Review on 🔌 DROK Digital Multimeter DC Power Monitor, 6.5-100V 20A Voltage Amperage Power Energy Meter with Built-in Shunt, LCD Digital Display Volt Amp Tester Gauge by Ron Houston

These things are bee knees. I have modified all my chargers on several diesel generators to charge through them. These are backup generators and starting on the first try is crucial. It used to be difficult to say exactly how good batteries were without stress testing or hydrometer readings. Those things are still important, but now we can see at a glance how the battery is performing and most importantly, how many watt-hours it's been using. If the voltage is low (on a constant voltage/limited current charger) or the watt-hours charged are too high, you know the battery needs a closer look. Inexpensive and recommended.