If you’ve recently tested your car battery using a diagnostic tool like the Konwei BT22, you might find yourself looking at a list of technical readings. Let’s break these down into plain English so you know what they mean and what to do with the information.
If you’ve recently tested your car battery using a diagnostic tool like the Konwei BT22, you might find yourself looking at a list of technical readings. Let’s break these down into plain English so you know what they mean and what to do with the information.
1. CCA Reading (Cold Cranking Amps)
CCA measures how much power your battery can deliver at 0°F (-18°C) for 30 seconds while maintaining at least 7.2 volts. A healthy battery should meet or exceed the CCA rating shown on the battery label. If your reading is significantly lower, it’s a sign your battery may be weakening, especially in cold weather.
2. Voltage Reading
This is the basic measurement of how much electric potential your battery holds. A fully charged car battery should read around 12.6 volts when the engine is off and around 13.7 to 14.7 volts when the engine is running. Anything lower might indicate a discharged battery or an issue with the alternator.
3. Resistance Reading (Internal Resistance)
This shows how much resistance is inside the battery. Lower resistance is better because it means the battery can deliver power more efficiently. High resistance suggests the battery plates may be deteriorating or sulfated (a buildup of lead sulfate crystals on the battery plates, which reduces performance and capacity) — a sign the battery is nearing the end of its life.
4. State of Charge (SOC)
SOC indicates how fully charged your battery is, shown as a percentage. For example, 100% means fully charged, 50% is half-charged, and anything under 30% may struggle to start the car. If your SOC is low, a recharge might solve the problem — but if it keeps dropping quickly, the battery might need replacement.
5. Ripple Voltage
Ripple voltage measures the stability of the charging current coming from your alternator. It should stay under 50mV (0.05V). Higher ripple voltage can mean a failing alternator or bad diodes, leading to inconsistent charging and possible damage to the battery or car electronics.
6. Loaded Voltage
This measures the alternator’s output when the engine is running and major accessories (lights, AC, radio, etc.) are turned on, creating a load. A healthy alternator should read 13.9 to 14.7 volts under load. If it drops below 13.9 volts, the alternator may be struggling to supply enough power, which could lead to battery drain.
7. Unloaded Voltage
This measures the alternator’s output with the engine running but without any extra load. It should typically stay between 13.7 and 14.7 volts. If it’s lower than this, the alternator might not be charging the battery properly. If it’s too high (over 15 volts), the alternator could be overcharging, which may damage the battery or electronics.
8. Waveform
Some advanced testers, like the Konwei BT22, provide a visual waveform of the battery’s performance over time. This helps diagnose irregularities such as voltage drops, spikes, or unstable charging patterns — useful for spotting deeper electrical problems. The waveform can also help detect parasitic drains (when an electrical component keeps drawing power after the car is off), which might explain why your battery keeps going flat unexpectedly.
Final Thoughts
Understanding these readings can help you catch battery issues early, avoiding unexpected breakdowns and saving money on premature replacements. If your results show signs of a weak battery, high resistance, or unstable charging, it’s worth getting a professional check-up — or replacing the battery before it leaves you stranded.
If you need help interpreting your battery test results or choosing a new battery, feel free to contact us. We’re here to make sure your car starts smoothly every time!