Almost every vehicle either in the air, on land and at sea have a battery. Start light to heavy duty equipment, therefore, you need a battery load tester available at any time. Having a system that is reliable and has proven to give accurate readings. With a final conclusion on the decision to use batteries that you have today, or you should replace with a new one.
Commercial battery load tester are priced from reasonable to more expensive, and the unit price and a higher offer is very good not only viral, but the stress test and alternator and starter testing as well. Many of these are built with the rugged “carbon” pile resistors (some variable) and some with microprocessor control and metering luxury.
So that you can know about a battery tester, here is a homemade battery load tester project, built with budget in mind. It consists of several “nichrome” wire loads applied to the battery through the starter contactor old, and LED bargraph voltmeter thrown for good measure. He also has a fan too.