KONNWEI KW371 Battery & Relay Tester — 6V/12V/24V Portable Analyzer with Relay Check and Cranking/Charging Tests

The KONNWEI KW371 is a portable 2-in-1 diagnostic tool that tests 6V/12V/24V batteries and 4/5-pin relays to quickly identify battery health, cranking issues, charging problems, and relay faults.

The KW371 combines a full-featured battery analyzer with a relay tester in one handheld instrument, built for workshops, fleet maintenance, and serious DIYers. It supports a broad range of battery chemistries and global rating standards while offering cranking and charging evaluations plus a dedicated relay check for 4- and 5-pin automotive relays. Rugged alligator clips supply power directly from the tested battery and the unit can export reports to a Windows PC.

How does the KW371 determine battery condition?

The tester runs a multi-parameter analysis to give a clear state-of-health result. It measures voltage, internal resistance, state-of-charge (SOC), and estimates state-of-health (SOH), then compares those values to the battery’s rated capacity and selected standard.

• Measures 10–2000 CCA and 5–220 Ah ranges for accurate sizing.
• Works with Lead-Acid, AGM flat/spiral, Gel, EFB, and Lithium types.
• Supports standards: CCA, JIS, EN, DIN, SAE, IEC, GB for worldwide use.
• Delivers simple outcomes: Good Battery, Replace, Bad Cell, or Charge Retest.

What information does it give during cranking and charging tests?

The KW371 captures dynamic data during engine start and alternator operation to isolate starting or charging faults. Cranking tests record minimum and maximum voltages and duration in milliseconds, while charging tests evaluate loaded and unloaded ripple to detect alternator or regulator issues.

• Cranking: reports starting voltage and cranking time to spot weak starters or depleted batteries.
• Charging: shows voltage under load and ripple readings to reveal alternator problems.
• Graphical waveform display shows real-time voltage behavior for clear interpretation.
• Instant verdicts help decide if the fault is battery, alternator, or starter related.

How does the relay tester function and why is it useful?

The integrated relay tester checks 4-pin and 5-pin automotive relays without removing them from the vehicle’s fuse box in most cases. It verifies coil continuity and contact switching, making it easier to pinpoint relay-driven circuit faults such as lighting, fuel pump, or fan failures.

• Diagnoses coil failure and contact wear for 4-pin and 5-pin relays quickly.
• Eliminates guesswork—no need to dismantle fuse boxes on many vehicles.
• Saves time during troubleshooting by confirming relay functionality on the spot.
• Useful for both professional shops and advanced DIY electrical checks.

What safety and usability features should I expect?

The KW371 is built to be used on-the-go with durable clamps and polarity reverse protection to prevent user errors. It offers an 18-language interface and USB connectivity for software updates and printing diagnostic reports from a Windows PC.

• Powered directly by the tested battery—no separate batteries required.
• Polarity reverse protection prevents damage from incorrect clip connections.
• Graphical display and clear pass/fail messages reduce interpretation mistakes.
• USB PC link enables firmware updates and report export for record-keeping.

Who is this for: The KONNWEI KW371 suits automotive technicians, fleet managers, RV and boat owners, and experienced DIY mechanics who need a single, portable instrument to diagnose batteries, charging systems, starters, and relays across 6V, 12V, and 24V vehicles. If you service multiple vehicle types or require quick, reliable on-site reports, the KW371 consolidates several diagnostic tasks into one tool.