Heavy DC Switches

[Ulu]

I have been calling boat shops and car shops, trying to find a heavy duty DC rated switch. I was hoping one of you guys could give me an idea of where to go.

 

This is the experimental electric boat X-36v. 14’6” with a 56” beam. She will cruise at six knots on a charge, and goes as long as I can stand to fish in a day.

 

I carry three group 29 RV batteries and to increase range I have room to add three more, but that cuts down on my cargo capacity.

 

My little boat motor is drawing up to 40 amps at 36 vdc nominal.

 

The fully charged pack is about 40 volts, from 3 group 29 RV batteries, so max 1600 watts at full speed. It’s possible it is drawing a little more than that because I put a stiffer propeller on it.

 

My main fuse is rated for 60 A at 125 V DC and it did not blow even though the circuit was clearly overheating at the switches. I have a spare fuses, so I actually disassembled the one I have been using to see if it had suffered any damage, and it had not.

 

 

Anyhow, I am not trying to switch power in and out under load, as the motor has its own switch and speed control. This is mainly a safety switch so the boat will be dead when I am not at the controls, while towing, charging, etc.

 

Right now I’m running two switches in parallel that are supposed to each handle 30 A at 12 V, but this is not enough, and they are heating up under continuous full speed. It was all I had available when I built the switch panel and now I am regretting what I did.

 

And I am hoping that one of you guys could give me a clue here.

[Plymouthy Adams]

did you consider any of the variety of battery disconnect switch often for on many little sport cars....most use these as quick disconnect for safety

[Tooljunkie]

Find someone that carries cole-hersee. Good battery disconnect switches. 

[maok]

Yep, as mentioned, any will do the job.

 

Universal Car Truck Vehicle Battery Disconnect Cut Off Rotary Switch Brass W9H3 | eBay

[Sniper]

Why are you using a switch rather than a relay?  Golf carts use relays that are rated for similar loads.

 

https://www.monsterscooterparts.com/36-volt-dc-contactor.html

 

https://www.mcmaster.com/relays/input-voltage~36v-dc/

Edited April 22, 2021 by Sniper

[DJ194950]

Sniper, I think you are differently on the right track there!

 

We had (back in the stone ages) electric battery powered scissor-lift type manlifts that were 12ft.x 14 ft. deck sizes that used 6-6 volt batteries that needed two young guys to but in place. They were wired up to run 36 volts and ran a motor that was quite large and it probably weight 100-150 lbs. to run a hydraulic pump for functions.

 

Forklift or this type of lift solenoids will handle the continuous draws!

 

AS seen they are available online.

 

DJ

[Ulu]

I looked at a couple of battery disconnect switches at the local auto stores and I thought they were imported garbage. I would not put them on the boat. I’d rather make my own.

 

In the end I decided to get rid of the switches entirely for now and just do what I always did when I had a gasoline motor: I took the ground strap off of the battery while I was towing a boat, and I put it back on with the wrench before we launched.

 

Since I am sitting directly between the batteries and the motor, there’s no reason to have any relay. I can touch the battery cables with my hand as I’m running the boat.

 

I can just put a switch on the wire.

 

The manlift has to use all the relays because, you can’t run 9 battery cables 50 feet up in the air. All the extra weight would reduce the capacity of your manlift LOL.

 

With relays they can easily be 16 or 18 gauge.

 

As an aside, I worked as a designer for Grove/Manlift back in the early 80s. I wasn’t too involved in the production but I used to get to drive various machines around so I could take measurements up in the air for the shop improvements I was doing.

I watched with the product engineers, while they tested a machine to destruction, while they were trying to design an aluminum boom. It was a pretty spectacular buckling failure.

 

I have a picture of us (the engineers & staff) all posing with a small scissor-lift machine we dressed up for the trade show in 1981. Pinstripes, clear coat over candy root beer metal flake, leather, and chrome wheels and all that ****. I’ll have to dig it out and post it up here sometime.

 

 

 

[Sniper]

3 hours ago, Ulu said:

I looked at a couple of battery disconnect switches at the local auto stores and I thought they were imported garbage.

 

Most consumer grade stuff is imported garbage.

 

Which is why I didn't link to any of them.