How long can I leave my lights on?

[Stan Major]

I like to fish early. I have dual 12 volt batteries which I try and make sure are fully charged before going out. My question is, how long can one sit in a fishing spot with all the lights on before worrying the battery drain will prevent you from having enough power to start your engine.

[Casey]

I suppose you could calculate the electrical drain by recording the wattage of each light used, add it up and multiply by hours of darkness.

Then again, since you have dual batteries, just move your "Perko-type" switch to a single battery, and fish away! ...you'll have the other battery as a reserve for starting and getting home. (Once you've restarted the engine, switch to the drained battery to recharge it on the way home.)

You may want to look in to switching your to LED lightbulbs and battery drain will be (virtually) a non-issue.

Best,
Casey&Mary

[dotnmarty]

[potter water]

My understanding is that the charge circuits on our late model engines do NOT like to operate without a battery loading the circuit. So, idealy, you'd shut down your engine and switch batteries and fire up again. BUT, you say, "what if the battery I want to charge won't restart the engine. Then, I say go ahead and make the switch with the engine running. I've done it on older boats many times, but they were older engines too. I think the charge circuits on out later engines will not fry in the momentary switch to the down battery. If they do, then the manufacturers should be ashamed. I think the caution is more of the don't leave the circuit without a load for more than a few seconds. HOWEVER, my 2007 Suzies require enough juice to run and it is conceivable that switching a running motor to a truly dead battery might cause the engine to stall and quit. Never tried that.

Good luck. Make sure you are at the dock when you experiment.

[olsurfdog]

I think that the "off-1-both-2" switches have juice going thru them all the time when going from 1to both to 2 but you never want to shut them to off when the engine is running as this will fry something. I have had both a Perko and now a Blue Seas that are this way (I think this is called "make and then break"as opposed to " break then make"). The "off" is the major NO NO! I'm sure some who really knows will chime in here and help us all!

[thataway]

As noted most of the modern Blue Seas and Perko switches are either make be fore break--that is the alternator is always connected to a battery. Some have a "field current" disconnect--and these are more for an alternator with a field current sensor which our outboards do not have.

The best way to solve this problem is a Voltage Sensitive Relay. This way the starting battery is charged first, then the aux or house battery is charged. When the engine is off, the voltage drops to below 12.7 volts and the batteries disconnect. These have come down in price so that they can be found for $70 to $90 dollars. A good investment and simple to wire in.

LED lights are excellent. The current draw can be 1/10 of an incandescent. They also have come down in price--and there are ways to convert the current fixtures for a fraction of the "store price", using strip LED's.

A group 24--the most common battery in your boat will have from 60 to 80 amp hours--and you can discharge this to 1/2 or 12.2 volts safely. So you have 30 to 40 amps available. Even with conventional bulbs you can run the running lights and a cabin light which draw 2 amps total for 20 hours. If you don't already have a digital volt meter, get one. They will measure current draw up to 10 amps. It is unlikely that the current draw will be near that, You can put the meter in series (in line) with the bulbs and measure the current draw.

Are you also running a chart plotter, depth sounder? An auto pilot would draw more--but it is unlikely you are running one.

[Sea Wolf]

Most all modern battery switches have what is known as "make before break" switching, which connects the next battery choice together with the engine before turning off the last choice.

So when going from "1" to "both" to "2" and back and forth, there is always a battery or two connected to the engine and therefore a load.

Do not, however, switch to "off", as this turns off all batteries and unloads the engine, allowing the diodes to "fry" .

By the same token, other battery switching relays, like a VSR (Voltage Sensitive Relay) that do automatic switching, have the same "make before break" feature incorporated into their design.

Just how bar you have to go back into time/history to find a battery switch without the make before break feature, i'm not sure, but probably into the early 1960's or 1950's. Bob would probably know.

Joe.

[Sunbeam]

As mentioned above, it depends somewhat on your setup. If you are running two batteries, you can "save" one just for engine starting, so not being able to start the engine won't be a factor. Still, for best battery life it's good to not run the "other" (or any) battery down below 50% capacity. If it were me, I'd want to know the size (amp hours) of the batteries, and the draw(s) of the light(s) (you can see or calculate both by looking at them for the numbers on them).

Once you know those figures, you can figure out about how long you can go before drawing down past the 50% stage.

It's another "thing" -- and not at all necessary just to figure out what you want to know -- but boy do I like having a battery monitor aboard. It's like a gas gauge for the batteries, plus a calculator for load draws. At a glance I can see the state of charge of my house battery (I run one start battery and one house battery), see what I'm drawing (or what anything I have aboard does draw), and etc. It was not difficult to install and (for me at least), worth the $149 cost. And it's small and light

I'm glad for the "jog'" as I just recently measured the draw of my various lights and appliances and was going to start a thread to list them, which I will do today.

Sunbeam

PS: I installed a Victron 600S (have had other monitors on other boats, which also worked fine, but I like how the Victron installed with the Cat 5 style cable connection).