Ok fellow scientists :) What is so special about the reverse polarity fuse circuit in a converter compared with just having a fuse on the positive output wire?I yanked the 7355 from the trailer to put in the truck camper, and that means it is now like a portable charger with 120v input (no neg wire though, just hot and neutral with a 7355) and pos and neg DC wires output.Its two 30 amp reverse polarity fuses are still on the DC fuse panel back in the trailer, doing nothing now. Somebody said here a while back that each 30 did half so it was like 60 (on the 55 amp converter)So how can I wire up a set of reverse polarity fuses for the loose 7355, or can I just depend on a 60 amp fuse on the positive wire?(AFAIK, I am also supposed to run a chassis ground wire for it now that it is no longer in its original power centre, same as you would for a deck mount.)Thanks.

The purpose is to prevent destroying the Power converter when you hook up the positive and Negative cables at the battery in reverse. It rarely works. But, sometimes it does. Doug

Use T rated ultra fast reaction fuses. Refer to good inverter reading like Outback or Magnum for an in-depth explanation of their purpose and function. I like inverter and charger products that scream polarity orientation via color. I.e. red wire to red terminal.

Hi doug,Reverse polarity fuses worked for a shop that managed to put one of the twelve volt jars in series with the others--presenting 24 volts to the converter.They also worked when I was attempting to do double conversion with my Magnum inverter. Double conversion with my old Cobra MSW was no problem. I don't understand why there was a difference.BFL13, yes fuse on the positive but use what mex has wisely recommended.

Not getting the info requested so far.I want to know if there is some special way you have to wire up a couple of 30s however they do it in a converter or over at the DC fuse panel, instead of using a 60 farther out on the pos wire. Why do they use two instead of just one big one? My PowerMax 100amper uses four 40s while the PowerMax 55 amper uses two 40s. The 7355 uses two 30s but they are over on the fuse panel.

Yes the reverse polarity fuses are in series with the output of the converterAre you actually using a single voltage Parallax converter???????? Two lower cost fuses are less expensive and easier to install Nothing more than a matter of cost for the manufacturer IMHO A parallel connection of a fuse is STUPID at best nothing more than a cost saving that the comsumer pays for sooner or later

Reverse Polarity Fuses Circuit Question | Good Sam Community

38 Replies

BFL13
Explorer II
Oct 04, 2015
I am still confused about series and parallel here. What is wired to which end of what? Two 30 amp fuses and one output pos wire. Now what do you do? Thanks.
RJsfishin
Explorer
Oct 04, 2015
I wondered why my new little 150 watt inverter had one 40 amp fuse inside the box, which blowed when I crossed polarity. I couldn't find a 40 amp fuse so used a 30. Seems to work, as I overloaded it several times since, and the 30 amp holds.
Good to know they are in series w/ the pos output, always wondered about that.
BFL13
Explorer II
Oct 04, 2015
Sorry I got confused there as to what is in series and what is in parallel. Is the pos wire split with a 30 on each leg then rejoined?
KJINTF
Explorer
Oct 04, 2015
Yes the reverse polarity fuses are in series with the output of the converter
Are you actually using a single voltage Parallax converter????????
Two lower cost fuses are less expensive and easier to install
Nothing more than a matter of cost for the manufacturer

IMHO A parallel connection of a fuse is STUPID at best nothing more than a cost saving that the comsumer pays for sooner or later
BFL13
Explorer II
Oct 04, 2015
Not getting the info requested so far.

I want to know if there is some special way you have to wire up a couple of 30s however they do it in a converter or over at the DC fuse panel, instead of using a 60 farther out on the pos wire.

Why do they use two instead of just one big one?

My PowerMax 100amper uses four 40s while the PowerMax 55 amper uses two 40s. The 7355 uses two 30s but they are over on the fuse panel.
pianotuna
Nomad III
Oct 04, 2015
Hi doug,

Reverse polarity fuses worked for a shop that managed to put one of the twelve volt jars in series with the others--presenting 24 volts to the converter.

They also worked when I was attempting to do double conversion with my Magnum inverter. Double conversion with my old Cobra MSW was no problem. I don't understand why there was a difference.

BFL13, yes fuse on the positive but use what mex has wisely recommended.
MEXICOWANDERER
Explorer
Oct 04, 2015
Use T rated ultra fast reaction fuses. Refer to good inverter reading like Outback or Magnum for an in-depth explanation of their purpose and function. I like inverter and charger products that scream polarity orientation via color. I.e. red wire to red terminal.
dougrainer
Nomad
Oct 04, 2015
The purpose is to prevent destroying the Power converter when you hook up the positive and Negative cables at the battery in reverse. It rarely works. But, sometimes it does. Doug

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Reverse Polarity Fuses Circuit Question

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