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ko4nrbs

Battery Internal Leakage

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I've been doing capacity checks on all my batteries on an annual basis.  After testing the IR (internal resistance) I discharge them to the OEM recommended discharge voltage then charge them in a charger that shows how many maH were put into the battery.  This has worked very well for me but by accident I discovered I had a few batteries that had lost considerable capacity sitting in the closet for a few months.  One or two were completely flat.  I only discovered this because my XTAR VC4 chargers show the maH put into the battery and it took a lot longer to charge these cells back up.

 

In the future I will first recharge all the batteries to see how many maH are put into them before I do the capacity test. 

Found this on this site.  Good rule of thumb on when to replace batteries.

Quote-  NiMH and NiCd belong to rechargeable batteries that have the highest self-discharge; they need recharging before use when placed on a shelf for a few weeks.

http://batteryuniversity.com/learn/archive/the_secrets_of_battery_runtime

Self-discharge increases with age, cycling and elevated temperature. Discard a battery if the self-discharge reaches 30 percent in 24 hours.

Chart for NiMh batteries:

The energy loss is asymptotical, meaning that the self-discharge is highest right after charge and then tapers off. Nickel-based batteries lose 10 to 15 percent of their capacity in the first 24 hours after charge, then 10 to 15 percent per month. Figure 7 shows the typical loss of a nickel-based battery while in storage.

Self-discharge as a function of time

image.png.67c896f0cd7f091e6d29e9b1f4b48a74.png

 

I now have a standard to measure my batteries against.  No use installing batteries in a build if they will exhibit unacceptable self discharge while in the field.

 

Bill

Edited by ko4nrbs

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Excellent info, thanks for sharing Bill.

 

Geo

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7 hours ago, bulltalk.65 said:

Excellent info, thanks for sharing Bill.

 

Geo

Your welcome.

I sure have to be a lot smarter as far as managing my stash of NiMh batteries. 

Bill

 

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