Battery quality and measurable resistance

softdown

It seems that is a strong correlation between battery quality and resistance. I have heard of manufacturers refusing to sell batteries that measure over 5 - though I have bought such a car battery from Interstate. My average battery measures about 3.5 using a common battery diagnostic tool. Even the AGM batteries noted for very high quality measure about 3.5   I am unsure how AGM compares with FLA (flooded lead acid) in terms of resistance. AGM wrapping the cells in an Absorptive Glass Mat.

As batteries weaken and wear out the resistance goes up. When retiring batteries I often find a resistance of ~7.5 or more.

Interestingly I bought a well used camper van last week - prepped for off grid camping. The previous owner did quality work and bought quality stuff. The 12V batteries measure only ~1.5 in resistance. By far the lowest measurement I have ever seen. Wondering about that.

Seems prudent to measure resistance when selecting new batteries for purchase. Anyone do that? I always forget.

Marc Kurth

Here is a link to Concorde's published Internal Impedance in Milliohms. Note the relationship between the L16 2v and 6v, and the 2v vs. 6v GC2 Tall.

https://centexbatteries.com/irissbattery.pdf

RCinFLA

Most of my flooded 100AH lead-acid 12v batteries measure less than 4 milliohms, measured with 1 kHz AC battery impedance meter.  

AGM's are generally lower because they have less migration path distance across electrolyte soaked glass mat and higher electrolyte acid concentration compared to flooded cells.  Some AGM's are significantly lower impedance but actual impedance depends on manufacturer.

Saggys

At work we use an Alber cell corder to measure individual cell voltage and resistance, it also measures connection bar resistance on our UPS batteries and commonly see resistance in Micro ohms.