TYPICAL PEUKERT'S EXPONENTS

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

CALCULATING PEUKERT'S EXPONENT

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 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

I2 = 225 amp hours/20 hours = 11.25 amps

n =

log t2 - log t1

=

log 20

- log 7.45

1.301

- 0.872

= 1.24

 

 

 

 

=

 

 

 

log I

- log I

log 25

- log 11.25

1.398

- 1.051

1

2

 

 

 

 

 

 

 

 

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