Problem With Power Outlet

Some more notes regarding this.

With engine off, I plug in the power inverter (with nothing connected to
inverter). Get low voltage alarm (< 11.5V), but inverter stays on.

I then plug in laptop charger (not connected to laptop), and lights in
laptop charger come on, and inverter stays on.

I then plug in laptop in need of charge, but with laptop itself turned off,
to laptop charger. Laptop lights show it's charging, and inverter stays on.

I then unplug the laptop from charger (while still in need of charge) and
turn it on. After laptop is booted, I plug laptop back into charger. Get a
long alarm (5 seconds) from inverter, and it turns itself off (indicating
that voltage is <10.5V).

Thus, it seems that even without a load, except for the inverter, it's
getting < 11.5V. And it's able to handle a small load, but not the load with
the laptop on. But, again, it's only a 90W charger. And, also, again, didn't
have a problem with past two cars I had.

Regarding the battery itself, there are my notes from the AutoZone battery
test.

628 cold cranking amps
12.8V with alternator off
13.82 with alternator on

Thanks for any input.

Neil

 

sounds like the battery has poor reserve power

 

First, you need to get a multimeter and check the actual voltage at the
power outlet. I don't know how this is wired, but if it is wired
directly to the battery bus then it should read the same open circuit
voltage as the battery. If it is running through a semiconductor
swithing device (such as the interior lights do), then you will lose
some voltage across that device (0.7V is typical for silicon if memory
serves). So this would drop the nominal 12.6V open circuit at the
battery to 11.9V open circuit at the power outlet.

You then said this is a rear outlet so that means it may have 20 feet or
so of wire. I don't know what the amp rating on the outlet is, but if
it isn't all that high, it may be wired with fairly small gauge wire.
If you are drawing 90W, this yields 7.5A at a nominal 12V and could be
even higher if the battery is dropping below 12V under load (unlikely if
the car still starts OK with this battery). Does the outlet cover have
a power or current rating printed on it?

Another possibility, if you happen to be exceeding the power draw of the
outlet, is that it may be getting shut down by a PTC or similar device.
I believe Chrysler uses PTCs to protect several of the body circuits.
These positive temperature coefficient thermistors will increase their
resistance as they heat up. They will heat up as the amperage draw of
the circuit they are protecting increases. Increased resistance means
increased voltage drop across the PTC and thus less voltage available to
the load. If the 7.5-8 amps you are drawing is anywhere near the limit
of that power outlet, then this could well be dropping the voltage below
10.5 volts as it heats up. And this would also account for the slight
delay before your inverter shuts down. With the engine running, you are
likely starting out with closer to 14 volts available rather than 12 and
this could well be enough to keep you above 10.5 even if the PTC were
dropping a couple of volts at the current you are drawing.

Just some thoughts.

Matt

 

This makes me even more suspicious that there is a PTC protecting this
circuit. Might want to find someone with a factory service manual and
review the schematics.


Matt

 

Repair places without voltmeters (multimeters)! What will they think of
next. Amazing. But I guess I'm not surprised.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Now you are getting somewhere. Matt is correct - you are getting
voltage drop - pure and simple - either due to wiring resistance or some
device in series that is inadvertently or intentionaly dropping voltage
or limiting current (sort of the same thing). You would not see the
effects of this back at the battery. The voltage drop (whatever the
cause) is seen across the cause of the drop (i.e., thermistor, entire
length of wire, or whatever).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

It has enough reserve to start the car, I don't think the inverter draws
more than the starter.

 

Yes, not even close. The above assertion isn't justified by the
information presented thus far. A starter can draw hundreds of amps for
a short time, far more than the 8 or so that this laptop charger is drawing.


Matt

 

Buy a cheap one at Radio Shack.

 

You need to find someone electrically and automotively knowlegeable
with a voltmeter to make the tests for you. Very basic test for those
who know about these things.

 

Buy one of those cheap power splitters. Plug the inverter into one
hole, and carefully connect the voltmeter to the second hole. If you
want to be real safe, get a cord that fits the plug, and connect the
voltmeter to that. Buy a cheap digital voltmeter for $5. The splitter
mabee another 5, and a cord, mabee another 5. Or salvage a cord from
an old device..

Or just get an extention cable, and split the conductors, strip 2
spots and connect the voltmeter that way.

 

Being a Dodge, I can say with almost complete certainty you have an
excessive voltage drop to the power outlet at the back of the van. The
wiring is WAY too light for anything more than a small trouble-light,
in my experience. A little inflator compressor will run about 2/3 to
3/4 speed under load compared to plugging in up front.

