A puzzling experience with LP-E6 batteries for 5D and 7D

[fotoray]

I recently had a curious experience with one of my LP-E6 batteries....

I have four LP-E6 batteries for my 7D.  All appear to be genuine Canon batteries - not counterfeit.  I have numbered them 1 to 4 and have them registered in my 7D.  I rotate them regularly and keep them charged using the Canon LC-E6 charger.

One day battery #2 would not accept a charge and was dead as a doornail when I put it in the 7D - could not operate the camera at all with this battery.

I put the battery aside convinced it was gone forever.   In spite of this, a couple weeks later I put battery #2 back in the 7D and saw a small trickle of life in it.   I then succeeded in charging the battery.  The 7D said it was 95% charged but had some degraded performance -- meaning only two of the three green bars were lit.

Batteries #1, #3, and #4 continue to work fine, so I am comfortable that my charger is working properly.

I accept that battery #2 may nearing it's useful life.
 
Or am I missing something?    Any advice on special battery care that I may not be doing?   

[CR Backup Admin]

That is strange.  The electronic circuitry inside the battery is supposed to shut it down before it discharges so much that it can't be recharged. (Li-on cells do die if fully discharged).  Apparently, there was a charge "bounce" that built up enough charge internally that it came back to life.  Temperature might be a factor too.

One of my 2-1/2 year old 5D MK II batteries now reads two stars, but it still takes 100% charge and lasts a long time.  The other 2-1/2 year old battery still read 3 stars the last I checked.

[neuroanatomist]

+1 on the strangeness, unless something untoward happened.  One thing many people are unaware of is the negative impact of high temperatures on Li-ion batteries.  If you leave a battery in a hot car for an afternoon, that could effectively kill it, especially if it was fully charged. 

Note that Li-ion batteries should be used frequently and lightly - unlike other types of rechargeables, Li-ion batteries have no 'memory' effect, and discharging them fully is deleterious over time (although that should not render them unable to take a charge, as ScalesUSA stated).   They do need to be used frequently - sounds like you rotate through them, and that's good.

[dr croubie]

My day job (well, not for long, today's my last day), is actually at a firm specialising in fast chargers for Lithium batteries. Blurb from our website:
"After 6 years of 24-7 cycle life testing with different lithium-ion chemistries, cells and packs from multiple suppliers, <company> has built a database containing over one billion records of test results. The Battery Knowledge Centre owns a knowledge base containing evaluations, profiles and in-depth studies on more than 100 battery makers and their products."

So i'll pass the question onto our guys here and ask them. if they don't know then i don't think anyone will...
I do know a bit about batteries, definitely a hot car is the best way to kill them. i've also heard (anecdotal) evidence of situations like yours being fixed by a few hours in the freezer.

I've actually had a problem similar to what you describe, now that i think about it. Customers ran down the battery almost to its failure point, then plugged it in to charge. The battery took on a little bit of charge, decided they were too low to charge, and switched off. However, because the unit in question was still plugged into the mains, our controller was powered on and kept talking to the batteries, depleting them slowly, past their point of no return. Once they hit that 'no return' stage that's it. chemistry changes in the batteries, dendritey things grow inside and can't be gotten rid of, chance of a failure increases a lot. (and failure means failure, explosions and the like, they're truck-sized batteries capable of 3000Amp short circuit current and can fail spectacularly)
end of that story was that we had to redesign our controller, and the customer had to get another few $k worth of batteries (i'm still not sure who paid for it though).

Thankfully, camera batteries won't fail so badly, but it does sound like you've done some permanent damage to it internally. What the inside of the battery looks like i don't know, but more than likely there's some circuitry in there that's powered on all the time, leaving a nearly empty battery alone for a while is a sure-fire way to kill it completely (whether you did or not for this one?).  was it in the camera being nearly discharged for a while before you tried to charge it? even in a damp or humid environment, leakage current does happen through the air (ok, very very very slowly) and will (very very eventually) kill it.

For our design (and maybe for the canon charger too), trying to charge it will inject a little bit of charge every time you attach it, then the charger will ask the battery how it's doing, and that's when the battery says "i'm not good enough to charge". unplugging it for 30s and trying again, you will eventually be able to charge it (which is how we fixed our problem above with a small hack of a timed relay), which may be what you (inadvertantly) did.

also, definitely keeping them fully charged in longer-term storage is a good idea, as is being cool and dry.

[dr croubie]

ps, i don't have my camera with me so can't check.

What type of battery are they? Lithium Phosphate, lithium, lithium ion, lithium polymer, etc?

[neuroanatomist]

What type of battery are they? Lithium Phosphate, lithium, lithium ion, lithium polymer, etc?

The LP-E6 is an 1800 mAh Li-ion battery.

