Storing equipment and battery charge

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I've read that when storing equipment for an extended time, the battery should be stored at 40% charge capacity. Is this correct?
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Diana Payne

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Posted 2 years ago

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David HD, Champion

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Official Response
Diana, you are correct.  Below is the specifics for "long term" storage from the battery manual for your reference.


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Blue Angel, Champion

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Diana, the most important two tidbits from the manual page David posted are:

1. Charge the battery every six months (or so) if not in use.

2. The battery automatically prepares itself for storage by self-discharging to 30% capacity after sitting unused for 30 days. No need to worry about getting it to the correct state of charge, the battery looks after it for you.

The ease of proper care is one of the many things that sets Ego's battery platform apart from the competition.
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Abbot Pennings

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Blue Angel - I would appreciate a further clarification:  When I initially put the battery into long-term storage, are you saying that I can have the battery at full charge?  Then, if I recharge the battery every 6 months of non-use, are you saying that it is again OK to leave it sit at full charge?  Would this repeated cycle of self-discharging to 30% after a month pose any possibility of shortening the battery's life?
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Jeff L

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I take the notice to mean  that the battery does NOT have to be on the charger to discharge itself to 30% of its capacity after one month. 
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Ken, Champion

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The battery will self-discharge whether it's on or off the charger as long as it has been inactive for 30 days.

That said, I try not to leave my batteries at full charge for more than a few days. I'll run them down some with my leaf blower if need be.
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Blue Angel, Champion

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Abbot, the automated self discharge is designed to keep your batteries at optimal health compared to leaving them fully charged. As Ken pointed out, storing lithium batteries at full charge for long periods can have a negative impact on their capacity. It is for this reason you'll find that lithium batteries are always shipped with a partial charge since the manufacturer doesn't know how long they will be sitting on a shelf before they're sold.

My personal preference is to charge them before use instead of after use, which limits the time they spend at full charge, but that's the Obsessive Compulsive approach... Ego's built in 30 day/30% automatic long term storage mode is the 90% solution, and will allow you to have batteries ready to go whenever you need them.

To answer your question more specifically, yes, during longer periods of inactivity you can charge the battery fully every six months and the automatic long term storage mode will do its thing. The suggested six month charge intervals are, in my opinion, a "safety" approach by Ego to ensure the battery can never self-discharge to a critically low level and cause damage to the cells. This could potentially be an issue if someone were to store a completely discharged battery for a long period of time.

Considering these batteries are designed for many hundreds, if not thousands of charge cycles, a charge/discharge every six months will have a negligible impact on the battery capacity... age will affect the cells at a faster rate.

NOTE: When the battery is performing its self-discharge after sitting for 30 days, the end cap of the battery will get warm to the touch near the power button. This is normal as the battery dissipates its energy through a bank of resistors built into the circuitry. I pointed this out to Ego a while back and suggested a warning be added to the manual, but as far as I know nothing has been added yet.
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Eric

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We've discussed this already, EGO has a great battery, but horrible battery maintenance techniques (primarily due to flaws in their charge as likely a cost saving factor).  Their recommendations are just plain bad and wrong.

If you want to do it properly...  Charge your battery before use.  After you're done, charge it until only the 2 of 4 lights is lit and take it off the charger.  That is the best that you can do with the charger they have today.  The whole discharge after 30 days is marketing junk and the damage is well under way at that point...because science (plenty of articles out there if you would like to read more).

Storing at 30-50% is indeed correct and ideal for these types.  If you want to pop it on the charger to ensure it's still at 2 or so bars ever couple of months, that is fine.  However, if it's down, then your battery has already started to go bad as they should loose little to no charge (one of the benefits of this technology).
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Blue Angel, Champion

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Eric, there's almost no limit to the amount of babysitting one could suggest in order to ensure one gets the absolute maximum lifetime out of a battery.  You could implement a Nest thermostat-like "learning" feature that monitored your usage patterns and pair that with wifi connectivity and a smartphone app based on a geofence around the perimeter of your home that, on Thursdays only, would start charging your battery when you were exactly 30 minutes from home... all in an effort to minimize those critical minutes the battery spent at full capacity.

