A flat battery usually announces itself with a slow, labouring crank or just a click when you turn the key. Batteries in Kenya's heat typically last 2–5 years. A jump-start from another car, or from a portable jump-starter pack, will usually get you going. Doing it in the right order matters: batteries give off flammable hydrogen gas, and a spark in the wrong place can cause a burst battery.
You'll need
- Jump leads (thick ones are better), or a charged jump-starter pack
- A second car with a battery of the same voltage (12 V for almost all cars)
- Gloves and eye protection if you have them
⚠ Safety first
- Don't jump-start a battery that is cracked, leaking, swollen or smells of rotten eggs. Get it replaced instead.
- Never let the red and black clamps touch each other while any clamp is connected.
- Hybrids and electric cars have specific procedures, and some mustn't be used to jump another car. Check the manual before connecting anything.
- No smoking or naked flames near the batteries.
Step by step
- 1
Position the cars
Park the helper car close enough for the leads to reach, without the cars touching. Both engines off, handbrakes on, ignition keys out, and lights and accessories off in both cars.
- 2
Identify the terminals
Open both bonnets and find the batteries (a few cars have them in the boot, with remote jump terminals under the bonnet — check the manual). The positive terminal is marked + and often has a red cover; negative is marked −.
- 3
Red clamp to the flat battery's +
Connect one red clamp to the positive (+) terminal of the flat battery.
- 4
Other red clamp to the good battery's +
Connect the other red clamp to the positive (+) terminal of the helper car's battery.
- 5
Black clamp to the good battery's −
Connect one black clamp to the negative (−) terminal of the helper car's battery.
- 6
Last black clamp to bare metal on the flat car
Connect the final black clamp to an unpainted metal part of the flat car's engine or body — a bolt or bracket on the engine block, well away from the battery. This earths the circuit, and means the final connection (which may spark) happens away from any battery gas.
- 7
Start the helper car
Start the helper car and let it run for 3–5 minutes at a slightly raised idle to put some charge into the flat battery.
- 8
Start the flat car
Try to start the car with the flat battery. If it doesn't start, wait a few more minutes and try again, cranking for no more than about 10 seconds at a time. If it still won't start after a few tries, stop: the problem may not be the battery.
- 9
Remove the leads in reverse order
With both engines running, remove the clamps in the exact reverse order: black from the bare metal, black from the helper battery, red from the helper battery, and finally red from the previously flat battery. Keep the clamps apart as you go.
- 10
Keep the engine running
Drive for at least 30 minutes (not just idling) so the alternator can recharge the battery. Avoid switching off until you're somewhere you could get help if it doesn't restart.
Pro tips
- A compact lithium jump-starter pack is one of the best things to keep in your boot — no second car needed. Keep it charged.
- If the battery goes flat again within a day or two, have the battery and the charging system tested. It may be an old battery, a faulty alternator, or something draining power while the car is parked.
- Clean white or green crust off the battery terminals (engine off, with a wire brush and a little baking soda and water). Corroded terminals can mimic a flat battery.
Stop and get a mechanic if…
- It clicks but won't crank even with a jump — possibly the starter motor or a bad connection.
- The red battery warning light stays on once the engine is running.
- The battery is more than about four years old and keeps going flat.
General guidance only. Your owner's manual has the final word on specs, fluids and procedures for your vehicle. Last reviewed 24 September 2026.