How long will a fully charged battery keep it's charge?

I just got a spare battery for my 5D III. How long will it usually stay charged before having to re charge it?

Thanks,

Christian

Huh, I have left batteries in my case for months and they still showed a near full charge. LiIon batteries discharge VERY slowly.

Lithium ion has a low self-discharge rate, about 1-2% per month. However, as the battery ages, its 'full' capacity becomes less and less over time, so that the amount of electricity it can store when three years old is a portion of what it could store when new.

And oh yes I have had LiIon batteries (Canon brand ones) just completely die at around the 3 year mark. They were BP-511A's FWIW.

ben_r_ wrote in post #14250222
And oh yes I have had LiIon batteries (Canon brand ones) just completely die at around the 3 year mark. They were BP-511A's FWIW.

My BP 511's had a high mortality rate as well. Funnily enough my E Bay cheapies are working just fine.
I recently wanted an extra battery for my 1D4, I could get a Canon one for 109 pounds - so I bought a non OEM one on e bay far 9 pounds INCLUDING a charger! No it is not perfect (I don't think the weather sealing is up to much) but as a battery it lasts just as long as the Canon original.