I just replaced the aux battery in my 2004 Prius @108.5 k. I am pretty sure this is the original aux battery. Below is a collage of photos. How do I tell the date of the battery?
The battery's demise was pretty sudden. I accidently shorted the dome light replacing the festoon lamp, blowing the 15A dome light fuse--as I discovered later. I was doing this at dusk, and everything went dark. I thought the lights timed out. So I tried to start the car. The dashboard started to light, then immediately faded out. Only a soft green glow fron the start button when I inserted the smart key into the key socket. No life. Battery at 12.6V. Break lights working fine. I would have expected more life. I put the battery on a charger. It's voltage undercharge came up to 15V in a few hours. The car would still not start, although I did hear Prius noises from the engine compartment. The voltage came down to 13.8 when trying to start it. I tried unplugging the two connectors from the + side for 10 min, but that did not help. The observed behavior of the battery makes sense to me for a weak battery. However I am confused by the behavior of the Prius in this instance. SPH-D700 ? 2
Are you confused because the Prius refused to start with a blown 15A DOME fuse? If yes, then please recognize that the DOME fuse provides power to much more than just the overhead cabin light. It also provides 12V power to certain ECUs and that is why, with a blown fuse, the Prius will not become READY.
Ok. Got me on that one. With all the circuits, I would not have suspected the dome fuse circuit would be critical to the Prius function. So the battery was actually still servicable. The fuse was the problem. I did not check the fuses and find the blown dome fuse until the next day when installing the new battery. And there is a spare 15A in the fuse box with the fuse changing tool too. SPH-D700 ? 2
Here is what relies on the 15A Dome circuit from p 372-373 of the section J of the wiring diagram. Air Conditioner Automatic Glare–Resistant EC Mirror Automatic Light Control Back–Up Light Brake Control System Clock Combination Meter Cruise Control Door Lock Control Engine Control EPS Garage Door Opener Headlight Headlight Beam Level Control Interior Light Key Reminder Light Auto Turn Off System Luggage Compartment Door Opener Multi–Display and Audio System (Built–in Amplifier) Multi–Display and Audio System (Separate Amplifier) Power Window Push Button Start System and Hybrid Vehicle Immobilizer System Rear Window Defogger and Mirror Heater Seat Belt Warning Shift Control System Smart Entry System and Wireless Door Lock Control (w/ Smart Entry System) SRS Taillight and Illumination Theft Deterrent TOYOTA Hybrid System Wireless Door Lock Control (w/o Smart Entry System)
I am now wondering if your 9 year old battery is still in tip-top shape. The voltages you mentioned seem to be too high for a 12V battery. I would expect your battery to measure below 12V when cold loaded (pressing start button twice without the brake). Now that your old battery is out of the vehicle, could you measure and let us know the voltage once it has been sitting for a while?
The battery was still servicable. 12.6V. The whole problem here was the dome circuit fuse. Just never occured to me that the Prius could be disabled this way. Easier than removing the distributor cap... On the up side. I have owned the car for 9 years and do not plan to replace it yet. So I would likely need to replace the aux battery at some point. Replacing it now gets me a new battery that should last for the life of the car. The story of the replacement aux battery is this. The battery store has a agreement to only sell the replacement battery to Toyota. I got lucky in that they had a new battery that had been sitting on the shelf for too long. So they could no longer sell it as new. As a result, they could sell me the "used" battery for $35. SOLD
