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Is slow charging Li batteries better than fast?

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stevensfo
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Is slow charging Li batteries better than fast?

#236995

Postby stevensfo » July 16th, 2019, 1:50 pm

I seem to remember years ago hearing that it's best to charge a battery slowly. No idea why.

Since I'm using 18v/36v cordless tools more and more and collecting 18v batteries, I'd like to get a 2nd charger and noticed that they all seem to be labelled as 'Fast 30 minute charger' as opposed my old Makita charger that takes a good 2 hours.

Are these okay to use, or will they shorten the life of the battery?


Steve

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Re: Is slow charging Li batteries better than fast?

#237066

Postby Breelander » July 16th, 2019, 6:29 pm

More than you could possibly want to know here at the Battery University...

https://batteryuniversity.com/learn/art ... _batteries

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Re: Is slow charging Li batteries better than fast?

#237502

Postby XFool » July 18th, 2019, 12:38 pm

stevensfo wrote:I seem to remember years ago hearing that it's best to charge a battery slowly. No idea why.

Since I'm using 18v/36v cordless tools more and more and collecting 18v batteries, I'd like to get a 2nd charger and noticed that they all seem to be labelled as 'Fast 30 minute charger' as opposed my old Makita charger that takes a good 2 hours.

Are these okay to use, or will they shorten the life of the battery?

I can only say, through personal experience with an Energiser fast charger for AA/AAA batteries, it appears to have shortened the life of more than one set of NiMH AAs. Through overheating.

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Re: Is slow charging Li batteries better than fast?

#237551

Postby Hardgrafter » July 18th, 2019, 3:20 pm

Steve,

Straight answer is YES. Charging fast reduces battery life. With mobile phone batteries, and fast charger reduces life time to 50 charge cycles, compared to 500 cycles for a the slow chargers. The mobile phone turbo chargers, which reduce the rate of charging after 85% full, are somewhat better than simple fast charging. But I doubt the simple batteries used in power tools will be so sophisticated as a computer in a mobile phone. See that Battery University for more details, but its mostly to do with crystal sizes.

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Re: Is slow charging Li batteries better than fast?

#237572

Postby stevensfo » July 18th, 2019, 4:18 pm

XFool wrote:
stevensfo wrote:I seem to remember years ago hearing that it's best to charge a battery slowly. No idea why.

Since I'm using 18v/36v cordless tools more and more and collecting 18v batteries, I'd like to get a 2nd charger and noticed that they all seem to be labelled as 'Fast 30 minute charger' as opposed my old Makita charger that takes a good 2 hours.

Are these okay to use, or will they shorten the life of the battery?

I can only say, through personal experience with an Energiser fast charger for AA/AAA batteries, it appears to have shortened the life of more than one set of NiMH AAs. Through overheating.



Well, I noticed that the so called Fast Li battery chargers have a fan to cool down the system during charging.

Though given the size, weight and shape of my Makita 18v batteries and therefore the distance that heat has to travel, I can't imagine a fan making a huge difference.

Steve


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