"USB drawing too much power"

I wouldn't be surprised if the case maker took some shortcuts in implementing the USB spec. It's also possible that they're designed to different versions of the spec, though I think in general later versions are designed so that devices won't cause any trouble when plugged into devices designed to earlier versions of the spec.

To be more specific, USB allows a device to draw 100 mA when it's first plugged in; to get more, it has to communicate via USB to the computer, and ask for more (500 mA, on a typical USB port). It's possible that the case isn't asking for this extra power. Some USB ports and the iPhone charger can actually give up to 1 A, so it's also possible that your computer is capable of supplying this, but the car isn't, and the car is detecting that the charger is drawing too much power when it tries to suck up as much as possible. The iPad charger can go even higher; 2 A.

As far as why it won't connect via Bluetooth, at least for straight internet access (e.g. for a laptop), the iPhone can tether via Bluetooth just fine, in addition to USB and Wi-Fi. And I know I've played games that work by sending data over Bluetooth, so apps can access Bluetooth too. So it's not like Toyota (well, Denso, I assume?) had no way of making 100% handsfree work...

In any case, there's probably not much you can do about it, unless you want to get creative. (e.g. rig up a crazy cable that grabs power from a dumb charger on the power port, but sends the USB data to the USB port, leaving its power unconnected. No guarantees that'd work, or that it'd be safe for either the car or phone, though.) Or, you can remove the case, find a different case, etc. Some such cases have a standby switch - if yours does, will it keep the case from charging itself, or does that just prevent the case from charging the phone?

 

Hello,
On my 2012 Entune 6.1 Nav unit, I am able to "tether" my iPhone 4S to my car via Bluetooth. I have a tethering plan. Whenever I make an internet request on the car, it creates a connection with the phone while in my pocket. They connection remains until I turn the car off.
Once the connection is made all internet based features (traffic, pandora bing etc) all function through the Bluetooth WITHOUT the Entune app on the iPhone.
Also, then I plug my iPhone into the port directly, it does in fact charge. If I turn off the tethering on my phone I do get internet on the car via the cable as expected.

 

I get the same error message on my Android Galaxy S.

 

I'm sorry I should have been more clear. I can connect through Bluetooth. I get the power consumption message when I try to connect the Android phone via USB. Entire is rather finicky so I often cannot even connect to the Internet and thus cannot use Pandora. I think I am figuring out the routine required to make it work, however.

This includes turning off Bluetooth prior to entering the car. Then trying to shut down Entune app on the phone. Starting the car than turning on Bluetooth and starting the Entune app. Then I pray.....

 

One thing I've learned about electronics is that when somebody (e.g. a case-maker) doesn't follow the spec, it still works most of the time with most devices (e.g. an Escape). But, sometimes, it doesn't work with another device that is following the spec (e.g. the Prius).

I'm not saying it's not Toyota's fault, or that it definitely is a problem with the case - though I would expect Toyota to have many more engineers working on this sort of thing than a case manufacturer would. I just don't think that there's any certainty that it's a problem with the car.

Of course, then there are the times that, even when two manufacturers follow the spec absolutely to the letter, their devices still don't work together, because the spec is fundamentally broken. That happens too. Then everybody gets really angry and argues over who is right and who is wrong. Hilarity ensues.

 

I am using a simple USB to mini cable. I receive the message about power consumption but that is all that happens. The phone continues to charge and everything seems to work but I need to double check that it is not switching to Bluetooth when that happens. I'll turn Bluetooth off and try it again on Monday.

 

This is no doubt exactly the case. Toyota chose to limit power draw to something like the 500ma Macman proposes and they won't allow you to draw more. They've decided for reasons of the circuit the USB port uses or size of wiring or whatever that the most your going to draw is what a iPhone 4 or whatever draws and that's it, your battery case draws more than that limit and the car blocks it.

I'll bet if you hook an iPad up to it it won't charge it either, if I remember I'll try tomorrow.

Bill

 

It's not really "limited". The original USB spec in 1994 said that devices could draw 100 mA, and could request up to 500 mA in 100 mA increments. The device supplying the power did not have to be able to provide power, however, and is allowed to decline the request. Some devices, like unpowered USB hubs, will never supply more than 100 mA.

These days, it's a lot more complicated - "normal" ports still go up to 500 mA, but some devices can also have a "charging" port that supplies 900 mA during data transfer, 1.5 A without any request for extra power, and 5 A maximum (though that's rare). When a device draws more power than the host can supply, the host is allowed to disable the port.

Apple is pretty notable at stretching the specs a bit; they make devices that comply to the spec, but also provide provisions outside the spec to allow for extra power when plugged into a USB port on a Mac that can supply the extra power. (For example, the MacBook Air can power a special Apple optical drive from the USB port, but no other computers - even other Macs - can.) They're also generally very good at making sure that their devices still adhere to the spec when connected to non-Apple products, though.

 

It's the case. I'm sure they just tapped the power line in the USB port and pass the data lines directly through to the phone. That means the phone is only asking for as much power as it is going to draw, and the case steals some more. This is a violation of the usb spec, so the prius shuts it down. It works in most other hubs because most don't bother to measure how much power the device is *actually* drawing and shut it down if it takes more than it has been authorized to.

Can you try to fully charge the case ( but not the phone ), then plug it in? I'll bet that works, since it won't be stealing extra power.

 

This is the way USB limits power to a device that tries to grab more current than it is allowed. The port gets shut down. If the host tried to throttle the current without shutting down the port, the supplied voltage would fall below spec and cause additional problems.

Several of my home machines predate the USB Power spec, and don't hesitate to shut down offenders that draw excess current without asking.

 

There are 12v powered USB hubs that can be interposed between your Prius and the offending USB devices.

JeffD

 

I get the same message with my Sandisk Fuze mp3 player. It isn't a crippling problem because I can use the audio port, but I'd like to be able to charge the player using USB. Oh well.