Unplugging charger with battery still attached to charger

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Is there any problem with unplugging the charger while leaving the battery attached to the charger?  The reason I ask is that I am considering building a circuit with a photocell that detects when the 50% light on the charger begins to blink.  After the 50% light is blinking for a few minutes, my circuit will cut the power to the charger so that the battery will stop charging after reaching about 30% charge.  I'm concerned that without power, the charger may begin to deplete or damage the battery.  Any comments out there?
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Sam Kaplan

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Posted 2 years ago

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Eric

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Following this one :)
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Jacob

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AWESOME IDEA
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Jacob

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And if there is an issue, thats unfortunate and not your problem. We have warranties remember. The charger should have a cut off at 50% feature anyways because its good for the batteries as i have heard on here before.
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Eric

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Wonder where you heard that one ... LOL :D
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Adrian Ramirez

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I don't stop at 50%, but I do delay charge, which requires the battery to be on the charger while the charger is unplugged. I just use a 7 day timer and set it to turn on Thursday a couple hours before I get home to mow. Then I use the battery and don't put it back on the charger for 2 weeks. I can get about 3 mows out of one full battery, so I started only charging after 2 mows and time it to charge right before I normally mow.


I haven't had any issues yet, but I don't keep it on the unpowered charger for weeks or months, only a few hours, maybe 2 or 3 days max so far without issues.


We have a Keysight DC power analyzer at work, maybe I'll bring the charger there one day and see how much current it consumes while unplugged. The analyzer is pretty awesome, can measure down to nA.
(Edited)
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Blue Angel, Champion

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Ever thought about that approach before... if leaving the batteries on the charger has no negative impact, I could use my WEMO (smart wifi connected plug) to turn the charger on remotely from anywhere if I thought I needed to mow right when I got home!
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Brad Carey

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I love this idea. I'm new to my mower and I often mow the grass on a spur of the moment decision and I don't like the idea of waiting for the 7.5 battery to charge before I can begin. Setting a timer for early Saturday morning would have it ready for the weekend but avoid it sitting fully charged all week long. I see this of a middle ground that works well for me and is better for the battery.
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Eric

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Testing iHome and WeMo myself now.  This is a great idea that I completely did not think about.
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(a)Typical Engineer

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Two things Li-Ion batteries don't like is being over charged, and being left in a depleted state.  I will usually use my tools, and if I run them down to red, I will let them cool for a few hours, and them re-charge them to 50%, and then shut-off the charger.  I would not leave a battery that is red until the next weekend (or longer).
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Blue Angel, Champion

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While we know the cells are safe down to a certain depletion voltage, there is likely a set voltage in the Ego battery system below which the battery will no longer charge. We would be wise to make sure that the battery could not be drawn below that point while sitting in the unplugged charger, no?
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Adrian Ramirez

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Good point. The charger probably has an under-voltage limit somewhere. The normal limit that I've seen in all designs I've looked at is 2V per cell, as thats pretty conservative for safety concerns. But I've also seen accidental limits higher than that because of noise issues in some designs. And since I have no idea where Ego sets their lower limit, i would agree it's probably best to stay away from the lower side.
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Adrian Ramirez

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Oh, and the battery doesn't appear to have any switch that I could find which would prevent it from being charged. It looked to me like all of their charge protection was in the charger.
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Blue Angel, Champion

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Agreed, though the battery does have the ability to communicate with the charger and could simply tell the charger not to proceed if it had monitored activity outside pre-set parameters. I would think at a minimum cell-to-cell voltages would be monitored inside the pack.
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Adrian Ramirez

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Yeah, you're probably right
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David HD, Champion

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Sam, below are my answers to your questions.  Sorry if they are "redundant" to other answers from above.  That said; I normally try not to "run down" my batteries during use.  In addition, I will not "fully charged" my battery until the day I do yard work.  This way, I don't have to worry about storing my batteries at 100% charged for more than a week.

Q1: Is there any problem with unplugging the charger while leaving the battery attached to the charger?

A1: No.  It is quite "safe" to leave your battery on the charger "plugged in" or "unplugged."

Q2: I'm concerned that without power, the charger may begin to deplete or damage the battery?

A2: EGO battery pack is equipped with an advanced self-maintenance function to extend the battery life. Depending on the battery charge, it will automatically perform a self-discharge operation after one month of storage. After this self-maintenance, the battery pack will enter sleep mode and maintain 30% of its charge capacity. If stored for a month or longer, fully recharge the battery before the next use. It is not necessary to run down the battery pack charge before recharging. The Li-ion battery can be charged at any time and will not develop a “memory” when charged after only a partial discharge. Use the power indicator to determine when the battery pack needs to be recharged.

