Key takeaways
- Slow cranking is the most reliable early warning sign of a dying battery.
- Dashboard battery-shaped icons usually indicate alternator, not battery, trouble.
- Any battery over 3 years old in San Diego should be load-tested annually.
- A single deep discharge can permanently reduce battery capacity.
1. Slow, labored cranking
A healthy starter cranks the engine at roughly 200 RPM. A battery that's failing struggles to hold that speed under load, producing the classic 'rrrrr... rrrrr... rrrrr...' before the engine catches. If cranking sounds noticeably slower than it did a month ago, the battery is on borrowed time.
2. Dashboard warning lights
The battery-shaped icon on your dashboard is misnamed — it's really a charging system warning. If it comes on while driving, the alternator is failing to charge the battery. The battery itself is fine at that moment, but will run down over the next hour or two of driving.
3. Dim headlights at idle
Notice your headlights get noticeably dimmer when you stop at a red light, then brighten when you accelerate? That's the battery running low and the alternator working overtime to compensate. Common warning sign of a battery approaching end-of-life.
4. Clicking noise when you turn the key
A rapid clicking (like a machine gun) usually means the battery has just enough power to engage the starter solenoid but not enough to turn the engine over. Time to jump start, then replace immediately — this battery is done.
5. Swollen or misshapen battery case
Battery cases should be perfectly rectangular. Bulging sides or a puffed-up top indicates internal damage — often from overcharging or extreme heat. This is not a repair situation; replace the battery and check whether the alternator is at fault.
6. Rotten egg smell under the hood
The smell of sulfur or rotten eggs means the battery is venting hydrogen sulfide gas — typically because it's boiling from overcharging or has an internal short. Do not attempt to jump start a battery producing this smell. Call for mobile replacement.
7. Corrosion on the terminals
Mild corrosion can be cleaned. Heavy corrosion — thick white or green crust that reforms within weeks of cleaning — usually indicates the battery is venting excessively, which points to age or overcharging.
8. It's simply old
In Southern California, batteries past 3 years should be load-tested annually. Past 4 years, replace proactively rather than reactively. A $200 planned battery replacement is dramatically cheaper than a $150 tow plus a $250 emergency replacement — and vastly less stressful.
Frequently asked
Common questions
Can I test my battery at home?
A basic multimeter reads voltage but not capacity. A proper load test — which our mobile trucks perform — is the only reliable way to know whether the battery can still deliver cranking amps under load.
How much does mobile battery replacement cost?
Cost depends on the battery your vehicle requires, plus a call-out fee. Members receive a reduced $55 call-out. We provide up-front pricing before installing anything.