12-Volt Outlet Charging Woes

[Dean Abramson]

I have had a West Marine handheld VHF for a while, and have always charged it using the charger with the 110 AC transformer at home.

On our recent trip, I decided to bring the charger along, and use the cigarette-lighter type outlet on the boat. It did not work. The outlet tested okay with my multimeter, but I decided to swap it out for a new one, thinking maybe there was a problem with how things physically mated up.

Still did not work. Did not work with a third one I bought either. Tried to plug in my wife's cell phone for charging. Did not work.

Plugged in a little 12-volt portable vaccum cleaner. That DID work.

Got home and found that VHF's charger does not work with 110 transformer anymore either. And found that my wife's cell phone will not charge from the cig-lighter outlet in her car anymore.

Somehow we fried the chargers or something. Even Rich Abato cannot figure this one out!!

The vacuum cleaner is an actual 12-volt device. The other two were attempting to CHARGE BATTERIES. That is the only difference I see.

Does anyone have any clues? We blew a fuse in the Radio's 12 volt charger-cord. There was no fuse we can find in the phone's cord. A new fuse in the radio's cord did not fix it.

What the heck is going on? All three outlets have tested right with the multimeter.

Dean

[jbenagh]

Dean,

is your 12V wired backwards? This could cause electronics to be damaged. I would think that the vacuum would run but I think it would blow rather than vacuum.

For the cigarette lighter, I believe the outside should be ground and the center positive. If you have a voltmeter you could check it without taking it apart to look at the wiring.

Jeff

[Dean Abramson]

Dean,

the outside should be ground and the center positive.

Jeff

Jeff, that's the way it is. (?)

[tartansailor]

Dean,
It looks like you identified the boat's charging system as the problem, therefore
it makes sense to compare the amps, voltage, and polarity (at the cigarette lighter receptacle) when the alternator is running to:
your house transformer-charger polarity, amps and voltage,
and
your wife's automobile system as well.
It has to be one of the 3 (amps, voltage, polarity) above.
My inclination is to suspect that your alternator is cranking out more than 14v, but that is just a guess.

Dick

[jbenagh]

Sorry Dean. I concur with Dick's advice.

Jeff

[Dean Abramson]

Electricity is not my long suit...

These chargers seem to have bitten the dust while the engine was NOT running. My batteries never, ever show more than 14V. My two AGMs have performed great for the four years I have owned them (and this boat). I would think that they would have suffered from chronic over-charging. No other anomalies have occurred in the 12V system.

Having said all of that, I have to admit I do not really understand, Dick, exactly what you are suggesting. I THINK we are okay on the polarity and the voltage. Are you saying plug in the vacuum cleaner and check the amps while that is running?

Please explain as in Electricity For Dummies!

Thanks,

Dean

[tartansailor]

Dean, you want to compare the amps going in to your VHF (at the VHF) from each of the supposedly 12V charging sources. home, car & boat.
In order to avoid errors in my communication, I have included a link which will give precise directions.
Hope this helps.

http://www.ehow.com/how_5073254_measure ... meter.html

1.
Step 1

Turn the digital multimeter on. Most digital systems run a self-check before they are ready for use. Allow a minute for the meter to complete its testing.
2.
Step 2

Set the function selector to read amps from battery power or alternating current. The function setting (A~) measures alternating current in amps or AAC; (A=) measures direct current in amps or ADC.
3.
Step 3

Set the range so the maximum is well above the highest reading expected. This will protect the meter from getting overloaded. If you overshoot the range and cannot get a reading, set it lower.
4.
Step 4

Connect the leads to the proper terminals for measuring current. Connect the black lead to the "COM" or common terminal. Connect the red lead to a terminal marked for low- or high-current measuring. The low-reading terminal may be identified as "300mA." This would give readings in milliamps, whereby 1 milliamp equals .001 amps. Multiply by 1,000 to get the figure in amps.
5.
Step 5

