Battery Issue? Volts vs. Amps

[chpthril]

Out on the water now. With the boat running One battery tested 12.5 and the other was 14.5

My gut says the 12.5V is on the house battery and the 14.5V is the main cranking battery. This is what I expected. House bank is not getting any alternator charger. Cable left unconnected is a very common thing this time of year.

[2014-Z3]

Sorry it’s been a bit since I could get back to the boat. I’m here now. Does anyone have a breakdown of which cables should go to each battery. I have the following cables:

Primary Ground
Primary Switch
Secondary Ground
Secondary Isolator
Primary Isolator
Starting Battery to Switch
Amp Ground

The obvious answer would be too match up primary and secondary with the respective batteries. Is that truly the case or is there some mixing involved based on how the switch is set up to get the batteries to charge. TIA

[chpthril]

Primary ground can connect to either battery ground. Secondary ground is what I think you are calling the ground link between the two batteries. Amp ground(s) can connect to which ever ground post it will reach and which ever has the least amount of terminals on it.

Two larg'ish cables come off the isolator to each battery positive. This is the electrical flow. In reality, the physical connection could be on the batteries or on the back of the switch.

There is a large positive cable from each battery to each side of the switch.

Starter cable connects to the boat side of the switch that mates with the cranking battery and amps and helm BUS connect to the post that mates with the house battery.

[2014-Z3]

The secondary ground comes off the Buss Bar and then I have another cable labeled Buss Bar to Starting Battery that is a ground cable

[2014-Z3]

Alright I may have gotten somewhere. I put the key in position “1” to the right. Not auxiliary (left) and not turned far enough that the boat would start.

With the switch in the “ON” position and not in COMBINE...I could hear the music playing but it was very quiet, I had to turn my phone all the way up and the sound system all the way up. The second I turned the switch to COMBINE...the sound system came on full blast. Any idea what the next step might be?

[IDBoating]

Are you certain that error being reported is "low amperage"? That's an odd thing for an amplifier to indicate. Low voltage makes more sense. The amp itself controls the amperage it draws based on its input signal(s). What "amperage" should it indicate during silent periods between songs?

I suspect it means "low voltage". I would be very interested in knowing the input voltage at the amplifier. That measurement will take into account everything else in the system. If that is low (by the amp's own specifications), then you can start working back toward the batteries and alternator to see where the voltage is being dropped (or, in the case of the battery/alternator/isolator, not connected).

Remember that a poor power or ground connection can still read full voltage when no current is being drawn. It's only when the amp starts pulling more current that the voltage will drop across a bad connection. If you find such a bad connection, you can prove this to yourself by putting the voltmeter across the connection. For a solid connection you should read little to no voltage at all. For a bad connection you may see several volts if the resistance and current are high enough. Ohm's Law has not been repealed! {grin}

[chpthril]

Out on the water now. With the boat running One battery tested 12.5 and the other was 14.5

Need to solve this. Why is one battery, suspect its the house battery, is not seeing alternator charge. Should have alternator voltage on both sides of the charge relay. If not, check the ground control wire. If its good, you have a bad relay.

[2014-Z3]

Update: Got it figured out. Thanks everyone for the input/help. It is much appreciated.

Here was the the solution:

Primary Ground and Ground from Buss Bar need to both be connected to the crank battery. The secondary ground and secondary isolator (+) both need to be connected to the house battery along with the amp ground.

Thanks again. I couldn’t help but play ‘We are the Champions’ over the system once it was working! Hope everyone has a great summer boating. Cheers!