MOD: Inverter Cutoff Switch

[NealC]

Originally Posted by hohenwald48

Actually, not all of us have read the magnum inverter fire stuff. I saw one report of an inverter fire but wasn't aware of it being a serious issue. My Google search returned 2 reports. 1 reported here and 1 on the FMCA forum. Can you elaborate or provide a few links please? Is it only a particular model or Magnums in general?

Here is the thread: http://www.irv2.com/forums/f103/magn...re-436453.html

Please keep any discussions related to that situation in that thread, this thread is strictly about adding an inverter cutoff switch which the RV manufacturer should include on inverter, house battery and for us with solar it should be in your solar setup as well.

In re-reading my post I forgot to mention make sure AGS is disarmed (not in AUTO) on your ME-RC/ARC panel.

[dp7]

As part of the planning process for adding a BMK & ARC, I was going to add a cutoff switch also. According to the Magnum manual, my MS2012 inverter has a max continuous current draw of 267A. So a switch rated at 300A continuous would be appropriate. For those that have an MS2812 inverter with a 373A max continuous rating, perhaps a larger switch should be selected.

After looking at switch ratings, I thought it might be a good idea to size a larger switch & use it for the entire battery bank rather than just the inverter. This would have to accomodate the total currents of all three load cables (inverter, coach & BIM). Not knowing the max continuous coach draw, I used 150A since this is the fuse size for that cable. Adding this to the inverter max continuous draw, yielded 267+150 = 417A. I was unable to find a fuse for the BIM cable, so unsure how much current to add for it. So it looks like a cutoff switch would need to have at least a 500A continuous rating.

I know there are some very knowledgeable people on the forum (Professors Martin & Redbaron come to mind). I welcome any guidance on switch sizing.

[twinboat]

Originally Posted by dp7

As part of the planning process for adding a BMK & ARC, I was going to add a cutoff switch also. According to the Magnum manual, my MS2012 inverter has a max continuous current draw of 267A. So a switch rated at 300A continuous would be appropriate. For those that have an MS2812 inverter with a 373A max continuous rating, perhaps a larger switch should be selected.

After looking at switch ratings, I thought it might be a good idea to size a larger switch & use it for the entire battery bank rather than just the inverter. This would have to accomodate the total currents of all three load cables (inverter, coach & BIM). Not knowing the max continuous coach draw, I used 150A since this is the fuse size for that cable. Adding this to the inverter max continuous draw, yielded 267+150 = 417A. I was unable to find a fuse for the BIM cable, so unsure how much current to add for it. So it looks like a cutoff switch would need to have at least a 500A continuous rating.

I know there are some very knowledgeable people on the forum (Professors Martin & Redbaron come to mind). I welcome any guidance on switch sizing.

If you have the newer BIM its either a 160 or 225 amp model.
That's what its designed to handle while using the boost mode, when 1 battery is low. During bi-directional charging, the current wouldn't be more the 100 amps.

You would not be running your inverter at max output, probably not any output, when using the boost mode, so you don't need to be added them together for a switch's amp rating.

A 500 amp disconnect would be my choice. A lower rated one could create some voltage drop under heavy load.

[dp7]

Originally Posted by twinboat

If you have the newer BIM its either a 160 or 225 amp model.
That's what its designed to handle while using the boost mode, when 1 battery is low. During bi-directional charging, the current wouldn't be more the 100 amps.

You would not be running your inverter at max output, probably not any output, when using the boost mode, so you don't need to be added them together for a switch's amp rating.

A 500 amp disconnect would be my choice. A lower rated one could create some voltage drop under heavy load.

Thanks Twinboat. I will check, but I am thinking that my BIM is the 225A version since I have a 240A alternator. Where did you find the 100A bi-directional charge spec?

[twinboat]

Originally Posted by dp7

Thanks Twinboat. I will check, but I am thinking that my BIM is the 225A version since I have a 240A alternator. Where did you find the 100A bi-directional charge spec?

Didn't find a spec, but your alternator is may be 240 amp rated but that's at full RPMs and cold. Alternators drop back on output when hot. Its also connected to the starting batteries which will absorb much of the output. You would need almost dead house batteries to get more then 100 amps thru the BIM and its designed to open the circuit if the the chassis battery voltage drops to low.

Your inverter/charger typically has about a 100 amp charger section and again connected to the house batteries most of that amperage will go to the house batteries..


Here is a 220 amp alternator temp chart and a link explaining them.

https://www.lifewire.com/understandi...ratings-534785

[dp7]

Originally Posted by twinboat

Didn't find a spec, but your alternator is may be 240 amp rated but that's at full RPMs and cold. Alternators drop back on output when hot. Its also connected to the starting batteries which will absorb much of the output. You would need almost dead house batteries to get more then 100 amps thru the BIM and its designed to open the circuit if the the chassis battery voltage drops to low.

Your inverter/charger typically has about a 100 amp charger section and again connected to the house batteries most of that amperage will go to the house batteries..


Here is a 220 amp alternator temp chart and a link explaining them.

https://www.lifewire.com/understandi...ratings-534785

Thanks!