Break into the circuit to measure its current. Set the red probe on 1 open end and the black probe on the other. This may require cutting a wire to get the probes in between the circulating current. The idea is to let the current flow

[valenteach]

I had similar problems when I first started charging my cell phone on my boat. I used the car charger that came with my phone. After a week the charger stopped working on the boat AND in my truck. There was plenty of power in both places. The boat outlet was on a 10 amp breaker. I didn't have a fuse on the wire at my boat's outlet though, but I'm pretty sure I had the polarity correct. I then looked up the power draw of my Verizon phone online. It was pretty low. I then took apart the phone's car (DC) charger adapter and found it had a main lead or internal fuse element melted. The charger for my phone clearly got too much juice. Let me know if you discover this to be what happened to your wife's phone charger.

My new iPhone came with a car charger from Griffin that is a DC to DC converter, taking a maximum 2 amps of power input between 12-16 volts and stepping it down to 5 volts at 500mA for the iPHone to consume while charging. It has a built-in replaceable 2 amp fuse. The DC outlet on my boat is a new one on a 5A breaker with the correct polarity. That has worked without problems.

A post on the Apple site mentioned that the charger requirement of the iPhone is 1000 mA (1 Amp) but that iPhones will go into "charging" mode even if the power input is as low as 500 mA. The specs on the AC wall adapter to charge my iPhone (made by Apple) say:

Input 100-240V ~ 50/60 Hz .015 A
Output: 5V 1A

So if you do the math my iPhone is getting 500 mA less when charging via the DC adapter as opposed to at home via the AC adapter. I suspect if the actual amperage that gets to other phones via a DC charger is less than the optimum amount the device's charge system was designed for the DC charging is not going to be equal, might fry the charger/adapter, or might not even be enough to send the phone into "charge" mode. What happens all depends on the sophistication of the charger plugged into the DC outlet. That might go for other devices like radios too. I've decided to assume that my breaker will probably send TOO MUCH amperage through an unfused DC outlet at some point, and I'm creating several DC outlets off shared breakers for dedicated uses - with different fuses protecting the actual outlets themselves. Something like:

Breaker 1 5A ----> Outlet A [PHONE 1A], Outlet B [PHONE 2A],
Breaker 2 10A ---> Outlet A [COMPUTER 5A], Outlet B [MISC 5A]
Battery Direct --> EMERGENCY Outlet [10A]. The emergency one will be wired direct to battery and fused there.

[Maine Sail]

Can you explain how you physically determined the polarity of the 12v charger socket? It really still sounds like a polarity issue to me. Just because a red wire may be connected to the center pin have you determined where it actually goes or that it was in fact supplying 12v?

Use a multimeter and ground the black lead directly to the boats ground buss or to the battery not to the lighter socket. Then turn it on to the DC setting. With the lighter socket turned on touch the red lead of the multi-meter to the center pin and see if you read voltage. If not touch it to the socket housing. If you get voltage at the housing the polarity is reversed somewhere,

[Sea Owl]

What may be at play here is resistance. Any electrical device at its connection has a 'resistance' in both the dc and ac world that varies from device to device. Your 12v charger socket, connected directly to your boat battery, has nothing to limit the current delivered by the battery, which for most of us, is as high a capacity as we can find.

The current pulled by the charger you plug in is going to vary according to the resistance 'seen' by the battery, and vary inversely as the resistance varies. Low resistance will get high amperage, and a higher resistance will get a lower amperage. It sounds to me (and I'm just an Enjuneer) that your are frying your chargers/equipment because they are drawing too much amperage. The voltage may not vary, but the current will! (Ohm's law!). Amperage (current) is what does the damage you have described.

Putting the a 5 amp fuse in for example, will limit the current from the battery to no more than that - but if your device is only designed to get say, 3A -- "POOF!".

Check the amperage requirements of what you plug in.....that will help you figure out what size fuze you may need to limit current.

[Ray Garcia]

Same exact thing happened to me when I installed a new replacement 12-volt outlet above breaker box. I blew the phone charger, then an AC inverter before I figured I had the polarity switched. Took apart the chargers and found the melted fuses which clued me in to my mistake.

