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Old 01-05-2015, 11:33   #1
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Too many Amps?

In an attempt to setup my mobile office I have a laptop and two external displays running off my 12V receptacle at the nav station. When I'm plugged in and the battery charger can run, all of these usually run fine. On batteries alone or with weak solar coming in (5 amps) everything will run but my computer is constantly switching back and forth to battery mode.

Do I just have too many items plugged in, would installing heavier gauge wire from the batteries help with that, or is that the first sign of aging batteries? I have two sets of 6V golf cart batteries and this will be their 3rd season.
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Old 01-05-2015, 11:48   #2
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Re: Too many Amps?

Those external displays probably draw a lot of power. Are they 12 volt displays or are you using a 12 volt car plug in adapter? How many watts are the displays?

IS this an apple macbook? They need a special car adapter.. they are not 12 volt devices.
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Old 01-05-2015, 12:47   #3
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Re: Too many Amps?

I have 12v Car adapters for all my devices. They are all set to the correct voltage. My Monitors each draw a little over an amp. The laptop is closer to two. The monitors never flicker or have power issues. My laptop just seems to be more picky. I have several 12v car adapters that I am using, each has its own adjustable voltage. the overall amp load doesnt seem to be that bad so I am confused as to why I have this issue.
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Old 01-05-2015, 12:58   #4
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Re: Too many Amps?

Are your plugs cigarette lighter type/style? Those have a really lousy contact on the positive pin, and the receiver for the pin in the receptacle can build up corrosion and cause voltage loss. When on shore power you're probably running at ~13.8V and can afford some losses. Without charging probably don't have that room. I'd check the contacts. Depending on how bad they are you might be able to clean them up with a pencil eraser.
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Old 01-05-2015, 13:02   #5
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Re: Too many Amps?

Yes, they are all round cigarette type contacts but they are also new so not corroded or anything. Maybe there is a better method of hooking everything up, I just have one 12v outlet on the nav station that I run to a 1 to 4 splitter and connect everything from there.
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Old 01-05-2015, 13:03   #6
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Re: Too many Amps?

Are these 120 volt or 12 volt monitors? How many watts total are all your devices? My macbook air alone is about 45 watts when charging. If I were to add another 30 watts (two flat panels at 15 watts each), I am at about 6 amps at 12 volts nominal, which is higher than your panel input.
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Old 01-05-2015, 13:06   #7
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Re: Too many Amps?

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Originally Posted by zboss View Post
Are these 120 volt or 12 volt monitors? How many watts total are all your devices? My macbook air alone is about 45 watts when charging. If I were to add another 30 watts (two flat panels at 15 watts each), I am at about 6 amps at 12 volts nominal, which is higher than your panel input.
Not sure on the watts, they are DC panels though. The call for 18V, at 1.5 amps that should put them around 30 watts each
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Old 01-05-2015, 13:15   #8
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Re: Too many Amps?

Quote:
Originally Posted by sunblock View Post
Yes, they are all round cigarette type contacts but they are also new so not corroded or anything. Maybe there is a better method of hooking everything up, I just have one 12v outlet on the nav station that I run to a 1 to 4 splitter and connect everything from there.
That could be your problem: voltage loss.

Each cig lighter is not so good. Running four devices off one is asking for trouble.

And, in many cases, the wiring to the cig lighter is sized for ONE device, not four.

Track down the voltage at the devices.

Or install more lighter plugs with hefty sized wiring. And fuses.
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Old 01-05-2015, 13:30   #9
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Re: Too many Amps?

Almost all electrical stuff has to put the watts or the amps/volts on a sticker on the device.
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Old 01-05-2015, 13:53   #10
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Re: Too many Amps?

Stu, I think you are right. I may install thicker gauge wire to this main outlet and then wire some more in versus using this splitter.

I'm going off memory on my panels, they are mounted to the wall of the nav station now and pulling them off would be a pain.

one thing I have noticed though, the problem was much more apparent when my laptop was nearly dead. I guess it draws way more while trying to charge the battery back up. Now that its 90% full, everything seems back to normal.
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Old 01-05-2015, 16:27   #11
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Re: Too many Amps?

The best thing you can do for you self is to buy a decent multimeter with a clamp ac/DC ammeter and learn how to use it.

Next look up wire gauge tables and see what you need to run the equipment you want.

Not trying to be harsh..but without some real data...all help is but a guess.
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Old 01-05-2015, 16:40   #12
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Re: Too many Amps?

Yes, a digital voltmeter would be the tool to see what the voltage drop is as you turn on the computer and monitors. Some computers and monitors have low-voltage switches in them that turn the item off if the voltage low enough to possibly damage the device.

Other members have posted how to check the wire size needed for a 12VDC line from the boat's power panel to the outlet. Remember that the wire size is determined by the total "round-trip" distance, that is, from the power source to the outlet and then back again via the negative line to the power panel. If you outlet has 6 feet of wire from the power panel then you would look up wire size for 12 feet.
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Old 01-05-2015, 18:56   #13
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Re: Too many Amps?

Or use the clamp as I suggested and find out the amp draw to properly wire/fuse the circuit.

The easier way for me...
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Old 02-05-2015, 06:33   #14
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Re: Too many Amps?

Lots of good suggestions here.
Another option is to install a dc voltage booster. This will maintain a constant 13.8v out with voltage in down to 9 volts, current rating is 25A peak so it will handle your situation fine. This is used in the ham radio world, I have one installed in my car. Just be careful not to run your batteries down to low.
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Old 04-05-2015, 09:35   #15
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Re: Too many Amps?

Thanks for all the help. What I have discovered is that while charging my laptop draws 6.5 amps at 19.5V, so I believe my cheap universal laptop chargers rated at 85W just are not up to the job. I'm going to pick up a beefier charger for this guy and I hope that will solve the issue.

Laptop is an MSI GS70 stealth so it is more of a power hog than than average.
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