Join Date: Oct 2007
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Re: Switching batteries to start the motor.
The only advantage to using the "both" position is the extra cranking amps as amps are additive and volts divide. It's very possible that a battery can show 12.6v and yet have no amps to crank.
Why, because the battery is deficient? I thought Volts are a indication of potential. Not necessarily so?
Therefore, use the designated starting battery to start - unless it won't, then switch to both, start and leave it there to charge (i.e., leave it on both to charge because something is wrong with the start - that way if the start is dead you can at least get something into the house while trying to charge the start).
Only turn the switch while the engine is running if you have a "make before break" type switch.
What is a "mbb switch"? Mine is a "Guest" and rotates from 1 to "both" to 2.
I assume the charging circuit is closed unless I turn it to the bottom position which is "off".? I would think the harm would be to the alternator if the switch opened the circuit while the motor WAS running.
YIKES....the more I learn, the less I know! Please explain.