Do you know about lithium iron phosphate batteries?
The difference between Cell, Batteries, and Pack
Cell: The most basic elements that make up batteries and packs, generally the voltage that can be provided is between 3V-4V;
Batteries: A collection of cells that form a single physical module that provides higher voltage and capacity (for example, a battery module that uses four cells in series to provide a nominal lifepo4 battery 12V, or multiple cells and for larger nominal 12V, or multiple cells and for larger capacity;
Pack: It is generally composed of multiple battery packs. At the same time, a battery management system is also added, which is the last product provided by the battery manufacturer to the user. That is, we often say lithium batteries.
The meaning, difference and characteristics of series and parallel
Series connection is one of the basic ways to connect circuit elements. Connect circuit elements one after the other, one after the other, end to end. A circuit formed by connecting various electrical appliances in series is called a series circuit.
Parallel connection is a connection method between components. It is a connection method that connects two same or different types of components, devices, etc. at the head and tail, and at the same time, the tail is also connected. It is usually used to refer to the connection of electronic components in a circuit, that is, a parallel circuit.
The internal resistance is different, the internal resistance in parallel is small, and the internal resistance in series is large;
The connection methods are different. The series connects the ends of the batteries, while the parallel connection connects the ends of the batteries in parallel;
The current flows in different directions. In series, the current starts from the positive pole of the battery and there is no shunt, while in parallel, the current is divided and combined in the circuit.
Features of tandem:
The current is equal everywhere;
The sum of the total voltage is equal to the sum of the circuit voltages of all parts;
The total resistance is equal to the sum of the circuit resistances of all parts;
The voltage at both ends of each part of the circuit is proportional to its resistance.
The total current is equal to the sum of the currents in each branch;
The voltages at both ends of each branch are equal;
The reciprocal of the total resistance is equal to the sum of the inverses of the resistances of each path;
The current flowing through each path is inversely proportional to its resistance.
Using correct units and abbreviations
A – amps, a unit of electric current.
V – volts, a unit of electric potential.
W – watts, a unit of power.
Ω – ohms, a unit of electrical resistance.
h – hours
k – kilo (SI prefix for 1000)
K – Kelvin, a unit of temperature.
m – milli (SI prefix for 1/1000)
M – mega (SI prefix for 1000000)
Current is measured in amps – A
A battery’s voltage is measured in volts – V
A battery’s current capacity is measured in amp hours – Ah
A battery’s energy capacity is measured in watt hours – Wh. Wh is simply Ah x V. Many times it is shortened to kilowatt hours – kWh. Example: 5120Wh or 5.1kWh.
An inverter is measured in watts – W. Many times a value is shortened. 4000W can be written as 4kW. Really large systems could be in megawatts (MW) or even gigawatts (GW). Small electronics might be measured in milliwatts (mW).
A wire’s resistance is measured in ohms – Ω. Many times the resistance is very small such as 0.002Ω commonly written as 2mΩ (two milliohms).
AC vs A/C – AC is alternating current. A/C is air conditioning
Did you write correctly?
The correct written form for lithium iron phosphate batteries is LiFePO₄, although most people find LiFePO4 much easier to type.
Incorrect abbreviations include LiFePO (lithium iron phosphorus oxide), LiFePo (lithium iron polonium), LiFePo4 (lithium iron tetrapolonium), LiFePO4 (use zero instead of capital O), LiFe (lithium iron), LifePo4 (wrong case in F and O).
Note that there is a type of lithium-ion polymer battery usually written LiPo. This is completely different from LiFePO₄. You don’t want to confuse the two types. Although both types are specific examples of the more general lithium-ion (Li-ion) battery.
Inverters: What size inverter should I get?
What do I do if I want 1kWh lithium iron phosphate batteries?
A 1kWh battery can have all kind of different physical sizes/shapes and electrical configurations, there is no standard or THE single solution for this.
If you have, for example, 2000mAh 18650s, then each of those stores 7.4Wh of energy, then you need 136 of them (1000/7.4 ~ 136) for a 1kWh battery. 136 in parallel will give you a 1kWh battery with a nominal voltage of 3.7V.
If you want higher voltage, and you probably will, you have to put them in series as well. 7s is a typical minimum for a LiIon battery. 136 cells can’t be evenly distributed over 7 packs in series, you then need 140 cells for a 7s20p setup. That will give you a battery with a nominal voltage of 25.9V (7 * 3.7V) and a capacity of 40Ah (20 * 2000mAh) which results in 1036Wh (25.9V * 40Ah).
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