Join Date: Feb 2010
Thanked 17 Times in 15 Posts
Rep Power: 8
Re: Effect of Current on Amp Hour Capacity
A few things to put Peukert in perspective.
Flooded lead-acid batteries have a self discharge rate of about 0.5% per day. At most discharge rates that's fairly trivial. But, for a large bank with a small load, self discharge can have more of an effect than Peukert, resulting in a lower capacity than Peukert would predict.
At the other end of the spectrum, very high discharge rates can also lower the capacity more than Peukert would predict (in part this is due to temperature effects).
Finally, Peukert's constant, k, is not constant through time; it will increase as the battery ages. If a battery company states that k = 1.25 (or whatever), that is undoubtedly the number they have empirically derived for a brand new battery. However, a four or five year old battery (particularly on that hasn't been treated very well) can have a significantly higher k. In other words, the batteries apparent capacity will fall off faster with increased load than would have been predicted by using the company's stated k.
Never forget them. Do something to prevent it from happening again.
Charlotte Bacon, Daniel Barden, Rachel Davino, Olivia Josephine Gay, Ana M. Marquez-Greene, Dylan Hockley, Dawn Hochsprung, Madeleine F. Hsu, Catherine V. Hubbard, Chase Kowalski, Jesse Lewis, James Mattioli , Grace McDonnell, Anne Marie Murphy, Emilie Parker, Jack Pinto, Noah Pozner, Caroline Previdi, Jessica Rekos, Avielle Richman, Lauren Rousseau, Mary Sherlach, Victoria Soto, Benjamin Wheeler, Allison N. Wyatt