How to maintain a cell phone battery pack for emergency purposes only?
September 21, 2017 8:26 PM   Subscribe

Hello everyone. In case of an emergency, I bought an Anker Powercore portable charger for my phone. I'm not going to use it for day to day use, just for an emergency. Might anyone know the best way to maintain it? I'm thinking it's not good to keep it always plugged in, right? Should I use it to charge my phone once or week or on some other schedule? Thanks in advance for any advice.
posted by holdenjordahl to Technology (11 answers total) 6 users marked this as a favorite
Theoretically, if you cared about the longevity of the battery, you'd store it at about 40% charge (and close to freezing). But that's less useful for your purposes of needing to charge up your devices in the case of an extended emergency. You can probably get a good mix of practicality and ease of use by storing it at 100% and using it somewhere between once a week and once a month to reduce its capacity to about 50% and then charging it back up to 100%.

The big thing is to keep it out of heat as much as possible. In my anecdotal experience (backed up by the studies), that's a far bigger factor than how long they're stored fully charged or discharged.
posted by Candleman at 8:42 PM on September 21, 2017 [1 favorite]

Thanks, Candleman!
posted by holdenjordahl at 9:20 PM on September 21, 2017

And if you are going to pop it in the fridge or freezer, bag it against moisture. It has electronics, which will eventually corrode if exposed to too much moisture. It'd take a long time with the cycle you're talking about, but all it should cost you is a dedicated ziplock bag. Keep in mind that the unit will sweat (you know, get some condensation) when you take it out of the fridge every month, or whatever frequency.
posted by Sunburnt at 10:32 PM on September 21, 2017

Thanks, Sunburnt!
So, seriously, in the fridge, wrapped in a ziplock bag, until I take it out for weekly or monthly or whenever occasional use?
posted by holdenjordahl at 7:52 AM on September 22, 2017

I have one of these and I usually just keep it in a little bag of dongles that I carry around with me in case I need it. I only recharge it after I have used it, which is maybe only once every two weeks or so. I've been doing this for maybe 3 years or so and never had a problem with it.
posted by greta simone at 11:01 AM on September 22, 2017

I have a cheap-o version of this, and I just carry it in my purse, use it when needed, and recharge then. Depending on my schedule, this could be a couple of times a week, or as little as once a month. I have not seen any performance problems, but the thing is cheap enough that I feel like I will just replace it when it dies.

In the fridge seems pretty useless, because if you're home, you presumably already have your regular power cord, right? The place you would need it is whenever you're out of the house and your phone dies? So seems worth it to get something portable you can carry with you. The little portable ones are also super cheap (I think mine was maybe $7 and works perfectly).
posted by rainbowbrite at 12:00 PM on September 22, 2017 [1 favorite]

You can probably get a good mix of practicality and ease of use by storing it at 100% and using it somewhere between once a week and once a month to reduce its capacity to about 50% and then charging it back up to 100%.

Lithium batteries have a lifetime that is limited by the number of charge and discharge cycles you go through. I see no reason to deliberately discharge once a week. This just reduces its lifespan and capacity. Lithium batteries don't have a "memory effect" like NiCads, so there is no reason to unnecessarily discharge them.

Lithium batteries have a very low self-discharge rate -- less than 5% per month. You can charge it to 100% and just forget about it for 6 months or even a year. Then top it off again. Don't leave it plugged in. If you always want it closer to 100%, just top off the charge every couple of months. It should last you for many years if you don't use it much. No special care required except the less you use it, the longer it will last.
posted by JackFlash at 2:25 PM on September 22, 2017

Keep in mind that Lithium Ion batteries will eventually degrade even if you charge, store and use them as recommended, so don't count on this as something that you can charge and then ignore completely. If you find that you have occasions to use an external battery charger (e.g. for traveling), bring it along and use it for that instead of reserving it for emergencies, as you'll be able to keep better tabs on its performance if you do use it at least sometimes.
posted by Aleyn at 9:16 PM on September 22, 2017

The longest-lasting batteries are Lithium batteries (not rechargeable; the similar sounding rechargeable batteries are lithium-ion).

You could get an AA USB charger and a supply of Lithium AA Batteries that have a 20-year shelf life.
posted by reeddavid at 9:20 PM on September 22, 2017

I keep mine in my backpack, to use if my cell phone or tablet dies when I'm out and about. I would not want to store it elsewhere unless I were sure that I could remember to put it in my backpack every time I leave the house. A mobile charger that is in your house when you are away from home is no better than not owning a mobile charger.

A mobile charger that has itself lost its charge is also no better than no charger at all. That has happened to me when my phone died while I was away from home, and it is very frustrating. So now I take two seconds every morning, right when I check my email, to make sure my mobile charger is at least at 50%, as per the charge lights on the front. Once it hits 25%, I charge it.
posted by merejane at 8:33 AM on September 23, 2017

Excellent advice, everyone - thanks!
posted by holdenjordahl at 3:08 PM on September 26, 2017

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