Battery Question

[Jack Dawe]

The battery for my EOS 7D2 takes just over an hour to charge. Very often I forget that I've put it on charge and only remember two, three or four hours later. Apart from wasting electricity, does over-charging damage the battery in any way? My battery doesn't seem to last quite as long as it used to, but I'm thinking that's probably just a matter of age. Just curious.

 

[Lyn2011]

The battery for my EOS 7D2 takes just over an hour to charge. Very often I forget that I've put it on charge and only remember two, three or four hours later. Apart from wasting electricity, does over-charging damage the battery in any way? My battery doesn't seem to last quite as long as it used to, but I'm thinking that's probably just a matter of age. Just curious.

Your battery is probably a bit old. I was told that over-charging is not good for safety reasons. Some chargers turn off automatically (gardentools from Stihl) when fully charged. But with camera and phone battery sometimes I forget it too. The battery from my old Canon SX50 is getting weaker, looses power when not in use and doesn't last long.

 

[Anton Largiader]

If a charger goes from red to green when a battery reaches full charge, then it’s not doing much (if anything) after that. It’s not ideal to leave it like that forever because the charger will try to keep it topped off (which might mean an occasional dip back into a charging mode) but a few hours or overnight isn’t anything to worry about IMO.

 

[Jack Dawe]

Many thanks for those thoughts!

 

[Wilt]

• The battery for your Canon is 'intelligent'...there is a monitoring circuit that stops charging (maybe it actually goes into slow charge 'trickle' mode) when the battery capacity is attained...uncertain about that)
• The battery for your Canon uses lithium in its construction, and starting from the day it is made it begins to slowly deteriorate and lose total capacity...so when it is 5 years old, it holds less total electricity (Amps) than when it was new, even though it retains its original Voltage.
• 'Fast chargers' are more harmful to batteries than slow chargers, because the build-up of HEAT in the charging battery is harmful to it. So the 'very fast' chargers for quickly recharging RC batteries harms them much more rapidy than the 'fast' chargers that take a couple of hours, The quick chargers that sense battery heat are the ones which do less damage.
• and the 12 hours (or longer) chargers do the least harm IF they go into 'trickle' charge mode and the owner forgets the battery in the charger for days! Many 'slow' chargers do NOT have trickle charging, and their usual 'slow' mode allows heat to continue, so long term battery storage in even slow chargers can harm them!

 

[Jack Dawe]

That's very useful info, Wilt. Thank you!

 

[gjl711]

An outstanding resource to learn more than you ever wanted to know about batteries is Battery University.

Learn About Batteries

Battery University™ is a free educational website offering hands-on battery information.

batteryuniversity.com

THe articles of most interest for the 7D would be these:

BU-204: How do Lithium Batteries Work?

Learn about lithium-ion batteries and their different types. They have high energy density, relatively low self-discharge but they also have limitations.

batteryuniversity.com

BU-808b: What Causes Li-ion to Die?

BU meta description needed...

batteryuniversity.com

BU-808: How to Prolong Lithium-based Batteries

BU meta description needed...

batteryuniversity.com

BU-802a: How does Rising Internal Resistance affect Performance?

How does rising internal resistance of a battery affect performance. Sulfation and grid corrosion are primary contributors.

batteryuniversity.com

There is much more as well. Very interesting read for those interested in batteries.

 

[West Coast Birder]

Good posts, Wilt! Yes, Battery University is an excellent site for learning more about this subject.

One minor correction:

/Pedant mode on

Batteries deteriorate with time, so older batteries hold less energy than newer ones.

Energy in this context in watt-hours or more specifically for small batteries, millwatt-hours. Often, battery capacity is listed as milliamp-hours at a fixed voltage, which is equivalent to milliwatt-hours since a milliwatt is simply the product of voltage (volts) and current (milliamps).

/Pedant mode off

 

[Capn Jack]

The battery for your Canon is 'intelligent'...there is a monitoring circuit that stops charging (maybe it actually goes into slow charge 'trickle' mode) when the battery capacity is attained...uncertain about that

and the 12 hours (or longer) chargers do the least harm IF they go into 'trickle' charge mode and the owner forgets the battery in the charger for days! Many 'slow' chargers do NOT have trickle charging, and their usual 'slow' mode allows heat to continue, so long term battery storage in even slow chargers can harm them!

Those statements seem contradictory. If the Canon battery is intelligent, it will stop the charging.

 

[Wilt]

Those statements seem contradictory. If the Canon battery is intelligent, it will stop the charging.

You are correct in pointing out the lithium ion battery protects itself...that second quoted statement of mine applies to NiMH chargers.

 

[gjl711]

You are correct in pointing out the lithium ion battery protects itself...that second quoted statement of mine applies to NiMH chargers.

One thing to keep in mind, name brand batteries protect themselves. Once you get into third party, it gets fuzzy. Reputable manufacturers like StirlingTek or Wasabi have never been an issue but once you get into the cheap China batteries, all bets are off. They might be protected but they might not.

 

[Capn Jack]

You are correct in pointing out the lithium ion battery protects itself...that second quoted statement of mine applies to NiMH chargers.

Are you sure? There was nothing mentioned about NiMH batteries in your post that indicated a change of subject. We were discussing Canon batteries and lithium ion batteries.