Take apart the outlet, switch the wires and try again. Also check the wiring downstream, an inline fuse or wiring may have been switched.

Vacuum probably worked since charging a polarity dependent battery is different from polarity independent motor.

[Dean Abramson]

The polarity is correct. It reads 12V when I touch the multimeter's positive probe to the center post. Also the vacuum cleaner sucks like it should; it does not blow air out.

The good news is that West Marine replaced the charging cradle under warranty. By using the new cradle, we can see that both the AC and the 12V DC cords work fine. I can now charge here at home, and in my car. This just took place, so I have not been to the boat yet...

I tend to agree with Sea Owl that it was(is?) related to excess amperage. When I first tried charging on the boat, it did not work, then I found the fuse in the cord blown. It was a 2-amp fuse.

I am thinking that the original 12V outlet had a short in it. Maybe the fuse did not blow quickly enough, and it fried the charger. After that, we plugged in the phone cord/charger, and we must have fried that too. The phone's doolie has no fuse that I can access.

Now I have a new charging cradle, and I am on the second of two new 12V outlets. The first new one was just like the old one, w/ mostly metal parts. The one installed now has more plastic, and seems to be of higher quality. (I know that sounds counter-intuitive.)

The question is whether I am brave enough to plug my new cradle (thru my old cord) into Outlet #3. The cradles are $20, and I am in a gambling mood. If my theory of what happened is correct, I should be okay. If not, then I buy yet another cradle, and resign myself to charging it somewhere other than the boat.

I looked at the cradle. I do not see a wattage rating, so I cannot determine what the amperage draw would be. My assumption would be that it is around a 24 watt (or less) device, since the fuse in the DC cord was a 2A fuse. Is my math right here?

Do you think I ought to test it with a 1A fuse first? Just in case the thing had the wrong fuse to begin with. ???

If I can figure out how to measure ohms with my multimeter (I am slowly learning here... maybe), how much resistance am I looking for in the charging cradle? 12 OHMs or more?

(A lot of the above may be hogwash, because I may be doing the math wrong. If so, please straighten me out.)

I cannot understand how I can measure amperage as suggested by tartansailor, because as I understand it, wouldn't I have to have something operating to measure current? And as of now, nothing (except the vacuum cleaner) works. If the other things worked, we would not be discussing this, right. Am I missing something?

The old cradle was declared dead by the West Marine guy. The radio's battery, and the radio, seem fine. It is still going on the last charge, in May.

Would you take this $20 gamble? I think that my chances are THEORETICALLY excellent, but in DeanBoatWorld, about 50/50, probably less.

Dean

[Maine Sail]

The polarity is correct. It reads 12V when I touch the multimeter's positive probe to the center post.

The vacuum cleaner may not be polarity sensitive as many devices are not.

The real question is where was the black lead of the volt meter when the red one was touching the center post of the receptacle. If the black lead was touching anything in that "circuit" such as the ground or receptacle housing the meter would still read 12v even if the polarity is reversed.

To check the polarity you can't touch the black lead to anything in that particular circuit it must go to the battery or the common ground buss bar or another circuits ground.

Touch your volt meter leads to a battery and then reverse them and you'll see 12+ volts either way, same with a cigarette lighter.

[marv brinn]

Place the neg black lead of the meter on ground of the engine.
place the positive red lead of the meter on the center of the adaptor (dc supply) if the meter gives you a + reading then the adaptor is wired correctly if not then it is reverse wired.

[Dean Abramson]

Okay, I will check at the bus. I see what you are getting at. Thanks. I did not realize that the vacuum cleaner might suck either way.

Actually, after all the failures I moved that outlet to a different circuit. I think it was on with Instruments, or something else that was undesirable to me. I put it on with the compass light for now, and if I get this sorted out, I may install a new breaker/circuit just for it and maybe another like it. I THINK I did it right, but I will double check.

Thanks,

Dean