However, the law of diminishing returns would guarantee that the lion's share of that effort would be wasted. ;-)

In my opinion, Ego has come up with an outstanding solution that allows people to keep their batteries charged and ready to go whenever they need them, but discharges them during periods of inactivity (like off-season) to minimize the effects of storage at full capacity.  Of course there will always be technical types who will try to improve upon that system, which is fine, but for the other 99% of people who just want something that works this system is hard to fault.

Don't forget that most of the studies you will link to are based on charging these cells to a full 4.2V and letting them sit for extended periods.  Ego's battery management doesn't charge the cells to their full capacity, nor does it deplete them to their minimum capacity.  That in itself will have an immensely positive impact on the capacity loss due to both storage and charge/discharge cycling.

If we look hard enough at just about ANY mechanical or electrical system, be it an industrial application or a consumer product, there will ALWAYS be ways it can be improved upon.  Engineering is the art of a good compromise... unless you were around in the late 50's, your name was Kelly Johnson, and you had an airplane to build for the US Military. :-)
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Jacob

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I want to steal this quote.
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Eric

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Some valid points, but still not to THE point ;)  The 30 day system is just bad and should not be used.  A quick bump charge to roughly 30-50% is much better for the battery, period.  The fact they shave fractional volts on the top and have a higher low voltage cutoff is irrelevant in regards to the way over recommended voltage storage for a very long time if at full (and 30 days is a very long time for it to be stored over-charged, a week is technically quite a bit of time).  There is no valid argument to this point.  
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Jacob

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How much life will really be shaved off if they are left charged and discharge after 30 days? Are we talking 50 cycles? 100? High level please. I'm not a scientist.10%. 5%...
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Eric

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The problem is, there are tons of variables here.  If you search for research papers and technical documents, the data is out there.  Technically some of the things that happen are in very broad terms: The internal resistance of the cells can get worse, the capacity can go down, leading to both a hotter and weaker battery.   From an RC side, I would say on average I see poorly maintained cells that are hotter and hold roughly 20-25% less (of the same brand and rough age) than those that maintain them well from both a voltage and storage temperature standpoint.  Cycles however is harder to gauge as every cell is unique, and the cycle count is a VERRRRY average number and most of us don't have 10-100 cells necessary, to cycle thousands of times, to get accurate information.  Some of the industry points to up to even a 40% decrease in cycle with poor maintenance and storage.

An interesting read for example (if you want your brain to bleed) lol:
https://pdfs.semanticscholar.org/3ed3/04146557a1904030e3365dfe5a90527013d8.pdf
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Blue Angel, Champion

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I don't have a deep understanding of RC applications, but from what I can tell the batteries are generally LiPo cells that are wrung to within an inch of their lives pretty much every time they're used... an abusive environment for sure!  I don't think RC batteries could draw too many parallels with OPE batteries.

The PHEV examples are probably not too far off the reality of OPE batteries; high power cells that are asked to put out reasonably high power for long periods of time.  Where PHEV's differ is designed charge cycles; they are assumed to have hundreds of cycles per year.

If charged and depleted daily on a five day per week cycle, a PHEV battery will accumulate about 250 cycles per year (50 weeks x 5 days).  A residential lawn mower will likely see one fifth that many cycles, and that would be in a warm climate with year-round mowing once a week.  As you travel farther North that number approaches about half that value, somewhere between 25-35 cycles per year in colder climates where mowing is only done for six months or so.

(Unless you're a freak like me who cuts twice a week.)

So if we assume a 500 cycle life for a lawnmower battery, worst case scenario would be around 10 years of service.  Best case scenario?  Well, let's just say the batteries would die of old age before cycling would get to them.

