How to minimise battery-related risks in materials handling operations
Are lead-acid and lithium-ion forklift batteries safe? Yes, as long as you use them correctly. Our guide summarises the key safety issues and precautions.
We’ll deal with Li-ion and lead-acid batteries separately, as they present different potential risks. But first, let’s emphasise that the battery manufacturer’s detailed instructions must be followed in each case. Another basic rule is that only suitably trained personnel should be charging, changing or maintaining forklift batteries. It’s also worth highlighting that forklift batteries are heavy – so you shouldn’t move them without using mechanical aids.
Lead-acid forklift batteries
The three main safety concerns surrounding lead-acid forklift batteries are:
1. They contain acid.
The sulphuric acid electrolyte can burn skin and eyes. It may also be inhaled as a mist. In addition, lead-acid batteries contain toxic lead compounds. The risk of contact with acid and lead applies mainly to ‘flooded lead-acid batteries’. Those are the traditional forklift batteries – still widely used today – which you top up with distilled water. The alternative ‘sealed lead-acid batteries’ can only spill their contents if damaged.
2. They produce hydrogen and oxygen.
That’s a potentially explosive mixture. The gases are released mainly during charging.
3. They can give shocks.
Depending on how high the voltage is, electric shocks from forklift batteries can cause severe burns. Meanwhile, short circuiting due to battery contact with metal objects may produce sparks. That’s another hazard, which may damage equipment or set light to gases.
To minimise forklift battery acid risks:
- Wear suitable PPE when charging or maintaining lead-acid batteries. That means goggles or face shield, gloves, apron and boots – all of which must be acid-resistant.
- Store the batteries upright.
- Make sure the electrolyte isn’t frozen, before charging. Check the electrolyte level and specific gravity regularly.
- Top up with distilled water after fully charging the battery and allowing it to cool down. Avoid overfilling, splashing or spilling.
- Charge the battery carefully, according to the manufacturer’s instructions. Use the correct charger, ensuring it’s manufacturer-approved and compatible with the battery. Avoid deep discharging, overcharging or undercharging.
- Clear up acid spills on floors to avoid slip hazards. First use a bonding agent, like sand, to absorb the acid. Then apply a neutralising solution such as sodium bicarbonate. Routinely clean the battery top, terminals, case and tray with warm water or battery cleaner to remove chemicals and prevent corrosion.
To prevent lead-acid battery explosions and fires:
- Store, charge and maintain lead-acid batteries in a cool, dry and well-ventilated area. The battery manufacturer’s instructions will specify optimum temperature ranges.
- Leave the battery tray cover or compartment cover open while charging, to dissipate gases. Check that the battery ventilation holes are clear.
- Keep the area clear of naked flames (NB no smoking), heat sources, and electrical devices which might produce sparks.
- Cover terminals and connectors with cardboard or other insulating material to minimise the risk of short circuits.
- Unplug or switch off the charger before connecting or disconnecting with the battery. Disconnect the battery from the truck and charger before maintenance work.
- Regularly check the condition of electrical cables, connectors, terminals and related structures for fraying, loosening, cracking, corrosion or other damage.
To prevent electric shocks from forklift batteries:
- Follow safe electrical practices as summarised above. (See last three points, on covering, unplugging and checking.)
- Take care when using metal tools. Use insulated tools if possible.
- Avoid battery contact with metal jewellery.
Li-ion forklift batteries
An intact Li-ion battery, used, charged and maintained in line with the manufacturer’s instructions, poses no danger. With no acid leak risk, there’s no need for PPE. No explosive gases are emitted during charging. There’s also less handling of the battery, as it needs no daily maintenance and isn’t usually removed from the truck for charging. That reduces the scope for electric shocks.
A battery management system (BMS) monitors the Li-ion battery and protects against conditions including overload, short circuit, deep discharge and overcharge. Each individual cell is enclosed by metal, and so is the overall battery structure. The battery itself is not flammable. It does contain some flammable and toxic substances, but these remain safely contained unless the battery is seriously damaged.
So why do Li-ion batteries sometimes catch fire?
The following catastrophic – and relatively rare – factors can sometimes overcome an Li-ion battery’s inbuilt safety features:
- Severe physical damage
- Exposure to a fire in the building
- Submergence in flood water
- Extreme overcharging or discharging
Importantly, the Li-ion battery’s resistance to such conditions depends on its build and design quality. Incidents of Li-ion fires are often related to use of cheap, poor-quality batteries. Breakdown of the battery’s safety defences may result in a ‘thermal runaway’. This is an uncontrolled release of heat energy, which can lead to a fire or explosion.
To avoid an Li-ion battery fire:
- Use high-quality Li-ion batteries approved by the forklift manufacturer. Steer clear of cheap batteries from suppliers or manufacturers without a strong reputation.
- Don’t disassemble or modify the battery in any way.
- Store, charge and maintain Li-ion batteries in a cool, dry and well-ventilated area. The battery manufacturer’s instructions will specify optimum temperature ranges.
- Keep the area clear of heat sources and protect the batteries from direct sunlight.
- Keep the area clear of combustible materials.
- Follow the battery manufacturer’s instructions for charging. Allow the battery to cool down first. Use only the manufacturer-approved charger.
- Routinely inspect and maintain the battery, charger cables and connectors according to the manufacturer’s instructions.
A note on safe battery recycling
Collection of end-of-life lead-acid and Li-ion forklift batteries for recycling should ideally be arranged with their supplier. Used forklift batteries awaiting collection should be kept separately from other battery types. Most importantly, Li-ion batteries should not be mixed with others. Keep them in a sheltered container, remote from your main buildings. These precautions are especially important if an Li-ion battery is damaged.
Lead-acid or Li-ion forklift batteries?
We offer a choice between Li-ion batteries and lead-acid batteries on almost all Cat® electric counterbalance and warehouse equipment ranges. You can expect unbiased advice on which is better for your operation. See our Power Sources guide for further information.
