How to isolate Alternator charge from Converter charge?

[PwrWgnWalt]

Something just occured to me, reading another post about a blown alternator from running the MH engine while hooked up to shore power or with the genset running...

So I've designed and built this 'modern' 12VDC system, but it occurs to me that I might trash my alternator if:
  1.  I run the genset while driving down the road (for A/C, since there is none on the chassis); or
  2.  I start that big 440 engine while plugged in to shore power.

I have Battery Disconnects (BD-2 and Intellitec solenoids) - one for the Coach Bty, one for the Chassis Bty - but they tie into the Blue Seas ACR-7610, which will connect the Batteries automatically when charging voltages are sensed from any source. 

On my MH, the converter/charger (Powermax Boondocker PMB4-75) is wired to the circuit breaker panel (gets 110 VAC power from either the genset or shore power) and feeds the Coach Bty. So with genset running - or plugged in to shore power - I would be getting a charge at the Coach Bty and so the Blue Seas ACR-7610 would automatically connect with the Chassis Bty.  If I then start the MH, and the alternator produces charging voltage, it sounds like I may have a problem (from what I read - because I cannot isolate the Chassis Bty from the Coach Bty at charging voltages, and both Alt and genset would be trying to send a charge to both Bty banks).
[The ACR-7610 does have an auto cut-out feature at anything => 16 volts... I know this feature works, due to the faulty voltage regulator I had to replace.]

So - what does your MH have for a solution?     Am I missing something easy and obvious?

I have considered 3 possible solutions:
  1. A manual override switch to keep the ACR-7610 from auto-connecting the Bty banks (I could wire into
      the SI (Starter Interrupt) line that disconnects when the ignition key is on 'crank'); or
  2. Put the converter/charger on a switched 110 VAC outlet, and could switch off the Converter/Charger;
      or
  3. Use the Bty Disconnect and turn OFF the solenoid for the Coach Bty (the way its wired, that would
      not let converter/charger power get to the Coach Bty or the ACR, but the alternator charge power
      would).

Either way, I would have to remember to flip a switch 'off', then later turn it 'on' again. 

[ClydesdaleKevin]

We start the RV all the time while still being hooked up to shore power...to keep the AC running until the last minute...and haven't had a problem yet.  Although since installing our solar power system I do unplug the Boondocker converter before starting the rig now...mostly so I don't forget to unplug it when we turn the inverter on...lol!  The inverter beeps like crazy and won't turn on if the converter is still plugged in.

So that is an easy cheap option.  Either unplug the converter/battery charger before startup, or add a switch so you can simply turn it off before startup.

Kev

[PwrWgnWalt]

Thanks Kev! 

Thought I'd provide some follow-up on running the 440 engine while either running the generator, or being plugged in to shore power...

1. Talked to a great tech (Dave) at Blue Seas Systems about the SI-ACR 7610.  My "Option #1" above was not quite on-target.  Dave said the small Ground wire (~14 ga.) to the unit is required for it to operate, so a simple On-Off switch in this line allows the user to turn it on or off. Don't want to run more wire, and this is not needed, so will scratch this option off my list.

2. Also talked to Randy at Best Converter, who advises that the Boondocker Converter/Charger can run all day long without being connected to a battery ('charging'), or it could be plugged into a switched 110VAC outlet and simply turned "off" when needed.  This 'swtiched outlet' will be my backup method.

3. In the end, I decided to just go with Option #3... Because I wired the Battery Disconnects so the "Load" side of the (Coach) disconnect goes to the bus for all coach electrical components, and the "Battery" side is where the SI-ACR 7610 and the Battery bank connects, I will just 'disconnect' the Coach battery. This will isolate the battery banks from the converter/charger (which would be producing a charge whenever plugged in to shore power or the genset was running).  This way, with the 440 motor running, the alternator would charge both battery banks and I would not be cross-feeding charging currents between systems.