Custom Lithium ion Battery Pack

Lithium battery maintenance methods

Dec 19, 2018   Pageview:34

Usually 18650 battery are in parallel to increase capacity, such as 20000mah mobile power is normally provided by a battery 8 or 6 3400mah 2600mah the 18650 battery into. The parallel connection adds 3.7V capacity. Then increase the voltage by series, 2 series is 3.7 * 2 = 7.4V, three 12.6V analogy.

 

Usually, electric vehicles and laptop batteries need to increase the battery voltage to 12V or 36V48v72V through multiple batteries in series. At this time, if the battery capacity or quality is not equal, there is always a loss in the use process. Like the short board principle of a wooden barrel, a battery or a group of batteries connected in parallel affects the total battery voltage and capacity of the entire battery pack.

 

The impact is that, for example, notebooks are generally 2 and 3 strings, which constitute a 10.8V ~ 12.6V battery. A group of two parallel batteries are depleted first, which will cause the entire battery to have a reduced capacity. Specifically, the battery has a short standby time, a fast charging speed, and a fast power consumption. The same is true for electric vehicles and other equipment.

 

At this time, it is necessary to replace the battery pack and avoid the barrel effect (short board principle - the barrel can hold water depending on the shortest board of the barrel). This will allow the battery to be used evenly and extended.

 

Directly measure with a voltmeter if the voltage across the 18650 battery is less than 2.7V or no voltage, which indicates that the battery or battery pack is damaged. The normal voltage is 3.0V~4.2V (the general 3.0V battery will be cut off, the 4.2V battery voltage will be fully charged, and the individual types will also be 4.35V)

 

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The battery voltage is lower than 2.7V. You can charge the battery with the charger (4.2V). After 10 minutes, if the battery voltage rises, you can continue charging until the charger is full, then look at the full voltage.

 

If the full-voltage is 4.2V, the battery is normal. It should be that the last time the power consumption was too much and the battery was cut off.

 

If the full voltage is much lower than 4.2V, it means the battery is damaged. If it is a battery that has been used for a long time, it can be judged that the battery life is up and the capacity is basically exhausted. It should be replaced. Basically there is no way to fix it. After all, lithium batteries have a long life, not unlimited.

 

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If the battery is measured, there is no voltage in the battery. There are two situations at this time. One is that the battery is good, and the battery is stored for a long time. This battery has a certain chance to recover. Generally, the battery is activated by a lithium battery pulse activation device. It needs to charge multiple times. It is possible to fix it. Generally, the cost of repair is not low, or buy a new one.

 

Another possibility is that the battery is completely worn out, the battery diaphragm breaks down, and the positive and negative poles are short-circuited. There is no way to fix this kind of thing. It can only buy new ones.

 

As mentioned earlier, lithium battery packs should often be unusable because one or a group of batteries is damaged. At this time, the voltage across each battery should be measured one by one, and the voltage or voltage should be severely low (the previous one is described). Come out and replace the new battery of the same kind with similar internal resistance.

 

After the replacement, the lithium battery pack can also be used up to the other battery life loss. This partial replacement is generally less expensive. It is also a commonly used method on the market.

 

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Lithium battery must be equipped with a protective plate to limit overcharge, over discharge, short circuit, etc., which is beneficial to extend the life of the lithium battery pack.

 

Lithium batteries cannot be short-circuited, and inspection must pay attention to

 

18650 lithium battery must be used with protective board

 

Lithium battery charging must not exceed the rated voltage and current, as well as charging time

 

Lithium battery chargers must have quality assurance to extend their service life.

 

First, the voltage class failure

 

1, 12v lithium battery voltage is high: after full power is placed, the battery voltage is obviously high, other monomers are normal.

 

cause of issue:

 

1 acquisition error;

 

2LMU equalization function is poor or invalid;

 

3 The battery capacity is low, and the voltage rises faster when charging.

 

Approach:

 

1 The voltage display value of the single cell is lower than that of the other monomers. The actual voltage value of the single cell is measured for comparison. If the actual value is higher than the displayed value and is the same as the voltage of other cells, the actual value is the voltage of the LMU cell. Calibrate; if the measured value matches the displayed value, the battery is manually charged and equalized.

 

2 Check if the voltage sampling line is broken or connected.

 

3 replace the LMU;

 

4 Replace the faulty battery pack.

 

2, pressure difference: dynamic pressure difference / static pressure difference. When charging, the cell voltage quickly jumps to the full-power cut-off voltage. When discharging, the cell voltage drops rapidly compared with other strings; when the discharge is stopped, the cell voltage rises faster than other strings.

 

Cause of issue:

 

1 Connect the battery bronze fastening nut loose;

 

2 the connection surface is dirty;

 

3 battery core self-discharge rate;

 

4 electric core welding connection copper plate open welding (causing the string monomer capacity is low);

 

5 individual cell batteries leak.

 

Approach:

 

1 tighten the nut;

 

2 remove foreign objects on the connection surface;

 

3 charging/discharging equalization of single string batteries;

 

4 Replace the problem battery pack.

 

4. Voltage jump: When the electrical equipment is running or charging, the voltage of the 12v lithium battery cell jumps.

 

cause of issue:

 

1 The voltage collection line connection point is loose;

 

2LUM failure.

 

Approach:

 

1 tighten the connection points;

 

2 Replace the LMU.

 

Second, the temperature class failure

 

1. Thermal management failure;

 

1 heating failure (heating sheet); when the temperature is lower than a certain value, heating does not turn on during charging.