• The battery for your Canon is 'intelligent'...there is a monitoring circuit that stops charging (maybe it actually goes into slow charge 'trickle' mode) when the battery capacity is attained...uncertain about that)
• The battery for your Canon uses lithium in its construction, and starting from the day it is made it begins to slowly deteriorate and lose total capacity...so when it is 5 years old, it holds less total electricity (Amps) than when it was new, even though it retains its original Voltage.
• 'Fast chargers' are more harmful to batteries than slow chargers, because the build-up of HEAT in the charging battery is harmful to it. So the 'very fast' chargers for quickly recharging RC batteries harms them much more rapidy than the 'fast' chargers that take a couple of hours, The quick chargers that sense battery heat are the ones which do less damage.
• and the 12 hours (or longer) chargers do the least harm IF they go into 'trickle' charge mode and the owner forgets the battery in the charger for days! Many 'slow' chargers do NOT have trickle charging, and their usual 'slow' mode allows heat to continue, so long term battery storage in even slow chargers can harm them!

 

[ChuckMiller]

Those statements seem contradictory. If the Canon battery is intelligent, it will stop the charging.

Which part interrupts the charging, the battery or the charging unit? It doesn't seem likely that the battery can disconnect an internal circuit.

 

[Wilt]

Good posts, Wilt! Yes, Battery University is an excellent site for learning more about this subject.

One minor correction:

/Pedant mode on

Batteries deteriorate with time, so older batteries hold less energy than newer ones.

Energy in this context in watt-hours or more specifically for small batteries, millwatt-hours. Often, battery capacity is listed as milliamp-hours at a fixed voltage, which is equivalent to milliwatt-hours since a milliwatt is simply the product of voltage (volts) and current (milliamps).

/Pedant mode off

Batteries store electricity in the form of chemical energy, converting it back to electricity as needed. 'capacity' is measured in 'amp-hours'...MilliAmp hour means how much current a battery will discharge over a period of one hour.

Are you sure? There was nothing mentioned about NiMH batteries in your post that indicated a change of subject. We were discussing Canon batteries and lithium ion batteries.

Sure about what?!
In my earliest reply, I had errantly included statement that applied to NiMH chargers (but not necessarily to chargers of Lithium batteries) Lithium has danger of fire when overheated, so smart lithium battery is often (I am not implying 'always'!) a feature for prevention of fire.

 

[Anton Largiader]

... 'capacity' is measured in 'amp-hours'...

But only in the context of a predefined voltage. When you take that away, it's Watt-hours.

Pushing an amp across 100V for an hour takes a lot more energy than pushing it across 1V for an hour.

 

[West Coast Birder]

But only in the context of a predefined voltage. When you take that away, it's Watt-hours.

Pushing an amp across 100V for an hour takes a lot more energy than pushing it across 1V for an hour.

This.

Like I said in my earlier post, capacity is simply the energy stored. Energy is measured in Joules or in the context of electrical system, in watt-hours. Watts are of course a measure of power which is energy expended per unit time, so it makes sense that the product of power (watts) and time (hours) is energy (watt-hours). Since power is voltage times current, you can also, for the sake of convenience, state capacity as Amp-hours (or milli-amp hours) at a fixed voltage. So, a battery that has 5 mA-hour capacity can provide 1 mA of current for 1 hour across a potential difference of 5V (this is all ideal situation and other factors come into play in reality).

I happen to be an electrical engineer in real life, so I can't pass up an opportunity to be pedantic about this stuff!

 

[Anton Largiader]

I was a battery guy for a long time. We nearly always used AH for capacity, because we were all on the same page about what the voltage was (usually 12).

 

[West Coast Birder]

I was a battery guy for a long time. We nearly always used AH for capacity, because we were all on the same page about what the voltage was (usually 12).

Absolutely. Your post was right on the money.

 

[Capn Jack]

Which part interrupts the charging, the battery or the charging unit? It doesn't seem likely that the battery can disconnect an internal circuit.

Lithium battery packs have circuitry that do things such as manage the charging and "balancing" the cells. Within a battery pack, some cells will have more capacity or charge faster than others. Balancing the cells means that those fully charged either aren't charged further, or the energy they have is used to top off the slower cells. Depending on the company making the cells, there is a range of protection for lithium batteries ranging from minimal to very good. This link is but one example of battery protection and balancer- this one has overvoltage protection: https://www.ti.com/product/BQ29200#features

The conclusion is that the battery package can interrupt the charging independent of the charger.

Batteries store electricity in the form of chemical energy, converting it back to electricity as needed. 'capacity' is measured in 'amp-hours'...MilliAmp hour means how much current a battery will discharge over a period of one hour.

Sure about what?!
In my earliest reply, I had errantly included statement that applied to NiMH chargers (but not necessarily to chargers of Lithium batteries) Lithium has danger of fire when overheated, so smart lithium battery is often (I am not implying 'always'!) a feature for prevention of fire.

I understand now. There was no mention of "NiMH" in your reply, so one would reasonably expect the comment to be about lithium ion batteries.

• The battery for your Canon is 'intelligent'...there is a monitoring circuit that stops charging (maybe it actually goes into slow charge 'trickle' mode) when the battery capacity is attained...uncertain about that)
• The battery for your Canon uses lithium in its construction, and starting from the day it is made it begins to slowly deteriorate and lose total capacity...so when it is 5 years old, it holds less total electricity (Amps) than when it was new, even though it retains its original Voltage.
• 'Fast chargers' are more harmful to batteries than slow chargers, because the build-up of HEAT in the charging battery is harmful to it. So the 'very fast' chargers for quickly recharging RC batteries harms them much more rapidy than the 'fast' chargers that take a couple of hours, The quick chargers that sense battery heat are the ones which do less damage.
• and the 12 hours (or longer) chargers do the least harm IF they go into 'trickle' charge mode and the owner forgets the battery in the charger for days! Many 'slow' chargers do NOT have trickle charging, and their usual 'slow' mode allows heat to continue, so long term battery storage in even slow chargers can harm them!

 

[ChuckMiller]

@Capn Jack
Thank you for the info.