Managing rechargeable batteries

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Mububban
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Managing rechargeable batteries

Postby Mububban » Thu Oct 19, 2017 2:32 pm

I read and hear conflicting advice on the best method for managing modern Li-ion rechargeable batteries to ensure long service life. Keep it between 20 and 85%. Run it right down to zero, then charge back up to 100%. Charge it to 79% under the light of a full moon while holding a fish in your left hand. Etc etc.

So what have people found to be the best way to manage rechargeable batteries for long life?

Edit - specifically I'm after advice on my Fly6 and Fly12 light/camera units
Last edited by Mububban on Thu Oct 19, 2017 3:13 pm, edited 1 time in total.
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madmacca
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Re: Managing rechargeable batteries

Postby madmacca » Thu Oct 19, 2017 3:07 pm

Mububban wrote:I read and hear conflicting advice on the best method for managing modern Li-ion rechargeable batteries to ensure long service life. Keep it between 20 and 85%. Run it right down to zero, then charge back up to 100%. Charge it to 79% under the light of a full moon while holding a fish in your left hand. Etc etc.

So what have people found to be the best way to manage rechargeable batteries for long life?


No, no, no. Are you completely #$%^ ignorant? It's gotta be in your RIGHT hand. :)

I have seen figures quoted that they typically lose about 20% effectiveness over 500 charge/discharge cycles, so many devices will probably be replaced on obsolescence long before the battery dies.

For long term powered-down storage, I'm pretty sure I have seen that 50-70% is best, which is why most devices arrive when purchased at less than 100% charge.

I also tend to fully charge and discharge a device once early in its lifetime, but this is more to calibrate the battery gauge and power management software, than the battery's physical life.

For the most part, I try to keep it in the 30-80% range.

For mission critical items like lights, I tend to charge to 100% to give maximum run time just in case, and accept the hit to battery lifespan. For things like my Garmin, I tend to charge it for a few minutes each day or two to keep it in the 50-70% range,

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Tim
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Re: Managing rechargeable batteries

Postby Tim » Thu Oct 19, 2017 3:17 pm

Lithium batteries don't like deep cycling ie. full charge-full discharge.
Best longevity is achieved by operating between 30-80%. Lots of little top-ups are better than one big discharge then full recharge.
Worst thing you can do is fully charge them when they are hot.
Read all about it:
http://batteryuniversity.com/learn/article/how_to_charge_when_to_charge_table
That said, I fully recharge my old (7 years) Edge 800 every time I use it and still get at least 8 hours of charge, not that I've done an 8 hour ride in recent times.

BTW. The above linked site is very interesting to gadget geeks and nerds like me. I've read the entire thing. :D
Makes me wonder how long these new home lithium Tesla type batteries will last in a domestic situation. Not to mention Elon Musk's new big battery in Adelaide.
Shhhhhh.... Don't tell Tony, he might build a new coal mine. :roll:

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Mububban
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Re: Managing rechargeable batteries

Postby Mububban » Thu Oct 19, 2017 4:57 pm

Tim wrote:Lithium batteries don't like deep cycling ie. full charge-full discharge.
Best longevity is achieved by operating between 30-80%. Lots of little top-ups are better than one big discharge then full recharge.


So what's considered a "cycle" then? Any time you charge it at all, or only when you're putting in say more than 50% charge?
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Tim
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Re: Managing rechargeable batteries

Postby Tim » Thu Oct 19, 2017 5:19 pm

A cycle is one complete 100% TOTAL combined discharge.
If for instance you discharge the battery by 20% then recharge it 20% and do this 5 times then that is considered 1 cycle ie. the combined total discharge is 100% of the battery capacity and the recharge is also 100% of capacity.

Shred11
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Re: Managing rechargeable batteries

Postby Shred11 » Thu Oct 19, 2017 6:37 pm

In addition to the earlier comments: avoid using or storing the batteries at high temperatures.

Also charging them when they are very cold seems to kill them. I learned this the hard way; riding to work in sub-zero temperatures and charging my Mobius camera as soon as I arrived. The first battery didn't last through one Winter. The replacement battery has been left to warm to room temperature before charging - two Winters later, it's still going well.

I think the myth that you should fully discharge Lithium batteries before charging them may come from Apple's advice to iPad / iPhone users to periodically fully discharge the devices, before doing a full charge. This gives the battery monitoring system a chance to re-calibrate to take in to account aging of the battery, so the battery gauge remains accurate. It's not good for the battery though.

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CaffeineAU
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Re: Managing rechargeable batteries

Postby CaffeineAU » Mon Oct 23, 2017 9:41 am

Most (well designed) devices that use lithium ion or lithium polymer batteries don't actually fully discharge the battery (because that will damage the battery) rather they have battery management circuits and/or software that will cut off the output when the battery is discharged to a low but safe level (generally no lower than 3V. The batteries are 3.6V (or 3.7V for LiPo) nominal and around 4.2V fully charged)

Lithium Ion batteries also don't have 'memory' effects that old NiCd batteries suffered. Don't be worried about frequent charging. My old Edge 705 (9 years old) gets charged every time I use it. It doesn't have wireless or bluetooth sync like current Garmins, so after every ride I plug it in to sync to strava and leave it there until the next ride. The battery is still in tip top shape.

For optimal battery life, you should only store the battery for long periods of time at 'storage charge' (3.8V per cell for LiPo) but you'll probably not notice any difference in lifetime or capacity if you fully charge it. LiIon / LiPo batteries also have very low self discharge rates, so you can leave them for a long time and they won't lose much charge (I found some 12 year old old LiPo batteries in my garage a few months ago, they were still around 95% charged)

Additionally, air transport requirements require batteries that are shipped as batteries (i.e. not installed in a device) be transported at 30% charge or lower. Batteries that are shipped installed in a device may be shipped at 50% charge or lower.

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AUbicycles
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Re: Managing rechargeable batteries

Postby AUbicycles » Wed Oct 25, 2017 3:43 am

How do a 70% or 80% charge. Are you testing the time required for a full charge then setting the alarm to 3:34am to wake up in tine to take it off charging.

The battery management system won't let batteries charge to 100% even if you havd a device that says fully charged ir a computer that says 100%, it is still actually less than 100% full.

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