Author Topic: Lithium Ion Batteries  (Read 5232 times)

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Offline Thistleman

  • Posts: 84
Lithium Ion Batteries
« on: January 02, 2017, 10:17 AM »
I was one of the lucky individuals to receive a 90th anniversary CXS in October 2015

However as I prefer the TXS form  factor it has remained unused in its systainer since arrival

Yesterday I opened it up and was surprised to find that the battery was still almost fully charged even though I have never charged it myself and it is as it arrived from Festool

My question is how long does a lithium ion battery hold its charge as 15 months to my mind is exceptional
Festool, Mafell and Felder

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Offline kevinculle

  • Posts: 103
Re: Lithium Ion Batteries
« Reply #1 on: January 02, 2017, 11:36 AM »
Lithium ion batteries are generally spec'd at about a 10% self discharge rate per month.  This would lead to a fully charged battery reaching a bit above 20% state of charge after 15 months (0.9^15).

Offline JimD

  • Posts: 322
Re: Lithium Ion Batteries
« Reply #2 on: January 31, 2017, 08:35 PM »
Lithium ion batteries make cordless power tools a lot more practical than Ni Cd.  More power for the size, hold charge better, etc..  Mine are Ryobi and the saws were not of much use with Ni Cds.  Very useful with Lithium ion.  Drills work with either technology but lithium ion will work longer and the drill is lighter. 

My batteries tend not to sit still for a week.  Not sure how long they would still have a charge.  My better two have little 4 position gauges. 

Offline atomicmike

  • Posts: 190
    • atomicmike
Re: Lithium Ion Batteries
« Reply #3 on: January 31, 2017, 09:24 PM »
Lithium ion batteries are generally spec'd at about a 10% self discharge rate per month.  This would lead to a fully charged battery reaching a bit above 20% state of charge after 15 months (0.9^15).

FWIW, Wikipedia's article on Li-ion puts self-discharge rate at 1.5-2% per month, so that would lead to a battery at close to 74% after 15 months in the worst case.

Offline Coen

  • Posts: 257
Re: Lithium Ion Batteries
« Reply #4 on: February 27, 2017, 03:58 PM »
Lithium ion batteries are generally spec'd at about a 10% self discharge rate per month.  This would lead to a fully charged battery reaching a bit above 20% state of charge after 15 months (0.9^15).

Self discharge rate drops off sharply, so maybe 10% first month, but then more likely not half that.

Offline nemesis23

  • Posts: 1
    • woodworking plans
Re: Lithium Ion Batteries
« Reply #5 on: March 27, 2017, 12:29 PM »
Lithium ion batteries are generally spec'd at about a 10% self discharge rate per month.  This would lead to a fully charged battery reaching a bit above 20% state of charge after 15 months (0.9^15).

Self discharge rate drops off sharply, so maybe 10% first month, but then more likely not half that.

In my experience and testing, the charge dropped about 5% only in first two months. (I tested by simply discharging it by button pressed)