 

cause of issue:

 

1 heating relay or BMU failure;

 

2 The heater chip or relay power supply circuit is abnormal.

 

Approach:

 

1 Repair or replace the fan relay or BMU failure;

 

2 Check and repair the power supply circuit abnormality.

 

2 Thermal fault (fan); after the temperature is higher than a certain value, the fan is not working.

 

Cause of issue:

 

1 fan relay or BMU failure;

 

2 Fan or relay power supply circuit is abnormal.

 

Approach:

 

1 Repair or replace the fan relay or BMU failure;

 

2 Check and repair the power supply circuit abnormality.

 

2. High temperature: one or some temperature points in the battery system are high, and the alarm threshold is reached during operation or charging.

 

Cause of issue:

 

1 temperature sensor failure;

 

2LMU failure;

 

3 electrical connection is abnormally localized;

 

4The fan is not turned on, and the heat dissipation is poor;

 

5 close to the heat source such as the motor;

 

6 overcharged.

 

Approach:

 

1 Measure the temperature sensor resistance value and compare it with the displayed value. If the actual value is lower than the displayed value and is the same as other temperature values, the LMU temperature value is calibrated according to the actual value;

 

2 tighten the electrical connection points and clearly connect the foreign objects;

 

3 Make sure the fan is turned on;

 

4 increase the insulation material and the heat source to isolate;

 

5 suspend operation for heat dissipation; 6 immediately stop charging;

 

7 Replace the LMU.

 

3. Low temperature: One or a few temperature points in the battery system are low, and the alarm threshold is reached during operation or charging.

 

cause of issue:

 

1 temperature sensor failure;

 

2LMU failure;

 

3 The local heating sheet is abnormal.

 

Approach:

 

1 Measure the temperature sensor resistance value and compare it with the displayed value. If the actual value is higher than the displayed value and is the same as other temperature values, the LMU temperature value is calibrated according to the actual value;

 

2 Check the repair heating sheet; 3 replace the LMU.

 

4, temperature difference; refer to high and low temperature troubleshooting methods. The difference is in battery heating.

 

Third, charging failure

 

1, DC charging failure; GB/T27930-2015 charging can not start, charging jump gun, SOC does not reset after charging.

 

Cause of issue:

 

1 Battery failure (voltage, temperature, insulation, etc.)

 

2BMU failure (charging module or charging CAN abnormal)

 

3 main negative, charging relay is abnormal

 

4CC1 ground resistance, CC2 ground voltage abnormality

 

5PE abnormal

 

Approach:

 

1 Troubleshooting battery

 

2 repair / replacement of failed parts

 

3 Intercept the charging message to analyze the cause of the failure.

 

2. AC charging failure;

 

cause of issue:

 

1 battery failure (voltage, temperature, insulation, etc.)

 

2BMU failure (charging module or charging CAN abnormal)

 

3 main negative, charging relay is abnormal

 

4CC earth resistance, CP to ground voltage abnormality

 

5PE abnormal

 

Approach:

 

1 Troubleshooting battery

 

2 repair / replacement of failed parts

 

3 Intercept the charging message to analyze the cause of the failure.

 

Fourth, insulation failure

 

The cause of the malfunction: the battery box or the plug-in enters the water, the battery core leaks, the environment humidity is high, the insulation is falsely reported, and other high-voltage components (controllers, compressors, etc.) of the vehicle are insulated.

 

Treatment method: 1 positive pole to ground, if there is voltage or insulation resistance value is less than the specified value, the negative circuit leakage is judged; if the negative pole is grounded, if the voltage or insulation resistance value is less than the specified value, the positive circuit is leaked. According to the magnitude of the leakage voltage divided by the single string voltage value at this time, the leakage point can be calculated, and then analyzed according to different situations.

 

Five, communication failure

 

LUM communication failure, BMU communication failure; the whole vehicle is one or several LMU information, or the vehicle does not have BMS information.

 

Cause of issue:

 

1LMU/BMU failure;

 

2LMU/BMU power supply circuit or communication line is in poor contact/fault;

 

3 signal interference.

 

Approach:

 

Refurbishment LMU / BMU;

 

2 check and repair the power supply circuit / communication line;

 

3 Check the shielded line and find the source of interference cancellation.

 

Sixth, SOC anomaly

 

1. Inaccurate;

 

Charging power ÷ nominal capacity = SOC of charging If the "SOC of charging" + "residual SOC" deviates from the actual display value or according to the correspondence between SOC and OCV, it is estimated that the actual power does not correspond to the SOC, we believe that the SOC is not accurate.

 

2, no change;

 

cause of issue:

 

1 communication error (data missing);

 

2 current abnormality (Hall and its input and output circuits);

 

3BMU failure;

 

4 Other battery alarms.

 

Treatment: 1 to ensure data integrity; 2 repair / replace failed parts; 3 eliminate all battery alarms.

 

3, the decline is fast;

 

cause of issue:

 

1 communication cycle is abnormal

 

2 current abnormality (Hall forward current is large, feedback current is small);

 

3 The cell voltage is low and the drop is fast;

 

4BMU failure;

 

5 low temperature.

 

Approach:

 

1 update the BMU program;

 

2 repair / replace the failed parts;

 

4, slow down;

 

Fault reason: 1 communication cycle abnormality 2 current abnormality (Hall forward current is small, feedback current is large) 3BMU fault.

 

Approach:

 

1 update the BMU program;

 

2 Repair/replace defective parts.

 

5, beating; confirm that the program version number is correct

 

Seven, the current is abnormal

 

cause of issue:

 

1 Hall and its input and output circuits;

 

2 Hall reverse loading;

 

3 When the BMS demand voltage or current is 0 during DC charging, the charger outputs according to the minimum output capability.

 

Approach:

 

1 update the BMU program;

 

2 Repair/replace defective parts.