Canon's DLC actually has a kbase article on the LP-E6.

[dr croubie]

Nice article there, one bit stuck out for me:
"The display shows each battery’s serial number, displays the last time it was charged, ..."

It depends how the camera works this, if it's "the last time you took it out of the camera before charging" or "the last time you put it back in the camera after charging".
But if it's "we know exactly the last time you charged it because there's a clock in the battery itself" then there's a thing, because that rtc has to be powered from somewhere, ie you leave a nearly-empty battery for a while and the internal clock will drain it until it's past dead (a good battery should turn all its sensors and clocks off before this point, but if it calculates the wrong 'point' then it can still be too far gone).

Does anyone have a battery they charged more than a day ago and not put it in their camera, can they check what date it says 'last charge'?


meanwhile, so far the response from my guys at work are:
"...it seems to me that the #2 battery has been deep discharged. It is illadvised to use this battery again..."
(he doesn't know it's a camera battery, so he probably presumes it's an electric car battery, in which case it can be unsafe to use it again. you're "probably" fine continuing to use it from a safety point of view, but it's definitely not going to perform optimally ever again)

he did raise another question, which in camera terms translates to "do you have a battery grip, or only use one battery at once?"

[neuroanatomist]

he did raise another question, which in camera terms translates to "do you have a battery grip, or only use one battery at once?"

I think even with a battery grip, the camera only uses one battery at any given time.  I do know that when I insert a fully charged and a partially discharged battery into the grip, the camera will drain the fully charged battery to the point where the two batteries are approximately equal, then start alternating between them from shot to shot based on the reported shutter count.  I do wonder how it handles operations like Live View or Video, though - does it switch between batteries during the operation, or only at a 'break' (could easily be tested).

[dr croubie]

he did raise another question, which in camera terms translates to "do you have a battery grip, or only use one battery at once?"

I think even with a battery grip, the camera only uses one battery at any given time.  I do know that when I insert a fully charged and a partially discharged battery into the grip, the camera will drain the fully charged battery to the point where the two batteries are approximately equal, then start alternating between them from shot to shot based on the reported shutter count.  I do wonder how it handles operations like Live View or Video, though - does it switch between batteries during the operation, or only at a 'break' (could easily be tested).

That's an interesting behaviour, but certainly understandable (and i should have thought of it already). Keeping the batteries at their highest level (ie, using the higher one before the lower one) is a good move by canon to keep battery life longer.

Electric car batteries connected in series have this thing called 'balancing' they do during charge, they engage resistors to burn off power until they all have the same voltage as the lowest cell. It (apparently) keeps the cells in better condition than if they were all different voltages (it does waste a lot of power though).

in the grip they're definitely not connected in series, that would double the voltage to everything, and i should have realised that they wouldn't be paralleled either without some kind of balancing...
I'd be interested too to see how it works under movie-mode, my guess is that since they say they can measure charge to 1%, as soon as one drops by 1% then it switches to the other (it's not so hard to keep it working during the switch-over)

[fotoray]

I originally posted this topic and appreciate the helpful feedback. 

Lithium-ion batteries do not have a memory problem, so the recommendation to keep the LP-E6 near full charge seems reasonable.  And to avoid full discharge!

The Canon LC-E6 charger circuitry prevents battery "overcharge", or overheating, so I often leave a charged battery in the (plugged-in) charger and grab it when needed.  This practice seems to maintain the battery at/near full charge - indefinitely.   

Anyone see a downside to this?



 

[neuroanatomist]

Anyone see a downside to this?

No, as long as you actually use the battery pretty frequently.  I don't think Canon makes specific recommendations, but Apple uses Li-based batteries in their laptops, and they recommend at least one cycle per month (a cycle is a full charge and discharge, but not all at once - e.g. one cycle could be 4 discharges to 75% capacity with recharges in between, or 10 discharges to 90%, etc.).

[dr croubie]

Anyone see a downside to this?

if the charger and battery circuitry are both designed properly, there should be absolutely no problem with leaving the battery constantly on the charger...

... but:
i wouldn't, a) because you can never fully protect against power surges. maybe the once every few year spike when it all goes wrong, it could easily arc over the internals of the charger and blow the battery (but then, you'd lose your pc, microwave, tv in that case too, if it happened).
b) charger constantly plugged in draws some power. constantly drawing some power produces some heat. some heat reduces lifetime of battery. maybe not by much, but it's nonzero. (and if any greenie comes past as says you should always remove everything from the wall socket to save carbon emissions, yes, that's true. or you could run your car for 2 seconds less each day, saves more carbon).
c) not relevant to you, but i've only got one battery. if it's not in the camera it's on the charger. if it's on the charger it's not on the camera. if it's not in the camera it's not taking photos. not taking photos makes me sad...