Which Engine Charges The Starter Bank And Which Engines Charges The House Bank?-gctid814596

[Old_Man_With_A_Boat]

I know this topic has been discussed before. But I don't think I remember reading a clear cut answer. I have a 1985 3870, with twin Mits. I would like to know which engine charges the starter bank, and which charges the house bank? I have always heard that you start the engine that charges the starter bank first. Then the engine that charges the house bank next. Or does it make any difference which one you start first?

[brad4550]

Hi Bill

As I under stand it Bayliner set it up so that Port Engine charges the Start Batts.and Stb Engine charges House Batts,

Good luck Brad

[SuperiorDiver]

Our 4087 is the opposite. I suggest you trace the wires from the alternators to their termination.

[MacPhid]

On my 38 the port charges the start, the starboard charges the house. When the house battery switch is on, my panel guages show the house bank voltage on the starboard voltage meter at both stations.

James

[Bay39]

Thanks for responding James as I thought something was wrong with both of my Starboard volt meters as they read a little above 13V at the dock even with the ignition switches OFF. I just asked a fellow friend (3988) with CUMMINS - the voltmeter doesn't give reading until the ignition switched to the ON position. As far as the charging of ENGINE bank versus ACCESSORY (House) - mine are Port - (Engine) and Starboard (House) in the manual. It doesn't hurt to perform a hand over hand trace from the alternator as suggested above since prior owners have a way of changing things.

[Norton_Rider]

"Bay39" post=814628 wrote:
Thanks for responding James as I thought something was wrong with both of my Starboard volt meters as they read a little above 13V at the dock even with the ignition switches OFF. I just asked a fellow friend (3988) with CUMMINS - the voltmeter doesn't give reading until the ignition switched to the ON position. As far as the charging of ENGINE bank versus ACCESSORY (House) - mine are Port - (Engine) and Starboard (House) in the manual. It doesn't hurt to perform a hand over hand trace from the alternator as suggested above since prior owners have a way of changing things.

Rather than tracing things it may be easier to check what's going on with a handheld voltmeter. First, turn off the battery charger circuit breaker or disconnect shore power. Measure the voltage on the start and house batteries. Start one engine and measure the voltage again. Shut down and repeat with the other engine. Also, with the engines shut down, turn the battery charger on and measure the voltage.

[SuperiorDiver]

"Norton Rider" post=814631 wrote:

"Bay39" post=814628 wrote:
Thanks for responding James as I thought something was wrong with both of my Starboard volt meters as they read a little above 13V at the dock even with the ignition switches OFF. I just asked a fellow friend (3988) with CUMMINS - the voltmeter doesn't give reading until the ignition switched to the ON position. As far as the charging of ENGINE bank versus ACCESSORY (House) - mine are Port - (Engine) and Starboard (House) in the manual. It doesn't hurt to perform a hand over hand trace from the alternator as suggested above since prior owners have a way of changing things.

Rather than tracing things it may be easier to check what's going on with a handheld voltmeter. First, turn off the battery charger circuit breaker or disconnect shore power. Measure the voltage on the start and house batteries. Start one engine and measure the voltage again. Shut down and repeat with the other engine. Also, with the engines shut down, turn the battery charger on and measure the voltage.

Good idea if the batteries are isolated from each other. I have battery combiners, so either engine will charge all batteries.

[Norton_Rider]

"SuperiorDiver" post=814876 wrote:

"Norton Rider" post=814631 wrote:

"Bay39" post=814628 wrote:
Thanks for responding James as I thought something was wrong with both of my Starboard volt meters as they read a little above 13V at the dock even with the ignition switches OFF. I just asked a fellow friend (3988) with CUMMINS - the voltmeter doesn't give reading until the ignition switched to the ON position. As far as the charging of ENGINE bank versus ACCESSORY (House) - mine are Port - (Engine) and Starboard (House) in the manual. It doesn't hurt to perform a hand over hand trace from the alternator as suggested above since prior owners have a way of changing things.

Rather than tracing things it may be easier to check what's going on with a handheld voltmeter. First, turn off the battery charger circuit breaker or disconnect shore power. Measure the voltage on the start and house batteries. Start one engine and measure the voltage again. Shut down and repeat with the other engine. Also, with the engines shut down, turn the battery charger on and measure the voltage.

