Mercruiser dual battery hookup recommendations
06-02-2003, 02:27 AM
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Mercruiser dual battery hookup recommendations
Multiple battery recommended hookup as per Mercruiser TSB No. 97-5
No. 97-5 TO: SERVICE MANAGER TECHNICIANS
PARTS MANAGER
Revised June 1999. Information underlined is new.
Multiple EFI Engine Battery Precautions
Models MCM, MIE Engines with Electronic Fuel Injection.
Situation
Alternators: They are designed to charge the battery that supplies electrical power to the engine that the alternator is mounted on. When batteries for two different engines are connected, one alternator will supply all the charging current for both batteries. Normally, the other engine’s alternator will not be required to supply any charging current.
EFI Electronic Control Module (ECM): The ECM requires a stable voltage source. During multiple engine boat operation, an electrical onboard device may cause a sudden drain of voltage at the engine’s battery. The voltage may go below the ECM’s minimum required voltage. Also, the idle alternator on the other engine may now start charging and this could cause a voltage ‘spike’ in the engine’s electrical system. In either case, the ECM could shut off. When the voltage returns to the range that the ECM requires, the ECM resets itself. The engine will now run normally. This ECM shut down usually happens so fast that the engine just appears to have an ‘ignition miss’.
Recommendations
Batteries:
Boats with multi-engine EFI power packages require each engine to be connected to its own battery. This ensures that the engine’s Electronic Control Module (ECM) has a stable voltage source.
Battery Switches:
While engines are running, battery switches should be positioned so each engine is running off its own individual battery. DO NOT run engines with battery switches in “BOTH” or “ALL” position. In an emergency, another engine’s battery can be used to start an
engine with a dead battery.
Battery Isolators:
Isolators can be used to charge an auxiliary battery used for powering accessories in the boat. They should not be used to charge the battery of another engine in the boat unless
the type of isolator is specifically designed for this purpose.
NOTE: Sure Power Industries Inc., Model 32023A meets this design specification.
1. The boat may have 2 engines connected to a single Model 32023A battery isolator.
2. The Model 32023A battery isolator is connected to 2 banks of batteries.
3. Each bank contains 2 batteries with the cranking battery for 1 engine in each bank.
4. The second battery in each bank is connected in parallel to the cranking battery.
5. The Model 32023A battery isolator is designed for this type of use; 2 battery banks, 2 charging sources, 120 amps (maximum alternator output).
6. When the engines are running, either engine’s alternator could be charging either bank of batteries through the Model 32023A battery isolator. Any other manufacturer’s battery isolator that is the same type as the Sure Power Inc., Model 32023A could also be used.
Generators:
The generator’s battery should be considered in the same manner as another engine’s battery.
If you have ran with "both" you have got away with it, and it IS NOT the CORRECT way to run for several other reasons as well. Merc figured KISS, but sometimes that won't work either...
No. 97-5 TO: SERVICE MANAGER TECHNICIANS
PARTS MANAGER
Revised June 1999. Information underlined is new.
Multiple EFI Engine Battery Precautions
Models MCM, MIE Engines with Electronic Fuel Injection.
Situation
Alternators: They are designed to charge the battery that supplies electrical power to the engine that the alternator is mounted on. When batteries for two different engines are connected, one alternator will supply all the charging current for both batteries. Normally, the other engine’s alternator will not be required to supply any charging current.
EFI Electronic Control Module (ECM): The ECM requires a stable voltage source. During multiple engine boat operation, an electrical onboard device may cause a sudden drain of voltage at the engine’s battery. The voltage may go below the ECM’s minimum required voltage. Also, the idle alternator on the other engine may now start charging and this could cause a voltage ‘spike’ in the engine’s electrical system. In either case, the ECM could shut off. When the voltage returns to the range that the ECM requires, the ECM resets itself. The engine will now run normally. This ECM shut down usually happens so fast that the engine just appears to have an ‘ignition miss’.
Recommendations
Batteries:
Boats with multi-engine EFI power packages require each engine to be connected to its own battery. This ensures that the engine’s Electronic Control Module (ECM) has a stable voltage source.
Battery Switches:
While engines are running, battery switches should be positioned so each engine is running off its own individual battery. DO NOT run engines with battery switches in “BOTH” or “ALL” position. In an emergency, another engine’s battery can be used to start an
engine with a dead battery.
Battery Isolators:
Isolators can be used to charge an auxiliary battery used for powering accessories in the boat. They should not be used to charge the battery of another engine in the boat unless
the type of isolator is specifically designed for this purpose.
NOTE: Sure Power Industries Inc., Model 32023A meets this design specification.
1. The boat may have 2 engines connected to a single Model 32023A battery isolator.
2. The Model 32023A battery isolator is connected to 2 banks of batteries.
3. Each bank contains 2 batteries with the cranking battery for 1 engine in each bank.
4. The second battery in each bank is connected in parallel to the cranking battery.
5. The Model 32023A battery isolator is designed for this type of use; 2 battery banks, 2 charging sources, 120 amps (maximum alternator output).
6. When the engines are running, either engine’s alternator could be charging either bank of batteries through the Model 32023A battery isolator. Any other manufacturer’s battery isolator that is the same type as the Sure Power Inc., Model 32023A could also be used.
Generators:
The generator’s battery should be considered in the same manner as another engine’s battery.
If you have ran with "both" you have got away with it, and it IS NOT the CORRECT way to run for several other reasons as well. Merc figured KISS, but sometimes that won't work either...
