How much battery capacity is lost annually?

[Stealth_Chopper]

"Pajda's Storage 50% SoC is without a BMS equipped battery. No one has yet too explain why dogman dan has the belief that a Full (or 95%) SoC when battery is equipped with a BMS is preferred rather than a 50% SoC for winter storage."

Pajda is testing batteries, not assembled battery packs, and the minor loss of battery capacity during these and other Pajda tests tell me the batteries are not the cause of the effects likely described as 'battery pack capacity' loss.
Right?

 

[john61ct]

Yes, different issues being conflated here because they seem similar.

True self-discharge is just decline in SoC% and usually involves only the cells. I have seen top quality LFP sit untouched for 12+ years with no detectable self-discharge. While some li-ion chemistries may lose a few percent of SoC per month. Temperature is also a factor.

So, once you have tested and know the SD rate, use that to inform how frequently you check voltage and top up as needed.

Now, at the whole-pack level, if the BMS is still connected while in storage, that adds another cause of the cells getting drained, and it is much more difficult to determine how much higher the SD rate may be.

Now, a third completely different concept is introduced - loss of CAPACITY. Nothing to do with the above dropping of SoC%.

As a battery WEARS out, its State of Health percentage is its loss of capacity. Can also happen in storage unused - called Calendar Wear but much much more slowly, as above varies by chemistry and build quality. Temperature a huge factor in calendar wear as well.

But usually cycling in use renders a pack scrap much faster, long before calendar wear becomes a significant factor.

 

[john61ct]

Excellent, well stated

 

[eMark]

There is no disagreement when it comes to ebuilder's two posts explaining why a 100% SoC for long term storage is NOT good practice for a Li-ion battery. The two posts here and posts in other threads by ebuilder have provided insightful informaton based of his wealth of real-life experiences. His freely shared knowledge is a valuable addition to these ES forums ... Welcome Aboard :thumb:

No one has yet too explain why dogman dan has the belief that a Full (or 95%) SoC when battery is equipped with a BMS is preferred rather than a 50% SoC for winter storage."

See explanation at top of this page as to the reality of what dogman dan is really expressing--harsh real world usage.

In the 1st paragraph i understand it's his belief that even with a 100% SoC over winter and topping it up at least monthly over the winter "two years of use is nearly certain". He's basing his sentimant on "real world harsh use" by the majority of ebike and standup escooter owners (see 2. 3. 4. at top of this page), NOT what's good for a Li-ion battery, but at least 2 years of use is nearly certain (his opinion?) even when stored fully charged.

About two years of use is nearly certain, provided you do store it full for a bms equipped battery. Meaning top it up at least monthly over the winter. Non bms storage is different, store that half full.

It's here in the 2nd paragraph that dogman dan is saying that "real world use is much harsher" ... "storing it full or nearly full all the time" again referring to the vast majority of users who've heard or been told to keep it charged. And the only way they know it's fully charged is when the green light comes on (100% SoC).

My experience is that nobody uses or stores a battery the way NASA would use a battery in a spacecraft. So real world use is much harsher. Often too hot in summer, or too cold in winter, and with a bms, storing it full or nearly full all the time.

Two other neighbors with same adult Liberty Trike that have read the Instruction Manual and watched the Instructional video believe it's best to keep a full charge over the winter. Their understanding of battery chemisty is such that they believe the Instruction Manual and instructional video recommending fully charged for winter storage.

Never bought into 100% SoC over winter and have never used a BMS. Similar to other knowledgeable ES members who believe the best BMS is between the ears (with supportive tools). The result being more than 2 years of very usable service from my DIY Li-ion battery without a BMS.

Trying to explain why the Instructional Manual and Instrutional Video 100% SoC for winter storage is wrong would be a waste of my time (harsh reality). Thus i now see that what dogman dan is expressing is for the most part is "real world reality". Even so like dogman dan says they should still get at least two years of use out of the battery.

People on this forum are way more vigilant because we understand this stuff on some level.

But, if you aren't going to check on your battery throughout an entire winter and your battery has a BMS and you charge it only to 50% to preserve cell cycle life, better check on it periodically or it could die...especially a battery that has seen better days aka many cycles of use as all batteries lose capacity with multiple cycles.

Well Said ... :thumb:

The majority of ebike and standup scooter owners don't have a DMM. Their only clue is with their redlight/greenlight charger as to when their battery is fully charged.

The last time dogman dan logged in was on 8/11/22. Hopefully, my explanation of his intent ... "provided you do store it full for a bms equipped battery. Meaning top it up at least monthly over the winter." ... is not that he approves of it as the best procedure, but rather just stating the harsh reality with those without a DMM and only a redlight/greenlight charger as their guide.