Alternator Field Disconnect?

[Chief Engineer]

All that for a cuppa coffee, a tv and a computer.......just kidding
Energy management can get complicated....

[Extemporaneous]

See Balmar's response to my email.
I obviously don't plan to have the two banks connected all the time, but his reply makes sense (to me). Can anyone think of any flaws in the logic?
Extemp.

Thank you for using Balmar products. There is really no reason to run the system with the battery switch set to both, but if you do, it will not affect the DDC as it will just go to sleep when it sees the higher voltage on the starting battery side. I would leave the switch set only to the house bank.

Regards,

Technical Support & Sales
18930 - 59th Ave. NE Arlington, WA 98223 USA
Phone 360-435-6100 Ext. 309 Fax 360-435-3210
www.balmar.net
View our 2009 Product Guide at http://www.balmar.net/2009-Balmar-Product-Guide.pdf

From: Extemp.
Sent: Saturday, January 24, 2009 8:47 AM
To: @balmar.net
Subject: Duo Charge Controller Question

I have Balmar ALT-120A alternator with a Balmar Max Charge Digital Regulator MC-612-H and a Balmar Digital Duo Charge Controller. Balmar’s Digital Duo Charge connects between the house and start (secondary) batteries -- keeping the two banks separate until the unit senses 13 volts at the house battery. Once voltage is reached, the Duo Charge supplies up to 30A to the secondary bank.

If/when I combine the house batteries with the starting battery and the engine is running, will I have to isolate or take the Duo Charge Controller off line? I don't know what would happen if the two battery banks were combined and at the same time the house batteries were supplying the Duo Charge Controller with power to charge the starting battery which is already being charged by the alternator because all the batteries are combined.
Anyone?
If the Duo Charge Controller has to be isolated when the house and starting batteries are combined, could that somehow be done with an AFD battery switch or would that portion of the AFD switch be too small to handle the potential 30amps that the Duo Charge Controller can put out?

Let me know how I handle this.

Best Regards,

[scherzoja]

Extemporaneous,

Take a look at this diagram.

Instead of thinking of 'combining' batteries, think about redirecting batteries.
Put a one/two or one/two/off (if that is all you can get) between the main positive bus and the main engine bus.

In normal operation, this switch is set on 1 (start battery feeds engine bus) and is never moved.

If your start battery is dead, move switch to 2, which will redirect current from house bank to the engine positive bus.

Alternator will send current to the house bank, where the Duo charger will siphon off some to charge the start battery.

Once start battery is charged, shut off engine, switch back to 1, then restart using start battery.


You Don't have to worry about depleting one battery when combining, don't have to worry about rotating a switch and frying diodes (alternator connects directly to main DC positive bus).

This is a simplified diagram showing only the basic, positive connections.

Note: This does not address the question of AFD to turn off Alt, just using house batteries to start engine.