small voltage regulator/dc-dc converter?

[weetsie]

hi, i need some help!

here is the story, i have a camera that takes a 2CR5 battery, a 6V lithium. it used to work fine but now the camera displays the low battery warning after only using the camera for a few minutes or straight away in lower temperatures. using a voltage meter i found that a new 2cr5 gives about 6.5V and the camera shows the battery warning when you drop below 6.3V and anything below about 6.2V wont turn the camera on.

so i bought this DC-DC switching converter from china which has a 6V 3A output, its designed for powering the radio receiver for RC stuff off the main battery. the DC-DC converter worked flawlessly with a 11.1V 3s lipo, giving a constant 6.6V output but the problem is it wont fit inside the camera, i really want to have a single cell be it 1.2V,1.5V,3.7V,7.4V or whatever so long as i can fit it in the battery bay for a 2CR5 along with something that will convert it to 6.4V or more.

what is the best way of going about this?

 

[bychon]

I'm afraid you'll need a magic wand for this. My camera eats AA batteries like popcorn and the only way I could fix that was to build an external batery pack and plug that into the camera's external power connector. However, I will be watching this to see if anybody knows something I don't know.

 

[weetsie]

ill stop you there

its an old film camera, usually the particular camera lasts several years on one battery.

however i have been thinking, is there such a battery that would give out 6.4-6.8V without me needing to regulate the voltage? i dont know what voltage i could safely use, im tempted to try a 2s li-ion at 7.2v.

 

[bychon]

Sorry. For a moment there I thought your camera displayed a low battery warning after only a few minures. My mistake.

 

[Hero999]

THat's what he said:

the camera displays the low battery warning after only using the camera for a few minutes or straight away in lower temperatures

It sounds like it needs a new battery, assuming it's rechargeable, if it's a non-rechargeable lithium battery, then he's either bought a bad batch of batteries or there's a problem with the camera.

 

[Vizier87]

maybe the joule thief can be used?

 

[BrianG]

That device you bought must be a BEC? Sounds like it. It's probably based off the LM2596 regulator if I'm not mistaken. Anyway, that's a buck regulator, which means you need an input voltage around 2v or more greater than the lowest output you want. Also, these devices are meant for higher loads (1A or more). Running them at lower loads (~500mA) makes them more inefficient unless you change the inductor (which can be determined by the LM2596 datasheet).

If it's what I think it is, there probably is a 5v/6v jumper on that unit. The IC used is usually the 5v version and they just put a 1k resistor in the feedback loop to boost it to 6v (actually measures closer to 5.5v). Putting the 5v jumper in shunts this resistor to give you the rated 5v. You can play a little with this resistor value to get values around what you are looking at. With testing, I've found the formulas for this resistor are:

Vout=(R*0.000533)+5
or
R=(Vout-5)/0.000533

But no matter what, these require a higher voltage. They work well when the input is above 3s lipo (11.1v).

Another alternative might be something like this: AnyVolt Micro - Universal DC-DC converter steps voltage down and up

 

[weetsie]

that dc-dc converter looks good, smaller than the 3A bec i was using so there should be enough room to fit two small cells in with it. only problem now is it draining the batteries when the camera is off.