jonny round boy
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- Joined
- Jul 21, 2007
- Messages
- 3,227
So glad I asked [doh]
[big grin]
[big grin]
Storing LI battery packs on the charger
- Thread starter woodnerd
- Start date
Well whatever Litheon Ion is used in the Milwaukee 28 volt batteries is total junk!! Never held a charge for more than a couple days. We had 8 different V28 tools and got rid of them all. Had power but were always dead when we really needed them. Ok for daily use but not intermittant.
I also have a Pany 15.6 volt drill and it is fantastic. Heavy compared to my T15-3 but otherwise an excellent quality tool. Had it about 6 years now and still original batteries.
I also have a Pany 15.6 volt drill and it is fantastic. Heavy compared to my T15-3 but otherwise an excellent quality tool. Had it about 6 years now and still original batteries.
Ah..now we are getting into the quality of those battery cells..another topic altogether.
Workmanship and standards set for the quality of those cells are varied from manufacturer to manufacturer. The V28 line has been plagued form its inception with issues. They make a real decent tool, and I sell a fair share of them, but the cells...
Workmanship and standards set for the quality of those cells are varied from manufacturer to manufacturer. The V28 line has been plagued form its inception with issues. They make a real decent tool, and I sell a fair share of them, but the cells...
Ken Nagrod
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- Joined
- Jul 15, 2010
- Messages
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Let me try and clarify some things. 1st Milwaukee's V28 or any V series batteries are very different from the current M series in the cell technology and circuitry. THERE IS NO COMPARISON.
2nd Lithium polymer, without getting into the science lecture, is very similar to lithium ion but it allows the cell to be a shape other than cylindrical. As an example, cell phones with flat batteries, Apple laptops.
2nd Lithium polymer, without getting into the science lecture, is very similar to lithium ion but it allows the cell to be a shape other than cylindrical. As an example, cell phones with flat batteries, Apple laptops.
- Joined
- Jan 22, 2007
- Messages
- 1,641
There was a very good response to this topic on another forum. I was so impressed with the information presented that I asked the poster for their permission to re-post it here at the FOG. Because the person wished it to be credited to his first name and forum name, I removed the hyperlink that reveals his last name.
Louie (aka crazy4wood)
[quote author=Louie (aka crazy4wood)]
I am coming late to this discussion but have something to offer considering I am a lithium ion battery chemisty by trade (PhD + 8 years experience,Google Scholar me if you want my references --Link removed )
There are numerous literature accounts for the phenomenon of high voltage and high temperature excursions affecting cycle life of a battery. This is something that has been well known in the industry for probably 12 years.
Here is one link I was able to find quickly (most of my PDF's are at work). Scroll down to page 20 of that document for an example chart on the effect of storage & operating temperature on achievable cycle life. What that chart is showing you is that, at moderate discharge currents (1C), charging and discharging at 25C (room temperature) will provide over 100 weeks of operation (they provide a reference to the standard BSF cycle life routine) whereas a battery cycled comparably, but at elevated temperature of 45C will only provide 50 weeks of charge & discharge events.
As the other poster mentioned briefly, this degradation in achievable cycle life is due to an electrochemical oxidation of the electrolyte present in the battery solvent, by the lithium cobalt oxide cathode. Basically, as you approach a full charged state, which produces a 4.2V difference between the lithium cobalt oxide cathode and the graphitic (carbon) anode, the high voltage present on the cathode can decompose the electrolyte that plays a huge role in shuttling lithium ions back and forth between the two electrodes (which is how a lithium ion battery functions). When you introduce extended "stays" at the elevated voltage (i.e. leaving your battery fully charged all the time), the amount of irreversible electrolyte oxidation increases. Increase the temperature of the battery and again, the effect is increased. Couple the TWO of them and it is increased again. Working in the battery industry providing batteries for the military, we frequently get asked "how many cycles will this battery run out in the desert" (where temperatures of 40C are the norm and 50C is not uncommon) and the answer is "bring extra packs because you're gonna need 'em". The thing is, discharging the battery at higher temperature is not bad, because you are lowering the voltage as you discharge. It is the charging process and leaving the batteries fully charged that is the culprit.
Let's see, what else... Oh, you can charge a lithium ion battery fairly high, I have seen studies charging conventional lithium ion batteries all the way to 4.8V. And guess what? You get MORE run-time out of them! Problem is, for every tenth of a volt you go beyond 4.2V that is the standard "charge to" voltage, you probably reduce usable cycle life by 15% (let's say you would get 500 cycles by charging to 4.2V in daily use, you would reduce that to probably 40-50 cycles by charging to 4.8V in daily use).
