Is a 12V battery a 12V battery?

[Craigums]

So I'm going to start out by stating that as far as electronics go in boats I'm pretty ignorant.

I just purchased an open water transducer for my flasher to install in my boat. When I use my flasher on the ice it runs of a small rechagable 12V battery, In My boat I use a car battery to power my little trolling motor which I believe is also 12V, So would I also be able to run my flasher in the boat off of the car battery I already have in the boat. Or do I have to use that smaller portable 12V battery I use during the ice season.

[LightningBG]

You can use the big battery. They put out the same amount of power its just a matter of how long they can put out that given voltage.

[Dave]

The device is what constitutes how much current it'll draw from the battery...not the battery size.

[BobT]

Dave is correct. Imagine what would happen to your home if the power supply determined the current the devices would use.

[Craigums]

Well then in theory couldn't I hook my Marcum which runs off a 12V battery to a 120V outlet in my home and have it still work?

[BobT]

Amperage (current from my previous post) is determined by the voltage applied and the resistance or impedence of the device. You increase the voltage on a constant impedence or resistance and current will increase proportionally. Power (watts in a dc circuit) will increase exponentially.

Your computer will use somewhere around 300w or more however the circuit you plug it in to is capable of delivering 1800w (15A) or 2400w (20A). If the power supply to your computer determined what the computer would use, it would be fried before you could have finished reading this post.

You will destroy your 12vdc Marcum by introducing it to 120vac supply.

[PierBridge]

If you are actually using a car battery you may want to get a Deep Cycle marine battery. Your electronics "Trolling motor, flasher,lights" will run much longer on a deep cycle versus a car battery which is made more to start things than to run electronics for long periods.

[Nick Kuhn]

A 12V device is a 12V device. Actually it'll probably run anywhere between 10V-20V so long as you provide the minimum current (which isn't a problem if moving up in battery size). There are nuances to different types of batteries but to the average user they need not worry about it. There should be a sticker on the back with all the info you need (input voltage and current), so long as you meet that it wouldn't matter if it were a battery, a solar panel, or a man on a bicycle it will work.

[jtroop]

Make sure you fuse it correctly regardless of the batteries capacity.

[Whoaru99]

Make sure you fuse it correctly regardless of the batteries capacity.

Right...and the bigger the battery the more important this becomes.

Generally speaking, the fuse is not to protect the device, IMO, it is to prevent the wires leading to the device from turning red hot and starting a fire. The fuse is sized to allow the device to run with out blowing it, but small enough to protect the wires from melting/turning red hot in case of an electrical problem (short circuit, etc).

A car battery or marine battery can turn even some fairly large gauge wires into red hot toaster elements real quick without the proper fusing/circuit protection AT THE BATTERY END of the cables.

Having 20ft of wire right off the battery with a fuse at the far end isn't a good plan.

[BobT]

An automotive battery has enough copacity and capable of delivering high enough currents to melt down a box end wrench or you could weld with one for a little while.

Quote:

Right...and the bigger the battery the more important this becomes.

Not necessarily. Your vexilar battery has enough capacity to do this so fusing is important for any size battery.

[fishwater]

Not necessarily. Your vexilar battery has enough capacity to do this so fusing is important for any size battery.

Good point. Shorted circuits and 'vex' batteries can start fires easily. I had a marcum dcs charger start on fire just this season. I plugged it into the wall and it nearly instantly burst into flames. I was extremely lucky; we intended to drop off equipment and quickly head back out the door to get some food. If it had ignited a bit slower, I would have most likely burned the cabin down.

[Whoaru99]

I understand what you're saying, but I'm still of the same opinion. The bigger the battery/current source, the more important is your fusing. It was not intended to minimize the necessity of proper fusing with smaller, yet still relatively high current, batteries.

[lakeshoremunster]

Well then in theory couldn't I hook my Marcum which runs off a 12V battery to a 120V outlet in my home and have it still work?

No do not do that, you will fry your unit in an instant. The reason other 12v units work in your house outlet is because they have a transformer on the power cord to convert the 120 to 12v, your flashers do not have the transformer on them that is why they come with a 12v charger.

If you wanted to run your flasher on your house outlet you can hook the power cable on the back of your unit to your supplied charger, because the charger has the transformer in it.

[JollyT]

I can tell you a battery story. I was out fishing with a buddy in a square stern canoe with a old trolling motor he had bought at a garage sale. We had the battery towards the middle of the canoe for weight distribution and the trolling motor leads were short, so he was sitting on them.

I was fishing out the front and he was banging around in back when I heard a pop and a cloud of smoke formed! I was about to go over the front of the canoe as I figured he had tipped the battery and dead grounded it, but once the smoke cleared, I discovered what had happened. The switch had gone to a dead short vaporizing the trolling motor leads and burning a hole in my friends butt while doing it. Luckily two of the women along on the trip were medical professionals.

[chris63]

What size boat are you talking here?I assume it's not a real large boat since you've stated that the trolling motor is small.Sometimes you can get interference when you run electronics in conjunction with trolling/light/other accessories.I like to use the 7/9 amp hour batteries for electronics all season to cut down on the weight.A trolling motor can draw down a battery quickly.So for that reason alone I like to keep it on it's own circuit.c63