Start engine with AC battery charger on?

[DoubleD]

Basic question that came to mind when reading about frying alternator diodes when changing and/or turning off DC battery switch. On previous sailboats, when starting the engine. I would turn off the AC switches and disconnect the shore power cable. My Caliber 33 has a 3GM30F diesel and a ProMariner ProSport HD8 AC battery charger. To help with starting in very cold weather, is there a problem/risk of leaving the shore power hooked up with the battery charger on? Or does the battery charger help during start up? I usually start with the battery switched to All.



DD

[rslifkin]

It won't hurt anything to start an engine with the battery charger running. The charger will momentarily end up supplying its maximum power while you're cranking the engine, so it'll assist the batteries slightly. The charger self limits the output current, so you won't hurt the charger.

[DoubleD]

Originally Posted by rslifkin

It won't hurt anything to start an engine with the battery charger running. The charger will momentarily end up supplying its maximum power while you're cranking the engine, so it'll assist the batteries slightly. The charger self limits the output current, so you won't hurt the charger.

Thank you for the response

[jordanbigel]

Originally Posted by rslifkin

It won't hurt anything to start an engine with the battery charger running. The charger will momentarily end up supplying its maximum power while you're cranking the engine, so it'll assist the batteries slightly. The charger self limits the output current, so you won't hurt the charger.

That has not been my experience in the past, with some chargers...

For years, I always remembered to shut off the AC to the charger before starting the engine. Then one day, I forgot.

At the time, I had a Xantrex Freedom 2012 - according to the repair technician when I explained what happened right before it went haywire, the large inrush of current coming from the alternator caused the problem and he admonished me to remember to shut the charger first next time (all while boasting what great gear the Xantrex is compared to the "lightweight" Victron).

I dumped the Xantrex after it broke a second time for different reasons 6 months after the first repair, and I have had a Victron Multiplus II now for over a year.

I am still not 100% sure the technician was right, but the coincidence is too strong to ignore. So, maybe not all chargers can handle this scenario. I know the Victron can because a few weeks ago I was testing a new temp sensor on the alternator and I started the engine and again forgot to shut the charger - but with the Victron, there was no problem.

[NewMoon]

On two different boats, I've had a Freedom 10 and a Freedom 25 inverter charger. On both, I've started the diesel several times with the charger going - no problems.

[smac999]

I always start with ac on. Unhook shore while boat warms

[rslifkin]

Originally Posted by jordanbigel

That has not been my experience in the past, with some chargers...

For years, I always remembered to shut off the AC to the charger before starting the engine. Then one day, I forgot.

At the time, I had a Xantrex Freedom 2012 - according to the repair technician when I explained what happened right before it went haywire, the large inrush of current coming from the alternator caused the problem and he admonished me to remember to shut the charger first next time (all while boasting what great gear the Xantrex is compared to the "lightweight" Victron).

I dumped the Xantrex after it broke a second time for different reasons 6 months after the first repair, and I have had a Victron Multiplus II now for over a year.

I am still not 100% sure the technician was right, but the coincidence is too strong to ignore. So, maybe not all chargers can handle this scenario. I know the Victron can because a few weeks ago I was testing a new temp sensor on the alternator and I started the engine and again forgot to shut the charger - but with the Victron, there was no problem.

In my opinion if the sudden load of starting and then the alternator coming online hurts the charger, then that charger is a poorly designed piece of junk.

[Stu Jackson]

Originally Posted by smac999

I always start with ac on. Unhook shore while boat warms

Downside of this is you don't know if you may have any trouble with your battery(ies) because keeping them on charge could mask a serious unknown battery voltage drop.


This is more the OP than you, smac99, 'cuz you know what you're doing.