Generator Start Battery

[safetyequip]

Quick question. We are liveaboards and we have a 5kva northern lights generator that we use for 2 hours a day. Is it recommended to turn the Generator battery isolation switch off after each use or can we leave it on and just turn off if we are away from the vessel.
Thanks Todd

[rslifkin]

I leave my battery switches (both engines and generator) on all the time unless I'm working on something or prepping for long term storage.

[d design]

Turn it off if your not starting it within 24 hours. Will keep your electrical connections on the unit free of electrolysis and you will ensure your isolation switch is in good working order.

[tkeithlu]

It's not quite the situation in you car, since the car is less exposed to electrolytes, but if you are using it every day, disconnecting every time is going to be a minor PITA for little benefit.

[redneckrob]

Do you really need a separate start battery from the engine start battery? I just use my engine battery for both.

[d design]

Originally Posted by redneckrob

Do you really need a separate start battery from the engine start battery? I just use my engine battery for both.

Three reasons that I can think of with varied importance:

Redundancy. Spare battery on board.

Preventing the very small genset alternator from attempting to charge any large bank, heavy loading during engine cranking, or winch and other power hungry operations that could result in alternator or genset failure.

Preventing voltage sag or spikes to the genset control circuits.

Three reasons not to have separate batteries I can think of:

More weight.(Could be good or bad)

Uses space.

Extra maintenance item.


You choose what you value. No system is right for everyone's application. If anybody knows an idiom for these situations let me know.

[wrwakefield]

We turn our starter battery switch [engine and gen share one start battery] off when we close the through-hull valves. [It is also a manual bank selector switch, and combiner for emergency starting.]

For convenience during routine usage periods [you mentioned yours is daily] I leave the through-hull valves and starter battery switch on for convenience- unless we leave the boat [even for day trips while at anchor...]

If we had an automatic generator starting device [e.g., one that starts the gen and charger automatically when the house batteries get low] we wouldh't have these options.

These are just our approaches and SOP's, but everyone has their own for different reasons...

In case this is useful.

Cheers! Bill

PS: As an afterthought, if your generator places some parasitic loads on its start battery [I'm not aware of any gens that do so...] that might be a good reason to disconnect the battery when not in use.