Battery care

Why your car battery goes flat

Most flat batteries aren't faulty – they just aren't being charged enough. Here's what drains yours, and how to make it last.

The number one reason batteries go flat? Not driving enough.Your battery only charges while your car's engine runs. When the car is parked, the clock, alarm and electronics slowly use power – and short trips aren't long enough for the alternator to recharge the battery.

The cycle that drains your battery

Day 21Start the carStarting the engine takes a big burst of power from the battery.Now starting from only 55% – the engine turns over slower.

Day 22Short tripThe alternator starts charging, but a short trip ends before it can put all that power back.Puts back even less – the battery can’t catch up.

Day 23ParkedWhile the car stands, the clock, alarm and computers keep using a little power.Drains what little charge is left.

Day 24Weaker batterySo the next start begins with less charge than the last – and the cycle repeats.Down to 10% – the next start may fail.

Start the carWon't start

Short trip

Parked

Weaker battery

Day 1Day 2Day 3 · Flat100%70%85%55%55%25%40%10%10%3%charge left

The result: a flat battery. Each short trip leaves it a little flatter, until one morning the car won't start. Stuck right now? How to jump-start safely.

Your car is never truly off

Modern cars keep some systems on standby all the time. A little drain is normal – too much and the battery goes flat fast.

Normal20–50 mAA 60 Ah battery lasts about 50 days parkedClock and alarm · Engine computer · Keyless entry and tracking

Worth checking50–100 mAA 60 Ah battery lasts 10–15 daysTracker on a flat backup battery · Badly wired accessory · Charger left plugged in · Boot or interior light on

Fault – get it checked100+ mAA 60 Ah battery lasts 3–5 daysDashcam with no cut-off · Stuck relay or short circuit · Computer not going to sleep

Times are approximate and assume a healthy, fully charged battery.

Have a tracking unit?Trackers run on their own small backup battery. When that backup runs flat, the tracker starts drawing power from your car battery – day and night, even while parked. Battery keeps going flat? Ask us to check your tracker.

Flat after 2–3 days parked, but tests fine when charged?Something may be draining it while the car is off. Come in for a quick drain test.

Ask us

Which branch are you closest to?Brackenfell Stellenbosch

How far must you drive?

Every start uses a big burst of power. Here's how far to drive so the alternator can put it back.

Guidelines only. Every car is different – not sure? Come in for a free battery check.

Drive most days?15–25 kmeach tripIdeally at 60 km/h or more, where the alternator charges best.

Can't drive every day?20–30 kmonce a weekA 30-minute highway drive tops the battery up.

Only short trips?Under 10 kmnot enoughThe battery never fully recharges, and damage can start within weeks.

A five-minute trip is like charging your phone for 30 seconds – better than nothing, but not enough.

What affects battery health?

What pulls your battery down – and what keeps it up.

Shortens its life

SulfationWhen a battery sits partly flat, crystals form on the plates and permanently reduce its power.

Often below 80% chargeA battery that’s often less than 80% charged starts to build up crystals (sulfation) and weakens fast.

Too few amp-hoursA battery too small for your car goes flat sooner.

Keeps it healthy

Use a trickle chargerCar standing for long? It keeps the battery full and stops sulfation.

Stay well chargedRegular longer drives keep it above 80%.

Fit the right AhChoose a battery with enough amp-hours for your car. What Ah means

How long your battery lasts

Typical battery life, depending on how the car is driven.

Highway drivingCharged fully and regularly

4–7+ years

Mixed drivingTopped up most days

3–5 years

Short tripsNever quite fully charged

2–3 years

Rarely drivenDrained, but seldom charged

1–2 years

The bottom line

15–25 kmmost days

30 minhighway, weekly

4–5+ yrsbattery life

Guidelines only. Not sure you’re on track? Come in for a free battery check.

Drive often enough, and at speed. Car standing still? Use a trickle charger – ask us about CTEK. Seeing warning signs? What test results mean.

Signs your battery is struggling

The engine turns over slowly
The battery warning light comes on
The radio or clock resets
Starting is harder on cold mornings
It's flat after 2–3 days parked
Headlights are dim when idling

Noticed any of these? Get a free battery test before it leaves you stranded. Battery light on while driving? It may be the charging: battery or alternator?

Battery going flat?

Bring it in for a free battery test at Brackenfell or Stellenbosch. We'll tell you if it needs a charge, a new battery, or a drain check.

WhatsApp us