12 Volt Battery
 

We purchased our TCH about a month ago. It is being used about once a week. I am finding that the battery is dead, or at least does not have enough power to start the vehicle after 4-5 days. It will start if jumped. I took the car to the dealer, after jump starting it and driving 2 hrs. Dealer said that the battery was 70% charged after a 2 hr. drive and said that the battery is smaller than a normal car battery, and that the charging system does not charge as fast as a normal vehicle. The owner's manual recommends running the vehicle every two weeks. I am getting a dead battery after 4-5 days of non-use, and see that others can leave it sit for a week or more and have it start. Could the battery be defective, or that the vehicle is drawing too much current when sitting? It is garaged and currently in a warm environment. Thanks.

Re: 12 Volt Battery
 

The battery should be fully charged LONG before 2 hours worth of driving was over... Have them do a load test on the 12 volt in the trunk and check the cables to make sure they are tight and clean.

I have left mine for as long as a week and a half at the airport and never have had any issues. If yours continues to discharge and the dealer can not find anything wrong, make sure that you do not have either of the keys near the car. Also check to make sure that nothing is left on (rear reading light for example) that will allow the battery to drain.

Re: 12 Volt Battery
 

Dennis,

You didn't say how long the car is running when it does run every 4-5 days; if it's only a few minutes (very short drive), I guess it's possible that the battery is not sufficiently charged.

But barring that, I would suspect a problem. (I should caution that I'm no expert, so hope that others will add to this.) Keep in mind that the 12V battery does not start the car; the "starter" (one of the electric motors) is powered by the traction battery. The 12V battery needs to have only enough power to run the electronics (computers, etc.) in order for the car to start.

Frankly, the dealer's line about small battery and slow charging sounds pretty bogus. A more plausible concern is that something is draining the battery, e.g., an accessory left on. Note that you may not be leaving anything on; there may be a drain caused by a faulty switch, relay, or whatever. Of course, a defective battery is possible as well.

I should add that our TCH frequently sits for several days without being driven; our record for consecutive days without starting it is about 33 days. We've never had any problem at all. Of course, our average use is more than once every 4 - 5 days, but even so....

Sorry I can't provide more specific information, but if I were in your situation I would be investigating further before accepting the small battery/slow charging line right now.

Re: 12 Volt Battery
 

Thanks for the replies. I doubled checked after the first episode of not starting. Nothing has been left on, and the keys are both in the house, not anywhere near the car. I will have the dealer look at this again, since it seems that this is not the usual case. The car is driven a minimum of 14 miles after starting, so I would think that the battery has enough of a charge to replace what was used in starting.

Re: 12 Volt Battery
 

I've left my TCH for over two weeks without driving it, with no problem starting when returning.

Re: 12 Volt Battery
 

Did you accidentally shut it off while in Drive??? We've done that once or twice. Didn't run the battery down but it sure as hell won't start until you get all the controls right. Also, the start sequence is kind of twitchy.... forget to put the brake on and you get things into a different mode and you have to start all over again.

Re: 12 Volt Battery
 

Two guesses:

1) Do you have ANY non Toyota accessories? LoJack, alarms, etc? If so you've probably found your problem.

2) You mentioned you just bought the TCH. Check on the door jam or some other labels. See if you can find a manufacture date. Your TCH might have set on a dealer lot (without being run) for over a long time. Or maybe someone left a dome light on after a test drive.

Either could have run the battery down. If so, your battery has been damaged. It will have less capacity than a healthy battery. This would explain the diminished capacity. You probably need a new battery.

Re: 12 Volt Battery
 

I just returned home from a trip. My TCH sat for 2 weeks with no one driving it and started up without difficulty. I second the comments of others, you either have a defective battery or something is discharging it.

Re: 12 Volt Battery
 

Make double sure your clock is off (black) when you shut off the engine with the lever in park. This is a small deep cycle battery to hold a charge for a long time. The toyota dealer should have a current drain meter to see if anything in the car is pulling the battery down. I would ask for a new battery that should be under warranty, now that you know others are not having this problem.

