Stupid idea? Use Both NiMH AND C123

While reading a post last night involving the common discussion of the pros/cons/merits of using disposables vs. rechargeables I began to think 'Why not have a flashlight that has both?'. I read an article recently about the IPod battery being made of a material that can be easily molded to fit most any space. To save space, perhaps a sleeve could be made of this pliable NiMH that would allow disposal batteries such as C123's to fit inside. Electronics would monitor voltage and would draw from the rechargeables until a cerain devel of depletion would cause a switch to the disposables. The one would have a flashlight that could be a duty light for daily, inexpensive, frequent use but could be relied on for tactical use as well.
Jeff

that sounds like it might be able to work but i'm not a battery expert and their might be some qwirks about using rechargables an lithiums together

I don't know but your scareing me. I have always been told to not mix cells as bad things could happen.
Topper

If you wanted such a setup, then the way to do it would be to run the two sets of cells in parallel and fully isolate them electrically. A diode on each set would prevent any chance of reversing the voltage into the Li cells.

I have a light body sort of like this (home made with build in twin battery tubes). I did it to get long run time - the first tube is used, then you switch over to the second - sort of like a dual gas tank on a pickup truck.

It's not scary - we're not talking about directly wiring different battery sources in parallel - we're talking about some internal switch knowing when to change. It's just like laptops that have modular drive bays that can also take a second battery. Mine does this - it uses the modular bay first, and when that's depleted it falls back to the main, allowing you to hot swap a new modular battery in. I love these ideas. I have a lantern like this built in 6v SLA and a 4 D cell compartment. The only drawback is the increased bulk of the resulting light. Also, you would need to regulate this light to compansate for the different voltage sag under load characteristics of the alternate power sources. I feel a project coming on... /ubbthreads/images/graemlins/thinking.gif /ubbthreads/images/graemlins/grinser2.gif