Start battery

[wyctoronto]

Start battery is an AGM Group 54 in place by PO. Need to replace as under load the cranking amps drop to 200 while the Voltage reading is still at 12.7. The two house batteries are 4D wet cell and are fine. What recommendations do you have. Generator and bow thruster appear to be wired to this battery. Power winch and windless appear to be wired to the 2 4D’s. Thanks

 

[Davidasailor26]

If the battery is still 12.7V while cranking I’d look for other causes to any problems. Sounds like there could be a bad connection causing voltage drop between the battery and starter.

Since your house bank is conventional wet cell I’d look for a wet cell replacement battery if it does turn out that you need one.

 

[wyctoronto]

If the battery is still 12.7V while cranking I’d look for other causes to any problems. Sounds like there could be a bad connection causing voltage drop between the battery and starter.

Since your house bank is conventional wet cell I’d look for a wet cell replacement battery if it does turn out that you need one.

Thanks, put it under load with a battery tester and then saw the amps go to 200 under load.

 

[Ralph Johnstone]

Are you seeing problems with the starting RPM while pulling 200A ? What do you expect or have seen the starter pull in the way of amps before this problem arrived on your doorstep ?

As @Davidasailor26 has said, you can't go much higher than 12.7V. If that doesn't supply enough starting RPM, another battery will only supply the same voltage and the same starting RPM.

The problem is somewhere hiding in your boat's wiring.

 

[Maine Sail]

Thanks, put it under load with a battery tester and then saw the amps go to 200 under load.

WHat is the tester ? brand/make?

 

[SycloneDriver]

Thanks, put it under load with a battery tester and then saw the amps go to 200 under load.

What kind of tester? This will tell us a lot.

To answer your question, use a large wet cell so it will match the house battery chemistry and charge requirements.

 

[wyctoronto]

WHat is the tester ? brand/make?

As soon as a load was applied the amps dropped to 200.

 

[SycloneDriver]

With that type of tester the voltage was not 12.7 when the load was applied but that's a different story. You are correct about the battery needing replacement.

 

[dlochner]

I am a little confused by this question. If the battery voltage is 12.7 and the starter is drawing 200 amps I don't see the problem, unless the engine is not starting. What does the engine do when the starter is drawing 200 amps?

 

[Ralph Johnstone]

You are correct about the battery needing replacement.

Can you share your thoughts as to why you think he needs a new battery. If the tester indicates 12.7V at 200A, isn't the battery pretty much 100% SOC and ready to rock ?

 

[wyctoronto]

I am a little confused by this question. If the battery voltage is 12.7 and the starter is drawing 200 amps I don't see the problem, unless the engine is not starting. What does the engine do when the starter is drawing 200 amps?

My understanding is that the voltage at 12.7 is fine however the cranking amps yielded may deteriorate over the life of the battery. When tested the battery is only delivering 200 amps which apparently is not enough to start the generator.

 

[dlochner]

My understanding is that the voltage at 12.7 is fine however the cranking amps yielded may deteriorate over the life of the battery. When tested the battery is only delivering 200 amps which apparently is not enough to start the generator.

Correct, over time the capacity of the battery deteriorates so it holds less energy however looking at voltage only it appears to be fully charged. 9 AAA batteries can be wired in series to yield 13.5 v yet it would not have the same amount of energy as a Group 24 battery.

Is there an install date on the battery? Does the motor turn over or does the solenoid just click?

 

[Maine Sail]

My understanding is that the voltage at 12.7 is fine however the cranking amps yielded may deteriorate over the life of the battery. When tested the battery is only delivering 200 amps which apparently is not enough to start the generator.

How are you determining 200A.? That tester only does 100A?

 

[wyctoronto]

Correct, over time the capacity of the battery deteriorates so it holds less energy however looking at voltage only it appears to be fully charged. 9 AAA batteries can be wired in series to yield 13.5 v yet it would not have the same amount of energy as a Group 24 battery.

Is there an install date on the battery? Does the motor turn over or does the solenoid just click?

The battery is 3 yrs + old. The generator turns over slowly and get slower as it is held in the start position.

 

[dlochner]

The battery is 3 yrs + old. The generator turns over slowly and get slower as it is held in the start position.

Assuming the battery has been decently cared for (a rash assumption perhaps), at 3 years old it should not be toast. That the diesel does not fire up quickly may be more a problem with the diesel than the battery. Things to look for on the diesel are good fuel flow with clean filters and compression in the cylinders. Also check all the battery connections on the starter, it may be drawing 200 amps, but is that getting all the way to the brushes on the starter motor?

 

[wyctoronto]

Assuming the battery has been decently cared for (a rash assumption perhaps), at 3 years old it should not be toast. That the diesel does not fire up quickly may be more a problem with the diesel than the battery. Things to look for on the diesel are good fuel flow with clean filters and compression in the cylinders. Also check all the battery connections on the starter, it may be drawing 200 amps, but is that getting all the way to the brushes on the starter motor?

Good point. It’s an AGM Battery. Note that when I try to start the generator with the boats engine idling the generator fires up immediately. Hence the thinking that the AGM isn’t delivering adequate amps.

 

[dlochner]

Good point. It’s an AGM Battery. Note that when I try to start the generator with the boats engine idling the generator fires up immediately. Hence the thinking that the AGM isn’t delivering adequate amps.

This is a critical piece of information. Is it correct that the generator start battery is charged from the main engine's alternator and from shore power?

 

[JamesG161]

Note that when I try to start the generator with the boats engine idling the generator fires up immediately.

If it is like my H430

Start Battery should be sized for Cold cranking Amps of your Engine.
The Alternators from Engine or Genset charge the Start Battery.

My Lead/Acid Start Battery cost $90 from Walmart.
Jim...

 

[SycloneDriver]

I

Can you share your thoughts as to why you think he needs a new battery. If the tester indicates 12.7V at 200A, isn't the battery pretty much 100% SOC and ready to rock ?

I'm very familiar with that tester. With the load (100 amps give or take) applied the voltage is a lot less than 12.7 if its indicating 200 CCA. Unless that battery is very small or very very cold 200 CCA is a failed test.

 

[wyctoronto]

This is a critical piece of information. Is it correct that the generator start battery is charged from the main engine's alternator and from shore power?

Yes. It’s charging from shore power, alternator when motoring and solar.