External charging points for can light.

[Packhorse]

Im thinking of using external charging points for my project.
The problem is how to avoid the points being active while not charging.

Option 1. Use diodes to block the current out of the battery pack.
This seems like the easiest way to do it. Only problem is that there is a voltage drop accross the diodes of .6 volts each or 1.2 volt total. When connected to a "smart charger" how will the charger react?
Do the chargers calculate the number of cells according to voltage? will the diodes effect this?
I could always use a "dumb charger" and put up with slower charge times.

Option 2. Use relays triggered by a reed swich and externally used magnet.
This requires a little more hardware.

The Solus SU 1250 seems to not use option 2. Does it use option 1 or perhaps option 3?
If so what is option 3?

 

[Hallmac]

Why not just place a waterproof charging post prior to switch.

If it is not exposed to the water, one way diodes are not necessary.

 

[Packhorse]

Because diodes are a much simpler solution. Simple is good.

The whole idea is to make the can water proof and totally sealed. A waterproofed charging point offers a failure point and if/when if does fail it would mean tearing the seal cannister apart.
I could charge it thru the light head but once again that means opening it up and I would rather have it sealed.

 

[reefduffer]

Have you looked at inductive charging? I haven't looked at the detailed design problems, but it seems to me to be perfectly suited to electric-powered dive gear of all sorts, for the same reasons you seem to be concerned about. Lights, computers, digital cameras (think bluetooth), ...

Maybe the power requirements of your light make this a problem in terms of physical size, but there ought to be a sufficient area for field transfer if you use the whole can cylinder length embedded in a charger. Maybe that's too radical for your DIY effort, I can understand that.

Please take this as more of a question than informed guidance about a better way. An LED dive light with inductive charge and a reed switch, which doesn't need to be opened for anything for years at a time, has alays seemed the ideal to me. Am I an impractical dreamer?

 

[Packhorse]

If you took a standard transformer and then unwind it and rewind the primary around the cannister and the secondary inside the cannister you basicly have it. But it would be alot less efficent than a standard transformer due to the distance between windings. So its size could be prohibitive. Then there is heat to worry about. You would also need to convert it to DC and regulate it.
Basicly the entire charger would have to be bult in the can. The size may be an issue.

SO it is possible but for me just not practical.