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 3 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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Adrian Ramirez

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I think there's enough buffer at the end of charge on these packs to keep the cells healthy for a while after the tools shut down. They're well over 3V after the cells relax and you don't really run into excessive capacity degradation or copper deposition until below 2V per cell. It wouldn't be smart to go all winter in that state, but a couple weeks are probably fine, assuming Ego has a good design that draws less than a couple dozen uA or so (which maybe isn't true, but I would think it is).

One cool feature of the Ego system is that the charger has a built-in cooling system that pulls air through the battery pack so that it can be charged quickly after using it.
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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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Blue Angel, Champion

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I think the main concern was whether the unplugged charger would somehow draw current from the battery. I don't believe this scenario is covered in the manual.
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Eric

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We've already discussed and proven time and time again that the self maintenance discharge is garbage and of little use.  By that time the damage is done.  I think this also does not apply here.

Agree about the main question here though, it's activation/deactivation of the AC to the charger WHILE the battery is installed.
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Blue Angel, Champion

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Garbage compared to what? All of the superior solutions being offered by Ego's competitors? Where are all of these superior solutions that would indicate Ego is behind the curve?

And who's we? I believe you are the one coming to these conclusions. ;-)
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Eric

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1) EGO's products are excellent, but still contain significant flaws that could be corrected.  What other vendors are doing is irrelevant.  Seat belts and air bags didn't use to be required and no one had them.  Didn't make it smart or correct.  

2) Because science.

;)
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Blue Angel, Champion

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Using your argument, today's cars should be considered "garbage" because they don't have Secure Foam yet:

https://www.youtube.com/watch?v=RnyhkBU1yaw

:-)
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Adrian Ramirez

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The discharge feature of the Ego battery is pretty helpful. It's not as helpful as it would be if I could choose when to do it, but it's still a great feature. The calendar degradation of li-ion cells is ongoing, so even though it takes a month for the feature to work, it still significantly reduces calendar degradation in the months following the discharge function, even though the degradation will be higher for that initial month. I think it's better than not having it at all.
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(a)Typical Engineer

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Until the BMS doesn't work, and then discharges your battery until it's a zero voltage (measured with a Fluke multi-meter).  Yes, this happened to a 5.0 battery, and Ego replaced it.  So while it's a good feature, that makes maintenance mindless, I too would prefer a switch to enable/disable that feature.
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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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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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Blue Angel, Champion

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eek... that's too close to the "voiding warranty" rabbit hole for me! :-)
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Jeff L

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I talked to Customer service about charging cycles for the lithium ion batteries.  He stated that a charging cycles one full charge from the red light.  partial charges are cumulative to a full charge, ie, partially charging the battery and then later finishing a full charge is one charge cycle.  Using a partially charged battery and recharging later would amount to one full charge +.  There is a site about how to prolong the life of  lithium ion batteries,  going to read up on this.
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Adrian Ramirez

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You're absolutely right Jeff. It also works for short cycles too. For example, a charge from 0% to 25% and then discharge back down to 0% would be 1/4 of a cycle and if you did that 4 times you would have an amount of cycle degradation equal to about one full cycle's-worth of degradation. The other half of li-ion degradation comes from calendar aging, meaning the battery just ages on its own when left alone at any voltage. It's less common for companies to perform calendar degradation testing because it's extremely time consuming and there's not presently a good way of performing accelerated life testing on this aspect of li-ion cells (except through mathematical chemical models, but then the accuracy of the model is in question and you would need test data to validate the model, so you're back to time consuming testing). But many companies (Ego included) perform accelerated cycle testing because you can run back-to-back cycles with little or no rest and get through hundreds of cycles in a matter of weeks or months, instead of years.

With calendar degradation, the higher the voltage on the battery cell, the higher the rate of calendar degradation. But extremely low voltage causes high degradation as well, and can also cause safety issues leading to thermal runaway (an un-extinguishable fire) in future cycles. It's generally best practice to store li-ion cells between 30% and 50% state of charge because that happens to be the sweet spot between low calendar degradation and long shelf life. Shelf life is limited by how much charge is on a battery cell, the lower voltage limit of that cell, and how quickly the cell discharges. How quickly it discharges is dependent on both the self-discharge rate of the cell itself and the amount of discharge that happens by the electronics that are attached to the cell. This is where the draw off the battery from an unplugged charger is important, because you don't want it to drain your battery really quickly to the point it can't be used anymore. And the Ego batteries don't have any internal switch (that I'm aware of) to turn them off when not being used, so any load on the battery would cause it to discharge indefinitely.

Depending on the use profile of a particular battery powered system, cycle degradation or calendar degradation can dominate the overall rate of degradation (or the two can be nearly equal). For my use of the Ego, I would estimate I use it for 28 out of 52 weeks here in Colorado. And since I can get about 3 mows per cycle on the 7.5 Ahr pack, that's only about 10 full cycles per year of degradation, which is a very small amount of degradation compared to the amount of time it sits in my closet. Without test data, it's difficult to compare the rates of cycle vs calendar degradation, but I'm fairly certain that 10 cycles a year is nearly nothing for these cells when compared to an entire year of mostly being stored. In my experience with other battery cell test data, a rate of calendar degradation of 3% per month when fully charged is not uncommon (although that % drops as the battery self-discharges, as long as it's not recharged). That number can be much lower, at less than 1% when stored around 40% or so.

With today's li-ion cells, it's not uncommon to get 1,000 cycles during cycle testing because the cycles are back-to-back and neglect calendar aging. But when the product enters the market and only sees maybe 10 or 20 cycles a year, the calendar degradation is not negligible and significantly reduced the number of usable cycles. In the case of the Samsung cells used in the Ego battery, I would guess maybe a 5 to 7 year life, so for me that would be 50 to 70 full cycles.
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szwoopp, Champion

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I am not following all of the details here but I am doing my best. 

Based on Adrian's concluding paragraph - is it then safe to say that for the average or nominal user where the battery is going to die from calendar long before getting close to cycles limit - all of the practices for long life i.e.
don't charge to 100%
don't store at full charge for a week
charge before using not after
let cool before charging
etc
really are not going to make much of a difference ? 
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Jacob

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Opposite actually. If you use the batteries all day every day the battery care would be irrelevant. If your getting 60 charges per battery for its life, you need to do everything you can to increase its calendar life.

If your a sad little man like me, ive got an estimated 400 to 500(rough estimate based on assumed values, but definately in that range) cycles out if my 4 ah battery... that battery will not die from age.

So if maintenance gives you another year, and you charge 10x per year, thats a 10% increase. I think.

This is just how I understood adrians post.
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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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