Car Charger: Cigarette lighter better than Car Stereo w/ USB?

[MBHockey]

I noticed recently that with my iPhone 3GS plugged into my car stereo (a Pioneer unit with USB) it charges, but not very well. If I'm running Navigon and playing music, it seems that the charge just holds steady instead of increasing. I thought this was normal because the GPS app needs a lot of juice, although I wasn't too happy.

Yesterday I was using Navigon in my brother's car who only has a tape casette adaptor and a Belkin cigarette lighter charger. We were using Navigon and playing music. Much to my surprise, the charger charged my phone up to 100% very quickly even with the GPS being used for about an hour along with music. I've gotten used to the fact that my stereo would simply hold my battery steady, or increase it a few percent while using Navigon (if it's just playing music, it charges faster).

But either way it seems the cigarette lighter charger is better/faster at charging than my Pioneer head unit with a USB plug.

Is this to be expected? Or is there something wrong with my Pioneer stereo?

 

[STEVESKI07]

I would say this is normal. The cigarette lighter is meant to be used as a power source and that's about it. The USB in your head unit's main function is not a power source and therefore probably doesn't put out as much power. Yeah it kinda sucks, but at least it stays steady or increases slightly. That's a lot better then it still draining. You could always just buy a $3 car charger off of ebay to use to charge your phone when you're plugged into the H/U.

 

[MBHockey]

I took it on a 1.5 hour drive today and used Navigon most of the time. The charge dropped from 100% to 92% while plugged in. I guess I can live with it. I'd like to compare actual numbers though, ie. the power output of the USB port vs a cigarette lighter charger. If anyone has any info on that I'd appreciate it.

Seems to be a substantial difference.

 

[m3coolpix]

The difference you are seeing In charging ability between the USB of the head unit and a car charger is due to the current difference for the supplied voltage to the dock connector.

Whether it was a design choice or not, the head unit is providing less current flow.

I've seen this even between different car chargers. My Kensington charges slower than one that I have from XtremeMAC.