42
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
Peukert's Exponent
log t
2
- log t
1
log I
1
- log I
2
n =
log 20
- log 7.45
log 25
- log 11.25
=
=
1.301
- 0.872
1.398
- 1.051
= 1.24
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.
t
1
= 447 min = 447/60 = 7.45 hrs
I
1
= 25 amps
20-hour rating = 225 Ah
t
2
= 20 hours
I
1
= 225 amp hours/20 hours = 11.25 amps
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