This isn't marketing. It's an open explanation of how QZ works — we write it because we also go in front of people who read data critically: scientists, engineers, workshops and fleets.
The 12V battery is today the most common cause of car breakdowns — per ADAC it accounted for 45.4% of callouts in 2025, and it is the leading cause regardless of powertrain, including EVs. verified
Meanwhile modern cars save fuel with smart energy management — start-stop, charge management, regenerative braking. Battery makers themselves say these systems "place increased demands on the battery" and often leave it working in a partial state of charge. verified With an unfavourable usage profile (short trips, long standing, heavy electrical load) the battery can spend a lot of time in a state that accelerates its degradation.
QZ makes that hidden at-risk time visible and warns you before a quiet decline becomes a car that won't start — and because it talks over 4G, it can warn you remotely, not only when you're standing next to the car.
QZ is not a workshop battery test. It does not replace a CCA / load test, real capacity (Ah) measurement, internal-resistance measurement, parasitic-draw diagnosis, or lab sulfation analysis. It is a predictive warning system, not a workshop-grade gauge. If QZ signals risk, a workshop makes the final diagnosis.
Voltage by itself is not clean proof of a battery's state — it's affected by temperature, surface charge, load, time since the last drive, battery type and the car's BMS strategy. So we do not claim "X volts = sulfation".
Instead of instantaneous voltage we work with risk-band exposure — how much time the battery spends below a healthy state of charge, corrected for temperature, driving, charging and battery type. QZ hypothesis Makers (e.g. Varta) state that when resting voltage falls below ~12.4 V the battery should be recharged as soon as possible, because sustained low charge leads to sulfation verified — but the exact risk thresholds vary by chemistry, age and temperature, so we don't present them as universal numbers until we confirm them by measurement.
| Type | Indicative life | Cycle endurance (order of) |
|---|---|---|
| Conventional (flooded) | ~3–5 yr | ~200–300 cycles |
| EFB | 3–5 yr | ~400–600 (~2× flooded) |
| AGM | 5–8 yr | ~400–800 (~3× flooded) |
| GEL | 6–15 yr | ~800–1,200 |
These are indicative figures from technical/industry sources, not cycles-at-50%-DoD from a specific maker's datasheet — makers publish engine-start counts and relative multipliers. Real-world life depends on usage profile, temperature and state of charge. GEL is mainly a traction chemistry, rarely a car starter battery.
Operating rule: AGM is replaced by AGM, EFB by EFB, and after replacement the battery must be registered/reset in the BMS — otherwise premature failure follows. verified
An EV has no alternator; its 12V battery is charged by a DC/DC converter from the high-voltage pack. The 12V problem exists in EVs too verified, but the mechanism differs — sleep/wake modes, parasitic drain, software wake-ups — not necessarily classic sulfation for the same reason as combustion cars. So we mark QZ's EV logic as continuously validated QZ hypothesis and don't overstate it.
The QZ device (based on the Teltonika FTC880) has a low own draw in idle modes (order of a few mA, < ~1 mA in power-off sleep at 12 V, per the maker's datasheet). verified In a typical "storage" profile it is far below the standby draw of many cars; we don't state it as a fixed universal multiplier, because cars' standby draw varies.
QZ does not guarantee detection of all faults and does not replace workshop diagnostics. It is a tool that turns the invisible at-risk time of a battery into an early warning and gives a person the chance to act sooner — before a breakdown, a replacement or a tow.
Related: How to monitor your car battery remotely — without Bluetooth →