A well-maintained battery improves starting reliability and reduces strain on the starter motor, charging system and electrical connections. Batteries often fail after periods of inactivity, poor charging, dirty terminals or repeated deep discharge rather than because of age alone.

1. Keep the Battery Clean

Dirt, moisture and acid residue on the battery top can encourage corrosion and small electrical leakage currents.

Check

• Battery case clean and dry
• No cracks or swelling
• Terminals free from corrosion
• Hold-down clamp secure
• Vent holes clear where fitted

2. Clean Battery Terminals

Corroded terminals can cause slow cranking and poor charging.

1. Switch off the machine and remove the key.
2. Disconnect the battery according to the machine procedure.
3. Clean posts and clamps.
4. Inspect cable ends for hidden corrosion.
5. Reconnect securely.
6. Apply a suitable terminal protectant if desired.

3. Check the Hold-Down

A battery should be held firmly without crushing the case.

A loose battery can suffer:

• Vibration damage
• Cracked internal plates
• Broken terminals
• Chafed cables

4. Check Electrolyte Level

Only service batteries with removable caps should be topped up.

Use

• Distilled or demineralised water

Do not add acid during normal maintenance unless a specific battery service procedure requires it.

Maintenance-free, AGM and gel batteries should not be opened.

5. Check Battery Voltage

A multimeter gives a quick indication of state of charge.

Measure after the battery has rested with no charging or heavy load for a period of time.

Voltage alone does not prove battery capacity, but it is useful for identifying a heavily discharged battery.

6. Keep the Battery Fully Charged

Leaving a lead-acid battery partly discharged encourages sulphation and reduces service life.

Common Causes of Undercharging

• Short engine-running periods
• Machine stored for months
• Weak alternator or dynamo output
• Electrical accessories left connected
• Cold weather

7. Use a Suitable Smart Charger

For machines that stand for long periods, a quality maintenance charger can keep the battery charged without continuous overcharging.

Check Charger Compatibility

• 6-volt or 12-volt system
• Lead-acid, AGM or gel battery
• Correct charging current
• Suitable maintenance/float mode

Follow the charger and battery manufacturer’s instructions.

8. Long-Term Storage

If a machine will not be used for several weeks or months:

1. Fully charge the battery.
2. Clean the case and terminals.
3. Check electrolyte where serviceable.
4. Disconnect according to the machine procedure if appropriate.
5. Use a maintenance charger if available.
6. Check the state of charge periodically.

9. Should the Battery Be Removed for Storage?

Removal may be useful if:

• The machine is stored in severe cold
• There is a known parasitic drain
• A mains maintenance charger is only available elsewhere
• The battery tray is exposed to moisture

Store upright in a cool, dry, ventilated place away from flames and sparks.

10. Cold-Weather Battery Care

Cold weather reduces available cranking performance while thick engine oil makes the starter work harder.

Before Winter

• Fully charge the battery
• Clean terminals
• Check starter and earth cables
• Use correct engine oil viscosity
• Check glow plugs or intake heater

A deeply discharged battery can freeze at a much higher temperature than a fully charged one.

11. Heat Also Damages Batteries

High temperatures accelerate internal battery ageing and water loss.

Check batteries mounted close to:

• Engine exhaust systems
• Radiators
• Hydraulic oil tanks

12. AGM and Sealed Batteries

AGM batteries are sealed and normally require no water topping-up.

Important

• Use a compatible charger
• Do not open the case
• Avoid excessive charging voltage
• Keep terminals clean and tight

13. Jump Starting

Jump starting should be done carefully.

Before Connecting

• Confirm both systems use the same nominal voltage
• Confirm polarity
• Check that the battery is not frozen or visibly damaged
• Switch off unnecessary electrical loads

Follow the machine manufacturer’s connection sequence where available.

14. Two-Battery Systems

Larger machinery may use two batteries connected in series or parallel.

Check

• Batteries are matched in type and capacity
• Connections are clean
• Interconnecting cables are sound
• Both batteries test similarly

One weak battery can pull down the performance of the whole system.

15. 24-Volt Systems

Many construction machines use 24-volt electrical systems.

Do not connect a 12-volt charger or jump source incorrectly. Confirm system voltage before attaching equipment.

16. Watch for Parasitic Drain

If a fully charged battery repeatedly goes flat while the machine is parked, check for an unwanted electrical load.

Possible Causes

• Radio memory
• Tracker or telematics unit
• USB charger
• Stuck relay
• Faulty alternator diode
• Damaged wiring

A current-draw test can identify a parasitic load.

17. Battery Isolation Switches

Machines stored for long periods may use a battery isolator.

An isolator can help reduce accidental drain, but it does not replace proper charging and maintenance.

Check whether the machine has systems that require permanent power before isolating.

18. Signs a Battery Is Near the End of Its Life

• Cranking speed drops quickly
• Battery needs frequent charging
• One cell repeatedly low
• Case swollen
• Voltage falls sharply under load
• Battery passes voltage check but fails load test

19. Load Testing

A battery can show acceptable open-circuit voltage but still have poor capacity.

A proper load or conductance test gives a better picture of battery condition.

20. Charging-System Check

Battery maintenance includes checking that the machine charges correctly.

Look For

• Charging warning lamp behaves normally
• Drive belt correctly tensioned
• Alternator/dynamo connections secure
• Charging voltage appropriate for the system

If the battery repeatedly discharges, do not replace it until the charging system has been checked.

Battery Maintenance Checklist

Item	Check
Battery case	Clean, dry, no cracks or swelling.
Terminals	Clean and tight.
Hold-down	Secure without case damage.
Electrolyte	Correct level on serviceable batteries.
State of charge	Battery kept fully charged.
Charger	Correct type and voltage.
Cables/earths	No corrosion or damage.
Storage	Charge checked periodically.

Related Agrimanual Manuals

Battery size, charging voltage, system polarity and electrical procedures vary by machine.

• Search Agrimanual for electrical and battery service information
• Search Agrimanual electrical workshop manuals
• Request a manual if your machine is not listed

Frequently Asked Questions

Should I disconnect the battery if the tractor is not being used?

It can help reduce drain, but first check whether the machine has equipment that needs permanent power. A maintenance charger is often the better option.

Can I leave a charger connected all winter?

Only if it is a suitable automatic maintenance charger designed for long-term connection.

Why does a battery go flat more quickly in winter?

Cold reduces battery output while the engine needs more cranking effort. A partly discharged battery also performs much worse in low temperatures.

Can dirty terminals stop a battery charging?

Yes. Corrosion creates electrical resistance and can affect both charging and starting.

Should I replace both batteries on a two-battery machine?

If they are a matched pair of similar age and one has failed, replacing both is often sensible because a weak old battery can affect the new one.