Internal Resistance of a Lead Battery

In summary, the approximate internal resistance of a typical lead acid battery, such as a 12V 20Ah battery, is around 20 milliohms. However, this may vary depending on the battery's construction and age, as well as factors such as state of charge and type of battery (AGM vs gel). Higher capacity batteries may have lower internal resistance due to larger electrode plates, but other factors such as electrolyte conductivity and ion mobility also play a role. Some examples of internal resistance values for different sealed valve regulated batteries are 3 milliohm for a 226Ah battery, 5 milliohm for a 154Ah battery, and 3-5 milliohm for a 140Ah battery.
  • #1
anhtho
9
0
Anyone knows what is the approx. internal resistance of a lead battery, say, 12V, 20Ah.
Thanks
 
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  • #2
Lead acid batteries typically have an internal resistance around 20 milliohms.
 
  • #3
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).
 
  • #4
I'm not 100% sure on this, but I don't think that the battery's capacity matters.
 
  • #5
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.
 
  • #6
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.
 
  • #7
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:
  • #8
Hi nsaspook, I agree that it depends on many other factors, and Ah capacity is the most important.
Thanks for the documents.
 

1. What is internal resistance of a lead battery?

Internal resistance of a lead battery is the resistance that exists within the battery itself. It is caused by the resistance of the electrolyte, the electrode materials, and the interconnections between cells. This resistance can affect the performance and efficiency of the battery.

2. Why is internal resistance important in lead batteries?

Internal resistance is important in lead batteries because it can affect the voltage and current output of the battery. High internal resistance can lead to voltage drops and reduced capacity, while low internal resistance can improve the battery's performance and efficiency.

3. How is internal resistance measured in lead batteries?

Internal resistance of a lead battery is typically measured using a specialized device called a battery impedance meter. This device sends a small current through the battery and measures the voltage drop, which can then be used to calculate the internal resistance.

4. What factors can affect the internal resistance of a lead battery?

The internal resistance of a lead battery can be affected by various factors including temperature, state of charge, age of the battery, and the quality of the materials used in its construction. Higher temperatures and lower state of charge can increase the internal resistance, while a well-constructed and maintained battery will have lower internal resistance.

5. Can the internal resistance of a lead battery be reduced?

Yes, the internal resistance of a lead battery can be reduced through proper maintenance and use. Keeping the battery at optimal temperature and avoiding deep discharges can help to reduce internal resistance. Additionally, using high-quality materials in the construction of the battery can also contribute to lower internal resistance.

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