I recently purchase VP2 and have started using 18650 batteries. The manual (not much there) that came with the charger is not particularly clear on the most advantageous charging strategy for long cell life. I have read that charging to only 4.1 volts is good for long life and get that. My real question is what charge rate should I choose? There are three choices: .25, .5, and 1.0 mAh What does each of these do? I am charging Panasonic 3400 mAh batteries. I have also read that these batteries like to be “exercised a bit during charge. Also, what state of charge should I store these at? I also read about a little device for analyzing batteries. Any input would be welcome!
Believe everything you read on the internet, its ALL true! 8)
…and then make an appointment to see your psych :Sp
Seriously, todays quality cells are a lot less fussy about charge rates that good chargers put out. They are much more sensitive about over/under charge states. All my cells lay around at full charge and ready to go. I have yet to can any cells due to utter failure to produce light. A couple of trustfire’s are pretty much at end of life… but I think they came to me that way.
If you want to be conservative, charge the 18650 at 0.5A and store them at 3.7V. Characterize your charger to know that it never charges over 4.2V although the cells have a +0.05V margin in the design. XTAR chargers are very good and should terminate right at 4.20V.
Sounds like good advise. How do I “characterize” my charger?
Take a known good DMM and measure good cells right when it comes off the charger and make sure it never exceeds 4.20V.
If you get consistent readings on both bays for a half dozen cycles, you know what to expect.
I have over 40 18650s and I group them in two groups, fully charged ready to go and 3.7v storage. Most of them are Panasonic 3400mAh and I only use 1A setting, this is still at very low 0.3C rate which helps with the longevity of the cells.
But honestly don’t even worry about having them fully charged all the time, the negative effects are minimal and li-ion batteries are getting really inexpensive now. I used to store 18650s in my flashlights fully charged over a year and they still work just fine.
Great advice guys. My paranoia about rechargeables and their potential dangers is fading fast. Can you recommend a good inexpensive DMM?
For measuring battery termination voltage I use a led display volt-meter (from RMM) it can be calibrated and throws more accurate readings than my cheap dmm, plus it’s easier to use.
The VP2 itself also has a very accurate volt reading.
+1 on the RMM meter. It tracked my very liable DMM perfectly as delivered.
Are you saying here that if your 18650s are not in a device you keep them charged anyway to 3.7v? I should be checking my stand by batteries? Just wondering as I am knew to rechargeables and have been only charging them before putting them into a light and otherwise as needed to keep them fully charged for use.
For what it’s worth, I’m using the Xtar SP2.
Technically at 3.7v the battery hold less than 50% of remaining power, and for long time storage (3+ months) this is the recommended charge level to keep. But I do this only because I have more batteries that I could ever need or use (don’t ask me why :~ ).
As I said before, don’t worry if you need to leave your batteries fully charged all the time, just empty and charge them at least once every couple months and you’ll be fine. Having to charge the batteries before using them it’s a lot of hassle, and the extra time it takes to babysit a $8 battery it’s not worth it.
Many of the things you may read on internet about li-ions being very dangerous and require special care are not longer applicable with today’s 18650s, these cells are now extensively tested for overcharge, over discharge, high temp operation, short, and they are way safer now.