The lithium battery protection board is the charge and discharge protection for a series lithium battery pack. It can ensure that the voltage difference between every single cell is less than the set value (generally ±20mV) when it is usually fully charged to know the equal charging of each single cell in the battery power, which effectively increases the charging effect in the series charging mode. It also detects the over-voltage, under-voltage, over-current, short-circuits, and over-temperature status of every single cell in the battery pack to protect and extend the battery life.
Under-voltage protection permits every single cell to avoid battery damage due to over-discharge when discharged for use. These are the normal initiatives of lithium battery manufacturers in the world committed to lithium battery safety.
What is the Solution of Lithium Battery Protect Board?
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What are the problems in the production of Lithium Battery Protect Board？
1. No display, low output voltage, and can not take the load
Such bad first exclude the core bad (the core formerly had no voltage or low voltage), if the core is bad should test the protection board the power consumption, to see if the protection board since the power consumption is too large resulting in a low voltage core. If the core voltage is normal, it is usually due to the entire circuit of the protection board no longer working (component soldering, false welding, FUSE bad, PCB board internal circuit no longer working, over the hole no longer working, MOS, IC damage, etc.). Specific analysis steps are the following.
With a multimeter black pen linked to the negative terminal of the core, the red pen in turn linked to the FUSE, R1 resistor terminals, IC Vdd, Dout, Cout terminal, and P + terminal (assuming that the core voltage is 3.8V), segment by segment analysis, these test points should be 3.8 V. If not, this segment of the circuit has problems.
2. Short-circuit without protection
VM terminal resistance problem: a multimeter can be connected to the IC2 pin, a pin connected to the VM terminal resistance MOS tube pin, confirm the size of its resistance value. Look at the resistor and IC, MOS pins have no false solder. 2.
IC, MOS abnormal: because the over-release protection and over-current, short-circuit protection share a MOS tube, if the short-circuit a good normality is due to MOS problems, the board should be no over-release protection function.
The above is the normal condition of the bad, may also appear IC and MOS configuration caused by poor short-circuit abnormalities. As in the case of BK-901, the delay time within the IC model ‘312D’ is too much period, resulting in the MOS or other elements being damaged before the IC makes the corresponding action control. Note: Among them, the easiest and most direct way to determine if the IC or MOS is abnormal is definitely to displace the suspected components.
3. Short-circuits protection without self-recovery
The IC used in the design formerly didn’t have a self-recovery function, such as example G2J, G2Z, etc.
The instrument set short-circuit recovery time is too short, or short-circuit test is not removed from the load, such as by using a multimeter voltage file for short-circuit pen shorting after the pen is not removed from the test end (multimeter equal to a few megabytes of load).
P +, P – between the leakage, such as the existence of impurities between your pads with impurities of rosin, with impurities of yellow glue or P +, P – between the capacitance is broken, IC Vdd to Vss between the breakdown. (Resis certainly once the value of just a few K to a couple of hundred K).
If the above is no problem, the IC may be broken, you can test the resistance value between the IC pins.
4. Protect board’s internal resistance is large
Because MOS internal resistance is relatively stable, there is a sizable internal resistance, the first suspect should be FUSE or PTC this internal resistance is relatively easy to change the components.
If the FUSE or PTC resistance value is normal, according to the structure of the protection board to discover P +, P – pads, and parts between the face of the hole resistance value, maybe over the hole micro-break phenomenon, the resistance value is larger.
If the above is more than no problem, we must suspect whether MOS anomalies: first determine whether there is a problem with welding; secondly, look at the thickness of the board (whether it is easy to bend), because the bending may bring about pin welding abnormalities; then MOS tube into the microscope to observe whether the rupture; finally, use a multimeter to test the MOS pin resistance to see whether it is broken.
5. ID abnormalities
ID resistor itself is abnormal due to deficient soldering, fracture, or because the resistor material is not up to par: you can re-solder the two ends of the resistor, if the ID is normal after re-soldering, it really is resistor deficient soldering, if fracture, the resistor will be cracked from it after re-soldering.
ID through-hole is not conductive: use a multimeter to test both ends of the through-hole.
Internal circuit problems: can scrape open the solder resist paint to see if the internal circuit is broken, short circuit phenomenon.