Powerchute reports low Est. Batt. Time for RS-1300

[Anonymous user]

I replaced the batteries of a Back UPS RS-1300. Powerchute reports a low Estimated Battery Time (EBT) of about 5 minutes, with a load of about 150W or less.

Not believing that this low number is correct, I installed the batteries in another UPS, an RS-1500 unit. They use the same batteries, only in a different physical configuration. Powerchute reports 25 minutes EBT on the RS-1500. The load here is 420W, almost 3 times the load on the RS-1300. On the RS-1500 with the original batteries it was reporting about the same EBT of 25-28 minutes.

Obvioulsy something is wrong here.

Question 1: Can I conclude that the RS-1300 is faulty?

Question 2: I don't know how the EBT is calculated/estimated. The intuition says that 2 healthy 12V batteries with different capacities, say 7AH and 9AH, may perfectly have the same output voltage given an identical load, at least at the beginning of their lifes. This is instantaneous voltage. So that the estimate is probably not a function of instantaneous voltage. Does anyone know, or can I read somewhere the method used to produce this EBT estimate?. Clearly over time this voltage changes and the change has to have a relationship with the capacity. Is this change what is measured? and extrapolated? I can't imagine other way of doing it. Can you illuminate me?. THANKS!

[Anonymous user · Accepted solution]

I replaced the batteries of a Back UPS RS-1300. Powerchute reports a low Estimated Battery Time (EBT) of about 5 minutes, with a load of about 150W or less.

Not believing that this low number is correct, I installed the batteries in another UPS, an RS-1500 unit. They use the same batteries, only in a different physical configuration. Powerchute reports 25 minutes EBT on the RS-1500. The load here is 420W, almost 3 times the load on the RS-1300. On the RS-1500 with the original batteries it was reporting about the same EBT of 25-28 minutes.

Obvioulsy something is wrong here.

Question 1: Can I conclude that the RS-1300 is faulty?

Question 2: I don't know how the EBT is calculated/estimated. The intuition says that 2 healthy 12V batteries with different capacities, say 7AH and 9AH, may perfectly have the same output voltage given an identical load, at least at the beginning of their lifes. This is instantaneous voltage. So that the estimate is probably not a function of instantaneous voltage. Does anyone know, or can I read somewhere the method used to produce this EBT estimate?. Clearly over time this voltage changes and the change has to have a relationship with the capacity. Is this change what is measured? and extrapolated? I can't imagine other way of doing it. Can you illuminate me?. THANKS!