3v rechargables

[BobBarker]

I was wondering if anybody knows what the actual voltage of the 3v rechargeables are?

I'm looking to use these in my Viridian laser sight. I know that it will handle 3.5v (i was getting nervous going any higher for now) operating (used my lap power supply). But I want to make sure what the cells resting voltage is (by people with experience, not the marketing people)...

Any help would be greatly appreciated.

Thanks

 

[45/70]

Hi Bob. It depends on the type of "3 Volt" cell you are using. There are two types of 16340/RCR123/R123 "3 Volt" cells around, LiCo and LiFePO4​. Both are around 3.2 Volts under load. The open circuit voltage varies quite a bit, however.

You might try a "Google search" using "3 Volt Li-Ion" in the box at the top of this page and check the "CPF only" box. There has been much discussion about these two very different types of "3 Volt" cells.

Dave

 

[Shadowww]

LiFePO4's are 3.6V when fully charged (but they also can be charged to 3.5V (which is what you want) without significant loss of capacity).

 

[BobBarker]

THANKS! Being that I have no experience with the LiFiPO4s, I didn't have a clue how they function. I just didn't want to fall prey to some marketing b/s about it being 3v when the charged voltage is really 4.1-4.3v. I know that the LiCOs were out of the question. I wouldn't want to even try 4v in the C5L considering that the website says not to use rechargeable. They sell house branded CR2 cells, so i figured that it might just be them trying to get people to buy their cells.

Thanks again.

 

[Shadowww]

THANKS! Being that I have no experience with the LiFiPO4s, I didn't have a clue how they function.

Here's a graph for you, to clear some things up:

 

[45/70]

As I mentioned previously, "3 Volt" LiCo cells have a similar voltage under load to the LiFePO4​ cells. Generally this is between 3.2 and 3.3 Volts under normal loads. By comparison, regular 3.6-3.7 Volt LiCo cells will maintain a higher voltage, as much as 0.5 Volt, under a similar load.

It is measuring open circuit voltage where the two types of 3 Volt cells are quite different. Depending on the internal impedance of the Voltmeter, LiCo cells will usually either read ~3.8 Volts, or ~4.2 Volts OC, when fully charged. This is due to the diode incorporated under the positive end, that reduces voltage under load. It is only when under a typical load, that these cells are 3.2-3.3 Volts.

LiFePO4​ cells, as Shadowww mentioned, usually charge to ~3.6 Volts OC. After resting a bit, they usually settle to 3.3-3.4 Volts. Under normal current loads, LiFePO4​ cells drop very little in voltage, usually less than 0.1 Volt and have a very flat discharge curve, unlike other Li-Ion chemistry cells.

As for use of either type of these "3 volt" Li-Ion cells in your laser sight, it depends on whether the driver circuit can handle the extra voltage of either cell. Between the two, LiFePO4​ is the safer bet, as these cells do not have a "hidden voltage" behind the diode, as well as a lower charged OC voltage. Under most situations though, their output voltage under load is about the same. Under high current loads however, the LiFePO4​ cells are likely to hold a higher voltage.

Dave

 

[Glock 22]

There telling you right about the LiFePO batteries. I'm using the ones that Surefire sells, which are K2 brand also AW sells a LiFePO battery as well. I use the Ultrafire WF-138a charger set on the 3.0 setting. It also has a setting for ~3.6 volts. But set to 3.0 before charging. And when they come off of the charger they will be around ~3.40 volts, then after setting a bit they drop and stay at ~3.39 volts, even setting overnight. I use this set up for my M31N in a E1B body and it works perfect.

 

[Mr Happy]

Here's a graph for you, to clear some things up:

Wow, that's my graph! :thumbsup:

 

[Shadowww]

Wow, that's my graph! :thumbsup:

Oh well, I hope you don't mind that I have posted it without mentioning source - I just used Google image search for "lifepo4 600mAh graph".

 

[Mr Happy]

Oh well, I hope you don't mind that I have posted it without mentioning source - I just used Google image search for "lifepo4 600mAh graph".

Here's the thread for anyone looking for context:

http://www.candlepowerforums.com/vb...ating-the-Westinghouse-3.2-V-AA-LiFePO4-cells