Questions conserve battery polymer lithium and lithium

[John rodrigues]

To preserve the useful life of lithium batteries and lithium polymer it is necessary to keep them charged I have the removable batteries BP-5L and BM20, what is the monthly discharge rate of these batteries? would i have to carry them 1x per month?

 

[c_mitra]

Yes, you should charge them before you store. It is generally suggested (depends on the manufacturer) that the cell should be charged to 50% and NOT 100% before you store. You should NOT store the charged cells for more than 1 year at room temp. For best performance during use, charge them to 80% capacity and discharge them to 20% (No deep charge or discharge). The % levels are related to the open terminal voltage and are easily measured. Unfortunately the datasheet for these two batteries are not discoverable ( means I cannot find them).

 

[John rodrigues]

How often should I charge these batteries that are stored? some speak 1x per month others say 1x per year, what is the truth?

if i recharge it at 50% and stored it will need constant charges

BP-5L 1400-1800mah BM20 2000mah

 

[c_mitra]

I quote from memory:

You may charge Li-ion batteries to 50-60% of their capacity, measured by their terminal voltage, before storage. You can safely store them for 1 year at room temp. If you wish to store them for another year, you need to charge them to 80-90%, use them with a load to discharge them to 10-20% and then charge them again to 40-50% before you store for one more year. I do not know how many times this can be repeated.

 

[John rodrigues]

If I charge these batteries 100% and store them for a year, will it be good for the conservation of these batteries?

 

[c_mitra]

I found one reference but this is not for the exact model of the battery you are going to use. But the characteristic we are discussing is broadly universal. see https://www.ineltro.ch/media/downloads/SAAItem/45/45958/36e3e7f3-2049-4adb-a2a7-79c654d92915.pdf

Batteries perform best when operated in the linear region of the charge -discharge curve. Unpredictable behavior can result if you charge 100% or discharge to 0% capacity. This in simple terms means that a battery labeled with a capacity of 2000 mAH has an usable capacity of 80% (or 1600 mAH) with 20% reserve for emergency application.

For routine use, charge batteries only to 90% of their labeled capacity. For extended storage, charge only to 50% of the capacity. Batteries are electrochemical devices and chemical reactions are notoriously difficult to to carry to 100% complete.

These are broad features that are applicable to most rechargeable cells. For example, you should not charge NiCd or NiMH batteries to 100% on a regular basis (or leave them on a trickle charge for extended period).

 

[John rodrigues]

For storage long period Recharging these BP-5L 1400mah and BM20 2000mah batteries in only 50% is it safe for her not to discharge before 1 year? if she discharges it will be very bad

i will use my chargers

 

[Audioguru]

If I charge these batteries 100% and store them for a year, will it be good for the conservation of these batteries?

Experts and www.batteryuniversity.com say to store a Lithium-ion or Li-PO battery at 3.7V per cell. If they are stored at 100% charge then they are slowly destroyed over a few months or 1 year. They also should not be stored or discharged below about 3.2V per cell.
The manufacturer of the Li-PO batteries that power my radio controlled model airplanes says to store them at 3.7V per cell over the winter. I do that and the batteries last for years. A circuit in the airplane pulses the motor as a warning when the loaded battery has dropped to 3.3V per cell so they there is enough power for a controlled landing then the unloaded battery voltage is about 3.7V for storage.
I have the Lithium-ion battery from my daughter's fist cell phone, it is 18 to 20 years old and is still 3.7V. I think it was 3.8V about 18 or 20 years ago.

 

[John rodrigues]

For BP-5L 1400 and 1800mah and BM20 2000mah batteries what % of charge should I store to charge again after 1 year?

 

[Audioguru]

Every "percentage of charge" indicator is different:
1) A voltmeter shows that 4.2V is 100% of a charge.
2) 2.1V is wrongly showed as 50% of a charge.
3) But about 3.2V is zero charge and about 3.7V is 50% of a charge. 3.7V is 88% of 4.2V. 3.7V is halfway between 3.2V and 4.2V.

A very cheap no-name-brand Lithium battery might lose its charge in 1 year. A good quality battery will not.

 

[John rodrigues]

my batterys

my charges

 

[Audioguru]

You must guess about the quality of your no-name-brand Chinese batteries.
On the other website forum I saw one that said "Samsung" but it might be fake.

 

[John rodrigues]

supposing that their quality is average because it is Chinese what is the answer to this question?

 

[Audioguru]

Good Quality Control lets all items to be good.
No QC means that there are some or many bad ones.

 

[c_mitra]

supposing that their quality is average because it is Chinese what is the answer to this question?

The reactions and the equations and the physics or chemistry are the same. The potentials are controlled by the Nernst equation (look it up!). The middle value, when both reductants and oxidants are present in equal amount, corresponds to 50% charged state (you can also call that 50% discharged state). basically it says (about the potential)


\[\displaystyle\]\[{E}_{ }=\]\[{E}_{ 0}+\]\[\frac{RT}{ nF}\]ln\[\frac{[Ox]}{[Red] }\]

From this equation you can see that 100% charge or 100 discharge is theoretically impossible (the log term becomes infinity).

Let us say that Ox is 1% and Red 99%; the ratio is approx 0.01 (easy to understand). We often use the Nernst equation is simple form:

\[\displaystyle\]\[{E}_{ }=\]\[{E}_{ 0}+\]\[2.303\frac{RT}{ nF}\]log\[\frac{[Ox]}{[Red] }\]

or, often we use \[\displaystyle\]2.303\[\frac{RT}{nF }\] as 60 mV (more accurately 59 mV but who cares?)

99% charged state will be equal to 120mV + the middle potential and 1% charged state will be -120mV + middle potential.

The middle potential for a Li-ion cell is about 3.7V and hence 90% and 10% points are about 3.7+/- 0.060V

The 99% and 1% points are, in the same way, around 3.7V +/- 0.120V

The system is highly non-ideal and these number are only theoretical values. The actual values are determined from the slope of the charge graph.

But it should be now clear why we want to store the cells at 50% charged (or discharged) state.

 

[John rodrigues]

storing these two batteries for long periods at 50% is the best option? at 50% the battery is zero charge before one year?

 

[c_mitra]

storing these two batteries for long periods at 50% is the best option? at 50% the battery is zero charge before one year?

Right.

If the battery is otherwise healthy, it will not become 0% charge after 1 year (perhaps 30-40% approx; not calculated). After 2-3 years at least 5-10% of the charge will be left. The battery should not be useful after 5 years. Best (use before) to use within 2-3 years of the date of manufacture.

This is a general guideline and assumes that the battery is otherwise healthy to start with. To extend useful life, use it with a load to discharge the battery to 10-20%, charge it to 80-90%, use with a load to discharge to 50% to store for one more year (should be good for 2-3 years).

Make sure that there is no corrosion at the terminals, there is no leakage (internal liquid coming out at the gasket), the battery is not bloated (should be discarded) or any sign of physical damage when you store for long term. Do not store at a place of excessive cold or heat.

The battery is NOT zero charge at 50%; at 50% the battery is in the middle part of the discharge curve. This is the point when the terminal voltage is arounf 3.6-3.7V.

 

[John rodrigues]

If I charge these batteries to 50% and store for 1 year after that period will these batteries be 0%?

 

[Audioguru]

High quality Name-Brand batteries might be at 49% in 20 years if you discharge them to 3.7V per cell.
Cheap poor quality cells might not be useable in one year.

 

[John rodrigues]

my batteries the BP-5L is an unknown chinese brand and the xiaomi BM20, how to store these batteries for long periods? are backup batteries