3.7V LiPo Battery Guideline

3.7v LiPo Battery Contents



LiPo Battery vs NiMH Battery

Parametric representation

  • Voltage
  • Capacity

Analysis of the loss capacity of 3.7V LiPo battery

3.7V LiPo battery charging

3.7V LiPo battery Electric vehicles & technical specifications

3.7V LiPo Battery Lists

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3.7v LiPo Battery Preface

This guide is intended to give people a better understanding of the 3.7V LiPo battery.

In daily life, we use lithium ion polymer battery in animal food device, car alarm, vehicle tracking, Bluetooth headset, mobile phones, laptop, personal digital assistant, blood pressure devices, body fat monitors……and more new applications of lithium polymer battery is also continually expanding.

Therefore, learning a 3.7v rechargeable LiPo battery is very necessary, we hope you can gain something from this guide.

Introduction of 3.7V Rechargeable LiPo Battery

Lithium ion Polymer batteries, abbreviated as LiPo, LIP, Li poly, lithium-poly(hereinafter referred to as”LiPo” battery).

LiPo battery is a rechargeable battery of lithium ion technology using a polymer electrolyte. As we all know, this new type battery now main uses in radio controlled equipment, personal electronics and electric vehicles.

These battery provide a higher energy than other lithium battery, but with long ran times and low-self-discharge rate. Moreover, they can be manufactured in any desired shape.

LiPo Battery                VS                   NiMH Battery


  1. Higher energy density
  2. Smaller and lighter
  3. Lower self-discharge rate
  4. Higher voltage output
  5. Faster recharge
  6. Good temperature tolerance


  1. Lower capacity
  2. Incompatibility sizes and shapes
  3. Have active material need be very careful


  1. High Energy Density
  2. Stardard size well compatibility
  3. More safer
  4. Completely discharged


  1. Much heavier, and limited on size.
  2. High self discharge rate
  3. Low voltage output
  4. Long charging time
  5. Unreliable foe low load devices

3.7V Rechargeable LiPo Battery Popular Models

3.7V Rechargeable LiPo Battery Parametric Representation

What we define a battery? It’s a rating system. This system allow us to compare the performance of a battery, and help us choose the best one battery pack to match our devices. If we want aware of the LiPo battery, we must learn two main ratings, capacity and voltage.

The Voltage of 3.7V LiPo Battery

The nominal voltage of a LiPo battery is 3.7V. If you want the voltage to be 7.4V, two batteries must be in series(which means the voltage get added together)

“2S” means there are two batteries in series.”3S” means there are three batteries in series. So a two-cell (2S) pack is 7.4V, a three-cell (3S) pack is 11.1V, and so on.

About Nominal Voltage

The  nominal voltage is  measured at the mid point between full charged and fully discharged based on a 0.2C discharge (where C is the rated capacity of the cell in mAh).  A single lithium battery cell  nominal voltage is usually shown as either 3.6V, 3.7V or 3.8V.

 A 3.7V lipo battery pack is composed of two or more lipo cells put together in series for increased voltage to 7.4V(2S1P), 11.1V(3S1P), 14.8V(4S1P), 18.5V(5S1P)… or in parallel for increased battery capacity.

LiPo battery pack configuration is denoted by the number of lipo cells in series and the number of lipo cells in parallel. 4S2P pack would have four cells in series, and two cells in parallel, using a total of 8 cells. 4000mAh 4S2P pack would have a capacity of 4000mAh (2 x 2000mAh), and a voltage of 14.8V (4 x 3.7V). It would internally consist of 8pcs 3.7V 2000mAh lipo cells. The lipo cells would be doubled up (2P part of 4S2P) to get 4000mAh, and there would be three in series (4S part of 3S2P) to get 14.8V (4 x 3.7V).

The Capacity of 3.7V LiPo Battery

Battery capacity, the amount of electric charge a lipo battery can deliver at the rated voltage. In other words, it’s a measure of how much power the battery can hold. The unit ensure is ampere hour, commonly seen milliamper hour(mAh or mA·h). How to convert mAh to Ah? Please see below:

How to convert mAh to Ah

The electric charge Q(Ah) in ampere-hours is equal to the electric charge Q(mAh) in milliamp-hour divided by 1000:

Q(Ah) = Q(mAh) / 1000

So amp-hour is equal to milliamp-hour divided by 1000:

ampere-hours = milliampere-hours / 1000


Ah = mAh / 1000

The capacity of the battery determines how long you can ran before you have to charge. The higher the number, the longer the run time.

