RV 12V to inverter problem

[hausmutti]

I bought a 300W inverter to charge a MacBook in the travel trailer.  When I plug it into the 12V outlet the inverter comes on charges for a bit then shuts off, then comes back on, shuts down, etc.  Battery on the RV is full, other things I plug into that 12V outlet work perfectly such as a fan or we boost and iPhone charger.  I took the inverter out to the car and tried it and it worked perfectly charging the laptop.  Then I hooked the inverter up to the JACO battery pack with the 12V adaptor and it's charging the laptop perfectly.  Any ideas as to why it won't work in the trailer?

 

[frater secessus]

Voltage sag due to wiring losses on the way to the trailer?  That could cause the inverter's disconnect to trigger.

Generally speaking, it's better to charge laptops from a 12v adapter than inverting to 120v then back to 19v (or whatever).

 

[Weight]

Those 12 volt outlets, commonly called cigarette lighter plugs, are not very good at supplying higher amp stuff. Also they do go bad due to corrosion that may not be evident. Your 300 watts could ask for 25 amps at 12 volts. That plug is rated for 10 amps on a good day.

 

[Trebor English]

Is the 12 volt outlet in the trailer a cigarette lighter socket?  Those can have high resistance, particularly in the center conductor.  

Did the inverter come with big clips that can connect direct to the trailer battery?  If that works it is proof that you have insufficient wiring from the trailer battery to the inverter.  If the inverter is connected close to the battery with a longer cord from the inverter to the 120 volt load it will be more efficient with less loss.

 

[John61CT]

Standard ciggie sockets are a dangerous abortion,  avoid like the plague for anything important, or that you use regularly, or for more than a few minutes. Never more than 5-6A and for short periods, even then they are risky. / Blue Sea has a nice socket design that twist-locks with the matching plug, but will also accept standard ciggie plugs for smaller (<10A) loads.

Also the BMW/ Hella/ Merit/ Powerlet "Euro-style DIN" (ISO 4165) style is very robust.

Anderson plugs for high amps.

If you standardize on one of the last two types, there are adapters for guests, temporarary use of devices with standard ciggie plugs.

 

[A Savage Adventure]

hausmutti, your 300W inverter documentation should tell you that you can only get about 100W max from the cig connector. To get more you need to connect directly to the battery terminals, or as I am doing, directly to where the battery connects to the power converter.

P.S. - I actually posted about the same issue before I found out this information. Had the same issue with two inverters. I thought the first one was bad until the second one did the same thing.

 

[OGGWild]

hausmutti, your 300W inverter documentation should tell you that you can only get about 100W max from the cig connector. To get more you need to connect directly to the battery terminals, or as I am doing, directly to where the battery connects to the power converter.

Can you explain what was involved in connecting your inverter to (or near?) the converter? Did you need a wiring diagram to locate where and what to connect to?

 

[DannyB1954]

Another issue that has not been mentioned is there are two different types of inverters. Pure Sine Wave and Modified Sine Wave.
The MSW does not always play nice with battery chargers. It might sense the charger for the lap top as a short circuit and shut down on it's safety circuits.

Like others have said you need heavy wires supplying power to get 300 watts output from an inverter. Watts is amps times volts so 300 watts at 12 volts is 300/12 or 25 amps. The cord that comes with the inverter will not handle this. The voltage will drop drastically and the inverter will shut down from low voltage.

Most inverters come with heavier wires and jumper clips. Put those on and attach to the battery and give it a try. If that still don't work, you may need to get a 12 volt mac charging kit or pure Sine Wave inverter..

 

[KathyC]

I also use a 300 watt inverter (modified sine wave) plugged in via 12 volt ("ciggy lighter") to charge my Mac in the van. The inverter was only working intermittently. Turned out to be a wire crimping issue. Once that was resolved, it worked (and continues to work).

Agree with others these plugs are not ideal and if you are highly dependent on this method to charge your computer, please look into a more secure solution.

PS: Don't worry about pure sine wave or not for Mac laptops. They charge just perfectly with modified SW.

PPS: Your laptop will charge significantly more quickly (and use less power) if you don't use it while charging.