Q3: This was not your question, but have been asked before as to "overcharging" of the battery?

A3: In the Operation Manual of the Standard Charger, bullet point #6 stated that the battery will not overcharge once it is fully charged (see picture below).


Standard Charger Manual (Operation):

(Edited)
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Eric

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Exactly my point as has been discussed in the previous charger / battery thread.  The "should have happened a month ago if we were looking to avoid damage feature" is really a moot point should they have spent that time / resources with a few minor tweaks of the charger instead.  A two or three button system would have been much better.  1) Do nothing, I'm just storing the battery here 2) Storage charge, i.e. put it at roughly 40% voltage or 3) charge it, getting ready to use it.
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Blue Angel, Champion

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Agreed that there's room for improvement.

Marketing is a tricky thing, though, and the average person wants the easiest solution. There's a fine line between offering features the customer will see as useful, and features that are just confusing. At some point some customers will compare two products, and see the Ego charger you suggest as "too complicated". In their mind the competitor's product doesn't require all that extra maintenance so it must be better. They both have warranties, right?

I'm willing to bet that the vast majority of users, even given the system you describe, would end up doing nothing with it and the on-board storage mode of the battery would end up managing itself anyway.

Believe me, I find it absolutely MADDENING that our world needs to be dumbed down to the lowest common denominator, but that's just the way things are... mass market products need to appeal to the masses. The same people who buy trucks and SUV's to commute to work with and then complain about the price of gas.
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Eric

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Sadly can not argue that point.  Personally I still feel it's the responsibility of vendors to give the option of doing the right thing to customers, and if they choose to ignore it that's another matter....
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Blue Angel, Champion

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Options are always good as long as they don't scare people! ;-)

One option I'd love to see in an ubercharger would be the ability to stop the charge at 80%. Not only would this drastically reduce the charge time, but for those who don't need the whole capacity of the battery to do the job it would remove the need to ever get the battery to full capacity.

My Makita 18V charger has this function. It doesn't stop at 80%, but it lights up to let you know it's there so you can remove the battery.

Add that to the wish list! Lol
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David HD, Champion

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I am one of those people who might need a "refresher" charge to finish the job, and not have to wait for a "complete" charge.  Love the idea and agree with you that "newer" generation EGO chargers should incorporate this ... :-)
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Blue Angel, Champion

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The more I think about this the more I'm really liking this idea of being able to remotely initiate charging. However, one thing we have not yet discussed is the impact of plugging the charger IN with the battery connected. That tiny insignificant detail slipped my mind! :-)

Gonna have to check that out.
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Adrian Ramirez

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I haven't looked at it on an oscilloscope, but I haven't had any problems with mine yet. My timer uses a magnetic relay to enable the 120V power.
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Adrian Ramirez

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The other thing you could do is wire a switch into the thermistor wire of the charger since it uses that for battery detection. Opening that wire should make the charger think there is no battery installed. Then you don't have to remove power from the charger
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Eric

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And Adrian Ramirez has done quite a bit of battery research, good to see more people doing this!

szwoopp, no I don't think Adrian is stating that at all.  Those things definitely have an adverse impact to the overall performance, reliability, and lifespan the battery.  Not only do the factors impact the cycles of the battery, but they can also change the internal resistance of the cells as well as capacity.  It's multiple factors that play into the long term (or short term if you do it wrong) life of the batteries.
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szwoopp, Champion

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All right - that makes sense - thanks for straightening me out.

And Jacob if we are talking an extra year over and estimated 5 - 7 year life - then I come up with a potential 20% increase. 
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Blue Angel, Champion

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Eric, Adrian designs Lithium Ion Battery Management Systems for a living. If anyone here knows their batteries, it's probably him! :-)
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Eric

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That would explain things :D
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szwoopp, Champion

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Step 1 on my road to be a better battery user.  Mowed the grass last night and did not put the battery on the charger when I was done.  I will wait until I am ready to mow again and charge before I use it.
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It is quite "awesome" to see the level of knowledge some of us have regarding Li-ion battery.  As for me, I follow the recommendation of the manual and try to protect my batteries for "long term" use - since I am "investing" in this technology.  That said; here are the steps I take for my batteries:

Before Use
  1. Charge my battery to 100%
  2. Remove battery "only" after charger fan stops
During Use
  1. Use appropriate battery for each tool (per EGO recommendation)
  2. Try not to "drain" down to 0%
After Use
  1. Store battery inside the house after battery cools down
  2. Store battery off of charger until the following week and repeat all steps
I am no Engineer by trade, but use "common sense" to protect all my power tools for "longevity."  In my previous post, I included an article from Battery University on how to "prolong" your Li-ion battery.

