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Old 04-08-2012, 03:16 PM   #51
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My mistake - too many open windows on the computer at once...

Power factor is a term used in AC power for a completely different purpose - be careful not to mix terms (completely different topic).

Inverter efficiency at the available DC voltage is the factor to be used in the calculation (in this example 85%, but can be found for the inverter you are using from its specifications).

The safety factor should have been calculated:
162A * 1.25 = 203A
with overcurrent protection using the 162A and wire sizing using the 203A value.

The problem is in the 'what if' scenerios. This is why we use Inverter rated max output power (2000W) and minimum rated DC voltage the manufacturer says this can be produced at (10.5VDC). The manufacturer further has a graph that shows the inverter effeciency across its operating range of DC voltage (85%).

So selecting copper conductors for use at 86 deg F, and not in conduit, we truly should use 2/0 UF conductors, which are rated for 225A.

Again, no consideration for voltage drop is used yet.


BTW, it is no longer acceptable in residential installations to use welding cable for battery connections to inverters. I am less knowledgeable about RV and SAE regulations.

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Originally Posted by herk7769 View Post
I understand that the "equalizing" of AC/DC wattage requires the power factor be used. I get your calculation logic (2000W / 10.5 VDC) * 0.85 = 162A However I am not following your 20% safety factor math. 162A * 1.25 = 138A (think an error was made here)

As I understand what you are trying to say though, adding a 20% safety factor means either "upgrading the wires to handle a load 20% greater than the maximum rated load; yet fusing for 100%" (Wire size based on 195 amps and fuse based on 162A - which I get) OR (Wires size based on 162A and fused for 130A (20% less than full load).

If you were to use 1.0 as a power factor, 2000/10.5 = 190 amps and fuse (15-20% less or 162-175A) accordingly it pretty much wipes out the power conversion factor and the safety margin math. Makes things easy for me.

In fact to make it even easier, if you use 12 VDC and a 1.0 power factor, the amp load is 2000/12*1 which equals 166 amps. Right about where you want your circuits fused.
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Old 08-04-2013, 11:43 PM   #52
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COMPLETE SUCCESS!!!!!!!

It's been a while since I added to this thread, mostly because I really hadn't done anything to the system since last reporting, other than use it..... But that has changed!

This Spring, I added two more 6v golf cart batteries, and replaced the existing two, giving me four new batteries, and 260 Amp-hours of power.

Today, I completed 10 days of dry, beach camping. We used the microwave oven, the Kuerig coffee maker, the toaster, the Margarita maker, and charged phones and iPads every day. Additionally, most nights, we ran a 12v Casablanca ceiling fan and a 120v portable fan most evenings, just to make it more comfortable to sleep. Additionally, my son ran a lead cord from the TT to his tent to keep HIS phone and Kindle charged.....

Ten days of this, and I NEVER ONCE started my generator! The 300w of panels kept the batteries full. Even on two days of dreary cloud cover and rain, I got enough recharge that the NEXT day I got off of MPPT and into "float"!!!!

Now if I could just figure out a way for the sun to refill my freshwater tank, and empty my grey and black tanks, I'd be all set!!!!!!
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Old 08-05-2013, 03:02 PM   #53
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As you still on Assateague or did you leave already???

Sounds like the extra battery capacity is the key...more so than the panels!!
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Old 08-08-2013, 05:15 PM   #54
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As you still on Assateague or did you leave already???

Sounds like the extra battery capacity is the key...more so than the panels!!
I was already back home when I posted that, but the extra batteries made a HUGE difference! It was apparent that with only having two batteries, I was fully recharged relatively early in the day, and switching into "float", often before noon! The extra capacity takes longer every day to restore, but allows for all kinds of use into the evening, all night, and the morning. Someone on the forum, early on in my planning, had suggested shooting for around a 1.50:1 ratio on battery amp-hours to panel watts. Each pair of 6-volts is 230 amp-hours at 112v, so I now have the 460:300, or 1.53:1 ratio. This seems to work well!

Well see how well it works in the lower Fall sun, when I do 5 or 6 days at Dover for the NA$CAR race at the end of September.
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Old 08-08-2013, 05:23 PM   #55
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Can you post a picture of your battery box and make and model of the batteries and box??

Have you checked your tongue and GVW since the most recent install??
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Old 05-03-2014, 10:16 AM   #56
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Not to hijack the topic or anything, but why are the prices of these solar panels so high??????????????!!!! I purchased two240w24v sharp panels for 299$ each two years ago.
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Old 05-04-2014, 07:34 AM   #57
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A couple of years ago, there was a "price war" of sorts. The Chinese government was apparently subsidizing the cost to manufacture the panels. Thus artificially low prices.

2000 Cherokee 31BH, "flipped axles and raised",LEDs, solar, inverter, etc..aka "boondock ready". '07 Tundra 5.7L DC-LB, modded as well.
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Old 10-09-2014, 02:05 PM   #58
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Have you thought about the possibility of getting your whole house on solar and getting off the grid? Is this still pie in the sky thinking or getting close?
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Old 10-10-2014, 03:34 PM   #59
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Me, never. It would take a tremendous about of battery bank and solar to maintain our lifestyle at home. But, we've been talking about building a cabin on our farm upstate. There, we could use solar supplemented by a generator.

To live off grid would cost a lot initially, but would be extremely satisfying. In an emergency, we can live in our camper.
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Old 09-09-2015, 12:00 PM   #60
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Hey Fire, great thread. After two years of use is there anything you would change if you were rebuilding from scratch ?


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