Battery dead after four days

Press lightly on the brake when trying to power up with a small battery, otherwise you activate the accumulator pump, which puts a big load on the 12V line.

If the relay was bad connecting the HV battery to the inverter, the HV battery would go flat, not the 12V.

 

Does anyone know if the Prius CANbus is capable of detecting the state of power relays? That is, does the CANbus actively scan for the actual operating state of a relay (On/Off) and if the operating state doesn't match, can it generate and store a code?

I ask as the Industrial Automation world has used various output logic checking and Intrinsic Safety algorithms for a long time now. Not only is this used for plant and personnel safety, it's also a very useful diagnostic.

As an example, say a motor is supposed to be off. The motor, typically a large 3-phase, is switched in an MCC (Motor Control Center). You use low voltage (Old way) or a momentary pulse to the correct IP (New way) to latch a relay (Mechanical or solid-state). A spare contact is used to positively verify the relay state, on or off.

Say you overload the motor and it trips. Since the heater element is in the relay, once it trips you have to physically push the reset button on the MCC panel to reset the contact. Otherwise the relay is completely de-energized and cannot work.

Or say an individual on the plant floor happens to poke the J/S station (Jog / stop): that will latch the relay on as long as the button is held, but the spare contact will also record the relay activity too.

In either case, the expected state (Off or On) isn't met, and a "Command Disagree" is sent, which is usually a critical alarm event.

It would be a lot easier for Geoff to troubleshoot this problem if the car could keep track of what the power relays are doing. It's obvious something is draining the battery, yet the dealer claims a "normal" parasitic loss.

 

Yes, there are codes for a stuck relay, both stuck open, and stuck closed. Not sure how it would sense it thought, other than the inverter informing the HV ECU. It is the HV ECU that activates/deactivates the relays. There are 3 relays: one for the (-) side, one for the (+) side, and one for the (+) through a resistor.

Again though, that would have nothing to do with the 12V system. Either the converter is providing enough voltage/current to charge the 12V battery, or it is not. If there is 14V on the 12V leads, it is charging. It goes down to 13.8 when it is still supplying power, but not charging. You usually get less voltage than that, about 12.5V if there is no current from the converter at all, and completely operating from the 12V battery, as can be seen in Ig-On or ACC mode.

 

My friend purchased one of the 'Charge it' battery chargers and has tried it out. It recharged the battery in about 15 minutes. It was about the same price and comes fully charged and is suppose to stay that way until you use it by plugging it into the cigarrette lighter or whatever we're calling it now. Then you just drive around for 1/2 hour or more with it plugged in to recharge it. He was pretty pleased and bought one for me, too, so I know I'm all set and don't have to remember (or figure out) how to charge my battery should the need arise. It is quite small - about the size of a flashlight - and fits in the little side cargo compartment. I reccommend it! 2 thumbs up.

 

My 2007 prius has needed to be jump started 4 times now. The california toyoto rep indicated there is a bug in the computer shutdown circuitry where it will draw power if not shutdown. Recommended always to put the car in PARK first then power down. It works fine 99% of the time without doing PARK first, but sometimes the computer is still running drawing power. There are some subtle light indications (that may be missed) on the dash that indicate this malfunction.

Without the startup battery with power, the computer doesn't work and the smart key doesn't do squat. Jumping the car always works. The local toyota dealer was clueless. The rep also recommended not running radio/CD without main power on since that will drain the startup battery too. Running it for an hour on accessory may be enough to drain all power.

There is tons of misinformation on this problem from well -meaning people based on non-prius experience. Just notice the Prius has a completely different startup procedure and without that puny startup battery power, the computer, smart key, etc are dead in the water. The main battery may be full of power, but it's not used until the engine is started.

 

If you have a 3 year old lead acid battery that has run flat a few times, it is time for a new battery.
Otherwise I have never heard this story in nearly 2.5 years on PriusChat, I think the rep is making it up as they go along.

If there is a bug, ask that it be fixed under warranty if the car is under 3 years old.

 

The rep is right about not using ACC for any length of time (so don't do that), but the shutdown part certainly sounds bogus. In any case by now the battery needs replacing.

Always lock the car when you park it. Leaving a door or the hatch ajar is a common battery-drainer. Locking the car will detect that and give a long warning beep.

 

I've never heard about a power down bug. I have read one story posted here about an ECU getting stuck in a high power mode, and only resetting after power cycling the 12V bus, but that's a different issue.

Tom