12v Battery Wires Sizing

[coachconverter]

Got the 458 20/21 Inverter wired up with 4/0 (man that stuff is fun to bend), but how about the 12v side? 
Any tables or specs someone can point me to? 
I have about a 10 foot run from 4 Optima Blue D34M 55AH/750CCA batteries, to a T-Fuse, to the disty panel.

Appreciate any help!

Todd

[Nick Badame Refrig/ACC]

Hi Todd,

I would put the t-fuse inline between the battery's and the inverter.

The cable between your inverter and your panel should be sized by your max load. Usually 4 to 6 ga  then always have a main curcuit breaker at

your panel before branching off to to other curcuits.  I will see if I can find the calculator for you.

Nick-

[Dallas]

Todd,

I have to agree with Nick, the T-fuse is for the protection of the inverter.

Figure up the amount of power you are going to draw for your 12V loads in amps and then add at least 50%.

I have a calculator if you need it, but you shouldn't need it. Just post back here what your totals are and we can tell you exactly.

Or you can call me tomorrow and I'll look it up for you.

Dallas

[Nick Badame Refrig/ACC]

Hi Todd,

Found it!

http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

Good Luck
Nick-

[coachconverter]

Thanks guys,

The guys from Xantrex told me I need to run one set of cables from batteries to the inverter, with the T-fuse, and a seperate set of cables from the batteries to the dist panel.  Does this sound strange to you?  It did to me.

I thought I could just tap off the posts of the inverter and upto the dist panel???

Todd

[coachconverter]

Also, the original manual with the 458 inverter recommends no less than 2/0 for the inverter if more than 5 foot of cable.  But the new specs on the website say 4/0 for 5-10 feet in an RV application.  So I put 4/0 between the batteries, to the T-fuse and upto the INverter.  Just kinda confused on what to run upto the 12v side of the dist panel, and where to run it from (inverter or batteries).

Thanks for your help.

Todd

[coachconverter]

Back to your question, not much on the 12v side, draw-wise.  I have 10 puck lights, 8 spotlights, one Fantastic power vent, 2 lights in the crapier, the power for the sat receiver and water pump. 

Yes, I'm too lazy to have looked up all the draws yet!

Thanks
Todd

[Nick Badame Refrig/ACC]

Todd,

At your inverter 12v lugs, you can run to your dist panel from here. This will make your run much shorter and still be covered by your 4/O t-fuse.

This is what I did and it may not be right but, that was my needs and your may be different. I stayed within my cable ratings for my draw.

4/0 is good for your battery app.

Nick-

[Dallas]

If you draw your 12V off the inverter terminals all of your power will be coming through the 4/0 cables and the T-fuse.

If your inverter is drawing max load, at say 400A and your 12V distribution is pulling another 50 to 100A then depending on your T-fuse size, you'll be exceeding it's capabilities, which means it's going to blow. Leaving you with no power to anything.

The Xantrex tech is correct, run a separate set of cables to the 12V distribution panel.

Here's a link to a wire sizing guide that may help:

http://www.skingco.com/portable_power/wiring_size_chart.htm

Here is a voltage drop calculator link:

http://www.powerstream.com/Wire_Size.htm

Scroll to the bottom of the page for the calculator.

Dallas

Thanks guys,

The guys from Xantrex told me I need to run one set of cables from batteries to the inverter, with the T-fuse, and a seperate set of cables from the batteries to the dist panel.  Does this sound strange to you?  It did to me.

I thought I could just tap off the posts of the inverter and upto the dist panel???

Todd

[coachconverter]

Thanks again guys, well I really need to follow the Xantrex guy's lead, as he put it in writing, and this is for a customer (liability/buck-passing) :-)

So I guess I just need to figure up the amps I'll be pulling, looks like the KVH A5 pulls about 5 amps, the Fantastic only 3 amps on high, the Shurflo says 5.5 amps max and I can't find anything on the puck and spot lights.  Any guesses?

Either way, with a total of 20 12v lights, I can't imagine they pull more than 1 amp each, so that puts me at about 33, plus 50%, that's 49.5 by my figuring.  From the chart on the link you sent, looks like as little as 6awg would work.  I'll probably go with 2 to have my normal overkill.  Sound reasonable?

Thanks
Todd

[Dallas]

Todd,

If you are using 20W bulbs the amp draw on each light is 1.6A@12v x 20(number of lamps) = 32A @ 12v

32A
5A
5.5A
-------
+42.5A
X1.5
---------
63.75A total

Voltage drop with 6awg will be .518v in a 10' run .. that's over half a volt loss.
Voltage drop with 2awg will be just .205v in a 10' run... a much better solution.

Thanks again guys, well I really need to follow the Xantrex guy's lead, as he put it in writing, and this is for a customer (liability/buck-passing) :-)

So I guess I just need to figure up the amps I'll be pulling, looks like the KVH A5 pulls about 5 amps, the Fantastic only 3 amps on high, the Shurflo says 5.5 amps max and I can't find anything on the puck and spot lights.  Any guesses?

Either way, with a total of 20 12v lights, I can't imagine they pull more than 1 amp each, so that puts me at about 33, plus 50%, that's 49.5 by my figuring.  From the chart on the link you sent, looks like as little as 6awg would work.  I'll probably go with 2 to have my normal overkill.  Sound reasonable?

Thanks
Todd

[Stan]

Why does the wire have to be sized to have everything turned on at the same time?  If you did that in a house, you would have to have a 600 amp entrance panel,

[belfert]

I think in a bus you're more likely to turn on a lot of stuff at once due to the smaller space.  Most houses are large enough unless you have a huge family that you're not likely to turn everything on at once.

[coachconverter]

Thanks Dallas,

Yes, in a bus, especially a Day Coach, it's very likely that everything could be on at once.  In fact the driver, at night, would probably turn everything on to "set the atmosphere".  So I have to plan for the worst case scenario.

Now on an RV, I would probably not plan on the owner running the toaster, microwave, clothes dryer and hiar dryer at the same time.  But maybe I would if it were a large family that eats a lot, washes a lot of clothes and takes a lot of showers :-)

Thanks again,

Todd

[TomC]

I have a Trace 2512, older modified sine wave.  Using two Lifeline AGM 8D's for deep cycle.  Have the big 4-0 cable (welding cable that is very flexible) on one positive lug to the inverter and on the other battery a 2-0 cable to my distribution for 12v power in the bus.  This lets the batteries be in between the two to buffer the voltage-whether it be drawing or charging from the inverter.  Personally, I would like to have one more 8D for a bit more buffering and more reserve power.  But when I need new batteries, Lifeline now has a 300amp 6V that I'll use.  The 8D's are just too heavy at 155lbs each, compared to the 93lbs for the 6v.  Good Luck, TomC