Multifunction digital car battery tester 12V 24V

Diagnostic instrument for 12V 24V car batteries

The main job of the FNBTM24 is assessing battery condition through a set of parameters that show whether the battery is still healthy or is starting to fade. The device measures voltage, internal resistance, state of charge (SoC), state of health (SoH) and CCA value, that is cold cranking amps, a key parameter for starter batteries. The CCA test is selectable up to 2000A, which makes the instrument suitable for a wide range of automotive and professional batteries.

In practice this tells a simply flat battery from one that is genuinely worn out. The internal resistance measurement, taken without discharging the battery, shows how far it has aged. The battery test result is shown in three state-of-health bands: poor from 0 to 60%, caution from 60 to 80% and good from 80 to 100%. That kind of at-a-glance verdict is useful when you have to give the customer a quick, understandable answer or decide whether to replace, recharge or keep watching the battery.

Works with several battery types

The device is designed for 12V and 24V systems and works with several battery types, including AGM, GEL, EFB and standard flooded lead-acid batteries. It supports six international reference standards: CCA, IEC, EN, DIN, JIS and GB. That makes it suitable wherever batteries with different specifications are in use, such as multi-brand workshops, fleet maintenance and technical work where nominal values quoted to different standards have to be compared.

Engine cranking test

As well as the static battery diagnosis, the FNBTM24 runs a cranking test, which shows how the system really behaves when the starter motor draws a heavy current. During the test the voltage drop is measured and compared with operating thresholds: a voltage of 10.2V or above means a good condition, between 9.6V and 10.2V a weak one, while values below 9.6V mean a critical condition.
This pinpoints not only tired batteries but also problems with the wiring or the supply system. Where starting is slow, ignition is difficult or behaviour comes and goes, it shows how the system responds at its most critical moment, which is a more reliable verdict than an open-circuit reading alone.

Charging system and alternator analysis

The FNBTM24 analyses the charging system by monitoring voltage while the vehicle is running. It identifies overvoltage, undervoltage or correct alternator operation, using dedicated reference thresholds for 12V and 24V systems.
Minimum and maximum voltage are recorded, along with any fluctuation under real load, which helps to pinpoint charging faults. This is particularly useful when the battery keeps going flat, warning lights show on the instrument panel, or problems come back even after the battery has been replaced. Looking at battery and charging system together gives a complete diagnosis and cuts the risk of a repair that fixes nothing.

Real-time waveform display

The FNBTM24 battery tester includes a graphic waveform display that shows voltage variations in real time during testing. It makes fluctuations under load, the progress of charging and the behaviour of the system during cranking immediately visible. Compared with a numeric reading alone, the graphic display is a more advanced diagnostic aid, making intermittent faults and electrical instability easier to spot. Particularly useful for professional work in the workshop, in technical service and in advanced maintenance.

Clear display, immediate reading

The device has a 2.4-inch colour screen with Day/Night modes, which keeps it readable in different lighting conditions. A waveform display is also available, useful for following voltage behaviour and load variations more intuitively than a numeric reading alone.
This display mode makes the data easier to read and helps you spot anything unusual during testing.

Non-destructive analysis, immediate diagnosis

The FNBTM24 battery tester carries out a full diagnosis quickly and without disconnecting the battery from the vehicle. A one-step automatic test analyses voltage, internal resistance, state of charge (SoC), state of health (SoH) and cranking capability (CCA). The colour display shows results and status indicators clearly, so the data reads at a glance. This quickly reveals inefficient batteries or problems in the starting and charging system, making it a dependable instrument for workshops, auto electricians and professional maintenance on 12V and 24V vehicles.

Advanced safety protection

The FNBTM24 battery tester includes advanced protection that keeps every measurement safe. Reverse polarity and overvoltage protection prevent damage to the instrument and to the battery even if the connections are wrong. The insulated clamps make stable, reliable contact, cutting the risk of sparks or poor contacts. That makes it particularly suitable for professional use in the workshop and in maintenance, where operating safety and reliability matter when working on automotive electrical systems at 12V and 24V.

Safety, build and portability

The design is compact and portable, measuring about 80.52 × 155.76 × 28.15 mm and weighing about 479 g. The insulated clamps make safe, stable connections during measurement.
Reverse polarity and overvoltage protection are built in, which adds to the operating safety and reliability of the instrument in daily use on the bench or directly on the vehicle.

Where it gets used

The device suits a wide range of situations. In the workshop it handles the first check of battery and charging system when a vehicle is booked in. In fleet maintenance it allows periodic checks on 12V and 24V systems, helping to cut downtime caused by weak batteries or charging problems.
In technical service it is useful for quick diagnosis in the field, since it works with the battery still installed. It can also be used in training, to study in practice how batteries and charging systems behave.

• Main unit
• Data cable
• Carry bag
• User manual

User manual (English)