I bought an even dozen of these from Lighthound just over a year ago. A little pricey but they have held up well and no failures. They get charged on a Pila but they only charge up to 4.17v. In fact all my batteries only charge up to 4.17v or 4.18v. I would like to figure out a way to tweak the charger for that last .02v. I know it doesnt matter much but it's annoying.
Are you measuring voltage while charging or after?
If you measure after charging, 4.17 to 4.18 volt is a very sensible value. Look at this curve from my charging:
When the charging terminates (at the yellow line) the voltage will drop a bit. How much depends on a lot of factors including termination current and age of battery.
HKJ - good question. The voltage I stated is measured immediately after the battery is removed from the charger. As soon as I read your response, I thought to my self - "I knew that". Momentary lapse of reason is my only excuse. I will measure one while it is still in the charger but fully charged. Might be a day or two but I will post up the numbers as soon as I have them. Thanks for your help.
If I understand correctly, what you are saying is the charger is probably charging the battery to 4.20v and what I'm seeing is voltage sag when I check it. I do understand the graph you showed. The voltages I told you about are literally within 1 minute of removing the battery after the LED changes from red to green. That's a pretty fast sag. What I'll do is monitor the voltage while charging to see what the voltage is towards the end of the charge cycle (still a red LED) vs the voltage after the LED turns green and stops charging. I have no doubt you are right about this. I just want to verify the Pila is working properly.
I see you are using the UNI-T UT61E and do your data logging with it. I'm ready to upgrade to something that gives me real time data monitoring and recording but already have a Fluke 87III (and an old Fluke 73) which has always worked well for me and I am thinking about getting a good hobby charger that interfaces to the computer via USB. Any suggestions for that? Money is not a big deal but I don't want to spend $1000 for the charger and power supply if I can avoid it. The graphs would answer a lot of questions for me. Not to mention, a ton of charging/discharging options. I like the Pila (I have two of them) but as the saying goes - "knowledge is power".
This is on a pila that it charges to 4.17 right? I remember from my days on cpf people have had similar problems with the pila and depending on which one you get it will terminate charging at anywhere from 4.13 to 4.21.
This is one of most popular models, it has PC support (USB), up to 10A charge rate, up to 7A discharge rate. No idea about power supply though, I feed mine from my PC's power supply via EPS12V plug.
According to LiIon specifications anything between 4.15 and 4.25 volt as charging voltage is ok, resting voltage will be lower.
Just because I have reviewed it?
My usual logging setup uses these meters:
Check the iChargers. The 208B has memory, i.e. you do not need a computer connection when logging, but can transfer the data later. At one time I was serious considering using them for my battery test, but I was not satisfied with the results (To much noise in the data).
It's big enough to use on the BB-2590's that I have for my Hellfighters but I would probably need a 1100w power supply for it. I doubt any of the old PC power supplies I have laying around are up to the task. I need to check out the power supplies from there and make a decision. I have a Brentronics BTC-70801 (really a nice charger) for the BB 2590's but it provides no data. It has a serial port for upgrading the firmware but that's all it's for.
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