Battery for 2000 380 Aft Cabin

Need some battery advice. When I start my engines the starboard batteries only read approx 13 Volts on the gauge on the instrument panel while the port batteries immediately read 14+ volts. It also appears the starboard engine is slower to start but eventually turns over. This is after the boat has been on shore power. After running the engines for awhile, the gauge reads 14 volts on starboard side. Is this an indication that the starboard batteries are not holding a charge and need to be replaced?

luckynac said:

Need some battery advice. When I start my engines the starboard batteries only read approx 13 Volts on the gauge on the instrument panel while the port batteries immediately read 14+ volts. It also appears the starboard engine is slower to start but eventually turns over. This is after the boat has been on shore power. After running the engines for awhile, the gauge reads 14 volts on starboard side. Is this an indication that the starboard batteries are not holding a charge and need to be replaced?

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The guages are notoriously inaccurate for voltage, but the symptom of a slow start might indicate an issue. You should test the voltage right at the battery after its been sitting for a while not on the charger. If that bank has lower "fully charged" volatge, you probably have a problem with the batteries on that side.

It might also mean that the starboard bank is made up of deep cycle batteries, which are designed for long slow discharge rather than cranking. On my boat the port bank is a set of two golf cart batteries for the house loads and the port engine. The starboard is two cranking batteries. The port side has far more capacity, but turns the engine over slower than the starboard.

Thanks for the reply. All the batteries are actually deep cycle batteries. Have a mix of one Interstate SRM27, 3 Trojan Deep cycle SCS200's, and 2 Trojan deep cycle 27TMHs. I just bought the boat this year so I am not sure of the age of each of the batteries. Haven't yet figured out which are the house batteries - stupid question - is there an easy way to figure this out?

luckynac said:

Thanks for the reply. All the batteries are actually deep cycle batteries. Have a mix of one Interstate SRM27, 3 Trojan Deep cycle SCS200's, and 2 Trojan deep cycle 27TMHs. I just bought the boat this year so I am not sure of the age of each of the batteries. Haven't yet figured out which are the house batteries - stupid question - is there an easy way to figure this out?

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The easist way is to try each battery switch and see which one kills what house functions when turned off. That assumes you can trace the battery cables to know which switch is which.

You should not have deep cycles on the non-house side. They don't have the cranking power and you don't need the deep cycle capability. You should also ensure that all the batteries on one bank are exactly the same (brand, type, age etc) or they will not last very long. Quite a few threads on that issue if you search the forums.