The battery manufacturers are not stupid, the 4.2V value was carefully selected as a safe point to provide reasonable capacity numbers and reasonable cycle life.
So, would I leave a power tool battery on a smart charger knowing that the smart charger will trickle charge the battery when it senses that the battery voltage has dropped below xx voltage? No. That being said, as someone else mentioned, the self-discharge rate of a lithium battery is low, only 2-3% per month. If you charged the battery fully to 4.2V, you would literally have to leave it on that charger for probably 5 months before the smart charger would "think" that the battery required trickle charging... so its not like leaving it on the charger should be a problem.
.... and I am HUGELY guilty of coming home and charging my cell phone into the charger EVERY single night knowing that I am leaving the battery darn near fully charged.... but the thing is, these new fandangled phones these days generally discharge most of the way through during the course of a day, meaning my phone doesn't spend much time sitting at 4.2V while it is on...
Hope this information helps! I have plenty of more references if anybody is interested, just have to dig them up from my compiled database of articles.
-Louie
[/quote]
Louie (aka crazy4wood)
[quote author=Louie (aka crazy4wood)]
I am coming late to this discussion but have something to offer considering I am a lithium ion battery chemisty by trade (PhD + 8 years experience,
There are numerous literature accounts for the phenomenon of high voltage and high temperature excursions affecting cycle life of a battery. This is something that has been well known in the industry for probably 12 years.
Here is one link I was able to find quickly (most of my PDF's are at work). Scroll down to page 20 of that document for an example chart on the effect of storage & operating temperature on achievable cycle life. What that chart is showing you is that, at moderate discharge currents (1C), charging and discharging at 25C (room temperature) will provide over 100 weeks of operation (they provide a reference to the standard BSF cycle life routine) whereas a battery cycled comparably, but at elevated temperature of 45C will only provide 50 weeks of charge & discharge events.
As the other poster mentioned briefly, this degradation in achievable cycle life is due to an electrochemical oxidation of the electrolyte present in the battery solvent, by the lithium cobalt oxide cathode. Basically, as you approach a full charged state, which produces a 4.2V difference between the lithium cobalt oxide cathode and the graphitic (carbon) anode, the high voltage present on the cathode can decompose the electrolyte that plays a huge role in shuttling lithium ions back and forth between the two electrodes (which is how a lithium ion battery functions). When you introduce extended "stays" at the elevated voltage (i.e. leaving your battery fully charged all the time), the amount of irreversible electrolyte oxidation increases. Increase the temperature of the battery and again, the effect is increased. Couple the TWO of them and it is increased again. Working in the battery industry providing batteries for the military, we frequently get asked "how many cycles will this battery run out in the desert" (where temperatures of 40C are the norm and 50C is not uncommon) and the answer is "bring extra packs because you're gonna need 'em". The thing is, discharging the battery at higher temperature is not bad, because you are lowering the voltage as you discharge. It is the charging process and leaving the batteries fully charged that is the culprit.
Let's see, what else... Oh, you can charge a lithium ion battery fairly high, I have seen studies charging conventional lithium ion batteries all the way to 4.8V. And guess what? You get MORE run-time out of them! Problem is, for every tenth of a volt you go beyond 4.2V that is the standard "charge to" voltage, you probably reduce usable cycle life by 15% (let's say you would get 500 cycles by charging to 4.2V in daily use, you would reduce that to probably 40-50 cycles by charging to 4.8V in daily use).
The battery manufacturers are not stupid, the 4.2V value was carefully selected as a safe point to provide reasonable capacity numbers and reasonable cycle life.
So, would I leave a power tool battery on a smart charger knowing that the smart charger will trickle charge the battery when it senses that the battery voltage has dropped below xx voltage? No. That being said, as someone else mentioned, the self-discharge rate of a lithium battery is low, only 2-3% per month. If you charged the battery fully to 4.2V, you would literally have to leave it on that charger for probably 5 months before the smart charger would "think" that the battery required trickle charging... so its not like leaving it on the charger should be a problem.
.... and I am HUGELY guilty of coming home and charging my cell phone into the charger EVERY single night knowing that I am leaving the battery darn near fully charged.... but the thing is, these new fandangled phones these days generally discharge most of the way through during the course of a day, meaning my phone doesn't spend much time sitting at 4.2V while it is on...
Hope this information helps! I have plenty of more references if anybody is interested, just have to dig them up from my compiled database of articles.
-Louie
[/quote]
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