NightBandit said:
...From what I'm hearing, maybe I want either a good battery charger (the Triton, Schulze, Maha or Lacrosse) or a good battery tester (ZTS)...
Or, a good battery discharge unit like the West Mountain Radio CBA if you're talking about secondary (rechargeable) cells.
... The Triton and Schulze look great, but it's more than I want to spend. With the Maha and Lacrosse, it looks like I'm limited to AA and AAA cells (my lights currently use AAA, AA, CR123 and D cells (plus hopefully more in the future)...
So, are you using or planning to use rechargeable versions of CR123 and D cells? If not, and you've got a mix of primary and secondary cells you want to test, forget the charger-based solution and the WMRCBA, and go straight to ZTS.
...The ZTS looks promising (if a little costly), but I have a question about accuracy. Obviously this works great for many people, but registering in 20% increments leaves some gray spots. There is a big difference between 81% and 103% (which I would assume both register at 100%) or between 61% and 80% (which I would assume both register at 80%). And also, does the ZTS make its readings based just on Voltage, just on amp hours (mAh) or on some combination of both?
The ZTS Mini will test all of the cells you've mentioned so far and it cost $29.95 last time I looked. In theory, you are right about the "gray spots" in the test results. In practice, you need to think about what you plan to do with the results. Generally, you are trying to anticipate your future need for a particular flashlight and decide if the exisiting partially-depleted cells are going to last, or if they need to be changed/charged... aren't you? For this purpose, I find the ZTS percentage readout is more than sufficient. If you have a more exacting purpose in mind, maybe you could explain it to us.
With my DMM, I believe (and I may be wrong here), that it will work on any cell size. My DMM will measure voltage, but it won't measure mAh (at least not that I can figure out).
Of course, your DMM is going to provide a voltage reading on any size cell under the sun. You are not wrong about that. And NO, it cannot measure mAh capacity. You are right again. The only way to
really measure capacity is to completely drain the cell while measuring how much time and how much current is required to do that. That will give you milliamps and hours... mAh, ta-da. (This is exactly what the WMRCBA does). But fully draining a cell, if it is not rechargeable, is obviously an exercise in futility. So people like ZTS have done extensive testing to learn how a cell reacts to a brief load that does NOT drain the cell significantly, and correlated this reaction to the percent of remaining capacity. They build this into the algorithm of the tester. You can do it yourself, but you'll be playing with your flashlights and DMM for a
long time before you can even hope to accurately approach the 20% resolution provided by the ZTS. (OK maybe it's your goal to play with your flashlights, this is CPF after all.)
It sounds like ideally I want to test my cells under load (a small load). kitelights suggested that I could take a reading on my cell, put it in my light and run it, pull it out and take another reading. This sounds relatively simple to me, but for how long do I need to run the cell(s) in my light (and I do realize that my cell(s) will lose power as I run them this way)? Is there some way to make a simple home set up that uses resistors (or something)?
There is no single correct answer to any of those questions. There are a number of problems with the above - for one thing, you will quickly learn that as soon as you remove the load from a battery, it starts to "recover". The voltage begins to inch its way back up. It's not actually healing itself although it appears to be. It throws a monkey-wrench into the idea of testing, running, and retesting. You would have to be super-consistent in the amount of time it takes to make your second reading after shutting off the light, or you're just wasting your time.
All that being said, this is not meant to be an exact science for me. I'm not testing batteries for reviews, I just want to when it's time to charge my batteries (and how full of a charge I'm getting) and for my non-rechargeables, how close to empty they are so I know when to carry spares. Maybe I should just let my light's performance tell me when to change batteries, but keeping track of cell levels seems like half the fun.
OK, there you go. It's not an exact science. (Is there an echo in here?) For the purposes you just described, you need a ZTS, end of story. And no, I don't work for them.
