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Toyota Prius Electrical and Lighting Questions



  • stevegoldstevegold Posts: 185
    Has anyone had to replace the 12V gel cell that starts the computer? After four years I had a problem starting the other day. The dealer can test it and install a replacement if necessary for $125.
    Is there another source of supply? It's a small battery located in the right, back near the spare tire.
  • pathstar1pathstar1 Posts: 1,015
    It's not a gel cell. It's a normal sealed lead acid battery with a vent tube (just like a motorcycle battery).

    If the dealer offered you one for $125 go for it. That's a good price. I've seen others pay $250 and up.

    I haven't seen or heard of another source, though you could check the size (measure it) and go to a battery specialty store. I know the Optima size 51 yellow top would just fit in there, but you'd have to do your own hold-down and terminal modification. It's $220 or so, as well.
  • pathstar1pathstar1 Posts: 1,015
    It's not normal. Was an interior light left on? Hatch not closed properly? A healthy Prius 12V battery can go for a month or longer without use. Do switch off the SKS (smart key system) to reduce drain (button under steering wheel). Do not leave the fob in the car (the car will constantly talk to it). Make sure the fob is at least 100 ft from the car, or in a metal box.

    If none of this helps, purchase a "battery tender". It's a small charger. You attach a lead to the under-hood charging points and plug the lead into the tender when you leave. It keeps the 12V system fully charged.
  • boraboraborabora Posts: 16
    thanks Pathstar1,

    no, i checked every light before i left, and i turned of the SKS, too.

    beside battery tender, what can i do then? changing a battery?
  • pathstar1pathstar1 Posts: 1,015
    The battery may have been damaged before the car was sold. That is, discharged and left that way for a few weeks. A good test is to disconnect the battery and leave it for a few weeks to see if it still discharges. Hard to do, as you want to drive the car.

    Check the battery connections. Make sure they are tight and clean. If they aren't it will never be completely charged. The 12V battery is in the right corner of the hatch area. Remove hatch floor, remove storage bin. Fold black plastic flap forward (away from hatch wall) and lift cover out. You will see the battery.

    Because it's such a small battery, load testers don't work very well. They are designed for larger capacity batteries.
  • jaxs1jaxs1 Posts: 2,697
    I read elsewhere that it is normal because of the battery's very small size and capacity and the solution is to have someone drive the car at least once a week, disconnect the battery, get a battery minder or simply be prepared to recharge the battery when you return from vacation.
  • suirpsuirp Posts: 4
    I disconnect the battery terminal under the hood when I leave my Prius garaged for up to 10 weeks each summer. Reconnect on return and it starts right up.
  • I made a mistake in thinking I could have my old Alpine navigation system installed on my new 2007 Prius. That system worked fine on three previous cars where there was plenty of room for it. But on the new Prius, it seems a gamble whether there is any room at all for the installation. People at the dealer's said there is too much wire and components in the dashboard area. Is it possible to get a look-see at that area without too much trouble?
  • vcgenovcgeno Posts: 5
    I have had my Prius for about 7 months without a problem. A few days ago after parking it 50 degree weather the utility battery died. No doors were open, no lights were on, and I can't figure out what happened. I had it checked out at the dealer and they said there was no problem with the battery or the charging system. It seems to be working OK now. Anyone else have this problem or know what might have gone wrong?

    I also found jump starting the Prius quite an adventure. Standard sized jumper cables are to big for the battery terminal. I had to find someone with a cheap set of cables in order to jump start the car. The slot where the positive terminal is is much too narrow. Anyone have any suggestions for me?

    That said I love the car.
  • stevegoldstevegold Posts: 185
    I have a 2004 Prius. The same thing happened to me twice, the first time after a month or two and the second time three years later. I probably left something on as those are pretty infrequent intervals. You do NOT have to get to the small battery to jump it. There are special terminals under the hood that make it real easy. Look in the book.
  • vcgenovcgeno Posts: 5
    It was not the other persons battery it was that the positve connection on the Prius is too small for the clamps on standard sized jumber cables.
  • pathstar1pathstar1 Posts: 1,015
    I made my own jumper cables using #25 Mueller solid copper clips on the Prius end and larger ones on the "doner car" end with #10 finely stranded wire (trolling motor cable). The Prius only draws a 1/2 sec. 40 amp pulse when you press on the brake, and another when you press "Start". This cable is heavy enough for that. I keep it in the "secret storage bin" in the front of the console (because you can't open the hatch with a dead 12V battery).

