How often should I charge?

[wilwi]

I have an ionic for a few days. Now I wonder, what is the best thing, charging the battery every day to 100% which is the easiest, or recharging at almost empty and then letting the ionic run off for some time.

Moderator edit: edited title for clarity

[Julia_G]

Hi, @wilwi, for modern lithium ion type batteries such as in Fitbits the best advice is to avoid deep discharges whenever possible.   So little and often is the best bet.  The ideal range is 30-80%

Charging for a few minutes every day is fine.  

[Rauser]

As far as I know especially for lithium based batteries it doesn't matter how much you discharge them. 

And "deep" discharge isn't possible in any way on modern electronic devices because they will switch off before the battery reaches a critical level. 

So, my pratical advice is: Put your Ionic on the charger while you're in the bathroom doing your everyday business. 

[Julia_G]

@Rauser, although I agree with your bottom line, of charging the Ionic daily while in the bathroom, your statements re deep discharge are incorrect.

You may want to look here for the physics (and further information): http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

The take away point is (from the article): "...the depth of discharge (DoD) determines the cycle count of the battery.  The smaller the discharge (low DoD), the longer the battery will last.  If at all possible, avoid full discharges and charge the battery more often between uses."

[Rauser]

Thank you for this interesting link.

But after reading it I had a a few questions left. First of all: Does the speed of discharging affect the lifetime in any way? We're talking about a tiny battery which is discharged very slowly.

And second: When I recharge my device every day a little bit instead of every five days, I must charge it five times more. Hmmm... 

But nevertheless... A full recharge of a smartwatch isn't practical in my eyes because you can't use it during this time, so this discussion about deep discharge is a moot point. 😉

[SunsetRunner]

One thing we don’t know about with the Ionic is whether the design is such that there is deep discharge protection built in to the circuits. Yes the Ionic will switch off at a certain low voltage but is that so low as to cause an issue with the battery. I don’t think so, especially noting the promoted 5 day battery life. If Fitbit was worried about deep discharging and 5 days was when this happened, then I doubt they’d be advertising it as such, given the harm that such a process would cause. I would like to think there is deep discharge protection built in and it is safe to recharge any time within the time the Ionic is “alive”.

In support of this thinking, my car is lithium ion powered and has such protection. It is impossible for me to drive the car until the battery is flat. The battery circuits stop outputting at about 30%. OK it may be wishful thinking that my £300 dollar watch is on par with my £40k car but just food for thought.

[Julia_G]

It may very well be that the Ionic has a protective algorithm causing it to turn off before it has completely discharged.  However Fitbit batteries (and those in other, small electronic devices) will continue to discharge (although more slowly) even while off, which is similarly deleterious to battery life.  So basically the advice is the same -- keep it charged between 30 - 80 % for best battery life.  You won't do a lot of damage by letting it run down until it turns itself off, but if you do this repeatedly, or let it sit for months unused in a drawer you will likely to find the battery's performance is eventually significantly affected,

If, instead, you charge it frequently (little and often) the battery will likely last long enough for the device to be totally obsolete for all kinds of other reasons, which have nothing to do with battery life.  That was the apparent thinking of phone manufacturers when they stopped having user changeable batteries.

[Julia_G]

@Rauser to address your specific concerns, my experience is that the Ionic charges very quickly and I keep mine mostly charged by plugging it in for about an hour every few days.  I expect 15minutes a day would have a similar effect of keeping it in the ideal range of 30-80%, so I don't see that this is a moot point at all!  You can still use your watch as a smart watch and keep it at ideal state of charge.

[wilwi]

I asked the question because I charged my surge every day and the battery only lasted 24 hours after 2 years fully charged. I do not want to experience this with my ionic

[bbarrera]

even by following best charging practices, no assurances your Ionic won the "battery lottery" on the production line -- if you are unlucky and your Ionic has a poor quality battery then it could happen again.

p.s. I've got an old iPhone 5s that won the "battery lottery" and still has great battery life for its age. Best phone battery of all time.

[Julia_G · Accepted solution]

@wilwi, as I am sure you know, all rechargeable batteries have limited life and how long they last depends on how you use them.  If I use GPS on my Surge then it needs to be charged every day, because GPS is very battery hungry.  If I don't turn GPS on, even though it is now two years old my Surge will still last two or maybe three days, but definitely not longer.

There are many other factors.  For example, high temperatures are one of the best ways of killing batteries, so in so far as you can control that, avoid excessive heat. As you can see from the link I shared above, lithium ion batteries will deteriorate more quickly when they are regularly exposed to temperatures above 30degrees C.  Also don't use any kind of fast charger.  Not relevant to Fitbits, but I can also tell you that wireless (Qi) charging gets batteries very hot and is not good for them!  (I know this from mobile phone charging).

Basically, no one can know how long your individual battery will last, but I think I have given you the best advice for prolonging the life of your Ionic battery:  keep it regularly charged, avoid deep discharges, don't use a fast charger, don't let it get too hot.  

You definitely will not do it any harm by normal, daily charging.

edited to add: @bbarrera is correct.  Battery life is a bit of a lottery, even if you do your best.  But you can improve your chances of winning, or make it more likely that you will lose.