Engine charging of coach batteries

wolfe10 wrote:

YC 1 wrote:
It would not take much to install a solenoid activated by a wire that is hot when the ignition is on. Or if you have an aux start switch that works just run an ignition wire to that solenoid.

MAYBE!

If it is a CONSTANT DUTY solenoid, that could work.

But many boost solenoids are only intermittent duty and certainly not designed for constant duty.

Actually it is the other way. BOOST solenoids(usually called BIG BOY solenoids that are rated at 200 amps) have to handle a LARGE amp load to power the starter. Charge solenoids handle a very small amp load as the Alternator is charging 2 battery systems. Most of the silver solenoids(what some would call too small) can handle 100 amp loads, which is way less than what will go thru them when chassis systems charge both banks. Older motorhomes did use those 100 amp silver solenoids as a BOOST solenoid and usually after a few times of boosting would burn out and then fail. Most common cause of the emergency start not engaging when needed. For instance, some use a FORD solenoid when they replace a silver solenoid because they look identical. BUT, a Ford Starter solenoid is indeed for momentary power to the starter and the internal make up of the copper disc is different. That is why people should NEVER use a Ford type solenoid when replacing those solenoids. They are not rated for the same amp load. Doug