二、Two points of explanation

1. Impurities (especially iron ions) are very harmful to the battery, which will cause the battery to self-discharge and shorten its life. Therefore, pay attention to purity when injecting sulfuric acid and water.

2. The hydrometer is an essential tool to repair the battery, but the commercially available hydrometer requires more electrolyte for measurement, which is difficult to use. The author used the center of the gel pen and the cap of the ballpoint pen to make a miniature simple hydrometer: put the hydrometer in pure water, and record the position of the hydrometer on the water surface, which is the scale position where the specific gravity is 1.00; Put the meter into a sulfuric acid solution with a known concentration (dilute sulfuric acid can be purchased at a battery store or repair shop, ask them to accurately measure the specific gravity of sulfuric acid, such as 1.28), and note the position of the hydrometer on the liquid level; The length of the specific gravity of 1.00~1.28 is engraved on the paper, and then the scale between 1.00~1.28 is divided into 28 equal parts, and the hydrometer is completed.

Battery failure and repair

Battery charging does not light up green

There are three reasons why the light does not turn: first, the charger parameters do not match, resulting in drift; second, the circuit problem; third, the battery factor: water loss, there is a single-cell short circuit inside the battery, and the vulcanization is more serious. Check method:

1. Check whether the charger is damaged and whether the charging parameters meet the requirements (some people use a 48V charger to charge a 36V battery pack) to see if the voltage is high (14.8V/above) or the trickle conversion current is low .

2. Check whether the fuse of the charging circuit is in good contact, whether the fuse holder has any burn marks, check whether the connection plug is in good contact, and the socket on the car including the plug of the charger.

3. Check whether the battery is dry, that is, whether the battery is seriously short of liquid. The dry battery should be supplemented with pure water or 1.05g/cm3 of dilute sulfuric acid, and repaired by maintenance, charge and discharge, and at the same time, measure the single-cell voltage to see if there is a single-cell short circuit.

4. It should also be checked whether there is irreversible sulfation of the plates. If the vulcanization is serious, the internal resistance will increase, and charging will cause serious heat generation.

The irreversible sulfation of the electrode plate can be determined by measuring the change of its terminal voltage by charging and discharging. When charging, the voltage of the battery rises very quickly, some cells have a particularly high voltage, and the voltage drops very quickly when discharging. When the above situation occurs, it can be judged that the battery has irreversible sulfation. If irreversible sulfation is found, it should be repaired by the equalization charging method.

Deformation of the battery

1. Cause of failure:

The deformation of the battery is not sudden, but there is often a process. The battery enters the high-voltage charging area when it is charged to about 80% of its capacity. At this time, oxygen is first released at the positive electrode, and the oxygen passes through the pores in the separator to reach the negative electrode. Oxygen reactivation on the negative plate:

2Pb+O2=2PbO+Heat

PbO+H2SO4=PbSO4+H2O+Heat

Heat is generated during the reaction. When the charging capacity reaches 90%, the oxygen generation rate increases, and the negative electrode begins to generate hydrogen. The increase in a large amount of gas causes the battery safety valve to open and the gas escapes, which eventually manifests as water loss.

As the number of battery cycles increases, the moisture gradually decreases, resulting in the following situations in the battery:

(1) The oxygen "channel" becomes unblocked, and the oxygen generated by the positive electrode can easily reach the negative electrode through the "channel".

(2) The heat capacity is reduced, and the largest heat capacity in the battery is water. After the water is lost, the heat capacity of the battery is greatly reduced, and the heat generated makes the temperature of the battery rise rapidly.

(3) Due to the shrinkage of the ultra-fine glass fiber separator in the battery after water loss, the adhesion between the superfine glass fiber separator and the positive and negative plates becomes poor, the internal resistance increases, and the calorific value during the charging and discharging process increases. After the above process, the heat generated inside the battery can only be dissipated through the battery slot. If the heat dissipation is less than the calorific value, the temperature will rise, the gas evolution potential of the battery will decrease, and the gas evolution volume will increase. The formation of a vicious cycle leads to "thermal runaway" and deformation occurs.

2. Failure inspection and handling

If a group of batteries (3 pieces) are deformed at the same time, check the voltage first. If the voltage is basically normal. The voltage of a single cell should also be measured to determine whether there is a short circuit. If there is no short circuit, it means that the deformation is caused by "thermal runaway" caused by overcharging. Should focus on checking the charging parameters of the charger. If the voltage is high (above 44.7V) without overcharge protection or the trickle conversion current is low, it is required to replace the charger.

Only 1 or 2 of a set of batteries (3) are deformed, and there are possibilities of the following failures:

(1) The battery capacity is inconsistent, causing some batteries to be overcharged and deformed during charging. The reason for the inconsistent capacity may be the existence of a short-circuit cell, or the user may discharge the battery test or self-discharge.

(2) Some batteries have irreversible sulfation of the plates, the internal resistance increases, and the charging heats up and deforms.

(3) When some batteries are connected in reverse, they cause heating and deformation during charging. Check the discharge capacity and self-discharge performance of the undeformed battery. If there is no abnormality, it is not a battery problem.

The measures to solve the deformation of the battery are as follows:

*Add as much liquid as possible on the premise of ensuring no leakage, in order to prolong or avoid the occurrence of "thermal runaway".

* Avoid internal short circuits or micro-short circuits, and tend to have micro-short circuits.

*The occurrence of over-discharge should be prevented during use, so that it can be stored with full power.

*Strictly check the charger, there must be no serious overcharge.

* When charging at high temperature, it is necessary to ensure that the battery has good heat dissipation. Cooling measures or methods to shorten the charging time should be taken, otherwise the charging should be stopped.

Fast self-discharge rate

When the battery is not working, the phenomenon that the power is gradually consumed is called self-discharge. Self-discharge cannot be completely avoided. It is generally considered normal to consume 1% to 2% of its own capacity every day. If it exceeds this value, it is abnormal self-discharge.

1. Reasons for self-discharge

(1) There are impurities in the plate material or electrolyte, so that a potential difference will be generated between the impurities and the fetters or different magazines, forming a closed "local battery" to generate current and discharge the battery.

(2) The separator is broken, causing a local short circuit.

(3) There is electrolyte or water on the battery cover, so that a path is formed between the positive and negative electrodes to discharge.

(4) The active material falls off, causing the plate to short-circuit and cause discharge.

(5) When the battery is stored for a long time, the sulfuric acid in the electrolyte sinks, so that the upper part has a small density and the lower part has a large density, causing self-discharge.

2. Processing method

To reduce self-discharge, the electrolyte must be pure, and the battery cover should be kept clean during use to avoid short circuits. If the electrolyte is impure, discharge the battery with a current of 1/10 of the nominal capacity to a single cell voltage of 1.7V, then pour out the electrolyte, clean it with distilled water, and then replace it with a pure electrolyte for charging.

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