Perko Switch for higher voltage?

[coldfish]

I'm running a 72v 100ah battery on my boat and I bought a backup battery. I had planned on just putting one of those perko switches so if the big one ran down, I could switch over to the backup. However.... I have since discovered that almost all of those switches are 48v or under.

Does anyone have any experience or suggestions for this?

[Bellinghamster]

Kilovac or equivalent contactor (big relay) and a low voltage toggle switch to energize the coil when needed.

https://www.digikey.com/en/product-h...-dc-contactors

Similar are available from Blue Sea Systems (https://www.bluesea.com/products/category/20/Solenoids). They also have some latching contactors that "stick" in either state of operation so you don't have to keep the coil energized.

[coldfish]

Originally Posted by Bellinghamster

Kilovac or equivalent contactor (big relay) and a low voltage toggle switch to energize the coil when needed.

https://www.digikey.com/en/product-h...-dc-contactors

Similar are available from Blue Sea Systems (https://www.bluesea.com/products/category/20/Solenoids). They also have some latching contactors that "stick" in either state of operation so you don't have to keep the coil energized.

I think that's exactly what I'm going to have to do. I mean, there's literally a relay already between the battery and the controller. I don't know why I thought I really needed some manual switch between the 2 batteries.

Maybe add some toggle switches on the dash and we'll be all set.

Thanks!

[mlydon]

Theoretically, so long as you’re switching without a load on the battery, it shouldn’t matter what voltage you’re running…..it’s contacting (or de-contacting) under load that causes the arcing that a voltage rating seeks to minimize….

Matt

[coldfish]

Originally Posted by mlydon

Theoretically, so long as you’re switching without a load on the battery, it shouldn’t matter what voltage you’re running…..it’s contacting (or de-contacting) under load that causes the arcing that a voltage rating seeks to minimize….

Matt

That's true enough. So as long as the motor is off and the other battery is disconnected, I could switch with no arc. I hadn't thought about that. Still, if I put in a switch that was not rated for 72v and the damn boat burned down, no matter how unlikely, I'd feel like a massive idiot.

I also realized, however, that I lose voltage with distance, so if I use a manual switch, as I had intended, I can't really put it anywhere convenient, but with the relay, I can just put the switches on the dash next to the ignition key.

So, I'll put the batteries in parallel and stick one of these solenoids on the positive of each one:
https://www.ebay.com/itm/40370946718...3-066ce37f55df

[mlydon]

With relays, be careful what youre using. Many are not designed for continuous operation (like a starter or windlass relay). Also, relays draw power in use- no fun to draw a continuous amp whenever your battery is on. Just saying, thoroughly look over the specs. Look into latching relays, as well - they draw big while closing, then a minor current holds them closed until interupted.

Matt

[coldfish]

Originally Posted by mlydon

With relays, be careful what youre using. Many are not designed for continuous operation (like a starter or windlass relay). Also, relays draw power in use- no fun to draw a continuous amp whenever your battery is on. Just saying, thoroughly look over the specs. Look into latching relays, as well - they draw big while closing, then a minor current holds them closed until interupted.

Matt

that's a very good point.

[Bellinghamster]

Originally Posted by coldfish

That's true enough. So as long as the motor is off and the other battery is disconnected, I could switch with no arc. I hadn't thought about that. Still, if I put in a switch that was not rated for 72v and the damn boat burned down, no matter how unlikely, I'd feel like a massive idiot.

I also realized, however, that I lose voltage with distance, so if I use a manual switch, as I had intended, I can't really put it anywhere convenient, but with the relay, I can just put the switches on the dash next to the ignition key.

So, I'll put the batteries in parallel and stick one of these solenoids on the positive of each one:
https://www.ebay.com/itm/40370946718...3-066ce37f55df

I agree. There's always a chance you might need to disconnect while it's under load (emergency cutoff?) or it unintentionally disconnects under load and a DC arc fire is no fun at all. Along those lines... I'd only use an Agency certified (UL, TUV, etc.) contactor for that application. The unbranded knockoff of a knockoff of who knows what with specs that don't make a lot of sense you linked to would give me the heebie jeebies. Also, you probably don't want to use a 72V coil, since then the toggle switch (and fusing!) used to power the coil would need to be rated for at least that DC voltage, which is fairly uncommon. Assuming you have 12V or 24V "house" power, it'd be much easier/safer to use that for the coil.

[Bowdrie]

Don't screw around.
Get a "real" switch, these guys can fix you up with something rated up to 6,000 amps at 600VAC/VDC.
https://www.divecommercial.com/produ...nife-switches/

[mlydon]

I just spotted this:
https://shallco.com/products/transpo...lay-br-series/

Might be exactly what you’re looking for. - it’s called a bi-stable latching relay - you only use power to turn it on on and off….rated to 1000volts, 300 amp (might be available with higher amp ratings), waterproof, runs on 12v.

Matt

[coldfish]

So, it seems I was confusing the volts necessary to operate the coil vs the volts the dielectric in the switch could handle. So, I've got a 12v "house" system that handles lights, head, instruments, etc... I was under the impression that I needed a contactor that was a 72v contactor, not realizing that I really needed a controller that would push a low amp 12v charge to close the contactor.

I kept thinking about how those Perko switches are rated for 12/24/48 battery systems, and just wanted to see a contactor that said 72!

the motor itself can only pull about 150amps, so a contactor rated for 200amps and +100 volts will do fine.

That latching relay seems pretty cool. $100 is a bit steep, but perhaps that's the way to go.

I'm able to go pretty far on just 72x100amp battery, but it will be great to have that backup!

Thanks everyone!

[Jammer]

Originally Posted by Bowdrie

Don't screw around.
Get a "real" switch, these guys can fix you up with something rated up to 6,000 amps at 600VAC/VDC.
https://www.divecommercial.com/produ...nife-switches/

Those are made by Filnor. Bring money. Also, they're big, and should have a clear plastic cover over them.


Filnor's standard product line includes knife switches up to 600 volts AC/DC and 6000 amps. If you want bigger, they'll custom engineer something for you.