Community Forums

HHIDan · 02-09-2015, 05:58 PM

I am looking to replace my inverter, more power and True Sine.

I see 2 pairs of wires going to battery bank, am guessing one pair to coach and one pair to inverter?

A3T300 fuse mounted next to battery tray, is this fuse on inverter wire or coach wire? Is there a similar fuse on the other pair of wires? Why is it a 300Amp fuse as my inverter/converter is rated 2000 watts (ME2012 Magnum)?

Magnum states I need a T400 fuse for their MS2812 or MSH3012 and 4/0 wire for up to 10 feet... Do I have 4/0 wire already? Am guessing there could be a little more than 10 feet, inverter is between rails, mid-coach and batteries are behind the tag axles? If I have to replace the wires, should I run another pair in parallel or exchange the wire for the largest I can find?

I now have 4 6V batteries but I plan on adding two more. I will move the engine batteries into the engine compartment, there is a nice spot where I can get a tray welded in...

My AC side is OK as it is easy to update/upgrade.

wb7auk · 02-09-2015, 06:21 PM

I see 2 pairs of wires going to battery bank, am guessing one pair to coach and one pair to inverter?
Correct

A3T300 fuse mounted next to battery tray, is this fuse on inverter wire or coach wire? Is there a similar fuse on the other pair of wires? Why is it a 300Amp fuse as my inverter/converter is rated 2000 watts (ME2012 Magnum)?

The reason for the 300 amp fuse is because of the surge current possible to the inverter.
No there is only the fuse between the battery and inverter.

Magnum states I need a T400 fuse for their MS2812 or MSH3012 and 4/0 wire for up to 10 feet... Do I have 4/0 wire already?
Hard to tell but should be.
Am guessing there could be a little more than 10 feet, inverter is between rails, mid-coach and batteries are behind the tag axles? If I have to replace the wires, should I run another pair in parallel or exchange the wire for the largest I can find?
Running another set of 4/0 wires would be the way I would do it that way the voltage and current losses will be very small.

HHIDan · 02-09-2015, 06:31 PM

Thanks Art, If I ran another 4/0 cable, is there a neat and reliable way to join the ends?

wb7auk · 02-09-2015, 07:50 PM

Quote:

Originally Posted by HHIDan

Thanks Art, If I ran another 4/0 cable, is there a neat and reliable way to join the ends?

You would have to put the proper ends on the positive cable running back
but the neg cable should be tied to the frame it would be strange if they
ran two cables when the frame is right there.

Just bolt to the same connection that is currently being used.

HHIDan · 02-10-2015, 04:43 AM

Quote:

Originally Posted by wb7auk

You would have to put the proper ends on the positive cable running back
but the neg cable should be tied to the frame it would be strange if they
ran two cables when the frame is right there.

Just bolt to the same connection that is currently being used.

I was wondering why not use the frame but I read the Magnum manual and came across this:

- Do not attempt to use the chassis in place of the battery negative connection for grounding. The inverter requires a reliable return path directly to the battery.

twinboat · 02-10-2015, 05:04 AM

Guess they don`t want 300 amps, running thru your cross member rivets.

wb7auk · 02-10-2015, 06:37 AM

They are trying to avoid as many poor connections as they can.
But they forgot about adding lots of ground loops to the system.
The whole thing boils down to good connections with proper size wire/cable

joes2901 · 02-10-2015, 07:47 PM

When paying for a bigger and better inverter/charger you want to get all the power it can give so do not use less than 4/0 cables and 400 Amp. fuse. Your RV is about 9 years old and if the batteries were the wet cell type then new cables with a shrink wrapped (red for positive and black for negative) seal to the terminal will be beneficial. A careful examination of the old cables may reveal corrosion down into the wires if the connection to the terminal was open to the air.

Magnum now has a hybrid model MSH3012 that will add inverter power to your AC needs when connected to a 30 Amp. power source that would be worth considering when doing this work. Check it out on Magnum's web site.

HHIDan · 02-10-2015, 08:31 PM

Quote:

Originally Posted by joes2901

When paying for a bigger and better inverter/charger you want to get all the power it can give so do not use less than 4/0 cables and 400 Amp. fuse. Your RV is about 9 years old and if the batteries were the wet cell type then new cables with a shrink wrapped (red for positive and black for negative) seal to the terminal will be beneficial. A careful examination of the old cables may reveal corrosion down into the wires if the connection to the terminal was open to the air.

Magnum now has a hybrid model MSH3012 that will add inverter power to your AC needs when connected to a 30 Amp. power source that would be worth considering when doing this work. Check it out on Magnum's web site.

Thanks!

I have now received info from both Magnum and Newmar.

Newmar state that I currently have 3/0 cable between inverter and batteries and they have said this should be fine for an upgrade to the MS2812. Magnum recommends 4/0 for a cable run less than 5 feet long and "larger" for up to 15 feet and this would be for both the MS2812 or the MSH3012 (Hybrid).

I have decided to replace the cable for a 4/0 and up the fuse to a 350. I will look at 6/0 cable and if it will fit, I might use that. I have an old friend mechanic that recommends replacing the cables as oppose to installing a 2nd run in parallel.

On the AC side Magnum have confirmed that a MS2812 would have internal circuit breakers (push button) of 30 amps on input and output. The AC cables in my RV are AWG10/2 and are protected with 30 amp breakers so this could remain unchanged if I picked up an MS2812.

If I decide to go with the MSH3012, that has 60 amp push button circuit breakers on input and output so if I wanted to take full advantage of the hybrid mode I would have to upgrade my AC wiring and external breakers (in the main panel and in the inverter sub-panel). It looks like this Hybrid inverter could take up to 60 amps from shore and up to 30 amps from the batteries in any combination provided that the total does not exceed 60 amps on output. I do not see that I would ever need or take more than 30 amps out of my inverter panel so I would probably leave the existing wires and breakers unchanged and if the breakers eventually trip, I could always upgrade then.

Have not made final decision but the MSH3012 is looking good.

Dr4Film · 02-10-2015, 08:41 PM

I don't understand your cable "logic".

If you currently have 3 aught cable WHY would you remove it and install 4 aught cable which is a smaller gauge cable?

That makes no commons sense to me!

Dr4Film ----- Richard

Bumps · 02-10-2015, 08:57 PM

I agree with the 4/0 AWG upgrade that your friend recommends. There will be fewer points of failure if a wire comes loose (road vibrations) and less risk of overloading a wire that may be too small for the amount of current the inverter may be pulling at the time. Just remove the smaller wire. 4/0 > 3/0 unless there is something that I don't know about 3/0 wire (never actually seen any). \ken

Dr4Film · 02-10-2015, 09:07 PM

I guess I don't understand wire gauges.

Willing to learn.

Dr4Film ----- Richard

Bumps · 02-10-2015, 09:16 PM

I was confused on this once, myself. From smaller to larger the AWG sizes would be:

4
3
2
1
0
00
000
0000

"4/0" is just an abbreviated way of saying "0000". Of course, there are more sizes than listed here.

\ken