    When you turn off the car, if you sit inside, the headlamps stay on. This can kill the battery. If you turn the car on and off from the passenger side you will not open the drivers door, and again, the headlamps will stay on, draining the battery. This is how most people kill the battery. So always be sure to open and close the drivers door when you shut off the car.

    I haven't needed the cable, and probably never will. But I have it ready, just in case. ;)
  • lnmlnm Posts: 14
    I hope I can describe our situation accurately as I was not the driver when the problem occured. My husband drives our 2005 Prius approx. 50 miles daily. One snowy morning, he left the house and proceeded normally to the freeway on-ramp, about 3 miles from our house. As he got on the freeway, the Prius dropped to about 20 mph. The car wouldn't go any faster no matter how much gas was applied. The speedometer reading, however, displayed inaccurate speeds - 80 mph. Unaware of what to do, he completed his commute and drove it home that evening. I checked the car in the evening and witnessed the same problem - car wouldn't accelerate no matter how much pressure was applied to the gas pedal, and the speedometer displayed obviously incorrect speeds. The technology display didn't indicate any problem and no warning lights were present. In fact, the display indicated that the battery was at 3/4 charge. He had just filled the gas tank the night before (he never lets it go below 1/2 full).

    Feeling it was unsafe to drive, I had it towed to Toyota. They took a look at it and told me that nothing was wrong with it - the battery had just gotten too low. First question, if the battery was low, why would it start and drive normally for 3 miles at all? Second question, would a low battery cause all the problems described (no acceleration, incorrect speedometer readings), or is it possible that the dealer just charged the battery, the computer reset, and the problem temporarily disappeared?

    I'm pissed about having to pay for the tow and the labor to recharge the battery, but I'm more concerned that the real problem hasn't been solved. The dealer explained that the battery that became rundown was the second, technology battery, so I assume he's talking about the 12V battery described in other posts above. Also, my husband does not recall leaving any powered accessories on or doors ajar, so it's inconceivable to us how this battery would have gotten rundown overnight.

    Any feedback at all is appreciated.
  • lnmlnm Posts: 14
    I just wanted to add to the above post. I called the service guy back to clarify the problem further. He said the 12V battery was completely dead and the main battery was almost dead. I asked what could have cause this to happen overnight (was driving fine at 5 p.m. the day before, problems began at 8 a.m. the next mornign), and he basically boiled it down to something (door light) being left on. I asked him about the car possibly needing a software update, a cell being blown or faulty, cold weather and he said no chance to all of those things.

    It seems to me that the service guy relies on a diagnostic computer to tell him what's going on with the car. I asked if he visually inspected the battery to see if it was faulty or a cell had blown and he said no, the computer would tell him if anything was wrong. I think I need to get another opinion on the status of these batteries. I've read in other posts that AutoZone will check a battery for free. I will be taking it there and reposting if I find out anything new. There is just no way that we left something on in the car, and frankly I resent being blamed for it. Even if a light was left on, would this cause a battery to go completely dead after just 15 hours?
  • pathstar1pathstar1 Posts: 1,015
    I have seen a few reports of a poor connection to the chassis from the 12V battery -ve terminal causing problems. It may be that connection failed. This -could- happen "suddenly", though it would be rare. Perhaps the bolt came loose.
  • Thanks for that info..
    This is exactly what happened to my brand new 2008 Prius with 1200 miles on it. I realise now that I must have left the headlight on as I powered off from the passenger side. After sometime, I was told that my alarm is going off (which is supposed to happen if the 12V battery is totally discharged (sounds counterintuitive to me !). My dealer Pat Lobb Toyota of McKinney was nice enough to replace my battery free of charge although the 'dead' battery was perfectly fine.

