Can engine alternator and Battery charger running simultaneous?

oscar1

This may a stupid question, but I am wonder if the engine alternator can be running at the same time you have your boat connected to shore power with the main battery charger on. Can the two running together damages each other or the battery there are providing charger. I normally turn off my battery charger when I run my engine at the slip, but I always have the consect if I don't have to do it. Like I a said, stupid question. Thx 

aero3113

Not stupid, I would like to know the answer also.
I’ve done it a couple of times by accident and haven’t had any issues that I know of.

PickleRick

I certainly hope it doesn't.  I have ran my generator many times while trolling for bass so the admiral could sleep in the AC.  I have both a volt meter on the dash and voltage appears on my Garmin, voltage never spiked or read above normal running volts.  

Our battery chargers have sensors in them so they automatically turn on and off when they read full/low and our alternators have built in voltage regulators so they cap @14.5 volts.  So I never play with breakers unless I want to run the microwave/air fryer/coffee maker while the ac is on.  I certainly hope I'm not damaging anything.... I've been doing it for going on 4 years now!  So far the only battery I killed was because of a disconnected battery charger wire. 


Every boat I've chartered had ac and they run the genset the entire fishing trip out to the reef and back.  I never thought to ask them if they kill the battery chargers while the drive motors are running.

TonyG13

Curious also. Never thought about it. There are many times I start the engine to let it warm up or to check things out while still connected to shore power. I've never had any issues so I'm assuming there is some built in protect between the two sources?

YYZRC

I often have solar + shore power AC charger + alternators all providing power to the batteries at the same time when I'm at the dock getting ready to head out.  The AC charger and the solar stop providing a charge (go into float mode) when they sense that the relevant battery is charged.

Pat310

Google researched it and seems to be split on opinions. Biggest concern was spiking the charger when starter is engaged causing voltage drop. I too have started the engines many times with charger on with no problems. I don’t disconnect when doing motor work at he dock. Between voltage regulators and battery isolator I think this goes in the old wive’s tales category 

DanW

I have heard you shouldn’t run engines with the battery charger on. However, I, too, have started the engine while still connected to shore power. I haven’t noticed anything bad happening but I try to remember to shut off the charger before starting the engines. 

Liberty44140

I always have my chargers on, running off generator, while the boat is running. Only way to charge thruster battery as it’s not in the bank off the alternators. No I’ll effect, no difference in performance, and I’ve done a bunch of reading on this and from what I saw it is just fine. Folks I know with thrusters all do the same. 

skennelly

Yeah.  I always start the engine while on shore power to let it warm up while I prep for departure.  Never thought about it.

LaRea

Yes, you can run the charger and engines.  I do it often.  I also did it before I replaced my original diode battery isolator with a modern digital isolator.  

Ian

I believe the smart chargers detect incoming charge and switch off. If I ma on shore power and engines running charger output is zero. After shutdown, there’s a delay and charger output kicks in.

oscar1

I am going to call mastervold who is the manufacture of my battery charger to ask them about it.

echandler1971

Liberty44140 said:

I always have my chargers on, running off generator, while the boat is running. Only way to charge thruster battery as it’s not in the bank off the alternators. No I’ll effect, no difference in performance, and I’ve done a bunch of reading on this and from what I saw it is just fine. Folks I know with thrusters all do the same. 

You should get an isolator with more outputs. That's what I did - I have 4 banks (1 for bow thruster). I put it on the least-important output.

Dream_Inn

echandler1971 said:

Liberty44140 said:

I always have my chargers on, running off generator, while the boat is running. Only way to charge thruster battery as it’s not in the bank off the alternators. No I’ll effect, no difference in performance, and I’ve done a bunch of reading on this and from what I saw it is just fine. Folks I know with thrusters all do the same. 

You should get an isolator with more outputs. That's what I did - I have 4 banks (1 for bow thruster). I put it on the least-important output.

You ran a wire from the engine room to charge the thruster battery?  that is a long way to run a fairly large wire.  I've never had a need to have my thruster battery charged while underway.  It usually is charged well at the marina before I head out and then if I use the generator. 

YYZRC

^^ same. Rinker pre-wired for an AC charger. Easy peasey. 

LaRea

Charge routing is handled by the battery isolator, not the charger. 

The isolator receives current from the alternator(s) or the charger bank(s), and sometimes from both.  The isolator sends power to the engine(s) and/or batteries as needed, while not allowing a battery to drain another battery.  

Grahamu

My battery charger is connected to the output terminals of the isolator, only the alternator outputs are going thru the isolator. On my last boat I installed an echo charger for the thruster batteries.