What is it about 32 volts?

[yupitsme]

I was/am looking for a small'ish battery disconnect switch ON/OFF. I've found one that has a rating of 100 amps continuous and 150 amps intermittent. Great! except... at Max 32 volts. OK, that works fine for a 24v system but what about a 36 volt system. At the 32 volt rating it handles 100 amps continuous. If I apply 36-39 volts with a current of almost 1/2(max draw 55 amps) of this switches rating at 32v - what happens. What are the ramifications? It seems like this switch should handle that application fine but I dunno. I found a lot of switches that invoke the 32 volt limit. So... trying to figure out if limiting current well below the 32v rating will it provide the switching capabilities I'm looking for w/o over-heating or failing?

[billnorman1]

The voltage rating of many switches is the design to prevent arcing when they open. If you open a circuit carrying 100 amps it SHOULD make a spark, you don't want to have a miniature arc welder on your boat, however if you are carrying (much) less current I wouldn't expect any negative effects. There are a lot of professionals here on BBC that constantly overbuild or engineer circuits, but I guess you can't be too careful with somebody else's boat, time and money.

Oh, the higher the voltage the further the spark will jump.

[yupitsme]

Yeah... that's kinna where my son ended up as well. Worst case scenario stall(weeds) full voltage/amps disconnect. Chances of that happening exist I suppose but it be pretty slim. So, it arc's. It's at the bow. I suppose fuel vapors could get trapped under the top cap and travel to the bow but with my boat that area is well ventilated both at the cockpit and in the rod lockers. If that happens I suppose it was simply my turn. I'll take's me chances.

The 32v criteria... Seems it's a function of rail road requirements back in the day. Some form of multiple 16v application the RR used.

[TomP.]

Every time it arcs will cause wear in the switch lessening it`s capacity.

[yupitsme]

Every time it arcs will cause wear in the switch lessening it`s capacity.

I'm not sure that's an issue. This switch is primarily an emergency disconnect. Then once the motor is stowed power is cut to the trolling motor via Power Pole stow function. Then... I may/or may not turn this disconnect switch off under no load conditions.

First and foremost, initially I'm sticking with my 24v set-up. The switch is rated for that condition so I should be good there. Once those batteries need replacing I'll consider moving to a 36v set up. Where, once again, the switch will see limited use under a load.

[xxstang90]

So you want a switch to disconnect power to the TM or something else?

https://www.bluesea.com/products/600...th__Knob_-_Red

[yupitsme]

So you want a switch to disconnect power to the TM or something else?

https://www.bluesea.com/products/600...th__Knob_-_Red

Thanks... I had a little more criteria: Fit in the bow panel at the bow. Looks like it belongs there. The switch you posted was perfect... except. It would not fit in the bow panel.

[xxstang90]

Hmm well a couple ideas if you don't find a suitable switch -

1- Install the disconnect connect switch in the bilge area. Find or 3d print a blank plate to cover the current hole in the bow panel.

2- Really over complicated but you could install a 36v contactor

[yupitsme]

Hmm well a couple ideas if you don't find a suitable switch -

1- Install the disconnect connect switch in the bilge area. Find or 3d print a blank plate to cover the current hole in the bow panel.

2- Really over complicated but you could install a 36v contactor

The contactor solution was EE's son first stab at it. Like you said too complicated. I could'a done it in the rigging compartment with a 60amp switchable breaker. But I wanted the disconnect on the bow for emergency situations. As noted above I did find such a switch - sorta. But for now it will work just fine.

Thanks for the suggestions!