Community Forums

robertj1979 · 12-23-2022, 11:04 AM

I have discovered that my 3000 watt Mastervolt Combi Inverter/Charger is wired direct from the batteries with no fuse. It was set up this way by Thor and is a 2022 model class B van. The batteries are Relion Lithium LT100's (2). The batteries do offer some protection would think since they have a BMS system unlike AGM or flooded. My question is should there be a fuse or way to disconnect the inverter from battery power if for no other reason than safety? The inverter/charger has a switch on it but that only functions to turn off the inverter but still leaves the charger functioning and power on to the device. Other problem with this setup is continuous battery drain during storage. The normal battery cutoff device does not cut power to the inverter.
Is this setup from Thor correct and should I add an inline DC fuse/disconnect to the inverter?

Terraboat · 12-23-2022, 11:15 AM

I would say you actually need both: on boats, a fuse is required within just a few inches of a source of power, the batteries; and a breaker to disconnect the inverter from the batteries to allow for any work on the inverter to be done without the potential for unwanted power to flow when it would be dangerous.

The size of the fuse needs to be based on the size of wire it's protecting. A short somewhere in that wire would cause it to heat up and become a fire hazard. The breaker needs to be sized according to the potential amperage available from the battery bank.

robertj1979 · 12-23-2022, 11:42 AM

That was my thought exactly. Not sure why it was set up that way from the factory.

I have planned to install a combination 250amp breaker/disconnect but I have a couple of concerns. Most of the breaker/disconnect devices I have found at that amperage are China/Amazon products of questionable quality. The other concern is that the recommended place for the fuse is on the positive cable according to the manufacturer of the inverter.
The batteries on this vehicle are very difficult to access (located underneath in front of the axels) and the easiest access to disconnect the cables is at the inverter itself.
That being said, if I add the fuse/disconnect there I will be holding a "hot" DC cable (carefully) if I can not access the cable to the batteries themselves to disconnect.
I understand the implications of touching any metal with the positive lead or tools and realize that is not really a good idea.
Also wondering if there are any advantages to the setup with the inverter being connected that way at all times or why Thor would have done that? Current setup has parasitic draw from the inverter alone at about 1 amp even with the inverter turned off. Thanks for reply.

hclark6345 · 12-23-2022, 11:59 AM

Disconnect the ground ( negative battery post ) before you try working on the positive leads. Without a ground, you do not have to worry about shorting out the positive side.

robertj1979 · 12-23-2022, 12:44 PM

Understood. However the problem is the batteries are very difficult to access given the installation but point taken. Also, when working with inverters, there can be problems unhooking the negative lead first. Have been advised this by Magnum Energy and Mastervolt technicians.

Terraboat · 12-24-2022, 05:22 AM

You will have more success looking for products for the marine market made by Blue Sea Systems: www.bluesea.com

This is the type of breaker you should be looking for: https://www.bluesea.com/products/900...Battery_Switch

robertj1979 · 12-24-2022, 06:57 AM

Thanks Alan and others for the information. I see too many bad reviews on the cheap circuit breakers and have not installed anything yet. I agree that looks like a better solution. I have had some problems with the inverter lately which is one reason for the inquiry. Further information is in this link if interested:

https://www.irv2.com/forums/f84/mast...up-601262.html