I need to be more careful running accessories

I thought that once you try to start the car, the traction battery could jump start the 12v?

 

<div class='quotetop'>QUOTE(Fred S @ Aug 11 2007, 05:48 AM) [snapback]493937[/snapback]</div>

Only if there is still enough power ni the 12V battery to start the car. It there isn't enough power left, then you need to use an external source of 12V to get the car started. Then you can leave the car on and the traction battery will charge the 12V battery back up.

 

I ran the 12V battery down at the car show today, buy leaving it on ACC and running the CD play, the undercar lights, and the door lights (the doors were left open for the show. After about 5 hours the car would not start. The ScanGuage indicated that the battery voltage was 7.6 V. I left it sit turned off for about an hour, and enough charge came back to start the car and recharge the battery.

Tomorrow, I put the car in Ready for a bit every 2 hours and keep an eye on the ScanGauge. This device actually turned out to be useful.

 

So when you ran it down to the 7.6 it was still able to charge back up off traction battery then right? I am a little surprised that there isn't a run-down protection system in place to atleast kill the radio when the battery gets low.


On a side note (non-prius related), ever notice people pulled over on the side of the road needing a jump start? They just don't get it... Why would someone's battery go dead while driving their 1984 Woodgrain sided panel van? And somehow when it gets jumpstarted it's gonna magically work again? I have had my alternator die in a few cars, it's not fun, once was night on a fuel injected (60psi fuel pump) so if too much juice was used for lights then the fuel would get a little low in pressure, driving home with no street lights was a blast but I made it using the DRL's which ran the high beams at 1/2 intensity.


<div class='quotetop'>QUOTE(Doc Willie @ Aug 11 2007, 06:23 PM) [snapback]494085[/snapback]</div>

 

<div class='quotetop'>QUOTE(Fred S @ Aug 14 2007, 05:29 AM) [snapback]495293[/snapback]</div>

No, to charge the battery you have to get into "ready", and to do that you have to have a good 12V battery, or close to 12V on the 12V line (from a boost for example). It is what powers the computers which close the relays in the traction battery box. It also provides the power to close the relays. With a dead 12V battery you are dead in the water. He had to wait for the 12V battery to recover some latent chemical energy (get back close to 12V) to power the computers and get to "ready".

I haven't yet seen any car with a low power disconnect system on the 12V line. It would be "problematic" to say the least. Like when you were trying to crank the engine (not a Prius of course) at -40C. It's not uncommon for old batteries to drop that low in that situation. Because the 12V system on the Prius is the "last resort" to get started, it shouldn't have a disconnect. A warning would be nice though.

 

<div class='quotetop'>QUOTE(Angel Flight Pilot @ Jul 27 2007, 02:55 PM) [snapback]486304[/snapback]</div>

Assuming that you're outdoors or in a garage *with the garage door open for ventilation*, just start the car. Leave it in Park with the parking brake set, and no worries. Of course you must remember to turn it OFF when you're done :_>

 

Batteries tend to bounce back a bit once the drain is removed.
Within limits.
.
_H*