I get just about all of my meters from China through eBay but Madvapes is carrying them now. These small meters are about an inch wide and will read voltages down below what is useful for an eCig so they work very well for eCig applications. They also do not need a separate power supply just for the meter itself. Perfect for eCig applications.
Most you get from China will have a bunch of pins. The left most pin with the digits facing you is negative and the very next pin to the right will be the positive. That will be the only two pins you need to use. The rest are for multiple cells of an RC controled plane or such but we do not need to use them. These meters are orignially used to test the Lipo batteries in model RC planes but work fine for showing the voltage of your NiMH batteries.
If wiring to your puck, just run a wire from the left most pin (negative) to the negative lead of your led (longer lead). Run a wire from the second pin (positive) to the positive lead of your LED (shorter lead, flat side of LED body).
With this hook up, anytime your led comes on, so will your voltage meter.
There is another device you can use from HobbyKing that will show your remaining charge on your batteries. It doesn’t read voltage numbers but gives you an indication of your remaining charge and it is cheap! It will give you a good indication of wether you need to replace your batteries or not before you leave the house for the day.
Important Note: These battery monitors work great for your eCig mods but they only indicate “unloaded” voltage. To use these, you must wire them so they are always on. I use a battery box with a switch so I wire the Puck mods to turn on the voltage indicator to be on whenever the Puck’s power switch is turned on. When you hit your vape button (loaded voltage), the low power light will light due to the load on the batteries but as soon as you let go of the vape button, it accurately tells you what the charge is on your batteries. I really like this little device.
It’s fairly small, flat and very easy to use. You can leave power applied to it since it is very low drain and doesn’t required very much current to indicate your charge. I have tested the levels it indicates and truly does reflect the amount of battery life left in your batteries. Another benefit is it is very inexpensive (a couple of bucks).
Here are some eBay links which are current now but will definitely expire so the links may break.
So now you have all of my “secrets” for using battery meters/monitors I use in Puck Mods. A lot of other people use the same devices but there is not a lot to choose from out there.