each and running the tap for an additional hour. When I'm doing computer work my laptop will probably be on for 10 hours. My computer reports that under normal usage with the screen at full brightness it is only consuming 28.5 watts, so at 12v that would be 2.2a. Add in the inefficiencies of the adapter (let's be pessimistic and say 20% loss) and I would peg it around 2.6a instead of 3.5a.

Cooking and water heating are done with propane.

I also have a 2000w Whistler Pro inverter for the occasional 110AC tool or appliance I may need to run. If I'm using power tools I won't be using the computer or other loads inside the bus. For heavy building I'll be using a generator.

Battery bank:
3x US Batteries 12v XC2 batteries in parallel @ 155ah = 465ah
http://www.usbattery.com/usb_images/usb_12V_data.pdf
Safe available amp/hours: 465ah * 50% = 232.5ah
Recommended bulk charge is ~10% of C/20 Ah rating. 155Ah * 10% = 15.5a

Charge controller:
40a Tracer 4210rn MPPT charge controller
Max charge rate is 40a. 40a / 3 batteries = 13.33a bulk charge per battery.
To fully charge the battery bank when 50% depleted it will take 232.5ah / 40a = 5.8 hours with ideal solar conditions.
33% (Winter worst case scenario) depleted it will take 153.8 / 40 = 3.9 hours
39% (Summer worst case scenario) depleted it will take 181.8 / 40 = 4.5 hours

Solar panels:
2x 300w ~36v Heliene 72m panels (Realistic output is between 220 - 270 watts)
http://www.heliene.ca/products/detai...,10,20,581,616
Charge controller converts voltage from ~36v to ~13v.
270 watts / 13v = 20.77a
In ideal conditions the charge controller will be receiving 41.54 amps. 1.54amps over the controllers rated input shouldn't be a problem. We'll see

Before buying and installing the wiring I figured out distances and intended power draw per run. All systems are installed with a 1% acceptable loss rate. This website is handy to calculate acceptable loss: http://www.solar-wind.co.uk/cable-sizing-DC-cables.html
Wall wiring in the bus is 8ga. Found it cheap at a local semi repair shop. Battery cables are 1/0ga welding cable. Praxair is practically giving that stuff away... I think it was $2.40 per metre, or $0.73 per foot!! For comparison, Home Depot is selling 12/2 Romex wire for around $0.80 per foot.

So with this set up I'll need to be conscious of my electrical demands, but I don't expect that to be a problem. We don't need much. Lights at night, a couple comforts and some electricity to play with when I'm working or the weather is foul.
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Old 05-06-2014, 11:35 AM   #30
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Re: Armageddon: the smell of airborne rust

Great info. A few folks on here will find it interesting.

Nat
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