Do lithium iron phosphate batteries need protective panels?

Lithium iron phosphate batteries monomer voltage of 3.2 V, now commonly used for electric cars and other power supply.

Electric vehicle battery lithium iron phosphate battery is made up of many pieces of monomer by series or parallel way to achieve different voltage level and capacity.Every impossible in the discreteness of battery (the same), so in use after a period of time, () in the process of charging and discharging, each battery voltage will appear more and more different, some is higher than 3.2 V, lower than 3.2 V, which had a great influence to the battery pack, the overall capacity of smaller, shorten service life.

Protection circuit board can detect series respectively, each cell in the battery voltage and current control battery charge and discharge process.Battery in each battery voltage are in charge of detecting the voltage and the discharge voltage, short circuit and the output, the MOS tube conduction, P +, P - output battery voltage, allow the battery to charge and discharge operation.In addition also has the battery protection board put protection, overcharge protection, over-current protection, short circuit protection, and other functions.

Power battery is to strengthen power protection board lithium ion batteries will match the safety of equipment.In most cases, the Li-ion battery protective plate should have control of lithium ion battery using the function of the working conditions, the working conditions including voltage, current, temperature, etc.Due to the particularity of lithium ion battery, power lithium ion battery must form a complete set with the protective plate used to ensure the safety and reliability of the whole system.

Charging voltage protection: to prevent resulted from battery charging voltage higher than the battery voltage limit, safety accidents caused by discharge voltage protection: to prevent the battery deep discharge, avoid shorten battery life or cause safety accident over-current protection: protective plate and battery limit current through the size of the short circuit protection: avoid the battery short-circuit accidents temperature control switch: protect battery and safety problems caused by protection plate temperature is too high.

Power battery protection board, there are two core components: a piece of protection IC, it is the exact comparator to obtain reliable protection parameters;Another is mosfet series ACTS as a high-speed switch in the main charge and discharge circuit, the protection action.Circuit principle diagram is as follows: 1, the following protection IC pin function: VDD is positive, IC power supply power anode, VSS v - is over-current/short circuit detection, dout is executive side discharge protection, cout is executive end charging protection.2, protection board port description: b +, b - are respectively batteries the positive and negative;P + and p - is to protect the board output of the positive and negative;T for temperature resistance (NTC) port, usually need to cooperate with electrical appliances of MCU protection action, later, the port labeled id, sometimes meaning identification port, at this point, the figure of r3 is usually fixed resistance resistance, let use appliances CPU to distinguish whether is designated as the battery.Protection plate work process: 1, to activate protection plate method: when the protection plate p +, p - no output in the protection state, can short-circuit b -, p - to activate protection board, at this moment, dout, cout, is at a low level (protection IC this two port is a high level protection, low electricity PingChangTai) open two MOS switch state.2, charging: p +, p - respectively after the charger is negative, the charging current after two MOS for rechargeable batteries.At this point, the VDD and VSS is both the power IC, and the batteries voltage detection (r1).As charging, batteries voltage rise gradually, when rise to protect the IC threshold voltage (typically 4.30 v, usually referred to as the overcharge protection voltage), cout immediately will output level corresponding to the MOS turn-off, charging circuit is disconnected.After the overcharge protection, batteries voltage drops, the moment to IC threshold voltage (generally 4.10 v, often referred to as the overcharge protection recovery voltage), cout open MOS switch to recover low level.3, discharge: also, the battery is discharging, IC VDD and VSS for batteries voltage detection, when the batteries voltage drop to IC threshold voltage (typically 2.40 v, usually referred to as the discharge voltage protection), dout soon will output level corresponding to the MOS turn-off, discharge circuit is disconnected.After discharge protection, batteries voltage increase, and when to rise to IC threshold voltage (3.00 v, usually referred to as the discharge protection recovery voltage), dout open MOS switch to recover low level.MOS saturation conduction is internal resistance, so the current between the flows through b -, p - creates a pressure drop on both ends of the MOS, protection IC v - and VSS (through r2) will always test the voltage across the MOS when voltage rise to IC protection threshold (for 0.15 v, commonly known as discharge flow test voltage), dout soon will output level corresponding to the MOS turn-off, discharge circuit is disconnected.See here, about students have to realize, if choose the MOS with low conduction resistance or discharge flow testing high voltage IC, can obtain larger output current, but also should consider to choose the MOS power and the capacity of the batteries.5, the action of NTC (t) : when the battery is working, there have been no charge, discharge or over current, short circuit, etc., but due to the work time is too long, cause the cell temperature rise (such as usual we are using a mobile phone to talk on the phone) soon.Temperature monitoring and NTC resistance against batteries batteries, NTC resistance gradually decreases as the temperature rises, with electrical CPU found this change, when resistance decreases to the CPU setting, the CPU is a shutdown command, stop the battery for its power, only to maintain standby current is small, achieve the purpose of protecting the battery.

Overcharge protection voltage: 4.25 + / - 0.05 v / 4.0 v (lithium iron phosphate battery overcharge delay: 80 ms overcharge lifting voltage: 4.1 + / - 0.05 v / 3.5 v discharge voltage protection: 2.80 + / - 0.05 v / 0.05 v battery (lithium iron phosphate) discharge termination voltage: 3.0 + / - 0.05 v / 2.3 v put delay time: 40 ms discharge remove method: disconnect the load, the monomer is terminated when battery voltage is higher than the critical value or charging terminated;Flow lift: disconnect the load release charging current: < 5 a balanced current: every road can be tailor-made special 50 ma each balance precision: 4.20 + / - 0.01 v / 0.01 v + / - 0.01 (lithium iron phosphate batteries over current protection: 40 a / 80 a (according to the requirements) static power < 0.5 ma battery protection board series: 3 series, four series, 7 series, 8 series, 10 series, 12 series, 13 series, 16 series, can be customized as required.

1.Output cathode anode c - p -, charging and battery cathode b, please press the order connection, please don't pick up the line, so as not to burn out circuit component.2.Charging line, put wires, battery cathode.With bold lines as far as possible, otherwise, I will large current, over-current protection, it will influence the circuit does not work.3.The positive output without a protection circuit, battery connected directly to the output.

The advantage of lithium iron phosphate battery is:

Lithium iron phosphate battery life is long, cycle life over 2000 times.Under the same conditions, the lithium iron phosphate batteries can use seven to eight years.

Use safety.Lithium iron phosphate batteries after a rigorous safety testing, does not an explosion in the traffic accident.

Charge fast.Use a dedicated charger, charging 1.5 C 40 minutes can make the battery is full.

Lithium iron phosphate battery high temperature resistant, lithium iron phosphate battery hot value can reach 350 to 500 degrees Celsius.

Large capacity of lithium iron phosphate batteries.

Lithium iron phosphate battery no memory effect.

Lithium iron phosphate battery of green environmental protection, non-toxic, non-polluting, sources of raw materials, the price is cheap.

The disadvantage of the lithium iron phosphate batteries are:

Lithium iron phosphate battery anode tap density is small, the density of general at about 0.8 to 1.3.Large volume.

Conductive performance is poor, lithium ion diffusion is slow, high charge and discharge, the actual low specific capacity.

The low temperature of the lithium iron phosphate battery performance is poor.

Lithium iron phosphate batteries of single battery life is long, in the 2000 times or so, however, lithium iron phosphate battery pack life is short, generally about 500 times.

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