Charging a laptop using 12 volts.

If the E4270 has USB-C port, you may want to consider charging through that.

If not, look for Dell's Auto/Air AC adapter part #A3163198. Sells on Dell.com for $144.99

@alan bailey  I can't find a Latitude E4270 on support.dell.com.  Are you sure you didn't mean the E7240?  If so, then unfortunately that system doesn't have a USB-C port, in which case I personally would recommend using Dell's official charger.  But if you have or ever get a laptop that DOES have a USB-C port and that supports being charged from it, I just bought this charger.  Its USB-C port is capable of 60W output, which is enough for the majority of laptops on the market.  Even some laptops designed to use more power for optimal function can still charge and operate at reduced speed from 60W.  And then it also has a USB-A port for some other device.  Can't beat the price either for what you're getting.  If you're not familiar with Satechi, they've got a solid reputation for quality products.  I also have this travel charger of theirs that I love because I can charge my laptop from the 60W USB-C port, my iPhone at max speed from the 18W USB-C port, my Apple Watch from one of the USB-A ports, and then some other device from the remaining port, such as my USB power bank, AirPods, Skype headset, etc. -- none of which need to be charged every night.  So that single charger is all I need for overnight trips nowadays.

Welcome to the Dell Community @alan bailey 

The center pin is used to communicate with the system.

It informs the system what type of AC adapter is attached.

This way the system can regulate the charging of the battery.

If it does not know what type of AC adapter is connected it may not be able to charge the battery.

Best regards,

U2

Its an E5470 (I have edited the original post, thanks for spotting my mistake) so there in no USB C port.

I work in electronics so interested in knowing exaclty what I need to do with the centre pin to get it to charge not just say plugged in.

If I need to charge in my car at present I use the normal charger from a 12 volt to mains voltage inverter.

Thanks for the reply.

Dell power cord has a chip inside, at the other end of center pin;  Dell BIOS reads information on that chip.  If there is no chip, Dell BIOS cuts off battery charging service, limits CPU to 1mhz.

If you could find a work-around this Dell feature (for the customer's safety, of course), many (many, many) of us would like to hear it.

Inverter is your best bet in a car

@First Name 

The "SMART" AC adapter does have a chip that uses the center pin to communicate with the system using the SMbus.

One of its functions is to regulate the charging/discharging of the battery.

A work around could be a very dangerous safety hazard and should not be encouraged.

Anyway what would you do about the "SMART" battery???

Best regards,

U2

Allegedly, this Dell feature (to protect the laptop from the consumer) came about as result of that laptop battery bursting into flames in that board-room some 15 years ago.

Now, this Dell power cord of mine is four years old, warranty expired a year ago, and it decided to stop conducting electricity.  Should I buy a no-name power cord from China for $12, or should I buy a Dell power-cord (also made in China;  might even be the same factory) for $112 ?  $100 is a bit hefty for a logo and a chip.

Ten years ago Dell could make power cord that lasted 10 years and more.  I have a 65watt cord, sold in 2009 with a Precision, which still functions.  I plug it into my 130watt e6540, bios gives me a notification, I ignore it, press F1, and everything works fine.  The laptop operates, the battery charges (perhaps a bit slower than with the 130watt cord).

So what is the real reason behind Dell's hostility towards $12, no-name power cords ?

Personally, i would use your inverter setup but kick it up a notch buy running main battery cabled through your firewall and into you car (high gauge)  Separate them appropriately so you don't accidentally find a way to short them with a piece of metal. and use a set of professional alligator clips to give your inverter all the loving amps it wants so it doesn't complain. Also as a side note.. this would make it incredibly easy to jump your car if you need too..  (I take no responsibility for this advice, use at your own risk)

Never felt bought a Dell AC adapter for $112.

I buy them used on eBay.

.