But some of the older chargers can and will over charge IMR cells. Like the older style WF-139 from UltraFire for example.
You should always check specs before just dropping a battery into a charger, just because its 3.7v does not mean it will work. Otherwise it could be dangerous.
As long as you don't leave the batteries on the charger much past when the light turns green you won't overcharge them. I've had the WF-139 for many years, as we use a lot of flashlights that use 3.7v lithium batteries.
We, also, have the WF-188. Although I don't recommend doing it, I have left the AW IMR batteries on the WF-139 several hours after the light turns green and the WF-139 has not over charged them.
I preferr the WF-188 only because it has a setting to more slowly charge the high drain batteries which is better for them. I don't like the new spring system and contacts on the WF-188 nearly as much as I do on the old WF-139.
If I were purchasing my first charger I would go for the WF-188 which can be purchased pretty inexpensively from RTD, referenced in above post #2. This charger also gives one the option to charge 3 volt batteries. I don't use it for that as all my 3 volt batteries are LiFePO4 which are much safer for stacking but do require their own special charger.
Alice
