If it is powered by the ACC terminal (as designed) none of these problems exist .
Sadly this rarely happens. Builders rarely install them correctly because they often just accept the standard engine panel from Yanmar, Cummins, Cat, Deer etc. that does not have an accessory terminal on the ignition switch.. They simply wire it to the ON/IGN position and send it out the door. Using the ACC position for a solenoid by boat builders or DIY's is about as common as builders or DIY's wiring & wiring properly the AFD feature of a battery switch, almost non-existent..
Using the ACC terminal still does not solve thrusters, inverters or other high demand loads pulling more current than is safe across the solenoid when the motor is running.
Also adding a switch with the ACC position, such as a CH 712, brings the cost and labor time up so the value proposition shrinks. I also would suggest using the 200A capable CH solenoid that use silver contacts as opposed to bare copper which again increase the solenoid cost a bit.
Solenoids
can be installed safely, and with good design, but rarely are. Today with the advent of VSR's/Combiners/ACR's/Echo's DC to DC chargers etc., and a large percentage of cruising boats, both power and sail, using alternative energy, the choice to use an inexpensive solenoid is a pretty rare one even for most builders.
An alternative to the ignition ACC terminal for solenoid activation is to use a separate manual switch just to activate the solenoid or to use the oil pressure circuit for the the solenoids excite. You can also create other methods too, or replace your key-switch, but this usually removes the "value" proposition of the inexpensive solenoid approach.
On nearly every boat that I have set foot on using an inexpensive solenoid, for charge distribution, the solenoid is excited before starting occurs and is excited by a basic ON/OFF ignition switch. I have worked on some boats with a separate "
parallel solenoid" switch but owners often forget to use it or forget to disable it when they hit the 300A - 400A bow thruster or when at anchor.
My most recent (June) was a lobsterman with a large John Deer. The builder wired a parallel solenoid to the ON position of the ON/OFF John Deer key switch in the John Deer factory panel.. Steve was replacing about two 85A Cole-Hersee solenoids per season. He also had no way to parallel banks if he killed one, which he had done twice when the solenoids died, another
builder blunder.. He now has an SI-ACR and a
manual emergency parallel / crossover switch. The whole rework cost him significantly less money, in time, materials and labor, than just one of the failures of his inexpensive solenoids cost him.
And eventually should it fail, a $20.00 unit is more likely to be found on board as a spare than a few hundred dollar item.
The Blue Sea 120SI ACR can be had for as little as $65.00. The more expensive ML-ACR, about $150.00 & is 500A continuous rated, is not really necessary in many applications.
The
spares discussion begs the real question though of why you would carry either an inexpensive solenoid or an ACR as a spare if your system is wired properly, with manual control & isolation, to begin with?
Neither are absolutely necessary, in a properly wired cruising system, they just make
automated charging easier and help to remove human error from the equation. The ACR makes charging
automated even when you're not there for solar & wind though and can also open itself when high loads are used.. This is something which a key on, manually excited device, can't do.
Still, you can easily live without either in a properly wired cruising system. Many owners do, until they murder an expensive bank of batteries, become stranded or require a tow.
Both an inexpensive solenoid and an ACR should be
redundant devices to simply automate charging. One automates it with any charge source and the other with only one source.
There are many other
spares, a whole other discussion perhaps, that can be significantly more important, such as a back up alternator, alternator re-build kit, starter, starter solenoid, spare motor mount, spare reversing gear, prop, prop shaft, injection pump, injectors, fuel pump, turbo, oil-cooler HX, HX, fuel injectors, belts, water pump, raw water pump, impellers, strainer gaskets etc. etc....
Everyone of the above items I have seen damaged or fail at higher rates than a $65.00 Blue Sea ACR yet none of them are a redundant device, unless you have a twin screw. An ACR
or an inexpensive solenoid would be redundant in a properly designed and executed cruising vessel DC system. Kind like carrying a spare tire for the spare tire...
Other than belts or impellers etc. very few boaters carry any of the above items as spares except for some very experienced world cruisers with many miles under their keels.
The items listed above, and more, would probably be considerably more important to carry on-board a voyaging world cruising boat well before a device that is already a redundant piece of gear such as an ACR or solenoid.
