More Bad Press for Lithium Batteries

Greg Elmassian

Greg Elmassian

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I agree and have seen both cases, I have seen computers that are plugged in 99% of the time for years and battery fine, and others that were in the same usage and the battery was bad within a year.

Nowadays, this happens less often because the batteries are lithium, and overcharging them usually results in fireworks... so the chargers are better. In the old days, as I said, chargers were not all of the same quality / "smartness" and it's very hard for a user to determine what the "smarts" of the charger are..

What was true most of the time 10 years ago is not necessarily true now..

Greg
 
GAP

GAP

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I agree and have seen both cases, I have seen computers that are plugged in 99% of the time for years and battery fine, and others that were in the same usage and the battery was bad within a year.

Nowadays, this happens less often because the batteries are lithium, and overcharging them usually results in fireworks... so the chargers are better. In the old days, as I said, chargers were not all of the same quality / "smartness" and it's very hard for a user to determine what the "smarts" of the charger are..

What was true most of the time 10 years ago is not necessarily true now..

Greg
I am guessing the the charger is built in because there is only a mains to Dc converter plugged into the computer.
 
J

John Le Forestier

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No..

A Li-ion battery looks very like any other cell you think of commonly.. - It is 'just' a different chemistry inside.

View attachment 263823

Left to right:
A '3S' block of 18650 Li-ion cells, an Eneloop NiMH 'AA' cell, a 14500 Li-ion cell..

Note the 14500 cell is physically the same size as the 'AA' cell, but 3.77V (as opposed to 1.2V for the Eneloop). - The difference being the Li-ion cell has a 'flat-top' positive terminal, which is 'better' (larger surface-area) for making into packs / having tags spot-welded onto.

So the Li-ion 'cells' are a metal can, just like the Eneloop cell. - Both will vent if abused, by the 'gland' around the positive terminal.

Li-ion cells are more robust, as the outer is metal, and the internal construction is more uniform.

A Li-po cell is (basically) a plastic-pouch, with flexible electrodes (and separators).. These can then be 'folded' into different shapes, or rolled-up, to fit into a soft/hard outer plastic case.

Part of the 'problem' with Li-po's is this folding, as it stresses the construction, and quite often brings the electrodes closer together. - This causes a 'point of stress' in the package as a whole.


Does that help at all?
Very much. Thanks!
 
justme igor

justme igor

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Sorry to say, i don't want to offend anybody, but THE secret is so very simple......regardless the mix in the lithium chemistry......
Balancing and cycle count (cycle count.....if you don't have the proper testing equipment....)
With 3 cycles a day...throw them away before winter.....buy new in spring...
With 100 cycles a year....buy new in 5 or 6 years....
Never charge them higher then 4.00v or discharge them to lower as 3.00v per cell that is.....(a good balancer is on ali 1 euro to 5 euro....depends on your demands of course...)
The cells will be very happy to: surf you for 700 cycles(one charge and one discharge is one cycle)
With this voltige span they can have 1500 cycles, before ANY danger.....even up to 5000 cycles if bought the right cells and with proper equipment.

To keep it simple....

Best
 
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Greg Elmassian

Greg Elmassian

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Not really a secret, cycles vs life has been published for many years. How they are charged and how they are discharged are the main factors in battery life.

One very important thing you did not touch on (or at least with the right numbers) is the percentage of discharge affects the total usable wattage over life.

You need to look at battery life in terms of watt hours you get over it's lifespan, i.e. how much you really "get". Lower discharge percentage (meaning top up whenever you can) will give more watt hours over it's lifetime.

Discharging down to 3 volts is the WORST battery life. Better to run the batteries "half way down" and charge up twice as often than run them as low as you can go...

This is one of the very big distinguishing factors of Lithium rechargeables.

Greg
 
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Paul M

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This is one of the very big distinguishing factors of Lithium rechargeables
That is what I have difficulty with, it used to be the case that the more you charged the battery the quicker the battery would die, but now it's a case of NEVER let the battery go anywhere near flat!
 
justme igor

justme igor

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@ greg,
You hit the nail right on the head.
My view on "standard" li ion chem is most from battery university.
The majority of the li ion cells (90%) can be discharged to 2.8v and charged to 4.2v.
If you discharge them to 50% (dod) you would have a v span from 3,2v to 3.8 volts.
Meaning in my eyes if you need 12v for your motor and 4 amp to play for four hours, you will need a pretty large pack.
When we look at the curves in varios chards there is not much above 4v or below 3v.
Now 12v with li ion is tricky 3s or 4s? I would take 4s and a voltige regulator.
If you would take 80% dod (3v to 4v) you can run much longer with less cells, but they will have a shorter life.
What could this mean for the cell's cycle life in the long run....probably 400 to 600 cycles extra, in your watt story: absolutely nothing.
Cous if you take more watts out 1 cycle and thus reduce his cycle life, or take less watts out and extend his cycle life, you are absolutely right.
The worst cycle life is if taken the full v span, 2.8v to 4.25v--> 400 to 600 cycles, depending on manufacturer.
From 3.0v to 4.0v would mean 6-700 to 8-900 cycles.
from 3.6 to 3.8 could mean up to 4000 cycles.
But what is the best watt/life/cycle ratio? I think that depends on the type of use you intend to, a 100kwh powerwall for your house is quite a different setup than for a 1.2v 0.2a motor.
If you really want to have a long life span or the most watts out of a device, than there are a lot of other chemistry's.
With li ion in this situation, i think they will rust away before they are giving up.
Lets assume 900 cycles, that would be 3 years every day one complete cycle, if you only drive in the weekends that would be 9 years...
Assuming you can complete one cycle in one driving day assuming your packs are big enough.
I have packs running that reaches there 1500st cycle and still holds 60% (soh)of there original capacity.
But i keep my c rate around 0.5 to max 1.5.
If they drop below 45ish% soh i change the whole string for lifepo.

