Computronic Controls Sentry - Manual (Page 6)

Sentry Iss7 Installation Instructions - December 03 - Page 6 of 6
Is there a standing load
present?
NO
Are electrolyte levels correct?
YES
Are batteries at end of life?
YES
Replace batteries
YES
Is standing load current
greater than charger output
current?
NO
YES NO
Battery Charger may be faulty
- Contact manufacturer
Top up batteries as per
manufacturers
recommendations
Replace charger with correct
size unit.
Two possible methods:
(1) Using Hydrometer or (2) Using a digital DC voltmeter
Step 1. Fully charge the batteries
Step 2. Disconnect batteries and leads and leave for 24 hours
Step 3. Measure either specific gravity (hydrometer) or terminal voltage
(voltmeter) and compare with table below.
% Charge Specific Gravity Voltage (DC) on a 12V battery
100 1.265 12.8
75 1.225 12.5
50 1.19 12.4
25 1.155 12.0
Discharged 1.12 11.5
If the voltage across the terminals shows around 10.5V, this may indicate
a shorted cell is present.
Step 4. If time is limited due to on-site testing, remove surface charge by
either applying a 20A load for 3 minutes or crank engine for 10 seconds,
then disconnect batteries and leads and leave for minimum of 10 mins.
NOTE: On this method, providing batteries have been sized correctly for
engine and charged correctly, an open terminal voltage of 12.5V or
greater should be present.
Lead Acid
• Physical damage to cells can cause
electrolyte to leak or evaporate
• High charging voltages will evaporate
electrolyte
Check charging voltage against battery type
and voltage
WARNING: If the batteries are being used
at above 20 DEGREES CELSIUS the
chargers output voltage should be
temperature compensated at -3mV/ºC/Cell
The battery charger will need
to provide both the standing
load and minimum charge
current
I.e. if a charging current of 2A
is required, and the standing
load is 1A then the charger
needs to be able to output a
total of 3 amps
REMINDER
FACTORS CONTRIBUTING TO
ELECTROLYTE LOSS
TROUBLESHOOTING FLOWCHART
START HERE
Are batteries charging?
YES
PROBLEM SOLVED
NO
Is a battery charger
connected?
NO
Connect battery charger
YES
Is correct mains supply
present on terminals?
NO
Check mains supply, fuses
and wiring.
YES
Is output voltage correct for
batteries?
NO
Replace with correct voltage
charger.
YES
Is output voltage correct
polarity on terminals?
NO
Check fuses and wiring.
YES
Is battery charger correct size
for battery?
NO
Replace with correct size
charger.
YES
Min Charge Current = AH Capacity of batteries
10
Max Charge Current = AH Capacity of batteries
5
Wet NiCad
Refer to genset manual for sizing of battery chargers to generator set. If
installing your own chargers, battery manufacturers recommend the
following: -
Minimum charge current should be approximately 5% battery AH capacity
Maximum charge current to be equal to 25% battery AH capacity
NOTE: When batteries are normally charged by a charging alternator, a
float battery charger rated at lower than the minimum charge current is
sufficient to keep batteries in fully charged state.
Lead Acid
12V 24V
Float: 13.8V 27.6V
Boost: 14.5V 29.0V
Lead Acid
12V (10 Cell) 24V (20 Cell)
Float: 14.1V 28.2V
Boost: 14.6V 29.2V
Wet
NiCad
Typical output with no battery or load connected:
SUL & ESUL models - 50% nominal charger voltage
MEASURING CHARGING VOLTAGE AND CURRENT
V
A
CHARGER
+
-
+
-
BATTERY
Figure (ii)
To check charger is working, follow these steps then consult expected conditions
for relevant battery type below.
(1) VOLTAGE - Place voltmeter across battery terminals (V on fig ii)
(2) CURRENT - Break the positive line to the battery and place an ammeter
between positive from charger and positive of battery (A on fig ii)
CURRENT FLOW FROM CHARGER TO BATTERY
If voltage at terminals is less than nominal battery voltage then the maximum rated charger current should
be present.
Note: Once battery is fully charged, output current should be between 0/1% and 0.5% of battery's AH
capacity plus any standing loads.
VOLTAGE RISE AT BATTERY TERMINALS
A gradual rise of voltage should be seen slowing as float voltage is reached. - batteries should NOT be
boost charged continuously (see page 3)
Note: If the battery voltage increases rapidly during charge and no or minimum current is measured then
the battery may have become sulphated and will not hold charge and may be unrecoverable
Lead Acid @ 20ºC
CURRENT FLOW FROM CHARGER TO BATTERY
The current should stay constant or near to constant
whilst charging.
VOLTAGE RISE AT BATTERY TERMINALS
A gradual rise of voltage should be seen until float
voltage is reached, once fully charged a slight drop in
battery voltage will be measured - batteries should
NOT be boost charged continuously (see page 3)
Wet NiCad