too many amps?

Lighthawk

Lighthawk

Weekend warrior
Joined
Jun 22, 2010
Messages
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Location
Nevada City, CA
Generally, I'm pretty handy, but electronics is a weak spot for me. I'm hoping one of our more knowledgeable members will help me with an issue.

We decided to install a 'charging station' in our Hawk. Instead of one 12V outlet located at the sink, we're installing a shelf on the passenger side of the Hawk next to the sliding cabinet. I bought a cigarette lighter splitter, which provides two 12V outlets and two USB outlets. I think it is rated at 1500ma.

http://www.amazon.com/gp/product/B003YJ8TVQ/ref=oh_details_o01_s01_i00?ie=UTF8&psc=1

I ran 18 ga. wire from the house battery to an inline fuse (20A), then a toggle switch.
As soon as I flipped the switch the splitter went 'poof' and I smelled fried electronics. My $13 investment was rendered useless.

Question: Will a 10 amp fuse solve this problem by gating down the amperage to the unit? I would like to install another device before we leave for our Christmas travels, but don't want to fry another unit. My local autoparts store has similar items.
 
Short answer - no. My question is what are you wanting to charge? How long is you wire run, where is your fuse located and how is your switch connected.
Cheers
 
Thank you, Captm

The largest item I would like to charge is a laptop 12v charger.
  • Input voltage: DC 12~16V max 10A 18.5v Output Current: 4.6A,85W

The other items would be phones, camera battery charger 12v

Wire run is <6 feet.
Power comes from battery directly to inline 20A fuse with toggle switch adjacent. Wiring goes through fuse, then switch, then device. I'm hoping I can do all of this without using the inhouse load center, which is on the other side of the camper.
 
18 gage wire will run 10 amp max load. See chart here

You said you "As soon as I flipped the switch the splitter went 'poof' and I smelled fried electronics. "

Did you have any load plugged in? If not there had to be a problem with the splitter. It was rated for 12 volts and that is all that would be going to it. With out a load there would not be any power running though the unit. Are you sure you did not have the polarity reversed? That would cause USB circuit to blow up, it is taking the 12v to 5.1v

Edit do you have a VOM? If not buy one and read or study on line on how it use it. This will save you a lot of time and $$.
 
Go to http://circuitwizard.bluesea.com/, and plug in your numbers. Let's use 12v, 20amps for load, 12ft(2x6)for length of conductor, 3% voltage drop (electronics), 90 for temp., 180 min. for duration, yes on fuse, yes on sheath. Calculate - Ok I'd go with awg 10, with Blue Sea sockets #1011 (12v) and 1017 (usb) or if you want really nice step up to the 1478. Check Amazon.

I use this system running a CPAP and charging 2 cell phones overnight with out any problems. Oh yea, I'm not an electrician but I did sleep at a Holiday Inn.
Cheers
 
Good points, Bill. There was no load, so what you say makes sense.
It's 50/50 odds the polarity was incorrect since I used unmarked zipcord and cable wrap.
The product label did not indicate any polarity preference.

Will take your advice to purchase a volt meter and with luck won't fry that too. :eek:
 
I checked the BlueSea calculator, Captm and I do see 10awg is rec'd for 20A load.
The laptop charger load by itself only calls for 18awg. It's 18.5v, but I tried the calculator at both 12v and 24v and got the same result.

I ran either 18 or 16 gauge. Truthfully, the #14 wire I bought at the hardware store was too short, so I raided my garage and used what I had, which was a lighter gauge. Apparently I underestimated the load on the conductors.

But the gauge of the wire didn't blow up the device. Seems like I may have reversed the polarity. I'll have to check carefully on the next device I try out. Most of them are ~1500MA at 12V. Can I wire this off a fuse protected branch direct from the battery? Or do I need something like this?
Blue Sea 6006 m-Series Mini Battery Switch Single Circuit On Off Red
 
You do not need that switch. You can fuse at /near the battery for your run. Your correct that the wire size was not the cause of your frying the splitter. As Bill suggested reverse polarity was likely the culprit. The Blue Sea sockets have +/- marked on them for easy connection. I would skip the all in one devices and go with a proven manufacturer. I'm just big on Blue Sea because their products have never failed me.
Cheers
 
I'm a bit confused on how you're going to get 18 volts out of that. From the link you provided that device won't provide that.
 
craig333 said:
I'm a bit confused on how you're going to get 18 volts out of that. From the link you provided that device won't provide that.
Click to expand...


T-tip 85W DC Power Car Charger Adapter For Apple Macbook Pro 15" 17" Mag SafeXD







  • Input voltage: DC 12~16V max 10A
  • Output voltage: 18.5v Output Current: 4.6A,85W
  • Cable length: 1.7m/66.9''
  • Size of Connector: 5pin Magsafe 2
  • Continuous with USB port 5V 1.5A


My goal is to provide at least one 2100ma USB outlet for the laptop and at least one 12V cigarette receptacle for phone/camera battery. The all-in-one was attractive and cheap. If Blue Sea made a charger with both USB and 12V, I would definitely be interested.
 
I am a lot confused. How did you wire without cutting the male plug off the end? Where did you attach the ground wire? Obviously, you have a direct short probably from reversing the wires. Most of these devices that I have seen are only good for 5-7 amps PER socket and have a 7 amp glass fuse under the + terminal that is replaced by unscrewing the knurled nut. The + is the center male and is usually a black wire with a white or silver stripe. The - terminal is usually black and is attached to the springs on the side of the plug. A 20 amp fuse is waaaaay too large. Go to 7-10 amp max. Size 16 wire is OK, but 14 is better. Just go direct to the + side of the battery with your switch and an inline fuse and find a good chassis ground for the - wire. Remember: volts x amps = watts, and while this unit states that it is good for 12 TOTAL amps, I wouldn't push it past 10 amps. My opinion.

CWD
 
For your application, I would use 14ga wire, install a 10a fuse at the source(positive side). Use red and Black duplex wire to avoid any polarity problems. You can use a jacketed duplex if you want extra wire protection. When finished, use a voltmeter to check for correct polarity if in doubt.
 
Looks like I've got some color coded 14 ga. wire and a new USB and 12v receptacle thanks to XP! Local connections are the best kind. Thanks Marc!
 
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