Li-Ion charger (18350/18650, etc.) that will keep the battery ready to go?

[tadakan]

Maybe it's because you aren't supposed to keep the batteries charged all the time, but I'm used to a NiMH AA charger that I have that will maintain the charge on the battery, or battery maintainers for 12v vehicle batteries.

Are there any round cell Li-Ion chargers that will maintain a battery so it's ready to go? Even at 80% or something? I don't use my flashlights every day, so when I need to swap a battery out, it might have been a couple months and it seems like the cells in my Fenix are-a4 are usually around 50% or lower which is annoying when I need to go work outside in the dark and rain.

It looks like maybe the SkyRC MC3000 will, but I'd rather not spend $120 for a charger when I probably won't use most of the features.

Thanks!

 

[sbj]

I don't know of any charger that keeps lithium-ion cells at the end-of-charge voltage of e.g. 4.20V indefinitely. And if there was, I wouldn't want to use it because it's bad for the batteries.
Lithium batteries feel most comfortable with a state of charge within 20 to 80% For this reason, I only charge my batteries to just over 4.0V and prefer to carry a spare battery, which I then hardly ever need.

This is a completely different case with lead-acid batteries for vehicles. They tolerate and like it when they are kept at 100% charge.

If your Fenix lamp loses around 50% of its capacity after a few months, which you should first check carefully via the recharged capacity, then it is very likely that the lamp is the cause, which still draws a small current when it is switched off.

With most lamps, this can be prevented by unscrewing the tail cap one turn. This is where the cause of the discharge will be found.

Of course it happens from time to time that a defective protective circuit can discharge a battery severely. This usually happens within a few days and you notice it immediately.

Lithium ion cells lose so little charge during storage that it is hardly noticeable after one or two years. For protected cells with a PCB, this is slightly more because the microelectronics of the protection circuit require a few microamps.
Nevertheless, only a little is lost here in a year.

 

[chillinn]

Maybe it's because you aren't supposed to keep the batteries charged all the time, but I'm used to a NiMH AA charger that I have that will maintain the charge on the battery,

Are there any round cell Li-Ion chargers that will maintain a battery so it's ready to go? Even at 80% or something?

Welcome to CPF, tadakan.

You're going about this the wrong way. It sounds like you are abusing your cells, and that is why they don't hold charge. It's no wonder your cells are not performing.

First and foremost, not all cells are created equally. Decent low self-discharge (LSD) NiMH such as Eneloop or any NiMH cells manufactured in Japan (FDK Corporation) will retain 70% capacity after 10 years of storage. Decent Li-ion cells only lose about 10% of their capacity or less per year of sitting.

But in order to get this performance you must not abuse your cells.

Constantly topping off charge for hours, days and weeks is abuse and will only result in a reduction of cell capacity, current, and ability to hold charge.

The same thing will occur with over-discharged cells below 0.95V for NiMH and below 2.5V for Li-ion (which with LiCo chemistry can cause them to explode or catch on fire if charging is subsequently attempted).

Pulling cells hot off the charger and immediately discharging is abuse. Putting cells immediately after use on a charger is abuse. Proper care of cells requires resting the cell after charging and before use and after use and before charging. The cell just needs to cool to ambient temperature, so it can take an hour or only 10 minutes of resting depending on the ambient temperature. Some here will rest their 18650 cells for 24 hours, but, in general, resting cells at least an hour is standard practice. The voltage you see after charging for a rested cell, such as 1.36V for NiMH or 4.12V for Li-ion, for all intents and purposes, means the cell is full. You're not losing any capacity allowing your cells to rest, you are preserving the cell's ability to retain capacity.

Also, since I mentioned the above, the only other best practice is to avoid dropping cells. This can also lead to reduced capacity, current, and the ability to hold charge.

Get decent cells, avoid abusing them, and you'll never have issues like this again.