If your car clicks or turns over slowly, and a jump start gets it going and it keeps running, it's the battery. If it starts on a jump but dies again after a few minutes, or it cut out while you were driving, it's the alternator. If your battery is more than three years old, it's probably the battery.
Quick answer · How to check, in two minutes
The easy test, no tools needed
Get a jump start. Then watch what happens.
It starts and keeps running. Your battery was flat. The alternator is charging it again. You need a new battery, because a battery that goes flat once will do it again.
It starts, runs a few minutes, then dies. The alternator is not charging. You need the alternator fixed.
It does not turn over at all, but your dashboard lights are bright. This is usually the starter, not the battery.
One warning. Do not pull off the battery cable while the engine is running. Old advice says to try this. On a modern car it can damage the computer and cost you far more than a battery.
What the signs mean
| What you see | Usually |
|---|---|
| Slow turning, or fast clicking | Battery |
| Dashboard lights go dim when you turn the key | Battery |
| Car was fine yesterday, dead this morning | Battery |
| Battery is over three years old | Battery |
| Engine died while you were driving | Alternator |
| Red battery light on the dashboard while driving | Alternator |
| Headlights dim when idling, brighter when you rev | Alternator |
| Whining noise or burning smell from the engine | Alternator |
| One loud click, lights stay bright | Starter |
| Nothing at all, no lights, no click | Battery, or a loose cable |
That last one matters. Nairobi roads shake cables loose. Before you buy anything, check both battery cables are tight and clean. We have driven out to cars that needed thirty seconds with a spanner.
The test with a multimeter
If you have one, take three readings.
1. Engine off, car parked for an hour
Red probe on the positive terminal, black on the negative.
- 12.6V or more — battery is good
- 12.4V — about three quarters full
- 12.2V — about half full, getting weak
- Under 12.0V — flat
2. Start the engine and read it again
- 13.7V to 14.7V — alternator is working
- Under 13.0V — alternator is not charging. This is your problem
- Over 15.0V — charging too hard. This kills batteries. It is why a new battery can die in a few weeks
3. Engine running, headlights and air conditioning on
It should stay above 13.0V. If it drops, the alternator cannot handle the load.
Most people never take that second reading. A car can start fine every morning for weeks on an alternator that is slowly dying, until the day it leaves you stuck.
Why this happens so often in Nairobi
Short trips in traffic. Your alternator needs a long drive to fill the battery. Twenty minutes crawling on Mombasa Road with the engine idling, the lights on and the air conditioning running uses more power than it puts back. Do that every day and your battery sits half empty for months. That wears it out early.
Rough roads. Shaking loosens the cables and damages the plates inside the battery.
Old batteries sold as new. Some sellers refurbish used batteries and sell them as new. They work on the day and fail a few months later. If a price is far below everyone else, this is usually why.
No guesswork
What we check before we sell you anything
When you call, Brown does not just arrive and fit a battery. He tests first.
He checks the cables — loose, dirty or swollen. That costs you nothing to fix and we would rather tell you.
Then he reads the battery voltage with the engine off. Then he starts the engine and reads the alternator, and checks it holds up with the lights and air conditioning on.
If your battery is fine, we tell you and we do not sell you one. We tell you what we found so you can go to a mechanic knowing what to ask for. We do not do alternator or electrical repairs, so we gain nothing by pretending.
That costs us sales. It is also why people call us again.
What it costs
Testing is free. The call-out is free. We do not charge to come and tell you your battery is fine.
If you do need one, batteries start at KSh 4,500, with delivery and fitting included and a 12-month warranty. You pay after your car starts, by M-Pesa or cash.
Questions people ask
Can a bad alternator kill a new battery?
Yes, fast. An alternator charging over 15V will ruin a new battery in weeks. If you just replaced your battery and it died again, get the charging checked before buying a third.
My car starts but the battery light is on. Can I keep driving?
You are running on the battery alone with nothing refilling it. You have maybe twenty minutes to an hour before the engine stops, usually with no warning. Get somewhere safe now.
How long should a battery last in Nairobi?
Three to five years. Closer to three if you mostly do short trips in traffic.
Will a jump start fix it for good?
No. A jump start gets you moving today. It does not repair a battery that cannot hold charge, and it does nothing for a bad alternator.
