On board charger

[DFTR Josh]

So done for the day and just want to swim and listen to tunes all night at the marina. If you plugged in your charger would it help tender the batts while stereo, cockpits, underwaters are on all night? Not even sure if I'm using the right word "tender" for what I'm asking.

[BrettLee3232]

My stereo guy told me I could listen "safely" to 1 battery with the charger plugged in. Not sure how well it will charge the battery while listening but I think you would be fine.

Not sure what happens if your switch is in the "all" position. Maybe MLA will clarify.


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[blackcup]

Good Q would love to know the answer to this as well. Just hooked up my charger the other day.

[gregski]

There are way too many variables in this question to provide any solid answer. You need to know your power/currents. A charger is your "power in", your load (lights, stereo, etc.) is your "power out". If "power out" is less than "power in" then the difference goes to charging your battery(s), otherwise the difference is taken from the battery(s). What is the power output of your charger? Maybe around 1A? That would be about 12W.

[David Analog]

So to begin with a battery charger is by no means a power supply...unlike a convertor class of battery charger. A smart charger is in a high current bulk mode for only a limited duration. A tender is simply a maintenance charger, and no more. If you exceed that duty cycle or current capacity you can expect an early demise. So the answer is going to depend on a number of variables. Since those variables are not stated, I'll give an example. Let's say:
After a day on the water the battery(s) is partially depleted. That alone might represent a 5+ amp draw.
The stereo at a moderate level might represent a 15 amp draw (definite not in full party mode).
The other accessories could add up to a 5 amp draw.
That's 25+ total amps. If the battery charger has a 25 amp rated capacity then it is much too small for the job.

[trayson]

Is plugging in a charger going to keep up with your draw? Probably not. Is it going to make your batteries last a bit longer before they're depleted, of course. Will it be enough to have everything fully recovered by the time you want to go out and take your morning set? Who knows. But if my choice was plugging it in vs not plugging it in, I would plug--even if is only helping some and not recouping the full draw.

[MLA]

Gotta 2nd David. Having a constant load drawing on the batteries while the charger is in use, keeps it chugging along at a high output. Ok for short term but extended periods and done frequently may shorten the life of the charger.

[zabooda]

Take a regular car charger along that has more output.

[David Analog]

Take a regular car charger along that has more output.

This would concern me. Typically a home garage emergency battery charger is not multi-stage, is a bit of a blunt object, and supplies one continuous current level per setting. A much larger home charger may be safe for the charger but unsafe for the battery. The moment the load is gone (stereo, lights, electrical accessories) I would unplug the home charger. Same with using a pure power supply connected to the battery....fine when there is a draw but unhealthy once the draw is gone. Just one of the many mistakes I've tried.

[ian ashton]

Is plugging in a charger going to keep up with your draw? Probably not. Is it going to make your batteries last a bit longer before they're depleted, of course. Will it be enough to have everything fully recovered by the time you want to go out and take your morning set? Who knows. But if my choice was plugging it in vs not plugging it in, I would plug--even if is only helping some and not recouping the full draw.

This.

I've done it for 3 seasons so far on a Prosport20 2 bank without issue - chargers are cheap enough, I wouldn't stress about it.

I have definitely noticed that there is a slight hiss through all speakers when on shore power, which is annoying.

[zabooda]

Car chargers are mostly 1/2 wave rectified which a battery doesn't care. Any charger with the batteries in place should be sufficient as the batteries works as a filter.

[BrokeGuy]

I'm going to say your okay. Your charger output is 12 amps. I doubt your pulling more than 10 amps

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[sivs1]

Last week used the stereo out of water on battery 1 I believe. Went to start motor today on battery 2 and no go. Had to use jump box, do have on board charger, not sure how it works.

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[DFTR Josh]

All great info, thank you guys! Opted to not plug in the boat and play on it all night, water was a little chilly.