Author Topic: NiCd, SoC, DoD, and Lifespan  (Read 4911 times)

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Offline MadScientist267

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NiCd, SoC, DoD, and Lifespan
« on: June 04, 2012, 07:28:15 pm »
Ok, so most know that the Lead-Acid chemistry has the preference of being held as close to full charge as much of the time as possible, and that not only the number of discharge cycles, but the depth of those discharges play a significant role in the overall lifespan of the battery.

A few other chemistries demonstrate this as well, such as Li-Ion, even though they in fact do better in storage at about 40% SoC (depending on the exact chemistry).

What about NiCd?

They can be stored at any SoC, and little is mentioned about the DoD other than the general consensus being that they should be kept above an average of 1.0 VPC in a pack so as to prevent cell reversal, which apparently is damaging to a cell when it occurs.

Many NiCds are rated to something around 1000 cycles before they need replacement. Can they be taken down all the way to 1.0 VPC on each discharge and still reach that number, or do they last longer if only partially discharged?

Steve
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Offline ghurd

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Re: NiCd, SoC, DoD, and Lifespan
« Reply #1 on: June 04, 2012, 09:05:48 pm »
"They can be stored at any SoC"

I disagree, from my personal experiences.

The kid would take the AA nicds for her walkman (or whatever).
When they went flat, she'd take more and drop the dead ones in a desk drawer, or on the floor to get kicked under her desk or bed or somewhere.
Might take a month or 2 before an adult would find them, and half of those were toast (some came back after sparkin-the-wiskers).

That said, I know I have used others well over 1000 cycles that still work quite well (but obviously below the rated AH).
Shortly after we bought this house, I saw a GREAT deal on a couple cleance price cordless phones (I opted for the wierd purple and the nasty green... no wonder they didn't sell).
The purple one had the pack (3 flat-top AAs) changed some years ago (thanks BruceS).
The green one still has the factory nicd pack.
These are the primary (only) phones in the house, and they got a LOT of use (back when there was a wife, pre-teen then teen then 20s girl without a cell phone, a business, 3 phone lines, and a cell phone we did not use often).

Can leave them off the charger for a week, and they both still work fine to this day.

And I bought them 16 years ago.
That's almost 6000 days.
G-