Advice needed for magnetic charging tail cap

[pir800]

I'm looking into making my own rechargeable light with a magnetic tail cap as the contacts, but I've run into conflicting information on the mechanical side of things.

I'm using the OLight S10R light as a basis for discussion.

What I'm trying to accomplish is a way to mimmic how the OLight works in terms of the magnetic charging tail cap. It's pretty obvious that the middle pin on the ring is negative, and I can only assume that the positive side is going through the actual body of the light because it doesn't look like there's any other way possible. I've always been told that it's a bad idea to use the body as the positive side. I also assume that the outside of the light is coated with an insulated material, but I wanted to get the thoughts on others that have experience making their own rechargeable lights.

Thanks all.

 

[spencer]

Just to start off, I don't know anything about the light in question but I did look at a picture.

Before I looked at a picture I assumed you meant a barrel connector and I have never heard of the centre pin being negative. Having said that, in this case the centre "pin" could be negative but on the other hand it is also extremely rare for the shell of the flashlight to be positive. It is possible that they did some sort of switch in the tailcap. It is up to you to probe with a multimeter and determine what the polarity is.

The outside of the flashlight is anodized which is an electrical insulator.

 

[pir800]

Spencer,

Thanks for the reply.

Yeah I'm certain that the center post is negative. I pulled apart the bottom of the cap and it's PCB with springs on both sides (nothing else on the PCB and no exposed etching around the perimeter). I also put a multimeter to the charging base to confirm.

This is how it appears (side view):

+lead ___________________ Chassis
-lead [- Battery +][PCB][Bulb]

Any idea how they would get the negative end of the battery back to the PCB?

 

[more_vampires]

If I am understanding correctly, what OP is describing won't work.

Your - lead would be fine. The + lead would not be accessing the + of the battery, but part of the driver instead.

A magnetic charging port would have to run straight to the - and + of the battery and not involve the driver.

The metal body current path is for the - battery pole. The + battery pole goes to the driver and not chassis or else you'd get a dead short when you screw on the tail cap.

 

[sunny_nites]

That's the tricky part about doing anything that requires both voltages at the tail of a round bodied flashlight; getting the positive routed back to the tail with the body being used as the negative path to the driver.

I'm not familiar with the light you mentioned but most lights that I've seen that have some type of magnetic or non battery removal charging system have the charging equipment closer to the front of the light as in the Klarus FL18 advertised on the home screen of CPF. The magnetic charging port is near the middle of the light which looks to be about where the front and positive end of the battery is.

The only way I could think of to get a charging port to the back of a round light would be to have some type of channel milled into the body for a positive wire to run to the back or something along those lines. If they've come up with some other method, I would really be interested in how they did it.

 

[DIWdiver]

Well, there's always someone more clever than us in the room. I really hesitate to say something is impossible, because many 'impossible' things have been done.

I have built a light with battery+ connected to LED+, LED- connected to body, body connected to driver, driver connected to battery-, with the multi-mode driver in the tailcap. This is one of the supposedly 'impossible' configurations. As far as the driver goes, it performs very well, but there were problems with the piezo switch control, difficult assembly, and mechanical zoom mechanism that made it a very disappointing build. Needless to say, I learned a lot.

I think the million-dollar question here is 'where does the outer ring of the external connection come into the circuit?'

Oh, and the other million-dollar question is 'what else does the battery- connect to besides the external pin?'