Will 12-volt Batteries be Relvant?

I suppose it the same reason why a computer motherboard has a dinky CMOS battery. To keep the settings when powered off. Plus, that huge battery would be active 24/7 just for seeking that fob.

 

<div class='quotetop'>QUOTE(Delta Flyer @ Nov 1 2006, 02:24 PM) [snapback]342162[/snapback]</div>

The power from the hybrid battery does go through inverters and transformers and supplies a number of different Voltages both AC and DC including 12 Volts DC. But when you power down the car the hybrid battery is disconnected and something is needed for accessories such as lights, door locks, windows, etc. Thus the small 12 Volt battery.

I think it's a good system because when you power down the hybrid battery is isolated and protected. It may also be a good theft deterrent.

 

Basically, there are two very good reasons for it. The first is safety: You don't want 200+ volts constantly available on the power lines - if you're doing any sort of work on the car, it would be easy to hurt yourself very badly. The second reason, just as important, is for battery life. All cars have a small power drain when off. It goes towards remembering stuff like your radio presets, and for the Prius powering the SKS and such. The SOC of the HV battery is carefully monitored when the car is on by the computers - they ensure that it stays within a proper range to ensure longevity. If the batteries were constantly connected, but the computers off, that couldn't be assured - and the price tag for a new HV battery is much, much higher than for the 12V battery. And even if the computes were on, they couldn't do anything to recharge the battery (since the car is off), so there wouldn't be a point...

During normal operation, as others have said, the HV battery is used to provide a range of voltages for various systems. This is done primarily by stepping it down to 12V, where it's used to recharge the 12V battery and run the electronics that most cars use the 12V battery and alternator to run.

The only reason they have the 12V battery is to provide that very small current when the car is off, and to start the computers and engage the relays to the HV battery when you hit the power button.

 

<div class='quotetop'>QUOTE(Delta Flyer @ Nov 1 2006, 02:48 PM) [snapback]342176[/snapback]</div>

I use my dog because he looks better than I do. B)

 

I remember that, some time back, folks were saying that automotive electrical systems would go from 12VDC to 24 (because, in part, the extra juice would be handy for active suspensions and stuff like that).

Hasn't happened yet; I suspect the 12V battery is also there because it's necessary for whatever systems in the Prius have commonalities with other cars (like the running lights, etc).