With this, so sorry to say, i dont agree on your quote:
Discharging down to 3 volts is the WORST battery life. Better to run the batteries "half way down" and charge up twice as often than run them as low as you can go...

This is one of the very big distinguishing factors of Lithium rechargeables.
My answer:
If you run the cells halfway down from 4.2v to 3.6v you will get not even 50% of the total capacity from a cell.
The culprit area in li ion cells are the 4.0v to 4.2 v span and 2.8v to 3v span, if you leave those area's unused you will get a double amount of usable watts back in the same cell life, however, it is very good for the cells health to charge it all the way up and discharge it all the way down once in a while, every 100 cycles or so.
You can charge li ion in every state of discharge, no need for difficult charging.
Run them as low as you can go??? i think you mean: not below 2.8v, i hope
Even if you take some charge out of the cell, it is not necessary to charge it immediately back up, you can drain it all the way down(max 2.8v) and then charge.
For a period of no use (~3 months) it is advisable to put them away around 3.8v, longer period of time 3.6v, but never put them fully charged or discharged away for longer then 3 months.

To keep it simple for people that dont want to dive into the deep like we did:
Charge to max 4v per cell, discharge to max 3v per cell.
Meaning if you have 3 cells in series max charge would be 12v and max discharge would be 9v.
You can charge the battery every time all day long and drain it 5% 50% or even 100%, just after use ---> charge, but...never ever exceed the max volt on a cell.
For discharge they can handle some abuse, but it is very wise to have a protection, like a volt cut off(diode, relais, v regulator ect) or bms.
Also a very important thing: balance.
You can buy very cheap bmses from ali express:

For charging li ion you can use almost anything, but dont exceed the max volt and as a golden rule dont charge more than 3 times the total ah.
Better is 50% of the ah.
The same applies for discharge.
Example:
If it is 3 cells of each 2000mah in series: 12v max and max 6a charge or 9v discharge at 6a.


Best
 
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stockers

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Blinking 'eck. I'll stick with digital.:)
 
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Michael

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In summary :) , from the battery university website:

Most Li-ions charge to 4.20V/cell, and every reduction in peak charge voltage of 0.10V/cell is said to double the cycle life. For example, a lithium-ion cell charged to 4.20V/cell typically delivers 300–500 cycles. If charged to only 4.10V/cell, the life can be prolonged to 600–1,000 cycles; 4.0V/cell should deliver 1,200–2,000 and 3.90V/cell should provide 2,400–4,000 cycles.

On the negative side, a lower peak charge voltage reduces the capacity the battery stores. As a simple guideline, every 70mV reduction in charge voltage lowers the overall capacity by 10 percent. Applying the peak charge voltage on a subsequent charge will restore the full capacity.
As a result of this I have been charging mine at between 4.0 and 4.1 volts per cell and never let them go below 3.4 volts. I also did some did discharge comparison tests on my 4 cell battery packs at charging voltages of 4.0, 4.1 and 4.2 volts. The reduction in capacity was in line with that given by the battery university website.
 
Greg Elmassian

Greg Elmassian

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Igor, sorry not only do I disagree with you, but you are dead wrong in some statements.

With this, so sorry to say, i dont agree on your quote:
Discharging down to 3 volts is the WORST battery life. Better to run the batteries "half way down" and charge up twice as often than run them as low as you can go...

This is one of the very big distinguishing factors of Lithium rechargeables.
My answer:
If you run the cells halfway down from 4.2v to 3.6v you will get not even 50% of the total capacity from a cell.
The culprit area in li ion cells are the 4.0v to 4.2 v span and 2.8v to 3v span, if you leave those area's unused you will get a double amount of usable watts back in the same cell life,
however, it is very good for the cells health to charge it all the way up and discharge it all the way down once in a while, every 100 cycles or so.

The part in RED is really wrong.

So, reading battery university does not make you an expert, but clearly you have not even read it through. Re-read what you can find, and when you come back and state you realize that is dead wrong, I will converse with you again. Until then you are not in a position to really tell anyone anything in MY opinion.

By the way, I have been studying rechargeables for 40 years, have several college degrees in directly related areas, and most importantly, have learned as the "common wisdom" has changed.

Sorry to be so forceful, but you are presenting BAD information to people who may not realize you are wrong.

If you are willing to learn, contact me by email and I will give you the information to substantiate what I say. I don't wish to debate this on the forum.

Greg
 
justme igor

justme igor

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Greg Elmassian Greg Elmassian
I am a hobbyist and by no means an expert, i hope you accept my apologies, i did not mean to offend you nor to spread wrong information.
What i stated was what i remembered and build my powerwall on.(106kwh in li ion)
I will gladly take your invitation to improve my knowledge with both hands, thanks for this opportunity.
Where where you 6 years ago?
Many thanks in advance, i will send a email.
 
GAP

GAP

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Greg Elmassian Greg Elmassian
I am a hobbyist and by no means an expert, i hope you accept my apologies, i did not mean to offend you nor to spread wrong information.
What i stated was what i remembered and build my powerwall on.(106kwh in li ion)
I will gladly take your invitation to improve my knowledge with both hands, thanks for this opportunity.
Where where you 6 years ago?
Many thanks in advance, i will send a email.
You built a 106KWh battery 6 years ago and have not blown yourself up yet? Hats off to you.

With that experience I think you may just have a bit of knowledge/authority to give advice on how to build a battery that powers small electric motors and some other small power accessories.
 
Rhinochugger

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Paul M

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They have beer in them, do they?