Analysis the loss capacity of lithium polymer battery

After analysis the loss capacity of 3.7v lipo battery, we got the main reason is overcharge that charging voltage is over the prescriptive voltage (4.2V) and then keep charging. In this process of overcharge will result in loss capacity of 3.7v lipo battery. The main points are as follow

  1. The overcharge of graphite anode of 3.7v lipo battery
  2. The overcharge of positive reaction of 3.7v lipo battery
  3. The oxidizing of electrolyte when overcharging

Lithium ion will be easy deposited on the cathode and stop lithium ion implanted. The efficiency of discharge and capacity of 3.7v lipo battery will be lost.

  1. The circulatory lithium ion will be reduced.
  2. The deposit lithium ion of metal will be reacted with electrolyte to Li2CO3 and LiF.
  3. The lithium ion of metal will happen between negative and septum, and it may increase the internal resistance of 3.7v lipo battery.

Rapid charging is another way to lose the capacity of 3.7v lipo battery. When we doing rapid charging 3.7v lipo battery, the discharge current is high, polarization will happen on the cathode, lithium ion will deposit obviously. The main reason for loss capacity of 3.7v lipo battery when we rapid charging is the matter of electronic chemical inertness, such as Co3O4, Mn2O3 and so on. They break the balance of capacity between cathode and anode. But the losing capacity of 3.7v lipo battery is irreversible.

Self-discharge of 3.7v lipo battery is the losing capacity when the battery is not using. It have two conditions when self-discharge happened. No.1 is reversible losing capacity and No.2 is irreversible losing capacity. Reversible losing capacity is the capacity of lithium polymer battery will be recovered in next charging. Irreversible losing capacity is that the capacity of 3.7v lipo battery can’t be recovered in next charging. The influencing factor has the material of cathode/anode, technology, temperature and so on.

Rechargeable LiPo battery charging

The rechargeable LiPo batteries must be charged carefully. The basic process is to charge at constant current until each cell reaches 4.2 V; the charger must then gradually reduce the charge current while holding the cell voltage at 4.2 V until the charge current has dropped to a small percentage of the initial charge rate, at which point the battery is considered 100% charged. Some manufacturers specify 2%, others 3%, but other values are also possible. The difference in achieved capacity is minute.

Balance charging simply means that the charger monitors the voltage of each cell in a pack and varies the charge on a per-cell basis so that all cells are brought to the same voltage.

It is important to note that trickle charging is not acceptable for lithium batteries; Li-ion chemistry cannot accept an overcharge without causing damage to the cell, possibly plating out lithium metal and becoming hazardous. Most manufacturers claim a maximum and minimum voltage of 4.23 and 3.0 volts per cell. Taking any cell outside these limits can reduce the cell’s capacity and ability to deliver full rated current.

Most dedicated LiPo chargers use a charge timer for safety; this cuts the charge after a predefined time (typically 90 minutes).

3.7V LiPo Battery Electric vehicles & technical specifications


These batteries may also power the next generation of battery electric vehicles. The cost of an electric car of this type is prohibitive, but proponents argue that with increased production, the cost of 3.7V Rechargeable LiPo batteries will go down.

Hyundai Motor Company plans to use this battery type in its hybrid electric vehicles. A LiPo powered Audi A2 covered the record distance of 600 km without recharging on October 26, 2010.

There are currently two commercialized technologies, both lithium-ion-polymer (where “polymer” stands for “polymer electrolyte/separator”) cells. These are collectively referred to as “polymer electrolyte batteries”.
The battery is constructed as:
Cathode: LiCoO2 or LiMn2O4
Separator: Conducting polymer electrolyte
Anode: Li or carbon-Li intercalation compound
Typical reaction:
Anode: carbon–Lix → C + xLi+ + xe−
Separator: Li+ conduction
Cathode: Li1−xCoO2 + xLi+ + xe− → LiCoO2

Polymer electrolytes/separators can be solid polymers (e.g., polyethylene oxide, PEO) plus LiPF6, or other conducting salts plus SiO2, or other fillers for better mechanical properties (such systems are not available commercially yet). Some manufacturers like Avestor (since merged with Batscap) are using metallic Li as the anode (these are the lithium-metal-polymer batteries), whereas others wish to go with the proven safe carbon intercalation anode.

