Does leaving a lithium-ion batter in a charger shorten its life?

February 2, 2008 11:22 AM

Does leaving a lithium-ion batter in a charger shorten its life?

Here’s one for the battery experts out there:

If I have a lithium-ion battery-powered device, which I only use infrequently, will it diminish its battery life much to always leave it in the charger?

Here’s the specifics:

I recently bought a Garmin Nuvi 250 GPS (Thanks Green - it’s awesome!) I pretty much only ever use it when I travel (and then, mostly, in a car, where it runs off the lighter adapter). But once in a while, very infrequently, I use it when walking or cycling, which means it runs off batteries.

Part of me thinks: Okay. Just leave it plugged into a charger all the time, so that on those off occasions I want it, I can use it. Part of me wonders if I’m squandering the health of the battery by doing this. My understanding is that all rechargeable batteries lose their zip through multiple recharging. How much zip am I taking away by leaving this thing in its charger?

posted by ManInSuit to technology (10 comments total)

MOST chargers turn off automatically after a preset amount of time, and only supply a "trickle charge" after that. I dont think the trickle charge is supposed to harm the battery in any way (its not the same as a regular recharge cycle at that point). This is what the literature that came with my battery charger said. It has all kinds of auto shut offs built into it and it only does the trickle thing once the battery is fully charged.

If your problem is that you are using the device infrequently and it needs rechargeable batteries, just by eneloop batteries (look for eneloop on amazon). These batteries DONT LOSE THEIR CHARGE OVER TIME so you can just leave them in the GPS or camera or wherever you're using them (unlike regular lithiums which do lose their charge over time and need constant recharging).

I bought a bunch of those and they've been great.
posted by jak68 at 11:27 AM on February 2, 2008 [1 favorite has favorites]

The Garmin doesn't have a user replaceable battery, but leave it on the charger - it trickle charges. If you look on the diagnostic screen (google for info) you can see the charge status - IIRC, it is expected to last several years, hence the non user replaceable.
posted by A189Nut at 12:00 PM on February 2, 2008

Yeah - it's because the battery isn't user-replaceable that I worry about its life.

But am I understanding right: Trickle-charge doesn't affect the life of a battery the same way regular charge/discharge does?

(jak68 - that's cool about the eneloop batteries. Not what I need for this application, but great to know for other cases...)
posted by ManInSuit at 2:00 PM on February 2, 2008

Unfortunately, I've found conflicting information relating to charging, with some advice seemingly a holdover from NiCad. People will tell you never using the battery shortens its life, heavy use shortens its life, leaving it always plugged in shortens its life, deep discharge shortens its life, storing it charged more than 50% shortens its life. The only thing everyone agrees on is that over time the battery will become less and less capable and lithium, in particular, has a fairly short lifespan. A laptop battery, as an example, that still held a useful charge at four years is the exception. It seems like most users get one to three years out of them, before time is measured in tens of minutes instead of hours. What is especially lame, though, is the general lack of studies given the prevalence of lithium batteries. Or at least I've not been able to find hard numbers associated with how a battery is charged and used.

My advice: use the device how you want to use it and accept that even expensive lithium batteries are consumables. A replacement battery for a still-decent laptop is (usually) a no-brainer. For a sealed device you'll have to decide whether or not replacement is worthwhile; it may be relatively easy for you to replace yourself with a common part or the difficulty or cost of a replacement may make a new device more attractive. Such is the price of our disposable and non-sustainable culture.
posted by 6550 at 3:13 PM on February 2, 2008 [1 favorite has favorites]

Li-Ion batteries degrade just by existing, not really through use. The only ways to lengthen their life is to keep them cool (store them in the fridge/freezer) or store them at 40% charge. Ideally you do both. Obviously this doesn't work for something with an integrated battery, but if you had some removable Li-Ion batteries that you wanted to store, that's what you'd do. See here for example.
posted by markr at 3:23 PM on February 2, 2008 [1 favorite has favorites]

I don't know the answer to your question but Battery University has some good info.
posted by davcoo at 3:32 PM on February 2, 2008

Apple has a page about getting the best lifespan out of the lithium-ion batteries they ship. short form is - don't store them somewhere hot, and give them a full charge cycle at least once a month (but there's no need to deep-discharge). so perhaps leave the lighter adapter unplugged every now and then.
posted by russm at 5:28 PM on February 2, 2008

Be aware that Lithium-Ion batteries begin to loose their storage capacity from the moment they are manufactured, and it can range from 5% to 40% each year, depending on the temperature they are stored/used at; with higher temperatures resulting in a greater loss. My opinion is that a 10 -15% loss in capacity is probably typical for most people. BTW, this is a function of time, not usage or charging. I'm not certain what effect those factors might have.

Wikipedia seems to have a pretty good article about these batteries.
posted by 14580 at 6:17 PM on February 2, 2008

What I've heard regarding Lithium is the above- store in a cool and dry place.

I've also heard that Li batteries, due to their chemistry MUST have smart chargers or they explode.

And I've also heard that they don't like being stored in an uncharged state. So yeah, leave it in the charger.
posted by gjc at 6:41 PM on February 2, 2008

Thanks! All those anwers are really helpful. I'll keep the thing in the charger most of the time, make it a point run the battery down occasionally, and live w. the fact that the battery capacity will decrease no matter what I do.
posted by ManInSuit at 6:58 PM on February 2, 2008