Hi, a working battery can’t have zero internal resistance. If the battery had zero resistance it would be shorted. Actually it happens sometimes. For instance LiPo batteries may became shorted if discharged too low. This is due the growth of so called dendrites in the battery between the layers.
Most probably the measurement instruments you used are not able to measure the Lead Acid battery internal resistance accurately.
Here is what I’ve found about the Lead Acid battery internal resistance:
Lead Acid Battery – the lower the battery internal resistance the more the battery in good condition.
To be exact, for a 12V Lead Acid Battery,
If IR>30 milliohm, battery is in very bad condition. Probably unusable.
If IR is between 10 to 30 milliohm, still poor condition but may be usable or revivable.
If IR is between 5 to 10 milliohm, it is in good condition.
If IR is less than 5 milliohm, it is in very good condition.
But all this given criteria are just an estimate and does not guarantee the battery condition. As the condition depends upon some other factors too.
I have one question more for curiosity, I did the same test on a 12v car battery (lead acid) and got a zero resistance reading…..is this due the construction type?
I tested the same battery using both a high discharge tester and an electronic car battery tester and both test said the battery is good (but that’s all they say). ]]>