Babying LiOn batteries

[arnstein]

Battery University explains the lifetime of lithium ion rechargable batteries: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries .

Here is a table from that web page. DoD means "depth of discharge."

Depth of discharge​	Discharge cycles​	Table 2: Cycle life and depth of discharge A partial discharge reduces stress and prolongs battery life. Elevated temperature and high currents also affect cycle life.
100% DoD​ 50% DoD​ 25% DoD​ 10% DoD​	500​ 1500​ 2500​ 4700​

My interpretation is that my battery life is maximized if I haul out the charger when the battery dips to 50% full. If I were to only discharge the battery 25%, the lifetime discharge cycles would go from 1500 to 2500. However, each cycle is half as long, and I don't get twice as many cycles to compensate for this.

Well, that's one county reporting. What do you think?

 

[litos]

Using only the values on that table, and interpolating between them, i get the best overall value at 62,5% DoD with 1250 cicles. At 75% DoD i get the same overall value with 1000 cicles, as at 50% DoD with 1500 cicles, and only 4% worse than the best value.


Based on this, i would usually go down to 60/65% DoD, going down to 75% DoD if i needed the extra runtime.

 

[ChrisGarrett]

Sorry bud, but if you think DoD is the only parameter that affects the 'life span' of a Li-Ion, you're missing out. I read though the tables the other night and it's kind of mind boggling.

I paid $20.39 delivered for a pair of EagleTac 3100s. I don't use lights everyday, but if I were to get only 500 cycles of full power, out of each cell, that's 2 pennies per charge.

My brain waves are valuable to me and I don't plan on wasting them by keeping track of storage temperature, humidity, state of charge, depth of charge, charging at 100%, 95%, or 80%, etc., lol.

Use them and don't abuse them, but they're not pretty gold bars.

Knock yourself out, but there's a lot of crud to keep track of.


Chris

 

[Russel]

[...]My brain waves are valuable to me and I don't plan on wasting them by keeping track of storage temperature, humidity, state of charge, depth of charge, charging at 100%, 95%, or 80%, etc., lol.
[...]

Keep in mind that your brain, like your muscles and bones and such, is "use it or loose it". Simple mental exercise is good for your brain. You do want your brain to be strong...don't you?

 

[reppans]

Glad you started this post as I've seen that page before and it confused me.

I hope I'm wrong, but I don't think you are interpreting it correctly for two reasons: first, it specifically states, "the smaller the DoD, the longer the battery will last," and second, anytime the term "cycle" has been used in a battery context, it has been defined as a full cycle (eg. 5x20% DoD=1 "cycle"). So my interpretation of this is that if we keep topping up after 10%, we can get the equivalent of 4,700 full (0-100%) charge cycles - or put another way 47,000 charges of 10%.

The flip side to this is that constantly topping-up maintains high voltage levels, almost akin to storage at 100%, which loses 20% capacity per year - according to the next chart.

Then lastly, of course, is the number of full charge cycles you actually get in before the useful life of Li-ion expires (3-5yrs?).

FWIW, I like to understand how to maximize Li-ions, not so much for removeable cells, but for my iPhone and other non-removeable Li-ion products. Dead Li-ion batts are what usually get me to upgrade - and I hate transferring all my data and configuring new smart toys.