I have not had to do it when using mine. For what it is worth I have heard nothing but negative comments about the green knob disconnects. I use the attached disconnects.

Dave

Pay attention to current draw capacity of any disconnect. I found many aren't rated for the draw of a 6v starter.

I agree with Dave. I used to have the green knob style of disconnect on my '28, but I found out that the weight of the cable caused the disconnect to NOT disconnect.

I replaced it with a big, heavy duty disconnect unit (like the one shown above) and have had no trouble since. 

Cheers, Dean

@rustoholic Dean, where did you buy the heavy duty one?

FWIW,  I’ve used the green knob type cutoff switches on my trucks for years.  I did have a problem with one of them breaking and needing replacement.  I think they are cheaply made and a bit junky.  What I like about them is that removing the green knob adds a bit of a theft deterrent.

I bought my disconnect switch at Napa Auto Parts. I purchased it online at https://www.napaonline.com/en/ and since I had a coupon from them AND the online shopping site accepted my credit card rewards, I got it for half off. 😉

It has a key that you can take with you for anti-theft purposes (or in my case, to prevent people from honking the horn at car shows!).

I made a bracket for the switch by drilling a few holes in a piece of angle sheet metal and bolting it to the side of the transmission, in between the tranny and the battery box. The switch interrupts the negative cable's access to ground. I ran the negative cable from the battery to the switch and got a new large diameter cable to run from the switch to ground.

The new cable was purchased at an Interstate Battery store near me. They cut it to length and crimped connectors on the end. The total cost for this cable was $15. 😉

Here's a link to the switch: https://www.napaonline.com/en/p/TWD248403BX

Cheers, Dean

I looked for a cut-off switch for the 38 and gave up because I couldn't find one with a current rating I could live with. The one Dean lists is rated for 175 amps continuous. The green knob switch is lower than that. The 216 starter draws up to 525 amps under load. I was afraid I would restrict the current by using one of those. Dean's does show up to 1000 amps "intermittent". I guess their definition of intermittent is the important metric.

@rustoholic Thanks Dean, I will try my NAPA store.  And thank you for the pictures!

@tiny Tiny, now you have me scared.   How did you disconnect your battery when not in use?

Posted by: @john-schildberg

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@tiny Tiny, now you have me scared.   How did you disconnect your battery when not in use?

I didn't. Not ideal but I lived with it.

Some specs of the Cole-Hersee I have pictured above ;

@tiny 

Hi Tiny

I think I'm with you on this.

A 2000 amp rating for 30 seconds sounds great, but...

The 30 second rating is because it's getting hot.

It's getting hot because of resistance.

On most cars this probably isn't a problem, but on some it might be.

The only batteries I have ever disconnect on the farm are the ones in newer equipment with the "built in run down feature" from electronics memories etc.

My recollection is a bit vague, but I recall the reason I started using a switch some 20 years ago, was because it eliminates one option for a potential fire.  If memory serves the lesson shared by a much older person at the time, was that if there was an undetected under the dash electrical wiring short it would be best to not have it discovered by a shop fire while the vehicle was in storage.  Seems like a little precaution is worth the hassle?

@lee I don't think anyone is disputing the wisdom of having a disconnect but rather the fact that the disconnects being used aren't sufficient to do the job they're asked to do. If you can find one that can withstand 500 amps continuous it would probably solve the issue.