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Battery design scheme-Worksite power tools

by:WORKSITE     2021-01-01
The biggest feature of Worksite power tool batteries is that the output power should be large enough, and the temperature control of the products should be done well. The cycle life of the battery will be affected due to excessive power and temperature control methods. How to balance? It is a question that must be paid special attention to for the battery of Worksite power tools. Our company chooses 18650 15C high-rate batteries for its Worksite power tool battery solution, and will do a good job of balancing function and temperature control (75 degrees) to ensure that it reaches the customer's request.

   One, Worksite power tool battery request:

  Worksite electric tool products have extremely large output power, so the usual capacity batteries cannot be satisfied, and only high-rate power batteries can be selected. Because the power is too large, it simply generates heat, and temperature control is required. The power management module adopts imported scallops, with a special equalization function. The specific parameters of the assembled battery are as follows:

  1) Lithium battery pack type proposal request: 18650-4S2P/3Ah/18V.

   2) Some schemes of the circuit request:

   1. Single cell overcharge protection voltage: 4.25±0.25V

  2, single cell overcharge recovery voltage: 4.1±0.50V

  3, single cell over-discharge protection voltage: 2.70±0.08V

  4, single cell over-discharge recovery voltage: 3.00±0.10V

   5. Combined battery over-current protection value (10ms): 30~35A

  6, charge balance current: 300±50mA

  7, charge balance voltage: 4.20±25mV

   8. Battery over-temperature protection value (recoverable): 70±5 degrees

   9. The finished battery also has short circuit and reverse charge protection.

  3) Request for battery cycle life plan: 500 times (national standard charge and discharge standard)

  4) Request for battery appearance standard solution: L(97.0)*W(73)*T(61)

   2. Worksite power tool battery solution:

1) Protection board (PCM): The first is the protection circuit for the rechargeable lithium battery pack. Due to the chemical characteristics of the lithium battery itself, it needs to provide protection functions such as intelligent power calculation, overcharge, overdischarge, short circuit, and overcurrent. In order to avoid causing incineration, explosion and other hazards.

  2) Protection IC (ProtectionIC): The primary protection function chip of the scheme, which conducts online monitoring of overcharge, overdischarge, overcurrent, short circuit and other functions of the cell from time to time. Make the batteries work in a safe, stable and efficient range.

  3) Charging balance module: balance the voltage difference of each cell during charging, enhance the consistency of the voltage of each cell to extend the service life of the assembled battery.

  4) Temperature switch: It is mainly about the temperature protection function program. When the temperature of the battery itself reaches 75 degrees due to other abnormalities, the temperature switch will act and reach the over-temperature protection. When the temperature drops, it will automatically recover.

  5) 18650 lithium ion batteries/18650/1500mAh/3.7Vl (high rate batteries).

  6) Field effect tube (MOSFET): MOSFET, which acts as a switch in the protection circuit, permanently prevents the voltage at both ends of the load from increasing or decreasing, ensuring voltage stability.
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