Internal Resistance of a Lead Battery

AI Thread Summary
The internal resistance of a typical 12V lead-acid battery is approximately 20 milliohms, but this can vary based on battery construction and age. AGM batteries generally exhibit lower internal resistance compared to Gel cells. While some believe that higher capacity batteries should have lower internal resistance due to larger electrode plates, the total ionic resistance is influenced by multiple factors including electrolyte conductivity and ion mobility. Measurements indicate that internal resistance can range from 3 to 5 milliohms for various sealed valve-regulated lead-acid batteries of different capacities. Overall, battery capacity does play a role, but it is not the sole determining factor for internal resistance.
anhtho
Messages
9
Reaction score
0
Anyone knows what is the approx. internal resistance of a lead battery, say, 12V, 20Ah.
Thanks
 
Engineering news on Phys.org
Lead acid batteries typically have an internal resistance around 20 milliohms.
 
Thanks Crosstalk for replying me.
You said 20 mOhms for a typical lead acid battery. But what is the typical ? 20, 40 or 100Ah ? (12V).
 
I'm not 100% sure on this, but I don't think that the battery's capacity matters.
 
Measurement of Internal Resistance: This is a for smaller cells but the principle is the same for "a typical lead acid battery". The IR changes as the battery ages and with State of Charge.
http://data.energizer.com/PDFs/BatteryIR.pdf
The battery construction (for Lead-Acid) affects IR, with AGM batteries having the lowest IR and Gel cells usually the highest for the same Ah rating.
 
Crosstalk said:
I'm not 100% sure on this, but I don't think that the battery's capacity matters.

I just think that the higher the capacity, the bigger the electrode plates, so the internal resistance should be smaller.
 
anhtho said:
I just think that the higher the capacity, the bigger the electrode plates, so the internal resistance should be smaller.

That's mainly true for the same type of battery construction but the total ionic resistance is a combination of factors like electrolyte conductivity, separator ionic resistance, ion mobility and electrode surface area.

Values for several different sealed valve regulated types.
3 milliohm 226Ah: http://www.power-sonic.com/images/powersonic/sla_batteries/pg_series/PG-12V200_11_Jan_12.pdf
3 milliohm 140Ah: http://www.power-sonic.com/images/powersonic/sla_batteries/ps_psg_series/12volt/PS-121400FR_11_Feb_21.pdf
5 milliohm 154Ah: http://www.power-sonic.com/images/powersonic/Info%20for%20PHR%20section%20of%20website%2011%20Nov%2015/PHR-12500_12_July_2.pdf
 
Last edited by a moderator:
Hi nsaspook, I agree that it depends on many other factors, and Ah capacity is the most important.
Thanks for the documents.
 
Back
Top