The principle of lithium battery protection board and the wiring method of
lithium battery protection board. Lithium battery protection board, as the name
suggests, is used to protect lithium batteries. The function of the lithium
battery protection board is to protect the battery from discharge, charge, and
current, as well as output short-circuit protection. There are two design
methods for lithium battery protection plates, namely positive plate and
negative plate. The principle and purpose are the same, but the device does not
support modifying the settings of the positive and negative protective plates
through software.
Introduction to the principle of lithium battery protection board
The reason why lithium battery (rechargeable type) needs protection is
determined by its own characteristics. Since the material of the lithium battery
itself determines that it cannot be overcharged, overdischarged, overcurrent,
short-circuited, or charged and discharged at ultra-high temperatures, lithium
battery components always appear with a delicate protective board and a current
fuse.
The lithium battery protection board is to protect the charge and discharge
of the series-connected lithium battery pack; when fully charged, it can ensure
that the voltage difference between each single cell is less than the set value
(generally ±20mV), achieving even charging of each single cell in the battery
pack. , effectively improves the charging effect in series charging mode;
simultaneously detects the overvoltage, undervoltage, overcurrent, short
circuit, and overtemperature status of each single cell in the battery pack to
protect and extend the service life of the battery; undervoltage protection
enables each When a single battery is discharged, it can prevent the battery
from being damaged due to over-discharge.
The protection function of lithium batteries is usually completed by a
protection circuit board and current devices such as PTC. The protection board
is composed of electronic circuits and can accurately monitor the voltage and
charge return circuit of the battery core at all times in an environment of
-40°C to +85°C. Current, timely control the on and off of the current loop; PTC
prevents severe damage to the battery in high temperature environments.
Ordinary lithium battery protection boards usually include control IC, MOS
switches, resistors, capacitors and auxiliary devices FUSE, PTC, NTC, ID,
memory, etc. Among them, the control IC controls the MOS switch to turn on when
everything is normal, so that the battery core is connected to the external
circuit. When the battery core voltage or loop current exceeds the specified
value, it immediately controls the MOS switch to turn off to protect the battery
core. Safety.
When the lithium battery protection board is normal, Vdd is high level, Vss
and VM are low level, DO and CO are high level. When any parameter of Vdd, Vss
and VM changes, the voltage of DO or CO terminal Ping will change.
1. Overcharge detection voltage: Under normal conditions, Vdd gradually
increases to the voltage between VDD and VSS when the CO terminal changes from
high level to low level.
2. Overcharge release voltage: In the charging state, Vdd gradually
decreases to the voltage between VDD and VSS when the CO terminal changes from
low level to high level.
3. Over-discharge detection voltage: Under normal conditions, Vdd gradually
decreases to the voltage between VDD-VSS when the DO terminal changes from high
level to low level.
4. Over-discharge release voltage: In the over-discharge state, Vdd
gradually rises to the voltage between VDD-VSS when the DO terminal changes from
low level to high level.
5. Overcurrent 1 detection voltage: Under normal conditions, VM gradually
rises to the voltage between VM and VSS when DO changes from high level to low
level.
6. Overcurrent 2 detection voltage: Under normal conditions, VM rises from
OV at a speed of more than 1ms and less than 4ms to the voltage between VM and
VSS when the DO terminal changes from high level to low level.
Lithium battery protection board wiring method
The connection methods of lithium battery protection boards are generally
three types of commonly used protection boards: negative pole same-port plate,
negative pole split-port plate, and positive pole same-port plate. The other
methods will not be described one by one. During the process, there are many
connection methods when testing the lithium battery protection board on
non-standard battery equipment. It is also worth getting familiar with the test
connection. The simple process is as follows:
1. Place the device on a relatively horizontal table and adjust the
stability of the device to make it stable;
2. Ensure that the humidity of the environment in which the equipment is
used is within the range of 30~50%. If the humidity is too high, it is easy to
cause leakage of the chassis and electric shock accidents;
3. Connect to the appropriate power supply (AC220V/0.1A), turn on the power
button of the main device, and turn on the respective power module buttons.
4. Check whether the device can display and test normally.
In fact, the wiring methods of each lithium battery protection board are
different depending on the number of series, and the wiring methods of the same
port and separate ports are also different. If you want to be precise about each
product, please check the protection board details page, but the overall wiring
remains unchanged. Wiring sequence: When assembling the wiring, correctly weld
the flex cable to the battery core, connect B- of the PCM to the total negative
pole of the battery core, and then insert the flex cable into the pin holder on
the PCM.
As the country vigorously develops new energy, many companies use lithium
batteries to replace the original lead-acid batteries, nickel-metal hydride
batteries, etc. Due to the activity of lithium ions, protective plates must be
added when using lithium batteries to prevent overcharging of lithium batteries.
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