- Feb 6, 1998
Usually just some cheap toggle switches or even a PWM adjustable dimmer.... You can build a home made dummy load pretty easily...Maine: For simple people like me when conducting the light bulb test: how does one add/subtract light bulbs load as the discharge hours transpire?
Lets say you're testing a 100Ah battery at 75F. Your dummy load should be 5A.
As battery voltage drops the current being drawn by the light bulbs also drops thus artificially inflating your true capacity if you don't add in more bulbs to maintain the 5A load..
A DC bulb drawing 1.4A at 12.72V is burning 17.8 Watts. As battery voltage approaches 10.5V that same bulb is now burning 13.1 watts and the current it is pulling from the battery has dropped to 1.25A from 1.4A. As the battery voltage drops you need to add more small lights to the circuit to maintain the desired 5A load. Course if you want a close enough figure just apply a 5A load at full charge and let it go to the 10.5V cut off. You will have a slightly exaggerated Ah capacity but at least you'll have a rough idea..