Magnum Inverter Update!

You have to disconnect the positive battery terminal first or risk damage!

Magnum says to disconnect the positive terminal first!

All I can say is WOW! Here’s my discovery timeline yesterday…

If you’re just joining this thread, two days ago I posted an article about RV battery safety where I stated that you should disconnect the negative battery terminal first, and then the positive terminal. This is to avoid the possibility of your wrench on the positive terminal making accidental contact with the chassis and causing a high-amperage short circuit.

Read Part 1 HERE

Read Part 2 HERE

First things first!

I contacted Magnum tech support who told me that Magnum required that you disconnect the positive battery terminal first or risk damaging their inverters. But the help desk guy couldn’t point to an official statement in the documentation, nor could he tell me why the damage would occur. But he promised to get back to me…

Next up, I start calling my speed dial list!

Not satisfied I called my contact at Progressive Dynamics and left a message. Unbeknownst to me, their lead field tech had already read my first two articles and set up a lab test to confirm that their inverters and converters were safe if you disconnect the negative battery terminal first. He called me back a few hours later to tell me I was correct, and it was safer to disconnect the negative terminal first to avoid a possible short circuit with a wrench.

I then called my contact at Xantrex and posed the same question. He said that a field engineer was available to talk and put him on speaker phone. The engineer had vehicle experience and agreed that no damage would occur to a Xantrex inverter if you disconnect the negative battery terminal first, and it was safer because this sequence eliminated the possibility of a short-circuit with a wrench.

Here’s the official statement from Magnum…

Laster that afternoon I received an email from Magnum tech support with the official statement that the positive terminal must be disconnected first. Here’s what they say…

And here’s the two remote devices they reference

What’s happening?

I’m still not convinced by Magnum’s explanation, but their design engineer hasn’t called me back yet to discuss the failure mechanism. So until I know differently I’m going to go by Magnum’s official statement that the positive battery terminal must be disconnected first on their inverters or damage is possible.

But both Xantrex and Progressive Dynamics said their inverters could have the negative battery terminal disconnected first without damage.

How to stay safe while doing this…

I found a socket wrench on Amazon that appears to be completely encapsulated in a non-conductive sheath. That would seem to avoid the possibility of a short circuit while disconnecting the positive battery first.

But if you’re using a regular wrench on the positive terminal first you should be extra careful not to contact the chassis with the wrench. I would even use e-tape on the wrench to make it safer.

That’s all for now…

Let’s play safe out there - Mike