In virtually all cases you can't "put greater than a 20 amp load" on a 20 amp alternator. If, for instance, you run down the battery the system voltage will just sag to a level that a 20 amp input will provide. The alternator won't be hurt by the process as alternators are current-limited devices. Incidentally, I like Rick's electrical configuration. Not quite as flexible as a full-redundant system, but significantly lighter in weight. The only issue I can see is if the starting battery goes completely dead the engine has to be cranked with the smaller battery. A very small disadvantage. Also, if the primary battery went completely dead the 100-amp current from the alternator would cause significant voltage drop in the 4-gage wire, reducing the recharge rate slightly - another very, very small disadvantage. I guess I would have been tempted to put the starting battery ahead of the firewall to reduce the weight of the 2-gage wire and improve cranking performance. Still, it's the best setup I've seen for a dual battery system.
ES N224SG, single battery, single alternator - I feel so old fashioned.
My "B" battery (pair) is connected to a 20 Amp SD20 backup alternator and to
the starter via a #2 cable
Rick,
I have a similar setup.
I wonder if anybody knows what happens to the 20 amp alternator if you put greater than a 20 amp load on it?
Also, how do you figure out what the load is if you are draining a fully charged battery at the same time?
Colyn
Regarding the oil question below, probably not a marketing ploy, but a legal one - anyone would be reluctant to "approve" use of their product when the pedigree is uncertain, so there is a tradeoff - tell you to use a product that is "several" years old and have potential liability, or tell you to throw it away at your expense and have no chance for liability. Let's see, which answer would they likely choose.... If it were me and I bought the oil originally and maintained possession of it for the whole time I would go ahead and use it.
I had a case of Shell 100 that was several years old and when I called
Shell, they told me that anything 2 years or older they would be real
suspect of. A marketing ploy?
Pat Brunner
IVP