Would that be shortened by leaving the batteries sitting at full capacity when not in use?  Sure, but the effect will depend on the cell voltage and the particular cells used... it has been shown that even a small reduction in the peak charge voltage has a hugely positive impact on capacity loss during storage.  That Ego vs Echo video on YouTube shows that Ego is charging their cells to a lower voltage than Echo is, so my bet is that Ego is on top of things from a storage perspective.

I'm pretty sure the average customer would be happy to get ten years of service out of a lawnmower battery. ;-)
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Jacob

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How can one find out how many cycles a battery has gone through? I want to know. Bet my 4 ah has over 300. Maybe even 400. It's almost out of warranty :(
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David HD, Champion

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A great question Jacob, I would be interested to know as well.  Maybe a great question for EGO engineering team ...
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Blue Angel, Champion

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Jacob, I'd say you could possibly have the most "experienced" battery and mower on the continent!  Ego should have a way to check charge cycles and then hand out a brand new battery to anyone completing 500, kinda like how Sabb used to give a new car to any original owner who clocked a million miles on one of their cars. :-)
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Jacob

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Hey ego we what a battery health device that wirelessly connects to our phones. Powered by the battery.

Talk about a sweet maintenance/ troubleshooting device. Live troubleshooting. Think of the possibilities.
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Jacob

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I think professional mower people have more time than I do of course.
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Blue Angel, Champion

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Quite possible, but how many pros are mowing with Ego mowers?  Not too many I'd bet.

Where's Steve Valdez? :-)
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Dane Earley

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Great comments so far. My plan is to also leave my battery at around 30% to 40% charged between uses. I've been putting the battery on the rapid charger until the 50% begins to blink then pull it off soon afterwards. One more important note re battery longevity: Store your batteries in a cool location whenever they're not in use. I believe below 60F is optimal but below 80F or so will do fine. I'll be keeping my batteries in my garage fridge which is kept at around 45F.
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Eric

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Typically you don't want them too cold, but yes, a very valid point for sure.
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Jeff L

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Would there be a problem taking a battery from cold storage to 80-90 deg, high humidity, charge and use it?  Condensation maybe?
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Blue Angel, Champion

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Condensation can be a real problem with electronics... it can wet places you never thought would get wet.  Though the electronics in the Ego batteries are fully potted, I might choose not to tempt fate.  Going from cold to hot AND humid on a regular basis might be asking for trouble.

A video reviewer on YouTube commented that they had accidentally left an Ego battery outside in the fall and got their first snowfall before they realized the battery was missing.  They found it in the spring after the snow melted and it worked fine after being buried all winter!  They can definitely handle some moisture but I still wouldn't go wetting them on purpose. :-)
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Amber F., Official EGO Rep

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Official Response
We have final word: unused batteries will automatically kick into self-storage after 30 days, whether or not they’re on the charger. Also, You may feel warmth from the button on the top of the battery- that’s normal.  Know that these are Lithium-Ion batteries that are designed to hold their charge for along time, so if your battery doesn’t kick into self-storage within 30 days, do not be alarmed.  It may take longer than that to actually trigger the self-storage discharge.
(Edited)
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Blue Angel, Champion

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Thanks for clarifying, Amber!
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Egocentric

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From kicking around this site, I have been trying to formulate my short term weekly in-between use method of storing batteries.  At first I was charging the battery immediately after use.  Then after reading some of the commentary here at this site, I decided to leave the battery as is when I pulled it out of the tool and charge it immediately before the next use.  But now I wonder if it would not be better as Dane mentioned above, to throw them on the fast charger and pull them off a few minutes after the 50% light starts blinking.  This should get them some place around 30%.   Am I doing anything for battery life or just assuaging the coward within (who does not die but only one death) that I am doing something positive.  Also I wonder what I may be doing to the fast charger, unplugging it under load.  I think it would be ill advised to pull battery off the charger under load, you will probably get arcing on the contacts and there could be a hydrogen hazard.   I am pretty careful to stop using the battery as soon as the red light comes on rather than to wait for it to blink.  But still it seems like it would be better to put a slight charge on them.  

Any thoughts from the Egomaniacs?         

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