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Lithium Ion Battery Question


Guest Jopopsy

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Guest Jopopsy

Quick question for you guys.  I just bought a DCD760KL and I just charged up the first battery.  Some of the rules change due to my batts being Lithium Ion. 

One of the reasons I bought this drill is that it will sit in the case for long periods between jobs/projects.  Is it adviseable to charge both batteries up, or am I better served leaving the 2nd battery alone until I start my shed project in the Spring?

I'm guessing the answer is charge them all up, given they have very little memory effect, are supposidely not supposed to go down to 0 charge ever, and shelf life/age will kill them faster than charge cycles.

Am I right?

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Source; BatteryUniversity.com

"........Preparing new lithium-ion for use

Unlike nickel and lead-based batteries, a new lithium-ion pack does not need cycling through charging and discharging. Priming will make little difference because the maximum capacity of lithium-ion is available right from the beginning. Neither does a full discharge improve the capacity of a faded pack. However, a full discharge/charge will reset the digital circuit of a 'smart' battery to improve the state-of-charge estimation

State-of-charge reading based on terminal voltage

The open circuit voltage can be used to estimate the battery state-of-charge of lithium, alkaline and lead-based batteries. Unfortunately, this method cannot be used for nickel-based packs.

On a lithium-ion cell, 3.8V/cell indicates a state-of-charge of about 50%. It must be noted that utilizing voltage as a fuel gauge function is inaccurate because cells made by different manufacturers produce a slightly different voltage profile. This is due to the electrochemistry of the electrodes and electrolyte. Temperature also affects the voltage. The higher the temperature, the lower the voltage will be.

Hints to long battery life

   * Limit the time at which the battery stays at 4.20/cell. Prolonged high voltage promotes corrosion, especially at elevated temperatures. (Spinel is less sensitive to high voltage than cobalt-based systems).

   * 3.92V/cell is the best upper voltage threshold for cobalt-based lithium-ion. Charging batteries to this voltage level has been shown to double cycle life. Lithium-ion systems for defense applications make use of the lower voltage threshold. The negative is reduced capacity.

   * The charge current of Li-ion should be moderate (0.5C for cobalt-based lithium-ion).

     The lower charge current reduces the time in which the cell resides at 4.20V. It should be noted that a 0.5C charge only adds marginally to the charge time over 1C because the topping charge will be shorter. A high current charge tends to push the voltage up and forces it into the voltage limit prematurely.

Note: In respect to fast-charging and topping charge, the charge behavior of lithium-ion is similar to lead acid. Here, the voltage threshold of 2.35V/cell during regular charge needs to be lowered to 2.27V/cell when the VRLA is on standby. Keeping the voltage at the high threshold would contribute to corrosion. A similar effect occurs with lithium-ion....."

Short answer to your question, Don't fully charge your batteries if you plan to store them for awhile.

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Guest Jopopsy

I posed this question to DeWALT - here is there response to me:

****************************

Charging the compact lithium ion battery - DCD760KL

Discussion Thread

Response (Sharon Gorsuch) 11/05/2009 04:23 PM

Dear Mike, we believe the following information addresses your inquiry.

The charging and maintenance procedure is the same for the NiCd batteries and the Lithium Ion batteries.

Thank you for allowing us the opportunity to serve you. If your question remains unresolved or if you require additional information please update this incident.

Sincerely,

Sharon Gorsuch

Auto-Response 11/04/2009 08:07 AM

Suggested answers displayed to customer:

Customer (xxxxxx) 11/04/2009 08:07 AM

I wanted to know if there was any differance in charging procedures or maintenance of the compact lithium ion battery included w/ my DCD760KL. The manual included w/ this drill covers many different model drills - the majority of which used NiCad batteries. There is no special section relating to Lithium Ion.

For instance, the manual states a weekly conditioning charge of 8 hours is recommended - however everything I have read about your lithium ion batteries leads me to believe that this is not necessary.

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