Good idea if the batteries are isolated from each other. I have battery combiners, so either engine will charge all batteries.

The voltmeter test is still appropriate. In this case it will show that both alternators are charging all battery banks.

[SuperiorDiver]

"Norton Rider" post=814908 wrote:

"SuperiorDiver" post=814876 wrote:

"Norton Rider" post=814631 wrote:

"Bay39" post=814628 wrote:
Thanks for responding James as I thought something was wrong with both of my Starboard volt meters as they read a little above 13V at the dock even with the ignition switches OFF. I just asked a fellow friend (3988) with CUMMINS - the voltmeter doesn't give reading until the ignition switched to the ON position. As far as the charging of ENGINE bank versus ACCESSORY (House) - mine are Port - (Engine) and Starboard (House) in the manual. It doesn't hurt to perform a hand over hand trace from the alternator as suggested above since prior owners have a way of changing things.

Rather than tracing things it may be easier to check what's going on with a handheld voltmeter. First, turn off the battery charger circuit breaker or disconnect shore power. Measure the voltage on the start and house batteries. Start one engine and measure the voltage again. Shut down and repeat with the other engine. Also, with the engines shut down, turn the battery charger on and measure the voltage.

Good idea if the batteries are isolated from each other. I have battery combiners, so either engine will charge all batteries.

The voltmeter test is still appropriate. In this case it will show that both alternators are charging all battery banks.

Agree, but it does not answer the original question of which alternator charges which bank. Or am I missing something?

[Norton_Rider]

"SuperiorDiver" post=815237 wrote:

"Norton Rider" post=814908 wrote:

"SuperiorDiver" post=814876 wrote:

"Norton Rider" post=814631 wrote:

"Bay39" post=814628 wrote:
Thanks for responding James as I thought something was wrong with both of my Starboard volt meters as they read a little above 13V at the dock even with the ignition switches OFF. I just asked a fellow friend (3988) with CUMMINS - the voltmeter doesn't give reading until the ignition switched to the ON position. As far as the charging of ENGINE bank versus ACCESSORY (House) - mine are Port - (Engine) and Starboard (House) in the manual. It doesn't hurt to perform a hand over hand trace from the alternator as suggested above since prior owners have a way of changing things.

Rather than tracing things it may be easier to check what's going on with a handheld voltmeter. First, turn off the battery charger circuit breaker or disconnect shore power. Measure the voltage on the start and house batteries. Start one engine and measure the voltage again. Shut down and repeat with the other engine. Also, with the engines shut down, turn the battery charger on and measure the voltage.

Good idea if the batteries are isolated from each other. I have battery combiners, so either engine will charge all batteries.

The voltmeter test is still appropriate. In this case it will show that both alternators are charging all battery banks.

Agree, but it does not answer the original question of which alternator charges which bank. Or am I missing something?

If there's a voltage rise on both banks with each engine individually, then both engines charge both banks. If there's a voltage rise on only one bank with only one engine, then that engine charges that bank.

[SuperiorDiver]

Sorry, but I am still missing something in the answer regarding how to tell which engine charges which bank. As I stated, if there are combiners, all batteries will show charging or a voltage rise with either engine. The only way I could tell which engine charges a specific bank was to disable the combiner. My statement was just a caution if there are combiners installed.

[Norton_Rider]

The way I see it, if there are combiners, then both engines charge both battery banks and that answers the question.

[SuperiorDiver]

OK, I quit. But here is the original question: I would like to know which engine charges the starter bank, and which charges the house bank?

[Old_Man_With_A_Boat]

SuperiorDiver I understand your line of thinking. Now let me throw a little something in to my original question. What I have gathered is if you have a jumper switch to connect the start bank with the house bank in the on position, then it does not mater which engine you start first. It will be charging both banks and when you start the second you will still be charging both banks. Is this right or am I missing something?

[SuperiorDiver]

I believe your thinking is correct. It appears to me this is what a combiner would do, except you wouldn't have the automatic function, you would need to turn the switch on/off manually.