In car chargers

[2badmice]

I have a charger for my car that I purchased when I had my HTC Desire HD, however it seems to not really add any life to my battery.

If my phone requires charging and I need to use navigation or make voice calls then by the end of a 30 minute journey the phone has not gained any extra life. I think the amp on the charger isn't suitable for this handset.

I've seen that the official chargers from Samsung are

 

[trucky]

The S4 likes to see a 2 amp charger, minimum of 1.5 amps to stay even if you're using any apps.

 

[Goodspike]

The S4 likes to see a 2 amp charger, minimum of 1.5 amps to stay even if you're using any apps.

After the upgrade to 4.3 you probably also need to have a heavy gauge cord. I have a 2.1 amp charger which only works with certain USB cables. In fact, it's possible the OP's phone isn't charging at all with that device--they should check the battery icon when it's plugged in.

This combination works for me, as would the 2.1 adaptor and the white USB cable which comes with the S4.

Amazon.com: PNY P-P-DC-UF-K01-GE 12 Volt 2.1 Amp Rapid USB Car Charger - Black: Electronics

Amazon.com: Monoprice 3-Feet USB 2.0 A Male to Micro B 5pin Male 28/24AWG Cable with Ferrite Core: Computers & Accessories

 

[itsallgood]

I use a stock OEM wall charger and cord. (Cost more, but worth the money in the long run.) It still charges the phone when using voice turn by turn navigation and streaming music at the same time. (No over heating either.) I tried using my OEM charger from my Atrix 4G, since I had an extra one, and it wouldn't even charge my S4, when doing any of the above task.

 

[Podivin]

I'm using one of the wireless chargers. Naturally that requires that you've added wireless charging capability to your phone.
I agree with others that your old charger simply doesn't have the output required by the S4 (or likely, any 'flagship' phone these days).