Both currently commercialized technologies use PVdF (a polymer) gelled with conventional solvents and salts, like EC/DMC/DEC. The difference between the two technologies is that one (Bellcore/Telcordia technology) uses LiMn2O4 as the cathode, and the other the more conventional LiCoO2.

Other, more exotic (although not yet commercially available) LiPo batteries use a polymer cathode. For example, Moltech is developing a battery with a plastic conducting carbon-sulfur cathode. However, as of 2005 this technology seems to have had problems with self-discharge and manufacturing cost.

Yet another proposal is to use organic sulfur-containing compounds for the cathode in combination with an electrically conductive polymer such as polyaniline. This approach promises high power capability (i.e., low internal resistance) and high discharge capacity, but has problems with cyclability and cost.

The Compare of Lead-Acid Battery, NiMH Battery & Lithium-Ion Battery

 There are three main types of battery in the cars, Lead-Acid battery, NiMH battery, and a lithium-ion battery. For electric cars, the lithium-ion battery is much better. You can see the advantages and disadvantages of the follows.

Lead-Acid Battery

The production process is much mature. The cost is lower than the other 2 types of batteries.

The electrolyte is not friendly with the environment. The working voltage & energy density are lower. The shape is limited. The weight is big.

The cost of lead-acid batteries is much lower than the type of batteries. But it limited by lower rating of charging & discharging for lower speed cars.

 NiMH Battery

The working voltage & energy density is higher than the lead-acid battery. It can support over-charging & over-discharging.

Memory effect is higher and the cost is higher, too. The most shape is columniform so that it can’t be used for the smaller applications.

Generally, it’s used for consumer electronics products.

Lithium-ion Battery

The energy density and working voltage are much higher than the other 2 types of batteries. It’s lighter without memory effect and friendly with environment. The battery life is long because of lower self-discharge. The shape is multiplex so that it can be used for different applications.

The cost is the highest. The working temperature is limited. The technology of lithium-ion battery hasn’t updated greatly.

It often used for 3C filed. More and more electric cars accept it.

Other Rechargeable 3.7V LiPo Battery Lists

Lithium Polymer Battery Applications

A compelling advantage of rechargeable lithium polymer batteries is that manufacturers can shape the shape of the battery almost as they wish, which is important for handset manufacturers to continue to develop smaller, thinner, lighter phones.

Rechargeable lithium polymer batteries are also becoming more popular in the field of radio controlled aircraft and automotive, where the advantages of lighter weight and increased runtime can be justified. For the above reasons and increased shooting speed, some airgun owners have turned to rechargeable lithium polymer batteries. However, special chargers for rechargeable lithium ion polymer batteries need to be protected from fire and explosion. If the rechargeable lithium polymer battery is short-circuited, it will also explode because a huge current flows through the battery instantaneously. Radio control enthusiasts take special precautions to ensure that their battery leads are properly connected and insulated. In addition, if a cell or bag is pierced, a fire may occur. Radio-controlled car batteries are usually protected by a durable plastic casing to prevent breakdown. Specially designed electronic motor speed control is used to prevent over-discharge and subsequent lithium ion polymer battery damage. This is achieved by a low voltage cutoff (LVC) setting that can be adjusted to keep the voltage of each lithium polymer battery greater than (usually) 3v.

Rechargeable lithium polymer batteries also occupy a place in the field of PDA and notebook computers, such as Apple’s MacBook series, Amazon’s Kindle, Lenovo’s ThinkPad X300 and Ultrabay batteries, OQO series handheld computers, HP (HP) Mini and Dell products featuring D-bay batteries. They can be found in small digital music devices such as iPod, Zune, Apple iPhone and iPad, and Sony PlayStation 3 wireless controllers. They are ideal for applications where small form factors and energy densities are greater than cost considerations.

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