 

Your battery is OK. Regardless what anyone else tells you.
Your 90 watt inverter is OK.
Your laptop charger is OK.
Your laptop is OK.
The wires to the back power outlet are too light for the length.
Get an automotive electrician to run a second(heavier) wire from the
fuse box back to the outlet. Connect it in parallel with the original,
from a s close to the fuse as possible to as close to the plug as
possible. Cost less than a new battery, and actually solve the
problem.

 

The voltmeter they were referring to was one that could test the voltage at
the socket (as the person had suggested). Neither said they had a voltmeter
that could test voltage at the socket, though they had regular voltmeters.

 

well Jesus Mary and Joseph, how f*cking difficult is it to reach down into
the g*dd*m socket and test it ?

or stick a probe in the wires coming off the plug and test it that way ?

here's a hint:

BUY YOUR OWN VOLTMETER AND LEARN TO USE IT, SO YOU WON'T BE AT THE MERCY OF
IDIOTS

 

They are ususally called voltohmmeters or DVMs, and that is bullshit since
the DRB scanner that all Dodge dealers have can make voltage measurements.
Besides that, Harbor Freight puts them on sale for under $5 all the time.
This is
a basic electrical test instrument and any automotive service place that
would
say that I would question their competence.

They are probably telling you that as a "go away and stop bothering me kid"
kind of response.

Testing system voltage with a voltmeter is a required part of checking a
charging
system before installing a replacement battery.

Ted

 

I think you've hit the nail on the head here. I did the same tests with the
front power outlet, and the inverter didn't shut off. So the issue is with
the wiring, as you said. However, we're not out of the woods yet.

I ran the same tests as noted directly below (only, instead of no key, the
key was in the Acc position, since the front power outlet requires that).
The first three steps yielded the same results. However, the fourth one
(with laptop on and plugged into the inverter) was different. Instead of a
long alarm and the inverter shutting off, there was a series of double-beeps
from the inverter; but it stayed on.

According to the FAQ page at the inverter manufacturer's site
(http://www.cyberpowersystems.com/faq_acmobile.asp) the double-beep
indicates either that:

- The unit may be overheating form an excessive load. Try reducing the
load placed on the unit.
- The power supplied to the Ac Mobile unit may be lower than 11 volts.
Try starting the car to recharge the car battery.

Since the unit had just been plugged in, it probably wasn't overheating (and
a 90W charger probably wasn't an excessive load for a 140W inverter). Thus,
it's probably the second one: power supplied to the unit is lower than 11V.

Thus, we have the following:

- From either the front or the rear power outlets, I get a low voltage alarm
when the invert is plugged in with no load. Thus, even the front power
outlet's not getting a lot of power.

- With the laptop on and plugged in, the rear outlet causes the inverter to
shut down completely; the front one causes it to continuously emit a series
of double-beeps, indicating it's not getting enough power (and probably
close to shutting down).

Thus, even with the light wiring to the rear causing the problems there,
there's still a problem overall in that even the front power outlet's not
supplying enough power.

A couple of other points:

1) Tonight I was driving with the laptop turned off but plugged into the
rear power outlet. Shouldn't be a problem (according to tests I've done)
with the engine off; but with the engine on, definitely shouldn't be a
problem. However, while stopped at a red light, the inverted emitted the
familiar 5-second beep, and turned off, indicating the power to the rear had
dropped below 10.5V. Unplugged the inverter and plugged it back in again,
and it worked fine from then on. But the fact that the power to the rear
would drop to below 10.5V while the engine was on and alternator was
supplying power is very disconcerting.

2) Something I've noticed a couple of times in the short time I've had the
car is that the headlights, every once in a while, will flicker off, then on
again, once or twice, within a couple of seconds, and then be fine. As
stated, this has only happened a couple of times, and I was hoping that it
would just go away. But this may be related to this problem. I.e., the car
may have some serious electrical problems in general.

Thanks for any input!

Neil

 

Yes, and as noted previously, the car starts right up with barely a touch
and no foot on the gas. If the battery was a little low, it would probably
require a little work and some extra gas to start the car.

 

You then said this is a rear outlet so that means it may have 20 feet or

No, nothing printed on it.

Yes, that's possible.

Thanks,

Neil

 

Yes, that's true. However, as I just posted to Clare, the front power outlet
also is not getting enough power, so there's something going on besides just
wiring to the rear outlet.

Neil