A car that sits won't tell you it's in trouble. You usually find out about a weak battery when you're standing next to it and it won't start. You can know earlier — and from anywhere.
A weak 12V battery is, per ADAC, the most common cause of car breakdowns — 45.4% of callouts in 2025, regardless of powertrain. For a car that isn't driven every day, several things add up:
The result: after a few weeks of standing the voltage can be in a zone where a start is no longer certain — and you can't see it from the outside.
A charger and QZ aren't rivals. The charger tops the battery up; QZ follows the voltage over time and warns you when it sees the battery getting worse — even when you're not at the car.
The difference isn't that it "measures voltage" — a cheap voltmeter does that too. The difference is that you find out even when you're not at the car — anywhere the device has mobile coverage. QZ talks over the cellular network (4G LTE is included in the device price, with no Wi-Fi and no phone pairing), so you don't need to be at the car or have internet in the garage.
QZ doesn't just watch the instantaneous voltage — it watches the battery's behaviour over time: how fast it drops, how it recovers, how long it spends in a risk band, in the context of temperature and battery type. When the behaviour worsens, QZ warns you. A warning can give you time to act (charge, a longer drive, a workshop), but it doesn't guarantee a successful start — QZ won't charge the battery for you, and some failures arrive without warning. Exactly what and how we measure is described in the QZ Methodology.
Price. 199 € incl. VAT — device, SIM, data and the first 12 months of service. Shipping 5 € (SK), 10 € (EU). Then 49 €/year, renews automatically, cancel any time.