Seneca Chassis Battery Charging

[James AO]

2014 Seneca Question: when plugged into shore power if you turn your key to the on position but don’t start the engine, typically what voltage do you see displayed on the dash display bottom left corner under the odometer readout? Mine reads only 12.2 volts, shouldn’t it be much higher like 13-14 volts due to the built in charger/converter? If I measure the coach batteries while connected to shore power they measure 13.4 volts. Is this an indication that the BIM is not functioning properly? Thanks!

[houstonstroker]

Might not be a problem, does it start OK? I think the glow plugs pull quite a bit of juice once the key is in the on position.

[Grumpy]

I think it only charges the chassis when needed since it is a trickle/maintainer charge system.

[SloPoke]

Welcome to the Seneca family on JOF.

When you turn the ignition key to run (before moving to start) a number of things are causing a heavy drain on your batteries in preparation for starting.

You will see the Intake Heater lamp on the dash illuminate as these components are preparing to start. Your voltage reading on the dash will fluctuate back and forth as the intake heater system is cycling on / off. Once we see the Intake heater lamp go out, we then will start the ISB.

Once the engine starts and until the running temperatures are no longer requiring the intake heater system, then you will see the voltage cycle back and forth. When the intake heater cycles on, we often see our voltage readings in the 12.4 range. Research indicated that the two intake heating components draw 95A each.

Once these systems are at temperature... all normalizes.

[James AO]

Originally Posted by houstonstroker

Might not be a problem, does it start OK? I think the glow plugs pull quite a bit of juice once the key is in the on position.

Thank you!

[James AO]

Originally Posted by SloPoke

Welcome to the Seneca family on JOF.

When you turn the ignition key to run (before moving to start) a number of things are causing a heavy drain on your batteries in preparation for starting.

You will see the Intake Heater lamp on the dash illuminate as these components are preparing to start. Your voltage reading on the dash will fluctuate back and forth as the intake heater system is cycling on / off. Once we see the Intake heater lamp go out, we then will start the ISB.

Once the engine starts and until the running

temperatures are no longer requiring the intake heater system, then you will see the voltage cycle back and forth. When the intake heater cycles on, we often see our voltage readings in the 12.4 range. Research indicated that the two intake heating components draw 95A each.

Once these systems are at temperature... all normalizes.

Thank you for the welcome and the answer. So to see if the converter is supplying charge current the best way is to measure the voltage on the chassis battery bank with the key off and shore power on and it should be around 14 volts?

[RVermont]

Not quite that simple. The voltage in your chassis batteries has to drop to a level that causes the battery isolation module to sense the difference and cycle into the correct position to allow the converter to supply to the chassis. I suppose you could turn the lights on and drain the batteries while monitoring the voltage. You would see slowly reducing voltage and then an increase when it starts to charge. Turn the lights off and see how high it gets.
Additionally the converter has a power control circuit which will vary on how much the charger senses the batteries need so it might be as high as 14 or so but not necessarily..depends on the program.

[James AO]

Originally Posted by houstonstroker

Might not be a problem, does it start OK? I think the glow plugs pull quite a bit of juice once the key is in the on position.

Yes, it starts fine so far. The rig is new to me.

[James AO]

Originally Posted by RVermont

Not quite that simple. The voltage in your chassis batteries has to drop to a level that causes the battery isolation module to sense the difference and cycle into the correct position to allow the converter to supply to the chassis. I suppose you could turn the lights on and drain the batteries while monitoring the voltage. You would see slowly reducing voltage and then an increase when it starts to charge. Turn the lights off and see how high it gets.
Additionally the converter has a power control circuit which will vary on how much the charger senses the batteries need so it might be as high as 14 or so but not necessarily..depends on the program.

I’ll keep an eye on it so I can watch for what you have described. Thanks!

[Crossingover]

What is the permissive ambient temperature for the intake heaters and glow plugs? I don't recall either of these dash lights coming on with our typical lowest ambient temps (70's). That's a huge current draw that I assume is cut out during starter operation.