Launched out on season opener this past weekend....short 200 mile jaunt to Point Lookout in southern MD - largest Union POW camp.....The Yank's version of Andersonville (Visiting as many Civil War sites as possible before "the home" is our multi-year mission)... Now a great state park at the confluence of Potomac River & Chesapeake Bay....Really enjoyable, despite our minor glitch (but the Striped Bass fishing made up for it!....)

As half-way expected, chassis battery finally passed away. Seven years of good service and the coach battery got me started so no big complaints. But it got me thinking of another scenario I've thought about before......

Suppose I were to lose the alternator out in the boonies (electrical, not mechanical like bearings, etc). If I were to start the 3.0KW genny, feed via the 13.6v, 45amp converter to the 105A coach battery with the aux switch ON to the chassis battery and shed all unnecessary loads, would I have perpetual motion, limited only by fuel supply? Would I be hurting something? (solenoid, etc) Should I limp to the nearest unknown fix-it man, or drive XXX miles home to trusted sources? Other considerations?.....

Just curious.......Thanks....

You should have a jumper wire (battery cable grade) ready to install between the coach and the chassis battery - this would get you home without any problems.

If you want to wire something in that's more permanent... a marine style - manual battery switch is the way to go.

Marine Guest - Highly Recommended

Unless you coach battery has an internal short, you can just use the aux switch to tie the two sets of batteries together. As long as you do not drive at night you can get hundreds of miles before your house batteries will die out.

If for some reason your coach batteries short out and try to discharge the house batteries you can disconnect one of the coach batteries post, negitive preferred and if the aux switch solinoid is powered from the house batteries it should keep the coach lines hot.

And if worse comes to worse you can go to the battery connect solinoid and take the cable of one side and attach it to the other making a permenant connection. Now you can take any battery out of the system by disconnecting the negitive post.

I hope you understood my ramblings

quote:

Originally posted by Lee:

Suppose I were to lose the alternator out in the boonies (electrical, not mechanical like bearings, etc). If I were to start the 3.0KW genny, feed via the 13.6v, 45amp converter to the 105A coach battery with the aux switch ON to the chassis battery and shed all unnecessary loads, would I have perpetual motion, limited only by fuel supply? Would I be hurting something? (solenoid, etc) ....

If your paralleling solenoid is a constant-duty one, you could drive as long as your finger can hold the switch with no harm. The catch here is whether or not your solenoid is constant duty. The intermittant service one looks like the constant duty one. If you bought a new one from a good place, you would be golden.

However, the finger on the parallel switch does get tired, so some jury rigging might be in order. Either at the toggle of the switch (baling wire) or behind the switch (move a coupla terminals around) or at the solenoid (again, move a coupla connections.) It might be a good idea to drill a little hole in the switch handle so you can wire it in parallel with SS safety wire.

Bill is right about carrying a paralleling jumper. However, a coat hanger will get you home if you don't have a jumper.

If you do go the battery switch way, be very careful about switching it with the engine running. Delcotrons don't like some switches.

Gary's ideas might require some extra length on some batt cables. Now might be a good idea to check if you can do that or need to do some rerouting or need longer cables.

Oh, yeah.....make sure all your batt terminal clamps take the same size wrench and have that wrench permanently available in the battery compartment for emergencies. I like to insulate one end of the wrench to avoid arcing or burning.

In my case, I can just switch the chassis cables over to the house batteries, leaving the house batteries connected. If the alternator's dead, I can run the genset, which only charges the house batteries.

As bill h mentioned, alternators can fry if disconnected from a load with the engine running; there are marine changeover switches that avoid this, either by paralleling the batteries first, or interrupting the alternator excitation (which requires some additional wiring).

Another consideration in your scenario is whether you're dealing with a diesel or a gas powerplant. With gas, you must have enough constant power to keep the engine electrical system firing through the distributor, spark plugs, etc. With the diesel you have only to run the fuel pump (unless you have the newer computer driven engines). In either case you must consider the need for lights and any other must have needs.
Corey

Good Info....Thanks to all.....

Since chassis & coach batteries are about 8' apart, and since I have access to welding cable in bulk, it sounds like I could just permanently couple the batteries together with a big fat ten dollar knife switch on the firewall......I'd be the only one to inadvertently mess with it.....

I don't have a MOM switch - it's an AUX switch that stays ON when switched. Don't know the quality of the solenoid, but I suppose by-passing a normally-open solenoid would be an energy-saver in itself when trying to shed loads......

'Course, I could take the billh approach and carry a spare alternator, but for me, that simply means that the existing one will then last for at least another decade and/or 100k miles +........

Interesting discussion...Thanks again.......

quote:

Originally posted by Lee:
'Course, I could take the bill h approach and carry a spare alternator, but for me, that simply means that the existing one will then last for at least another decade and/or 100k miles +

Hasn't worked that way for me.

My spare is just to get me to the nearest Kragen to exchange another "lifetime" alternator. Or have a clerk tell me that 15 volts is within acceptable range.

Last year when I drove my 28' 454 home for the first time, I drove from just north of Thurmont Maryland home on the battery alone. It was daytime and I was very concerned about battery useage. I watched the battery voltage like a hawk. I believe this was about 100 mile trip, and I was able to re-start the coach when I arrived home without charging it.
The 84 ignition did not draw too much power, so that and the occasional brake light were the only battery load. I probably could have driven much further, but not adviseable.