Peukert Calculator

[AbyssUnderground]

Hi all,

I found this on the web while I was looking for some information on split charge relays. I knew it would be useful for myself but I also thought it might be useful for others. I modified it slightly, just increasing the graph height and adding in the text for default peukert value. The worksheet is locked to prevent accidental changes.

The values in orange are the user modifiable values.

Comments welcome.

http://www.otherpower.com/images/scimages/5410/peukert_calc.xls

[wooferhound]

What is a Peukert ?

[scottsAI]

Hello AbyssUnderground,

Interesting, 100ah battery discharged at 0.2a will have 262.65ah! Wow.

Time frame is long enough that self discharge needs to be considered!

1313.26hr / 24 = 54.74 days. Shows the dangers of spread sheets. Just because it can be calculated does not make it right.

Thanks for the spread sheet.

Wooferhound,

Name of an inventor, wrote equations to predict the capacity of a battery at different discharge rates.

Have fun,

Scott.

[AbyssUnderground]

Peukert is the effect upon battery discharge. It basically means the higher the discharge rate the less available AmpHours the battery will give. The lower the discharge rate, the more AmpHours it will give.

Do a quick google search and find the wiki for it. It should explain everything you need to know about it.

[jimovonz]

262Ah from a 100Ah battery.... Was this Peukert fellow an advocate of over unity? Obviously there is a lower limit to the relative discharge rate to get sensible info out of this.

[scottsAI]

Jimovonz,

Looking at the spread sheet, about 1/10 rating would be the limit.

2a load shows 131ah probably within reason. 60Hr discharge time.

I am writing code for a ADuC7030 battery monitor chip.

With all the published data about batteries, not much real code??

I plan to publish it when done.

Charging efficiency is something to look at, along with self discharge.

And other things...

Any good links? Spent hours looking not too happy with what I have found.

Nothing solid, like the Peukert equation. I can use that.

What is not covered by the Peukert equation is if the discharge drops, what is the capacity of the battery? I know it can recover if given some time, but how much time? Inverse of equation?

Have fun,

Scott.