What's in a lead-acid battery

Automotive batteries

1 General information
2 Hazards from lead-acid batteries
3 protective measures


1General information

Lead-acid batteries are usually used as starter batteries in vehicles with internal combustion engines. Most electric forklift trucks and electric pallet trucks are also equipped with lead-acid batteries to power the electric motor. Lithium batteries, like the ones we use in electronic devices such as B. Laptops, cameras, cell phones are now usually only installed in vehicles with electric or hybrid drives.


Lead-acid batteries

The structure of the battery is very simple: the electrode plates are made of lead, and in between there is dilute sulfuric acid as an electrolyte. Today, most lead-acid batteries use a gel rather than liquid acid.

The typical application of this type of battery as a starter battery corresponds to the requirements for a motor vehicle with a combustion engine, which requires a very high starting current of a few hundred amperes (!) To start and is then immediately recharged by operating the engine. These batteries are able to deliver a very high current for a short time at high and low ambient temperatures and to store the electrical energy for a sufficient period of time. They can also be recharged again and again

In mobile homes and camping vehicles as well as on boats, a further stationary battery is used in addition to the starter battery.


Lithium-ion batteries

The use of lithium-ion batteries is a matter of course today. Due to the large number of electronic devices, these batteries can be found in every company and every private household. But the use is also risky and not completely harmless as it appears. When working on electric and hybrid vehicles, special training is required due to the significantly higher voltage of the lithium-ion batteries (400 or 1000 volts).


2Hazards from lead-acid batteries

  • Skin and eye damage from chemical burns When filling a battery for the first time with liquid acid (concentration 37% sulfuric acid), if the acid splashes. Battery acid can also spurt out when topping up with distilled water. The first filling in a workshop has become rare, since today most batteries are already filled with gel and pre-charged.
  • Back problems and health problems due to the heavy weight of a car battery when installing, removing, lifting and carrying.
  • Serious physical and material damage by explosion. When charging, hydrogen is produced, which forms an explosive atmosphere in air from a concentration of only 4%. Hydrogen is invisible and odorless, so that it cannot be perceived.

    There is therefore a particularly high risk of an explosion with a corresponding extent of damage when charging batteries in small and unventilated rooms, such as B. in a small storage room without ventilation.
If individual batteries are only occasionally charged in a large workshop, natural ventilation is usually sufficient to avoid an explosive atmosphere.

It is also critical if, to end the charging process, the pole terminals are removed first and then the charger is unplugged. This can cause sparks in the immediate vicinity, which can also lead to an explosion.

  • High risk of explosion when "overloaded"

    If the charging process is not completed after a battery has been fully charged or if too high a current flows into the battery via the charger during charging, the battery also begins to gas violently and the battery acid bubbles. A very large amount of oxyhydrogen gas is generated in a short time through the release of hydrogen and oxygen. In this situation, the longer the process takes, the greater the risk of an explosion.

When using modern electronic chargers, the charging voltage is automatically reduced when fully charged, so that only a very small amount of oxyhydrogen is released. Older chargers can easily "overload". Nevertheless, it is not uncommon to find such old chargers in workshops.

  • Fire and explosion due to a short circuit in the battery

    If a battery shorts, the current flows so high that thinner metallic objects immediately glow and burn. With thicker metal objects (e.g. wrenches) the current flows so high that the battery acid foams violently. Large amounts of oxyhydrogen are released suddenly. The battery usually bursts (explodes) and battery acid splashes around. If other ignition sources are present, further explosions and fires can occur.
Particularly critical situations that can lead to a short circuit:
  1. Improper disconnection of the battery (before removal or during electrical work on the vehicle), e.g. B. first disconnect the positive pole.
  2. Storage of removed batteries without pole protection caps in the workshop or in a storage area. Even with supposedly old, discharged batteries, a short circuit can occur.
  3. Incorrect jump-starting of vehicles with a different battery. The danger lies in the wrong procedure when connecting and disconnecting the jump starter cables.

3Protective measures

  • To avoid chemical burns When filling, it is essential to use a suitable filling hose with an acid-proof pump or a tilting device when filling the battery acid from a larger canister and to wear personal protective equipment (PPE).

    The following PPE is necessary:
    1. Protective gloves against the effects of sulfuric acid
    2. At least basket safety goggles, better face protection as well
    3. acid-resistant apron

The PSA must always be used when filling small batteries (motorcycle or small car) or when filling small containers. It is advisable to at least wear protective goggles when lifting, carrying and transporting a battery.
    Additionally must
    1. Each container (jar, bottle, canister) is made of plastic or stainless steel and is labeled with battery acid (or sulfuric acid 37%), hazard symbols and hazard and safety instructions.
    2. the employees are instructed before handling the acid using the operating instructions.
  • To Avoidance of back problems Use means of transport and lifting aids as often as possible. It is best to store and provide batteries at waist height on shelves, not on the floor.
  • To Avoiding the risk of explosion adequate ventilation is necessary. As shown above, a large workshop hall with natural ventilation is sufficient. When using modern electronic chargers, less hydrogen is released during charging.

  • When the charging process is finished, it is important to avoid sparks in the vicinity of the battery that the mains plug of the charger is unplugged first and then the pole terminals of the charging cable are removed.

    The avoidance of an increased risk of explosion in the event of “overcharging” can be achieved by using electronically controlled chargers. This technically excludes overcharging.
  • To Avoidance of a short circuit With a car battery, it is necessary to inform and sensitize the employees, since the safety here is exclusively determined by the behavior of the people. The instruction must show the particularly high risk and clarify the necessary protective measures.
    Instruction content

    1. When properly disconnecting a battery, always first disconnect the minus pole, which is connected to the vehicle body, and only then disconnect the plus pole. After disconnecting the minus pole, the pole terminal should be fixed with the connection cable in such a way that contact with the battery pole is impossible. If possible, put on the terminal protection cap now. If this is not reliably possible, the pole terminal must be covered with an insulating tape.

    2. If the batteries are removed, put on the terminal protection caps immediately.

    3. External starting by an auxiliary battery only in the following order: