Thread: How can I power my car from a standard outlet?

Here is the one I would go for rawpwr, link, but these do not output a constant 13.8 volt power supply. Can I use a 4 pole car battery to act as a "filter"?

Originally Posted by BoyRacer0013

Here is the one I would go for rawpwr, link, but these do not output a constant 13.8 volt power supply. Can I use a 4 pole car battery to act as a "filter"?

13.8v +- 0.5v is considered constant in this situation.

They way these work is by switching on and off at the speed the input power alternates, so they quickly switch b/w off and 13.8v.

Originally Posted by BoyRacer0013

They way these work is by switching on and off at the speed the input power alternates, so they quickly switch b/w off and 13.8v.

Yes it's a “Switch Mode” supply like almost every SMPS supply available and this has nothing to do with load regulation or what you are using this device for.

The main problem with SMPS is the interference to RF devices if the SMPS is not correctly designed and filtered.

Okay, so these will work to supply me with a 12 volt power supply that is safe to run my electronics from?

Safety is relative and it depends on the design, not on the design principles.

IE - A Linear supply will destroy electronic equipment just as easily as a SMPS if overvoltage and over current protection have not been correctly implemented.

Depending on the size and construction of the transformer, a 30A Linear supply can have around 20v to 28v on the input to the regulator, this will blow most electronic devices designed for a nominal 12v if the regulators short and overvoltage protection is not tripped or designed correctly. SMP supplies are increasingly used in Commercial and Amateur Radio systems with transceivers worth anywhere from $1,000 to $18,000.

Unfortunately with everything in electronics only a manufacture could give you a money back guarantee if their PSU blows your equipment. Bet it would expensive though!

It sounds like you do not want any reconnection, hence you are looking at a battery charger option.

[ Yes, using an ATX supply means reconnecting the load off the car battery to the ATX. Because you want to power other car stuff as well, it means disconnecting the car battery and using the ATX instead. ]


You can't connect a 12V power source to a car battery - it needs to supply higher than the battery voltage - ie, 13.2-14.4V.
And to avoid switching dropouts (eg, when switching lights on), a battery is required.
Hence add a suitable charger.


Many use a dual-battery system instead.
Where one battery can easily handle the expected "non-charging" use, it is connected via a battery isolator (typically a relay controlled by the charge light) and fuses at each end.
In your case, maybe it should be rigged as a spare cranker - ie, since your lights etc are connected to the normal battery, use the main as you "load" battery. The aux battery is then the emergency jumper battery. (Mots power their extra loads off the aux battery.)

Originally Posted by OldSpark

It sounds like you do not want any reconnection, hence you are looking at a battery charger option.

[ Yes, using an ATX supply means reconnecting the load off the car battery to the ATX. Because you want to power other car stuff as well, it means disconnecting the car battery and using the ATX instead. ]

The goal here is to be able to simply hook up the power leads and maybe flip a switch or two.

Originally Posted by OldSpark

You can't connect a 12V power source to a car battery - it needs to supply higher than the battery voltage - ie, 13.2-14.4V.
And to avoid switching dropouts (eg, when switching lights on), a battery is required.
Hence add a suitable charger.

The converter I'm looking at is rated for 13.8v (+/- 0.5v).

Originally Posted by OldSpark

Many use a dual-battery system instead.
Where one battery can easily handle the expected "non-charging" use, it is connected via a battery isolator (typically a relay controlled by the charge light) and fuses at each end.
In your case, maybe it should be rigged as a spare cranker - ie, since your lights etc are connected to the normal battery, use the main as you "load" battery. The aux battery is then the emergency jumper battery. (Mots power their extra loads off the aux battery.)

My car is a sports car , I would like to keep the weight down as much as possible.

You can get some relatively compact, switch mode chinese made power supplies that are capable of 20 amps from eBay for about $40 (available in 12V, 15V, 24V and etc). They even have a potentiometer to adjust the voltage slightly by about +/- 10%. That's what I did to my car. I got a 15V 20 amp supply, adjusted the output to 14V, then connected the output with a high current diode (of which you can find in an old ATX power supply) in parallel with the car's electrical system and installed everything neatly near the spare tire compartment in the trunk.

Bam, now I can run an extension cord to the car whenever I want to work on the carpc or have the music running while Im in the garage.