Peukert's Exponent

 

Surrette and Rolls Batteries

Model Volts

Res. Min. 20-Hr. rating "n"

EHG-208

6

345

208

1.42

EIG-225

6

350

225

1.54*

EIG-262

6

395

262

1.72*

24/90

12

165

90

1.16

27/12M

12

190

112

1.23

30H/108

12

230

108

1.08

HT/4D

12

348

170

1.15

HT/8D

12

450

221

1.20

*Use Max allowed "n" of 1.50

Example of using Reserve Minutes @ 25 amps

and the 20-hour rate to calculate "n".

First convert Reserve Minutes to hours, then find the discharge current at for the 20-hour rating. Finally, use a calculator to solve the arithmetic.

Trojan T-105:

 

 

 

 

 

 

 

Reserve Minutes = 447 min @ 25 amps.

 

 

 

 

 

 

 

t1 = 447 min = 447/60 = 7.45 hrs

 

 

 

 

 

 

 

I1 = 25 amps

 

 

 

 

20-hour rating = 225 Ah

 

 

 

 

 

 

 

 

 

 

t2 = 20 hours

 

 

 

 

 

log t2 - log t1

 

I1 = 225 amp hours/20 hours = 11.25 amps

n =

=

log 20 - log 7.45

1.301 - 0.872

= 1.24

 

 

 

 

 

=

 

 

log I

1

- log I

2

log 25 - log 11.25

1.398 - 1.051

 

 

 

 

 

 

 

 

 

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