Scorpion mod: Difference between RCR123a and RCR123?

Okay, this question might be a little confusing, but bear with me.

I've been reading on the forums here that the Streamlight Scorpion can be easily modified by replacing the lamp with a TL-3 lamp and using two RCR123a's (which appear to be 3.7v) or two RCR123's (which appear to be 3.6v).

My first question is: Which of these is the correct set of batteries to use for the Scorpion mod: the RCR123a, or the RCR123?

My second question is: I have an Ultrafire Multi-Battery Charger (http://www.lighthound.com/index.asp?PageAction=VIEWPROD&ProdID=2566) that says it is a 3.7v charger and can charge RCR123's. The confusion here is the fact that RCR123's are 3.6v (not 3.7v) and that RCR123a's, which it doesn't mention, are 3.7v.

Am I making sense? I figured you guys would be able to help me out here.

Thanks,
- Joe

Hello Joe,

Welcome to CPF.

When Li-Ion cells first came out, they were rated as 3.6 volts nominal. You charged them to 4.1 volts. As things evolved, the nominal rating was raised to 3.7 volts, and now we have some cells that are rated at 3.8 volts. The nominal voltage refers to a mid point voltage under a load that drains the battery in around 2-5 hours.

At this time, there are only a few specialized Li-Ion batteries that limit the charge to 4.1 volts. Even so, they are listed as 3.7 volt nominal cells.

The bottom line is that the Li-Ion cells you are interested in, regardless of what their nominal voltage is, all charge up to 4.2 volts.

The primary (i.e. non rechargeable) cell in that size is often referred to as a CR123a. The CR stands for a higher discharge rate cell (BR cells are only capable of very low discharge rates), and the 123a means that in size it is a single cell (1) the size of a 2/3 A cell.

So, what we have is some inconsistencies in labeling. RCR123 = RCR123a = R-CR123.

As far as chargers go, the R-CR123 chargers should work fine. However, if you get into the hobby chargers, if you select charging a 3.6 volt cell, it will only charge to 4.1 volts. Whereas if you select a 3.7 volt cell it will charge ti 4.2 volts. In both cases your battery will get charged, but in the case of charging to the lower voltage, you will get less runtime but more cycle life.

Tom

I think you just answered all my questions in one post, which is a rarity for me on the internet. Thanks, man!

- Joe