Why does my camera battery only charge to 75%?

Question

I have a Nikon D7000 and I have a battery problem. My battery never charges more than 75%. The charger say is full, but I put in the camera and it says 75%.

Why is this, and how can I fix this problem?

I tried to charge it for long hours and the problem is the same... charge it all night and still 75%. Is this the battery or a camera problem? How can I fix it.

With the battery at 75%, I can take like 700 shots, with picture preview and some using the menu to check the battery.

The battery is new - I have had it a few days. Battery serial says 2015. Camera "age" meter displays 0 (new).

Answer 1

I'm guessing your battery is just old. It's a lithium battery, and lithium batteries inherently lose capacity with age. The D7000 was released some six years ago, so 75% is actually not horrible. You're still getting 700 shots with it, so you could either just live with it, or pick up a replacement. This battery, the EN-EL15, is still used on current model, so it shouldn't be hard to find — either Nikon-branded or possibly a generic replacement.

Answer 2

I think what you're seeing is likely an artifact of the battery pack having sat around for a long time without being charged, and may go away on its own by discharging and recharging the battery pack fully (to the point where the camera shuts off) a few times.

The charge controllers inside each battery pack store some information about the state of the battery—the number of charge cycles, information about how quickly the battery takes a charge, current cell voltage, etc. This information, combined with... IIRC the resistance across the entire set of cells, is used by smart chargers to determine how fast to charge the battery pack and to determine when to stop charging.

When a pack sits for a long time, you could potentially (IIRC) get into a situation where weak cells self-discharge at a faster rate, so that the cells are unevenly charged. In that case, the battery pack as a whole could quickly hit the point where the nearest cell is essentially full, causing charging to shut down before the other cells get fully charged. Over time, the charge should migrate to other cells, and you will be able to top up the pack, or you can just charge up the pack all the way and discharge it all the way a few times, and the charge should average out quickly enough.

Another possibility is that the charge controller crashed and lobotomized itself because it ran out of power. Assuming it came back to life (i.e. assuming you aren't getting "Camera cannot communicate with battery" errors), it could take a couple of full charge-discharge cycles for it to properly calibrate itself to the current state of the pack.

Specifically, if the pack crashed from losing power, the cycle count could actually be much higher than the battery reports. Normally, batteries recalibrate their charge indication based on their estimated full-cell capacity at the end of the last few charge cycles, so they should always says "100%" when they are fully charged, even if that represents only 75% of the battery's original capacity. However, if the battery was fully drained to the point that the charge controller forgot the cycle count and calibration data, it would have to rebuild that data over the course of several charge cycles.

Either way, it is almost certainly a battery issue. I suspect that several charge/discharge cycles in a row will either entirely fix the problem or will at least fix the reporting problem so that it reports itself as being 100% full (but you might still only get three-quarters as many shots per charge).

If it doesn't start reporting itself as 100% charged within a couple of complete discharge-recharge cycles, I would suggest replacing the battery. A battery that continues to report 75% after multiple charge-discharge cycles might have something seriously wrong with it that is causing charging to terminate prematurely, such as dendritic growths, which means it should probably be recycled ASAP before it becomes a safety problem.

That said, I am not a battery engineer, and this is all from memory, so I could be off a bit. Take this with a grain of salt.

Answer 3

It sounds like your battery is just old and has lost some of its capacity as all rechargeable batteries do. Matt's answer covers that part well.

If the battery isn't the problem then the next likely candidate is the charger you are using. Sometimes a manufacturer will modify the capacity of an existing battery. If you use an older charger with a newer, higher capacity version of a battery the charger may still stop charging the battery when it reaches the lower capacity of the original version of the battery for which the charger was designed. The newer versions of the charger for that battery will continue to charge until the higher capacity has been reached.

Also note that "75%" may well mean anything between 50% and nearly fully charged with some systems that don't provide an exact percentage. I'm not familiar with the Nikon system to know if once you start using the battery it will decrease in increments of 75%, 74%, 73%, etc. or 75%, 70%, 65%, etc. or even 75%, 50%, 25%, etc. In the past some Canon batteries used with lower tier models would show 25% for a range from 0-25% capacity, 50% for a range from 26-50% of capacity, 75% for a range from 51% to about 95% of capacity, and "Full" for 96-100% of capacity.

Answer 4

Try discharging the battery to see if it clears some of the memory the tend to build up if they are used only a little bit before they are recharged. Same as a battery conditioner.