To Fully Charge or not to Fully Charge, that is the Question.

[Alexander108]

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I am (was) still struggling to find a way of dealing with my M10/M11 batteries. Keeping them fully charged, which is always advised against, seems not to be an option in an ideal world.  

I tried to find an answer given that I know that you should not store a fully charged Li-Ion battery. But is that the case? So I spent two hours or so to research this. 

Nerdy background:

• The typical Li-Ion battery max voltage is 4.2V per cell for a 3.7V rated battery (8.4V / 7.4V for two cells like Leica batteries). 
• However, a fully charged M10 (BP-SCL5) battery has a rated final voltage of approx 8.25V whereas the rated voltage is 7.4V.
• For some reason, a fully charged M11 (BP-SCL7) battery has a rated final voltage of approx 8.4V.
• Hence, the M10 battery won't be fully charged while the M11 battery will be fully charged.
• Researching some discharge diagrams I found that the M10 battery is charge only up to roughly 90% of the possible max capacity. 

I tried to find evidence of whether or not to store a fully charged camera battery. I found something in a Nikon manual:

• After 6 months of not using a battery: charge it and store it. No word of interrupting the charging process whatsoever. Just fully charge and store.
• Have a fully charged spare battery at hand.
• Have more than one fully charged spare battery at hand when shooting in cold conditions.
• It seems Nikon also pursued the more conservative and practical approach to charge their batteries (at least for that camera) to 90% max.

Leica states it differently in the M11 manual (there is no such comment in the M10 manual):

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To me, this is not a practical approach and I wonder why Leica went from charging to 90% only on the M10 to 100% on the M11. 

Key takeaways M10 batteries: 

• Leica M10 batteries are deliberately not fully charged by their chargers. This prolongs their lifespan.
• Storing a fully charged M10 battery is the way to do it. 
• Re-charge a stored and not used battery after 6 months.
• I will now change my paranoid practice of trying to keep batteries at 50% to 80%. Instead I will store them fully charged. This way I am always ready to shoot. 

Key takeaways M11 batteries: 

• Leica M11 batteries will be fully charged to 8.4V. 
• Storing a fully charged M11 battery should not be done. 
• Re-charge a stored and not used battery after 6 months.
• With M11 batteries I try to store them at 50% to 80%. Less practical but prolongs battery life. 

Is there anything in my thought process that you disagree with? Thank you!

[LocalHero1953]

I suspect some of the difference lies in the word 'storage'. Advice to keep them partially charged might apply only when you put batteries way for a long term. If you use them regularly and rotate them as I do, I see no problem in 'storing' them fully charged for the short term while they wait their turn in use.

Edited 10 hours ago by LocalHero1953

[PhotoCruiser]

I suspect also that importance lies in short term, or better how long short term is.
Having uncountable amount of batteries for many devices i usually charge them full, leave for 6 months to Costa Rica for work and when i returned i recharged them again. Ni-Mh, Li-Io, 12+36V LiFePo and 12V AGM batteries. The only ones who discharged completely and went dead were the 12V wet-cell batteries.
I run refresh cycles some times on A/AA/AAA batteries as their charger could do that.

All others get a full charge and then stored dry and cool for months, half year or even up to a year for some devices i rarely use.

There is probably a measurable higher degrade if fully charged then only 80% but the question is how much this degrade influence battery life.
My iPhone and MacBooks charge to 80% only as i have a setting or software who manage that, but on all other batteries i would need to disconnect them in the to me unknown 80/90% state of charge. The only charger what show SoC are the NiteCore USB chargers but then i would constantly need to check SoC to take the battery out to stop charging.

The only way to know would be to have same two new batteries and charge one to full and the other to 80-90% and then use them over years to check if and if so what charge system leads to longer battery life. That is not very scientific, but show real life battery life depending on charge method.

As most here use the original Leica battery in the original Leica charger and there is no particular complaints about log-term battery life i suspect that the Battery and Charger developer knew what he was/is doing.

Chris

 

[intangiblethings]

If digital Ms are never a “forever thing” I’m also not going to go through these steps to prolong my battery life.

It seems fairly good and affordable third-party M10 batteries have entered the picture which make me want to prioritize “grab and go” more than anything. 

[pgk]

I store and use my batteries as I need them. Some M8 batteries are still working after all this time. Life is too short to worry about the state of charge of batteries. When you need them they need to be charged. Best advice is simply to use them.

[marchyman]

9 hours ago, Alexander108 said:

To me, this is not a practical approach

May I ask why?  A calendar reminder to put your unused batteries on the charger for 15 minutes once every 6 months does not seem onerous.  That is the rule for unused batteries, i.e. batteries you are storing for the long term (many years) not batteries in use.

When I have multiple batteries that I rotate between I  charge them until full when I swap them out of the camera.  Will that give me maximum potential battery lifetime?  Probably not.  It's not something I tend to worry about.

 

[Alexander108]

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vor 1 Minute schrieb marchyman:

A calendar reminder to put your unused batteries on the charger for 15 minutes once every 6 months does not seem onerous.

That is not a problem as every battery will be used within 6 months. 

It is storing batteries at 50% and not being able to just grab the camera w/o charging first. 

I think the approach with the M10 battery with a maximum capacity of 90% seems most practical.

Although not ideal, leaving a 90% charged battery alone for 12 weeks does way less harm than with the 100% charged battery of the M11.

But I need to figure it out. The best approach I have seen were the DJI drone batteries. They automatically discharged to 80% or so after a few days. Recharging did not take long and the battery could barely be damaged. Those batteries were much larger, though.