Preface – 2004 Prius - I live in rural Alaska and can’t just go to the dealership (unless I can train by Prius to fly or float). I have been working by phone/fax with the closest Toyota repair center, but I’m soliciting other opinions/thoughts. Just before I had my car brought to my town by private landing craft, I had two recall notices dealt with SSC 40D (on-board diagnostic) and SSC 40L (Brake Light Switch). This was at the beginning of October. I have no idea if this or something else may have caused my problems. For the preceding 1.5 years, my car had been idle for much of the time with periodic multi-day road trips. This probably didn’t help the accessory battery. Scenario – About a month after my car was brought to my town, I started experiencing accessory battery issues (or so I think). It started with intermittent problems at start up after a 2-3 day absence of driving to now when the battery won’t hold (or perhaps won’t receive) a charge. If I put a battery charger onto the posts in the engine area, I can generally start the car without any problem. Sometimes, however, it gives a touchscreen warning regarding the parking brake not being set correctly. This is generally accompanied by a lot of fluttering of the brake pedal (power brakes?). In all cases so far, if I turn the engine off and let it charge a little more, this problem goes away completely. I’ve used a multimeter at both the front engine terminals and in the trunk at the accessory battery. I can never get a constant voltage in the engine compartment. The readings bounce all over the place from near 0 to 15. Is this normal? Is this being affected by AC or otherwise? At the battery, I can get a good reading. When the car is running, the voltage will be 14+ (which suggests to me the battery is charging?); however, the voltage quickly drops once the car is turned off. I fully disconnected the accessory battery, then charged it, then monitored voltage. The voltage dropped to about 10.4 V after several hours. At this point, the Toyota dealership said I had a bad accessory battery, which they ordered from the lower 48 and will take several weeks. Is this battery so different? In the interim, I have reconnected the battery and have learned that if I charge it a bit and start it, the car runs fine. Am I hurting the car by tricking it to start? Even after several hours running or in “Ready,†the accessory battery’s voltage won’t come up anymore. For instance today, I left the car on/â€Ready†while I ran errands for 3 hours. When I got home, I finally turned it off and the accessory battery was down to 9.8 V. I’d be happy if the car only needs a new accessory battery, but I am fearful I’ll wait a few more weeks for the battery and that won’t be the quick fix. Can anyone suggest other tests to troubleshoot what may be going on with the car? How can I test if current is being drawn from the battery, particularly when the car is off? How can I tell if the battery is charging? I read another thread that discussed the grounding wire. Any other suggestions. I’m not well-versed in mechanics, so please be very descriptive! Thanks, 2004 Prius in rural Alaska!
The problem does sound like a bad battery, I hope the replacement solves the problem. The only other "hidden" drain on the battery that comes to mind was a problem with the sound system, I don't recall the details but it is probably discussed in the Audio and Electronics forum. I vaguely recall it had something to do with the top end radio. Good luck and keep us posted!
I recently had my battery changed on my 05 after bringing it in the second time for the same problem. Either would not power down or would not power up. Bat voltage did fall below 12V with a 3 V drop at front jumper point. Since the exchange all readings are well above 12V. With the diagnostic screen its really easy to monitor SOC. You get that by powering up to Acc or ready mode, hold down info button and turn on/off headlights three times, then menu, display, signal check. (if my exact order is correct) You can even drive with it in this mode. Another check that's possible for Battery drain is to connect a ammeter in series with either the ground or the positive posts and you can monitor for leakage current with car parked and not powered up, with SKS and dome lights in off mode. All somewhat complicated and a lot of trouble, plus you will lose all your presets. I'm sure a new Bat will solve your problems. You can always do what the Japanese used to do when they first started building the Datsun. That was to bring your Bat into the house every eve, to keep it warm! Oh, in charging mode my Bat reads 14VDC.
I forgot to mention that since the Bat is probably not up to snuff, you should not leave the car in ready mode while running errands for 3 hours! Be extremely conservative with your Acc Bat use. No it should not hurt to separately charge the Bat overnight, in fact do it consistently, you have no other option until the replacement comes in. Buy a small gel Bat for emergency jumpstarting out on the Tundra, keep it charged! Good Luck.
I agree that you most likely have a bad battery. One test you could do is to remove the battery from the car IAW the instructions in the owners manual. After you get it out charge it up and then let it set for a while and check it's Voltage, if it goes much below 12 Volts it has problems. If there is an automotive electric shop nearby you could have them do a test discharge on it while it is removed, that would answer your "is it good/bad" question. When you take Voltage readings under the hood make sure you have a good ground, i.e. unpainted metal. As far as I know the only things that makes this thing a "special battery" that costs a fortune from Toyota are due to its location. It is in a place that has no ventilation, thus the sealed battery and the little tube going out the bottom of the compartment. If it were not for the lack of ventlation you could use a lawn mower or motorcycle battery which would cost a fraction the price of this one and most likely last longer.
I especiall agree with that last paragraph. Having owned a bug for ten years I believe the thing about ventilation is a crock. Overfilling with water and getting dilute H2SO4 on the floor, now that's another problem. I think any 25AMP battery would do fine and sealed would be better!
