Coyote Chris
Site Supporter
When I worked on Police cars, I had a car battery load tester. You put these two big clamps on the battery terminals and hit the switch to engage this big wire wound resister that simulated some load, say a starter motor load, and watched an analog voltmeter that had ratings like Good, fair poor, etc. on its face, as well as volts. With a bad battery with high internal resistance, what you would see is the voltage drop...say to 9 volts...and then slowly plummet....
So I got to thinking today. I hadn't ridden my NT in two weeks, so I put a digital and analog voltmeter on the battery. 12.64 volts. Then I turned the key on, which engages the headlight and waited 10 seconds...the voltage dropped to 11.81 volts and stayed there. Then I hit the starter and the bike fired right up, but not before I saw the voltage drop to 11 .00 volts. It may have dropped more but without an oscilloscope, it would be hard to see on an analog meter as the bike fires right up. At idle, the voltage was 14.5.
If we knew the starter motor load (it may be in the book) we could build an easy to make battery tester and establish a voltage baselines for new, good serviceable, or poor battery conditions under load. It would be a piece of cake to make with a free Harbor freight voltmeter and a wire wound resister, although I bet there is a cheep analog meter out there that would be better. Just have to know the amp draw of the motor. Just a thought.
Plan B would be to pick a resistor that pulled a fixed current at 12 volts....say 20 amps....., and put that with a voltmeter across the battery and have folks see what their batteries say after perhaps one minute.
So I got to thinking today. I hadn't ridden my NT in two weeks, so I put a digital and analog voltmeter on the battery. 12.64 volts. Then I turned the key on, which engages the headlight and waited 10 seconds...the voltage dropped to 11.81 volts and stayed there. Then I hit the starter and the bike fired right up, but not before I saw the voltage drop to 11 .00 volts. It may have dropped more but without an oscilloscope, it would be hard to see on an analog meter as the bike fires right up. At idle, the voltage was 14.5.
If we knew the starter motor load (it may be in the book) we could build an easy to make battery tester and establish a voltage baselines for new, good serviceable, or poor battery conditions under load. It would be a piece of cake to make with a free Harbor freight voltmeter and a wire wound resister, although I bet there is a cheep analog meter out there that would be better. Just have to know the amp draw of the motor. Just a thought.
Plan B would be to pick a resistor that pulled a fixed current at 12 volts....say 20 amps....., and put that with a voltmeter across the battery and have folks see what their batteries say after perhaps one minute.