Below is another article "recommending" similar steps on how to "protect" your Li-ion battery.  From what I have seen, you can get "super technical" to "simple" regarding who you are talking to - as for me, I am somewhere in the middle!

http://lifehacker.com/5875162/how-often-should-i-charge-my-gadgets-battery-to-prolong-its-lifespan
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Adrian Ramirez

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Battery university is a great website, I've used it many times and highly recommend it. It is owned by a company out of Canada called Cadex and I was honored to be able to work with them on a project at my last company. We did our battery design in house, so I didn't really get to work with their battery design group, but their manufacturing engineers were the best I've worked with. Out of ICCNexergy, Electrochem and Cadex (the only 3 battery manufacturers I've worked with so far), Cadex comes out on top.
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Thanks for the perspective!  I reference Battery University website quite a bit for myself.  I love how they explain everything from "super" technical (tables and charts) down to a "simple" paragraphs.  I always learn something new from this website ... :-)
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Brad Carey

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I missed the appropriate battery for each tool discussion, apparently. Can you give me a summary or point me to the thread(s)?
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Blue Angel, Champion

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Brad, I believe David is simply referring to not using the small 2Ah and 2.5Ah batteries in the larger tools (mowers, snowblower etc). They will work, but may not drive the tool to its full potential and will offer very short run times.
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Dang Blue, you are way too fast with your fingers.  I was typing a response to Brad and you beat me to it .... That said; that was exactly what I was trying to communicate below ... :-)
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David HD, Champion

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No wonder .... you are "gifted" with 31 fingers, while the rest of us only have 10 - not fair Blue .... LOL!!!!!
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Jacob

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He has a mental uplink to the site.
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Sorry Brad but you missed the HUGE block party Blue & Adrian had over the weekend ... it was a Li-ion battery BBQ Block Party.  Anyone who was anyone was there, sorry we missed you - just kidding!!!!




That said; my post was simply to say that I tried to use the "appropriate" Ah battery for each tool, to get the best performance of the tool and battery.  For example, a backpack blower would work with a 2.0Ah battery, but EGO recommended 5.0Ah or higher for greater performance - that was it.
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Brad Carey

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I didn't realize battery size could have an affect on performance, I thought only run time was affected. It'll be interesting to see the real world difference between the 2.5Ah and 7.5Ah in the 21" SP after my Bermuda goes "carpet mode" as I like to call it.
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Brad, like I said in my post from above, I am not a Li-ion battery guru, but I try to keep up with the knowledge of this "current" technology.  That said; the link below is a good read from Pro Tool Reviews on How It Works: Lithium-ion Batteries Explained.

This article ( April 2013) will gives you a good perspective on the different Ah batteries and how they are made.  The article is about 4 years old, but good enough to help you understand why you should use the "appropriate" Ah battery for each tool - happy reading .... :-)

https://www.protoolreviews.com/news/how-it-works-lithium-ion-batteries-whats-the-big-deal/5331/
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Sam Kaplan

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It is interesting how far this conversation has deviated from my original question, but some of your comments and observations have been informative.  However, one thing still puzzles me and that is: how do you know the charge level of a battery after use?  I notice that after using my new 7.5Ah battery in my EGO lawn mower for about 40 minutes and then placing it in the charger, it is not clear that the blinking lights tell how much charge is left in the battery.  Upon placing the battery in the charger I first see the 25% light blinking and after about a minute the 50% light starts to blink.  After a couple more minutes the 75% light starts blinking, at which point I removed the battery from the charger.  Does this mean that, when first placing the battery in the charger, there was still at least 50% charge remaining?  I'm sure the battery is not charging that quickly, and so I suspect that it takes a while for the charger to learn what the battery charge level is.  Can anyone comment on how to determine the approximate level of battery charge after use?
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Brad Carey

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Great question because I too have noticed that it often goes quickly from only the 25% light up to the 75% light.
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Blue Angel, Champion

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If it jumps quickly to the 75% light it's probably safe to assume the battery had more than 50% charge remaining. If it jumps to the 50% light and holds there the battery likely has over 25% charge remaining. If the charger sits with the 25% light flashing for a while and the indicator on the battery hadn't yet started glowing red in use, the battery likely had between 15% and 25% charge remaining.

Not too scientific, but I think that's about as good as we can do with the Rapid charger as a guide.
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Eric

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Probably a fair assessment.

From my personal knowledge, just like charges of the past technologies, most current chargers still use calculations that vary during the process.  These calculations are primarily based off of the current reading voltage from the full or individual cells (depends if individual cells or the whole pack is being changed).   It isn't as easy as somehow reading there's 3200 of 7500 left to change.  That's how we do it in other hobbies/technologies, so assume the EGO charger is doing something similar.

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