Battery Internal Resistance
Seasoned HDF Member
Joined: Sep 2017
Posts: 12,271
Likes: 4,952
From: England
I have a device that shows the effective internal resistance of lithium polymer cells.
It is measured in milli ohms, a very small number.
It affects cold cranking amps and is part of what load testing shows.
A perhaps simple test is to have a very accurate resistor and voltmeter. The resistor is applied and the voltage is measured. There will be a difference between what the resistor should draw to what current is actually drawn. The small difference will be the internal or effective internal resistance.
That difference in current can then be used to compute the resistance.
It is measured in milli ohms, a very small number.
It affects cold cranking amps and is part of what load testing shows.
A perhaps simple test is to have a very accurate resistor and voltmeter. The resistor is applied and the voltage is measured. There will be a difference between what the resistor should draw to what current is actually drawn. The small difference will be the internal or effective internal resistance.
That difference in current can then be used to compute the resistance.
Intermediate
Joined: Aug 2010
Posts: 36
Likes: 16
From: VIC, Australia
There is no correct number as there are too many variables, like chemistry, capacity, temperature etc'.
It directly affects cranking capacity, and a good indicator of age - higher is worse .
I have a battery analyzer, and it's a very handy tool that will measure cranking current and internal resistance in mΩ .
I record the measurement for a new battery , and gives a good indication when to replace.
It directly affects cranking capacity, and a good indicator of age - higher is worse .
I have a battery analyzer, and it's a very handy tool that will measure cranking current and internal resistance in mΩ .
I record the measurement for a new battery , and gives a good indication when to replace.
Stage II
Joined: Mar 2026
Posts: 2
Likes: 0
As for how much resistance is too much, it can vary depending on the type of battery. For example, a healthy lead-acid battery typically has internal resistance values ranging from a few milliohms to about 20 milliohms. If you start seeing values significantly higher than that, it might indicate that the battery is aging or has developed issues.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,638
Likes: 6,445
From: Honah Lee
I wouldn't try checking it with your ohm meter. Just feed it with about 13-14 DC maintenance juice. Don't feed it all the time however. Let your motorcycle do it's thing.
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Stage II
Joined: Mar 2026
Posts: 2
Likes: 0
As for how much resistance is too much, it can vary depending on the type of battery. For example, a healthy lead-acid battery typically has internal resistance values ranging from a few milliohms to about 20 milliohms. If https://tropical-casino.com/ you start seeing values significantly higher than that, it might indicate that the battery is aging or has developed issues.
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Grand HDF Member
Joined: Jan 2012
Posts: 4,459
Likes: 2,897
From: Oklahoma
Finding "recommended" values has required quite a search. A search for internal resistance in motorcycle batteries uncovered this guidance. Below 10 milliohms is a good battery, 10 to 15 is marginal, and above 15 means it will let you down in the near future. Nowhere in my search was the effect, if any, on the charging system of high internal resistance. High resistance may be what contributes to voltage regulator and/or stator failure when trying to stretch that last season out of an old battery.
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