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I learned that these of these two methods the one-tier method can only measure the internal resistance of a battery but you get more information from the two-tier testing method. However, the resource I was reading either didn't specify the benefits of using this method or I didn't grasp the concept well enough. What advantages are there to using the two-tier dc method? Is it more accurate or does it provide more information?

Edit: This is where I found it: battery-university |You can find what I mentioned under the 'DC Load Method' section.

Matthew3302
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    OK, I need more info from you because I never heard about one-tier method or two-tier method to measure battery internal resistance. A web search was unsuccessful as well. Please post a link to a web page that mentions these. – Davide Andrea Jun 30 '23 at 18:26
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    @DavideAndrea This is where I found it. Scroll down to 'DC Load Method'. However, I made a mistake and the one tier method is actually called the DC load method in the article.https://batteryuniversity.com/article/bu-902-how-to-measure-internal-resistance – Matthew3302 Jun 30 '23 at 20:06
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    Thank you. I was aware of it, but I never before heard it called "two-tier". – Davide Andrea Jun 30 '23 at 22:13

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Regardless, you always use two different current levels to evaluate battery resistance. The difference is that, in what you call "one-tier method", one of the current levels is 0 A, and in what you call "two-tier method", both of the current levels are more than 0 A.

The advantage of using two non-zero current levels is that it eliminates the effect of hysteresis and minimizes the effects of relaxation. At 0 current, the battery voltage is at a level that depends on how the battery had been used recently (charging or discharging). Even if you wait a long time for relaxation to end, there is still some hysteresis in the voltage. At a positive discharge current, those effects are masked by the voltage sag. Therefore, using two voltage readings, both during discharge, albeit at different current levels, gives you data from which you can evaluate the resistance more accurately.

Davide Andrea
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