    Interesting side note: Realised that the 12V has to be active for switching the car to Neutral.. :)
  • I have had my brand new '08 Prius for 2 weeks and 2 days. I just filled it up for the first time this week, which is great. But, today I pushed start and the screen was still blank...Yikes! I thought...maybe I don't have the break pressed down. Nope. So, I turned the car off and restarted...Yikes! No screen. It drove fine, but I cannot operate things beyond the "manual" steering wheel controls. I'm taking it in tomorrow and hoping it's something simple...frustrating and I'm trying to be patient. If it's a fuse, why would a brand new car already be blowing fuses? Did I get a lemon?? :lemon: Hopefully not!! I was really excited about my first new car purchase and it felt like a good decision...too good to be true maybe?
  • Dealer had to replace my left HID bulb this week. They initially thought it was likely the controller card behind the light, but it passed all the diagnostics. So they decided it must be the bulb. I was told that the part would have cost $400 if not covered by factory warranty (only 23K miles). I think they had to pull off the fender or bumper to get at the assembly.

    Symptoms: headlamp would occasionally dim or go out completely. Cycling the lights off and back on always seemed to correct the problem for a while.

    The dealer (Bob Bridge Toyota in Renton, WA) did have to keep my car for a few days while waiting for the part. They said it was the first time they had seen this type of failure in a Prius. I didn't ask about HID failures in other Toyota models.
  • birgerbirger Posts: 80
    Hi viking,

    $400! That's unfortunate news. It's probaly correct that the bumper has to be removed to get at the headlight assembly, although it should not be necessary just for a bulb exchange.

    I take this opportunity to give an update on what's happened to our Prius (light-wise) since I last posted quite a while back. Sorry for the long post following.....

    The Philips H4 ExtremePower bulbs were (after having aimed the headlights a little less "conservatively") a pleasant surprise, for conventional headlights, although of course not a match for the Bi-Xenons on our then other car, a Mercedes ML 320CDI. But as a relatively cheap, easy solution, they're really OK:

    However, apart from the excellent lights, our particular ML was rather a :lemon: , so it was replaced in June by a Lexus RX400h, which - like the Prius - is pure bliss to drive.

    To my surprise I found out that the Lexus came with only low-beam Xenon headlights (it must be the only brand that offer swivelling, but not Bi-Xenon headlights), and driving long distances at night was something of a challenge, having been used to Xenon hi-beams for seven years or so.

    Quite quickly, I found a solution via EBay - a Chinese/American company who in no time shipped me a HID replacement kit for the 9005 hi-beam bulbs on the Lexus. And now even my previous Bi-Xenon equipped cars look weak in comparison!!

    The kit was really very easy to fit, of an impressive quality, and cost only around $100 (the price has since dropped radically to only $42.99). After a while, the idea of "Xenonising" the Prius too from the same source matured, and in the late fall I ordered a set of H4-compatible units from the same company. Because there's slightly more hardware and electronics involved, they are a little more expensive (the current price is $ 85.99).

    Shipment was again quick, but due to work I had the kit siting around for some time before fitting it to the Prius. Again, impressive workmanship, no wiring has to be cut, and I did the installation in a couple of unstressed hours. It achieves hi/lo beam by a retracting metal cutoff shade - just like the units used on some Volvo models, IIRC.

    The low beam light pattern is VERY close to the original, with minimal stray light and really no blinding of ooncoming drivers. And of course with a vastly improved output - this really is the thing to get if you didn't get Xenons from the factory, and you plan on any kind of longer distance night driving. The high beam light is very much better than standard, but not quite as much a revolution as the low beam is.

    We have just come back from a 1500 mi trip, most of which was done in the dark, and it was very, very zen - no stress from not seeing enough, and no stress from oncoming drivers flipping their lights at you either.

    Highly recommendable!

  • Hi Birger,

    Just to would have cost $400 plus labor, but since the factory warranty still applied, I paid nothing.

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