larryepage Loc: North Texas area

There have been a number of recent posts asking about batteries discharging when equipment is not being used. There are several reasons that self-discharge routinely occurs, related to the chemistry in the batteries and the fact that the insulation between the poles of the battery is not perfect. In addition, those batteries with imbedded chips must power those chips 100% of the time. It is possible to find numbers that differ a little bit, but this chart is from a site called BatteryUniversity. Of course the nice formatting doesn't copy, but I've tried to make it readable.

Self-discharge as a function of time.

Battery system / Estimated self-discharge

Alkaline / 2–3% per year (7-10 years shelf life)
Lead-acid / 5% per month
Nickel-based / 10–15% in 24h, then 10-15% per month (NiCad and Nickel Metal Hydride)
Lithium-ion / 5% in 24h, then 1–2% per month (plus 3% for safety circuit) (So 4-5% per month if not in the camera.)

Actual discharge that we will see in our camera bodies will be higher, because if you look carefully, they probably never power down completely. Parts of the LCD are typically continuously powered, along with the clock and calendar, and other functions may remain active during powered down periods.

Edit: Lithium Ion Batteries that have been deep-discharged even once will have a slightly higher self-discharge rate. Those that have been stored in a discharged condition for 14 days will typically have a self-discharge rate that is 3.5 times higher than an undamaged cell. So don't over discharge these batteries, and recharge them before putting them away.

And of course, as others have noted, "Your Mileage May Vary."

jerryc41 Loc: Catskill Mts of NY

Thanks. Interesting. I keep charged Eneloops handy, but I usually top them up before I use them.

PixelStan77 Loc: Vermont/Chicago

And spares are always a good idea.

Leitz Loc: Solms

Anyone who can think a bit can simply follow the guidelines in the user's manuals.

MT Shooter Loc: Montana

You will also find that the cameras these batteries are stored in make a huge difference in their storage life as well. Sony cameras are notorious for idle discharge rates when just sitting. I have a Sony A7 that will completely discharge its battery in 3 weeks on non-use. And yes, that rate has been verified with multiple batteries, makes no difference if its factory or aftermarket.

larryepage Loc: North Texas area

I spent several years working in three different industries. On average, in all three companies, we found that we could count on between 5 and 9% of folks carefully reading and understanding the instructions.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

The longest lasting battery chemistry is Lithium/Iodine. This chemistry has a flat discharge curve and delivers starting voltage for 10 years. It is the standard battery used in pacemakers and implantable defibrillators. It is outrageously expensive. A camera battery with this chemistry might cost about 5 or 6 grand. A touch pricey for camera usage, and they are not rechargeable. And they probably woundn't last as long in a camera as they use more juice than a pacemaker.

Leitz Loc: Solms

Indeed? I wouldn't have thought the percentage to be so high!

jerryc41 Loc: Catskill Mts of NY

Then you need better writers.

burkphoto Loc: High Point, NC

That's why you repeat the same information at least three times in six different ways (media).

fourlocks Loc: Londonderry, NH

My other hobby, is radio control aircraft and I have about 25 lithium polymer batteries for the aircraft and transmitters. These range from 7.4 volts at 250 milliamp hours, to 18.5 volts at 3,000 milliamp hours. I store these batteries at 50% charge over the winter and come spring, they have lost only 2 to 4% of their charge in a 4 to 5 month period. Some of these batteries are over 7 years old and I've probably charged and discharged them (in use) several hundred times with no change in their power or capacity. Lithium Polymer is a little more "tricky" than Lithium Ion but apparently perform much better especially in my transmitter where a single charge may last several months, depending on use. I'd bet the power demands for a transmitter and camera are about the same so I wonder why my Lithium Polymers do so much better than Lithium Ions? And why don't camera manufacturers use Lithium Polymers?

LFingar Loc: Claverack, NY

The instructions exist to help you figure out what you did wrong AFTER you screw up! I think that fact is mentioned in the first chapter of the book "How To Be A Typical Guy". I used keep my signed, first edition copy right on the coffee table that I built myself, but, for some reason, it kept sliding off onto the floor.

OddJobber Loc: Portland, OR

My Eneloops did not come with a manual.

larryepage Loc: North Texas area

Please remember...the chart shows discharge rates just for the battery...if it weren't in the camera. Any drain caused by the camera (or other system) drawing current would be in addition to what is shown.

Leitz Loc: Solms

Neither did mine, but there was a leaflet with general information on use, charging, &c.