JHZR2
Staff member
Was playing around with a few batteries today, as the WM battery in my truck was not holding charge. Used my HF battery test tools, and shot their use with my iphone.
The videos are in HD, but I guess I shot them the wrong direction, so they display wrong in youtube. Pardon my poor discussion, I spoke to all of this on the fly with no script, and I dont have a good recording voice.
Anyway, first I tested the 1 year old Group 75 battery from my truck. I used the digital and carbon pile tester. While my charger says it was sulfated, and voltage always drops fast when not under charge, I cant say I got a compelling result from either test.
After that I took a known good group 49 battery that is at least 6 years old, and did the same tests. I wanted to video a few different aspects, and also verify similarity in result.
One thing that I show in this is the determination of impedance. In this video, open circuit resting voltage was 12.47, and under 400A of load on the carbon pile, I got to 10.36. Remember that Vt=Voc-IR, so we have 10.36=12.47-400*R, so R=0.005275 Ohm. The significance of this is that the digital meter gave a reading of 4.56 mOhm = 0.00456 Ohm. So let's say that the carbon pile tester is off by a bit and was actually pulling 460A, well then the resistance is identical on the two. Here is the group 49 video:
Another interesting thing to note is that while on the lead post battery, the multimeter voltage and digital tester voltage were identical, on the side post battery where I used a steel threaded connector to have a post that I could attach to, the multimeter and digital meter did not provide the same voltage. This could be seen in my first video and in this one, of a new, replacement group 75 battery which I got today from Walmart on exchange for the other that would not hold charge. Given ambient conditions, full charge should have been around 12.53V, and this one read below that so it was slightly undercharged, but that's OK. It tested well, though the CCA was a bit low. Might be the steel bolts used in the screw terminals...
The new battery:
The videos are in HD, but I guess I shot them the wrong direction, so they display wrong in youtube. Pardon my poor discussion, I spoke to all of this on the fly with no script, and I dont have a good recording voice.
Anyway, first I tested the 1 year old Group 75 battery from my truck. I used the digital and carbon pile tester. While my charger says it was sulfated, and voltage always drops fast when not under charge, I cant say I got a compelling result from either test.
After that I took a known good group 49 battery that is at least 6 years old, and did the same tests. I wanted to video a few different aspects, and also verify similarity in result.
One thing that I show in this is the determination of impedance. In this video, open circuit resting voltage was 12.47, and under 400A of load on the carbon pile, I got to 10.36. Remember that Vt=Voc-IR, so we have 10.36=12.47-400*R, so R=0.005275 Ohm. The significance of this is that the digital meter gave a reading of 4.56 mOhm = 0.00456 Ohm. So let's say that the carbon pile tester is off by a bit and was actually pulling 460A, well then the resistance is identical on the two. Here is the group 49 video:
Another interesting thing to note is that while on the lead post battery, the multimeter voltage and digital tester voltage were identical, on the side post battery where I used a steel threaded connector to have a post that I could attach to, the multimeter and digital meter did not provide the same voltage. This could be seen in my first video and in this one, of a new, replacement group 75 battery which I got today from Walmart on exchange for the other that would not hold charge. Given ambient conditions, full charge should have been around 12.53V, and this one read below that so it was slightly undercharged, but that's OK. It tested well, though the CCA was a bit low. Might be the steel bolts used in the screw terminals...
The new battery:
