Copyright © BEP Marine Limited, All rights reserved
Product version: DCM3.2
Page 10
Date: 12/05/05
7 Factory settings
The 600-DCM3.2 is factory preset with the following settings:
§
Battery Capacity
220AH
§
Charge Efficiency
85%
§
High Volts Alarm
15.00V
§
Low Amp Hours
100AH
§
Low Volts Alarm
11.00V
§
Peukert’s Exponent
1.25
§
Reset capacity
5 amps
Amp Hours display is battery capacity remaining
Peukert’s Discharge Rates Calculation
This is an exponent, which changes the discharge current to an effective discharge related to battery capacity.
Most marine batteries are Capacity rated at the 20-hour rate. Ie: A battery discharged for 20 hours to a terminal
voltage of 10.5v = Amp hours.
C = A x T20
C = 5 x 20 = 100 Amp Hours.
C = Battery capacity
A = Amps discharge
T20 = Time20 hours
Peukert’s Equation
An x T = C
C = is battery capacity at 20hrs discharge
A = is discharge current in Amps
T = is discharge time in hours
n = is related to battery construction & is relatively constant for any given battery with in a similar discharge
time.
Exponent “n” can be calculated for any given battery bank by comparing two discharge cycles.
First fully charge battery bank from shore power/genset & discharge at 50% of expected average load (Note
time & amps) to 10.5volt terminal voltage (12v system). Recharge fully & discharge at 150% of expected
average load. Use the following equation.
n = Exponent
t1 = The hours of first discharge at amps A 1
t2 = The hours of 2nd discharge at amps A 2
Example:
8G4D 180A/Hr
Discharge 1 = 24 hours @ 7.8 Amps
Discharge 2 = 8 hours @ 20.7 Amps
Program this exponent in to Peukerts.
Log t2 - Log t1
Log A1 - Log A2
Log 8 - Log 24
Log 7.8 - Log 20.7
0.9 – 1.38
0.89 – 1.32
0.48
0.43
= 1.1
n =
Log t2 - Log t1
Log A1 - Log A2
n =
