Battery Switch E29 Atomic 4

[Don Kerr]

1. Can anyone verify whether or not you can switch batteries while the engine is running? I have a placard on my recently acquired boat that states "do not change batteries while engine is running". On a previous boat I used to start the engine with battery #1 and then switch to "both" so that the engine would charge both Batts.

2. Does anyone have any experience with battery isolators?

Thanks,
Don Kerr

[Glyn Judson]

Don, If I understand all this correctly, newer battery switch contacts maintain contact full when the knob is turned. This I'm told prevents damage or outright failure of the diode(s) in your alternator. Older switches don't have this feature and will actually break and make contact when rotating the knob and can damage the diode(s). Anyone out there who knows the real truth, please feel free to correct me and educate Don. Cheers, Glyn Judson, E31 hull #55, Marina del Rey, CA

[C Masone]

I recently re-wired my batteries according to a diagram in Don Casey's book "Sailboat Wiring Simplified".

In this wiring scheme the alternator circuit is wired direct to the house battery to protect the alternator diodes and the engine battery is charged through a battery combiner. Has worked very well this summer.

[Mort Fligelman]

Don: Many years ago a friend of mine who was an electrical engineer, and fellow boater showed me an interesting trick to see if the switch was a "shorting" switch.....meaning except for the off position it was on in all other positions without breaking the circuit.

Simply take an ohm meter....clip the leads to the terminals and turn the switch.....if there is no break in contact you have a "shorting" switch......problem solved.....

As to the isolater......when I attended a Nigel Calder talk, he asked if anyone was using one.....I raised my hand and was told to throw it overboard.....they rob voltage....the newer battery combiner is the way to go....check out the West Marine Advisor in thier catalog.....or buy Nigel Calders book....

[Bill Sanborn]

On my 79 E29 I have a Off/#1/Both/#2 switch. I have always switched between batteries with the engine running but NEVER to the off position. The switch has a warning on it to not switch to OFF with the engine running.

Have never had any alternator problems.

IMHO adding gadgets to the system reduces reliability makes troubleshooting more difficult. The existing switch provides isolation.