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My battery (in the trunk) needed replmnt after 6 weeks!!

4893 Views 6 Replies 6 Participants Last post by  Ed
I bought my Prius 8/31/02 and have loved every minute of it! Except for this morning when I tried to start it. It would not start and my car alarm was making a wierd low pitched noise. I had an alarm installed shortly after purchasing my car. The alarm was chirping very softly non-stop. At first, I thought: My husband wanted me to have this stupid alarm and now it has recked my car!! But, after speaking with the store where we purchased the alarm, they had us check several things to help diagnose the problem and it turns out the battery was dead!
We jumped the battery and it started, thank God! But now I have a new problem--my headlights will not turn off! I will need to take it to the dealership in the morning to get a new battery but I worry why and how did this happen? Is my battery going to call the quits every 6 wks?? This doesn't make any sense to me. Has anyone else experienced this kind of problem?
Also, for the battery, I got a kick out of going to Wal-mart. No one had a clue of what kind of car or battery I had. They kept saying what kind of car is it? Are you sure that's what it is called? What is it? A H-y-b-r-i d? Being this happened to me on a Sunday, (of course) there is no way I could go to the dealership until Monday. Does anyone know if there is a battery compatible with the Prius and not that you can only go to the dealership for it? It should be covered anyway, but just wondering.
Thanks for letting me vent....
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There is two batteries in your trunk. One battery that is like any other car battery for starting your car which is normally located of course under the hood of normal cars. (This is what is dead on your car)

On the Prius, this same battery is used to start the car and run anything that is 12volts, like radio, dome lights, headlamps, and CAR ALARMS.

This same 12 volt battery has a small discharge, which if you did a search on this site you can read on some techno stuff I cant really explain, other then the cars battery could drain if not used for say more then 2 weeks. Like if you went on vacation. Its best to take the battery cable off if its going to be unused. The battery discharges even when the vehicle is off for several small electronic items in the car. Again. Someone like Graham or Jeff could do better here on this. But just to give you the idea.

Now, the HYBRID battery is totally different. This battery is several batteries combined and it is sealed, also located in the trunk of your car. This battery pack is not what is at fault. And does not need to be replaced, unless you want to spend about $5 grand for a new one. This battery is what runs the Hybrid portion of the car, electric motor, and takes electrical charge from the brakes and electric motor. This battery runs at approx 276 or 278 volts. Thats more then what your clothes dryer runs at! This is the battery that is under warranty from Toyota for the 8 years 100k miles. Along with the rest of the Hybrid system.

I would say that with the normal discharge that the prius has on the 12 volt battery while the vehicle is off. YOUR CAR ALARM has greatly accelerated this rate. I would be willing to bet that your dealer will tell you the same. I would find out how much current your alarm system draws while in standby (armed). The Toyota comes with a very good security system in itself. The ignition key is a major portion of it. and this would be a good reason not to get a second alarm. Without this key your car wont start. Toyota also makes a glass breakage sensor. I would check into these as they have or are already on the Prius's. And have been tested to perform under normal circumstances.

I hope this helps, and I dont claim to be an expert on the Prius. Just what I read, and the help of these other wonderful folks that post on here. But I think I would take your alarm back and get a refund. Especially if Toyota proves that they also think your new alarm drained the 12 volt battery.
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Thanks for your help

Dear Smitty,
Thanks for your input and help. I dropped my car off at the dealership so the battery can be replaced. As for the alarm, not sure what I'll do yet but I really appreciate your insight. I think your right, it may need to go or else it will be more trouble than it's worth!! I am kind of disappointed that the place who installed it did not warn me about the charge it would take from my battery. I only hope I can get my money back.
Thanks again,
My battery (in the trunk) needed replmnt ...

All I can add to Smitty's message is the current scoop on leaving the car standing while on vacation. As long as you are careful to turn the lights off at the switch, that is, not rely on the car to turn them off for you, you will be OK for up to four weeks. Personally, I would (and did) take precautions if I was going to be away for three weeks so as to have some margin of error. I chose to have someone drive the car rather than disconnect the battery. As Smitty says, this goes all to hell if you install some gizmo that draws current from the battery when the car is off.
Hi Milly,
If you'd rather not part with your alarm system, it should be possible to fit a larger 12V battery into the compartment on the left side of the trunk, but it would take a bit of modification of the current battery holder. The reason WalMart had a hard time finding a replacement is the size of the Prius battery is pretty small compared to most other cars (it's ok for normal use since there's never a big starter motor draw on it).

Ask around for a mechanic that could build a new battery frame inside your trunk compartment. There's no high voltage stuff in there, just the 12 volt, so it doesn't have to be a Prius trained mechanic.

Be sure to write down all the radio presets you care about before disconnecting the 12 volt battery, the radio will forget them.

Good luck, let us know what happens.
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>Be sure to write down all the radio presets you
>care about before disconnecting the 12 volt battery,
>the radio will forget them.

If you have a nav system, also be sure to write down all of your nav presets, it won't loose nav points, but you will loose your routing options (aka will default back to avoid toll roads).

2002 blue moon pearl 13K miles 5 months
> If you'd rather not part with your alarm system,

Maybe I'm missing something. The Prius comes standard with a car alarm and anti-theft system. I know, I once returned to my Prius at the grocery store parking lot and the alarm was sounding. (I'm not sure why, either it was a false alarm or somebody really did try to break into my Prius while I was shoping.)

Also, pages 184-187 of the Prius NCF book give some details of the operation of the car alarm.

What advantage is there to adding a second alarm system?


PS. The Prius alarm system has a bit of a reputation for draining the 12 volt battery when the car is left parked for more than a few weeks. I'm sure adding a second alarm only drains that battery quicker.
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