Alternator diagrams

[ndutton]

This thread from earlier this year addresses alternator temperature directly:

http://www.moyermarine.com/forums/showthread.php?t=5360

[jpian0923]

Nice thread.

I run the inverter off one battery. When it's time to charge, should I switch to charge both batteries? Will the alternator see this as a higher average voltage and work less hard?

[ndutton]

Yep. (10 character minimum)

[jpian0923]

Tried it tonight. Seemed to work. The only data I have is the change in RPM when switching from one battery to both batteries during charging. Thanks Neil.

Clarification: When charging the single depleted battery, rpms were low (alt working hard). When switched to single fully charged battery rpm went up (alt not working hard). When switched to both, seemed like rpms were somewhere in the middle of the two. Strange though...tach (mechanical) went out at some point. Have to check the linkage on that. Was judging by ear at this point.

[sastanley]

Make sure your battery switch is a make before break style..you do not want the alternator to see 'no' load at any time..it can ruin it. Most switches are built this way..if the lights stay on (i.e, don't flicker), when you switch batteries, you're probably OK.

I also think it is a good idea to only switch the batteries around when the engine is at idle. I am not sure how the alt. likes those sudden changes in load when it is spinning at a few thousand RPM...this is just a personal opinion though.

[ndutton]

Yeah Jim,
The RPM behavior you report is exactly right. The alternator load on the engine is what causes it. In a way you can use your ears as a seat of the pants indicator of battery state of charge.

[jpian0923]

I'm assuming make before break battery switch. When I was "green" I messed with the switch, turning it to "off" (momentarily) and engine kept running. Had no ill effects from it, that I can tell.