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Old 11-08-2015, 19:15   #16
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Re: Is boat 12v "smooth" enough for a computer

So I run a small pc that uses 110v 60hz to it's power supply, which I feed from a small, cheap, "square wave" 150w inverter that plugs into a standard 12v cigarette socket. I use a 12v battery that is intended to be used in a UPS, rated at 12 AH, wired in parallel with the 12v bus and that cigarette socket feeds directly from the small battery. This allows me to keep the computer tucked away from any possible splash or spill, which always worried me when I was running a laptop - even a coffee spill can bring down your nav system.
Originally the lighter socket was wired so that it would cut out when you crank the starter, now the small battery is more than enough to keep it running while that happens. This would also work for shifting multi-bank batteries- eventually I will upgrade to a dual bank system.
Just replace the small battery any time you replace your house battery, they don't last forever.
If you are running a laptop with a 12v power plug, it is actually a DC-DC buck converter, because laptops these days run on 19v DC. So that bumps up the 12v to 19v and charges the laptop battery. If you use the small battery trick as well, you are going to filter out everything short of a lightning strike. Even so, I would carry a spare 12v adapter.

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Old 12-08-2015, 10:32   #17
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Re: Is boat 12v "smooth" enough for a computer

12v off a battery bank even with the alternator running will be just as clean as the 12v system on an automobile. If it works on your car it should be fine on a boat.
I would be far more worried about how exposure to high humidity, especially in a salt water environment would affect the inverter, computer etc.

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Old 12-08-2015, 10:46   #18

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Re: Is boat 12v "smooth" enough for a computer

"If it works on your car it should be fine on a boat."
Those inept, self-serving, untrustworthy technical employees at places like Westinghouse, GE, Delco, Raytheon...pretty much everyone in the "electrical gizmo" businesses says that spikes ARE normal. Batteries WON'T absorb them all. And that they all get many devices back for repair after spike damage, from routine installations.

They do not install spike protection devices in their equipment (usually) because all spike protection devices cost money, and eventually they wear out and fail from repeated spikes, making internal protection a futile venture that only makes their product economically uncompetitive.

Case in point, Delco made a car alternator series with added internal spike protection, to protect the "new" computers and electronics in GM cars. The new alternators had higher failure rates because of the spike protectors eventually failing (i.e. at 100k miles) and shops didn't want to deal with them. So, they stopped making them that way.

If your electronics are running off one breaker, it is also pretty simple to put a protection device on that breaker--and protect them all at once, inexpensively. Last time I did a major rewire, I put a couple of spike protectors (transzorb, zener diode) in a small box, added a piezo buzzer that will go off if any of them fails open, and an extra crowbar fuse, so if the protection fails shorted, it will also immediately blow a fast-acting fuse in the box. Maybe $25 in parts in a silver "cigarette box" next to the breaker panel. No icebox or big things like that on it--but all the instruments are protected.

Adding a simple diode or transzorb across the power line AT each device would work almost as well, very simple and cheap, while it lasts.
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Old 12-08-2015, 10:53   #19
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Re: Is boat 12v "smooth" enough for a computer

Originally Posted by esarratt View Post
Any problems with weird, spikey energy in boats?

I was wondering if some form of protection, besides fuses, was necessary for non-marine electronics used aboard boats.

I use a Panasonic laptop for my charts (and everything else) and I don't want to fry my computer.

I will be using a 12v car adapter with the laptop and there will be at least two fuses in the circuit, 1 in the laptop adapter itself and another in the fuse box.

OR does the computer's own power box smooth out the voltage for the laptop?

If you have sufficient house battery capacity 12V DC power will be far smoother and cleaner than AC. The issue with DC is running the batteries down. Once your supply voltage under load drops below what your consumer can handle you will see erratic power supply behaviour.

Most laptop power supplies today cope well with a wide range of AC voltages and frequencies. We run almost exclusively on 12V. We use goodnquality 300W inverters for powering laptops and our tv. Our NAS and routers are running of 12V. We hardly use our 2000W inverter any more.

Once the next generation of laptops arrives with Usb power and we ditch the smart (dumb) tv we'll be able to ditch all the 110 AC loads. That makes for a much simpler electrical system which is by far the most complex boat system.

Converting from ac to dc and dc to dc is so inefficient. Our power sources are solar and wind so dc makes much more sense on a boat imho.

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Old 12-08-2015, 11:32   #20
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Re: Is boat 12v "smooth" enough for a computer

A nearby lightning strike can induce transients in the DC wiring of any boat. Most regular cruisers have seen enough nearby strikes to realize that it can happen. This alone is enough to make me want to take steps to protect my critical electronics with transorbs/Transzorbs/avalanch diodes.

Your automotive electronics fail, you pull over and get help. It can be a little more problematic at sea. Better to do what you can to minimize the risk, as it isn't that hard to do.

What are the odds that such protection will in the end make a difference? Probably not high, but...

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Old 12-08-2015, 17:08   #21
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Re: Is boat 12v "smooth" enough for a computer

I hear you on the electrical strikes.

Thanks everyone for the advice. My fears are calmed. I did not know that 12 volt off a battery was safer than 110 Volt. Interesting.

I follow on the salt water issue, but that is OK as the laptop is an old Panasonic (and I am surprised it is still working). It is a Toughbook CF-52 that I bought new about 6 years ago. I highly recommend them and will be buying another when this one dies.

All I do is keep replacing the battery (am on #3 now); no new hard drive or anything.
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Old 12-08-2015, 19:02   #22
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Re: Is boat 12v "smooth" enough for a computer

I am not sure why it is but I am sure I have seen pretty many reports of car laptop adapters fail. Perhaps avoid cheapoes, or get a spare.

Now the 110/220 adapters not always co-op with inverters. Solution I think is get a good inverter ... and test your mains laptop adapter before you cast the lines.


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