Optimate TM72 Adapter Cable

[Andrew Shadow]

I have an old Optimate 3 battery maintainer.
It came with a TM-72 AMDC adapter cable like the below. It is used to plug the charger in to a Hella style socket, or a cigarette lighter type socket by removing the red adapter that you see removed in the below photo.



The red arm that you see in the above picture folds out 90°. See below. I have never figured out what that arm is for. When I do a search I find many references to this plug, but no explanation of what this arm is for.
Does anyone know?

 

[Larry Fine]

I bet it's for pulling the red adapter out if it gets stuck in a socket.

 

[Andrew Shadow]

I had that thought but, the hook you see on the end is really, really small. I think that anyone would be hard pressed to use it for that.

That red adapter locks in to place quite forcefully. It doesn't come off very easily.

 

[GGely]

I’m thinking it’s used to lock into the appropriate female connector. Kind of a positive latch.

I would’ve assumed there are two, in that case, but that’s my best guess.

 

[Larry Fine]

I’m thinking it’s used to lock into the appropriate female connector. Kind of a positive latch.

I would’ve assumed there are two, in that case, but that’s my best guess.

I'm thinking you're right, now that I look where the tip of the hook is when closed.

Maybe it's supposed to be squeezed to release, and not normally be flipped open.

 

[Andrew Shadow]

I plug the Optimate in to a Hella plug on my motorcycle using this plug. I have tried it with this arm retracted and deployed. It seems to make no difference in either position.
It doesn't seem to make any difference whether it is deployed or not when it is plugged in to a cigarette lighter socket either.

 

[GGely]

It looks to my eye that the Optimate socket would lock to that piece.

However, I wear trifocals so all bets are off…

I’d send OptiMate a note.

 

[Andrew Shadow]

It looks to my eye that the Optimate socket would lock to that piece.

I never noticed that it engaged anything. I'll try again and have a closer look.

I’d send OptiMate a note.

They haven't answered.

 

[Andrew Shadow]

A little more information in case anyone has an idea.

The below shows what that arm looks like retracted.


The below shows the hook on the end of this arm. It only measures 1/16" in depth.


The below shows this adapter plugged in to a 12V accessory socket. The plug does not penetrate the socket deeply enough for this arm to have any influence on anything. I tried it in three different 12V sockets. All were the same.


The below shows this adapter plugged in to a DIN, or BMW style socket. The red adapter that goes over the end that is needed to plug in to a 12V accessory socket has been removed.
The red retractable arm comes no where near having any influence when plugged in to a DIN socket.


The only use that I have ever thought that it might have is as a retractable handle to facilitate unplugging it from a socket. I can't see this being its function however. It doesn't seem to make sense that this would be its purpose as there is absolutely no need for it. The plug removes easily whether plugged in to a DIN socket or a 12V accessory socket. If it is intended to be a handle, what is the hook on the end for?

There seems to be a lot more webpages in German that come up on a search for this. I can't understand them so, if anyone reads German and feels like having a look?

 

[Larry Fine]

There seems to be a lot more webpages in German that come up on a search for this. I can't understand them so, if anyone reads German and feels like having a look?

You can copy and paste sentences in most languages into Google and get a translation.

 

[ST Gui]

I bet it's for pulling the red adapter out if it gets stuck in a socket.

I bet that's exactly what it's for. That's probably why there are cutouts in the rubber adapter. Sure the hook is small but it's probably up to the task. At least as long as the driver/rider doesn't have St. Vitus' Dance.

 

[Andrew Shadow]

I bet that's exactly what it's for. That's probably why there are cutouts in the rubber adapter.

The red adapter has to be rotated about 90 degrees to lock it in to place on the end of the plug. On the underside of those cutouts are protruding nibs that fit in to a matching notch on the plug. When this adapter is rotated, those nibs need to move up over a raised lip before they can drop in to their notches. It is these nibs being in these notches that locks the adapter in place preventing it from rotating off. These cutouts provide the flexibility to allow the nibs attached to this part of the adapter to move up and down as they rotate in to and out of place.

 

[Andrew Shadow]

Optimate responded. They wrote that it is a pull handle to be used if extra force is required to pull the plug out of a socket. It read as though it was written by a 17 year old paid to respond to emails, not from someone with any technical knowledge.

This could be the case, but I find it hard to believe that they would go to all of the trouble to design and engineer something that would require much more complicated tooling and manufacturing complexity than just a straight blade that would do the same thing.

Added to that is that it is a pretty flimsy little piece of plastic. I can bend it to where it feels like I shouldn't force it anymore with an easy push of the tip of one finger. If ever I needed enough additional force to remove this plug that a protruding arm is required, I don't think that this arm would survive the ordeal. Being only on one side of the plug, pulling on it tends to caulk the plug sideways and make it even more difficult to remove. I am more inclined to believe that it is to be used as retrieval tool than it being able to withstand being a pull handle.

I responded and asked if that was actually the function that is listed on a technical document, or if this is a response based on what they assumed that it was for, but I doubt there will be any further explanation.

I was curious, and I gave it a shot.