Battery Confusion for Li-Polymer

Dear All

I am having a attached Battery.

The part no is LP602040 (3.7V/450maH) Capacity.

now the attached image shows me Charging voltages is 4.2v.

and Battery Nominal voltage is 3.7v

If i charged at 4.2v then will it not damage?

Kindly explain how the Battery Chemisry exatly works.

and what is voltage of charger i need to apply in the CC/CV Mode.

Totally Confused..

Thanks
Marx

Hi,

Please check below links:



https://en.wikipedia.org/wiki/Lithium-ion_battery#Charging_procedure

Amit

you need to set your charging current, not voltage i believe... then stop charging when battery gets above 4.2V i think.

OK Treez.

I suppose to be battery Voltage would be 4.2v after Charging.

But Datasheet shows the Nominal Voltage is 3.7v

What is 4.2v and What is 3.7v..?

Confused..!!

I have been researching this for quite some time, and agree, its all terribly confusing.

There seems to be no consensus on what is best, but "best" depends on what you are trying to achieve.

Do you want maximum battery performance, and are prepared to accept a short battery life to get it, or do you want your battery to last ten or fifteen years ?

If its going into some high discharge hand held gizmo, you probably want maximum battery performance between recharges.

If its a $10,000 solar battery storage bank, you care less about performance and expect not to have to replace that battery after only six months of use.

Same (or similar) battery chemistry, widely different expectations.

What seems to be going on here, is that these lithium cells seem happiest at around 3.2 volts. They will last forever at that voltage, and it corresponds to about 40% to 50% of stored capacity.
They have negligible self discharge at 3.2 volts, and that is normally how they are supplied when you buy them.

Minimum voltage at end of discharge is about 2.9v to 3.0v depending on rate of discharge, anything less will reduce battery life. Every time you over discharge the battery it causes slight but irreversible damage and reduced capacity.

At the other end of the scale charging up to about 3.4 volts will be nowhere near full capacity, but the battery will last for years if you never charge beyond that.

Charging up to 3.7 volts will get you near maximum capacity, but it will cause an accelerated life reduction, and self discharge will also increase.

Charging at 4.2 volts is about the limit of useful capacity, but again it is a trade off of performance versus battery life.
It may be a good tradeoff for some small high rate of discharge application, where the batteries are taken straight off the charger and immediately used, and high self discharge from that elevated voltage is of no interest.

Over four volts you gain nothing in capacity but can seriously irreversibly damage the cells.

So what is correct ?
I really do not know, it depends on what you expect from the battery.

The wider the voltage swing either side of 3.2 volts the more you are punishing the battery, but the higher the performance will be, up to a point !

The hot tip seems to be not to float charge these cells.
Run full charging current up to the cut off voltage, then completely stop charging.

The cutoff voltage might be anywhere from 3.4 volts to 4.2 volts.

The battery manufactures know all this, but they also know that if they say charge to 3.4 volts, their battery capacity will be very poor and not competitive with competing batteries.

If they advise charge to 4.2 volts, their battery will have a huge capacity but will quickly die, but they never mention that.

If YOU were a battery salesman, trying to sell a lot of batteries, what would you advise ?

Thanks Warpspeed..

Good Explanation in simple manner..!!

Never mind using a Li-Po battery at only 3.2V because then it is dead and its load should be disconnected. A Lithium rechargeable battery is charged with a limited current (at its rated capacity current or more) until its voltage reaches 4.20V then its charging current is measured and continues until it drops to 1/40th of its rated capacity, then it should have the charger disconnected. Its voltage drops like all batteries as it discharges, from 4.2V to 3.2V then its average voltage is 3.7V. The Li-Po batteries that I buy are always 3.7V to 3.8V and that is the voltage I store them at during winter.

Go to www.batteryuniversity.com to read all about it.

Yes, that is fine for the very small Li-Po batteries.

For the larger more expensive ones where you expect to get many years of life, the recommend voltages are rather lower.
Something like 14.4v for four cells or 3.6v per cell maximum charging volts for automotive use.
Anything over 4.2 volts is pretty lethal to long life.

https://www.ev-power.com.au/-TECHNICAL-ARTICLES-.html

EV power are the biggest supplier in Australia for the larger Li-Po batteries used in electric vehicles (EV) and solar power storage, where many years of reliable service are expected.

The article about electric vehicles talks about the lower voltage LiFePO4 batteries they use, not the higher voltage Lithium Cobalt batteries that we are talking about.

What is the Battery Voltage vs State of charge/battery capacity gor LI-POLYMER 3.7V..??

Bjtpower said:

What is the Battery Voltage vs State of charge/battery capacity gor LI-POLYMER 3.7V..??

Click to expand...

The voltage vs state of charge is not accurate because the battery voltage drops as it is discharged then its voltage returns when resting without a load but its capacity does not return unless it is charged.
The voltage also changes after it has discharged a little depending on if it has a load or not.

A cell phone or laptop computer uses an accurate history of discharges with the current and duration recorded then it accurately reports the state of charge.

yes, that is a problem with batteries of lithium, you can only know state of charge accurately if you have logged all the charge going into it and coming out of it historically. That is difficult with portable radios which people take out of the charger, then they put them back with the charger having had no idea what charge was taken out of the portable radio when it was carried around...so they get round it by just jamming charge in as much as poss without overvoltaging it, and its not ideal , but is the only way.

The question, "What charge state does voltage x correpsond to?" is the commonest question in the world of batteries and there is no answer to it.

If I want my Lithium rechargeable battery powered item to run for its maximum duration then I measure the voltage of its battery cell and select one that is more than 4.1V.