RC-Monster Forums - View Single Post - Converting 2-AA battery Powered Devices to Lithium Power

BrianG · 03:28 PM

Seeing as how LiFe peak voltage (3.6v) is only 0.6v higher than 2 AA's, you might be able to get away with no step down device at all.

If you use lipo, things get a little trickier. Consider the following lipo voltages:

- 4.2v off the charger. Any regulator should work here.
- 3.7v nominal. You would need a low drop out regulator to make sure you get around 3v at the output. Regular linear regulators (like the LM317T) need at least 1v input than the output. So, if you want 3v out, you need at least 4v in.
- 3.0v-3.2v cutoff. Even a low drop out regulator wouldn't be enough here.

You could set whatever regulator you use for ~2.5v (which is around the nominal voltage for NiMH) and that would give you a little more wiggle room at lipo cutoff, but would still need a low dropout type for stable output And the use of any regulator "hides" the actual battery voltage, so even if the camera has a battery guage of sorts, it wouldn't be accurate.

The next obstacle is using some type of cutoff device. Unless your camera has a voltage display/guage of some kind, you could run the risk of discharging lipo too far. Even LiFe might not like that.

The final obstacle is mounting, Most cameras I've seen are quite packed with circuitry and there is usually circuits inside the rounded area where the AA's go. So modding the holder to fit a lipo/Life cell may be difficult.

You could connect wires to the camera battery terminals and use an external battery pack consisting of whatever battery you want, but then the total package gets cumbersome.

In the end, you might be better served to get a newer camera with a better battery life.

	(#2)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	12.20.2009, 03:26 PM Seeing as how LiFe peak voltage (3.6v) is only 0.6v higher than 2 AA's, you might be able to get away with no step down device at all. If you use lipo, things get a little trickier. Consider the following lipo voltages: - 4.2v off the charger. Any regulator should work here. - 3.7v nominal. You would need a low drop out regulator to make sure you get around 3v at the output. Regular linear regulators (like the LM317T) need at least 1v input than the output. So, if you want 3v out, you need at least 4v in. - 3.0v-3.2v cutoff. Even a low drop out regulator wouldn't be enough here. You could set whatever regulator you use for ~2.5v (which is around the nominal voltage for NiMH) and that would give you a little more wiggle room at lipo cutoff, but would still need a low dropout type for stable output And the use of any regulator "hides" the actual battery voltage, so even if the camera has a battery guage of sorts, it wouldn't be accurate. The next obstacle is using some type of cutoff device. Unless your camera has a voltage display/guage of some kind, you could run the risk of discharging lipo too far. Even LiFe might not like that. The final obstacle is mounting, Most cameras I've seen are quite packed with circuitry and there is usually circuits inside the rounded area where the AA's go. So modding the holder to fit a lipo/Life cell may be difficult. You could connect wires to the camera battery terminals and use an external battery pack consisting of whatever battery you want, but then the total package gets cumbersome. In the end, you might be better served to get a newer camera with a better battery life. Last edited by BrianG; 12.20.2009 at 03:28 PM.