Your main concern is the battery supplying 12 volts to your ecu (computer) to boot up so as to start the car. The car starts from the large traction battery. I once read the charging circuit charges the 12 volt battery from part of the traction battery. You can see your traction battery at any time by pressing the display button on the steering wheel a few times. If it shows to be about 40% at any time the car should start right up.

You can always try another dealer.

Re: 12 Volt Battery
 

Thanks for all the helpful replies.

The manufacture date was October of 2008, so it probably sat for a while. I will have them check the battery for sure. I believe the starting sequence and the shut-down procedures are per the owner's manual. Hopefully I can get it to the dealer ths or next week. I will let everyone know what they find.

Re: 12 Volt Battery
 

Odd....

I got really sick last winter (almost died in Feb) and my 2007 TCH sat outside for 4 months without being started. When I finally did get into it in April, it started right up as though I had shut it off just the night before.

The brakes - however - were not as cooperative. The right rear rotor was rusted tight - although it did break loose after rocking the car back and forth. The pads have since been replaced.

It's cold here in Minneapolis in the winter. Our coldest day was around -25f (without windchill). Maybe the cold helped in this case?

I was really expecting to find that the battery was dead and broken (they break when they freeze)...

Re: 12 Volt Battery
 

The AGM (Absorbent Glass Mat) batteries are much more able to handle temperature extremes than the traditional fluid electrolyte types. These are also a 'deep cycle' type battery that can withstand deep discharges without damage.

From what I gather, the 12v battery is used to power the electronics (computers, radio, climate control, etc...) and the engine uses the traction battery to start.

There is even a "legend" about "some guy" using a couple of 6v lantern batteries to start his Prius.

Re: 12 Volt Battery
 

Include the fans under the hood, headlights, taillights and anything else that uses 12 volts for power.

I believe that to be true if the fellow disconnected the deep cycle first. Evidently the ECU itself don't draw that much current. A smaller 12 volt source may be enough to boot up the ECU for it to start the engine.

The heavy current drain on the deep cycle battery is it's ability to run all the AC fans, while sitting at long red light in the hot summer heat.

Re: 12 Volt Battery
 

Big-Foot, sorry to hear about your February illness. I had the flu twice in the past and thought I would never pull though. About the time I was to give up I started getting better. I still don't see how a microscopic bug can knock over a big dude like me.

Re: 12 Volt Battery
 

This last week I documented the voltage drop of the battery. It dropped from 12 volts down to 10.5 volts in several days. After charging, it dropped to 11.3 volts the next morning, and of course was dead. The dealer checked the amp output after I had driven for 2 hours and found it at around 36 amps. They charged it for an hour and brought it up to a little over 70 amps. It should have been somewhere in the 300's. Battery was replaced under warranty. I believe the problem was that the battery sat for long periods and was found dead numerous times, since it only had 28 miles on the odo when I purchased it in June. I am hoping that this should solve the problem. Now I am wondering about the traction battery not showing a full charge after a day of driving. Could not being used for long periods of time, between manufacturing, shipping, and sale, effected the traction battery as well?:)

Re: 12 Volt Battery
 

I hear you... I had/have a nasty case of Atypical Trigeminal Neuralgia - I won't go into details here but Wikipedia has a pretty knowledgeable writeup on it... I'm back but not at 100% yet...


I think you had a battery with a bad cell. Batteries can also short out internally. If someone else runs into this - I would have the battery out of the car, charge it all the way up on a 5 amp charger overnight/ Then remove the charger and see how fast it bleeds off the surface charge. You can also have a Load Ballast put on it which will approximate the loading of your car's systems on it.. After 30 seconds with the load cell on it - the battery should still read over 12v. If it doesn't - your battery is ready for the recycle pile.

Re: 12 Volt Battery
 

Is the Onboard Diagnostic System (or what ever that think is called where they hook up a plug to the car and figure out what's wrong) smart enough to tell if some of the cells in the battery are bad, or going bad?

Re: 12 Volt Battery
 

Honestly - I don't know... But I doubt it...

It's not like the technology isn't there, but I think they've already got a full bevy of other technology embedded into the car and for them to have a load-cell embedded in the car's system would take additional weight/space and for what little use it would actually get - I just don't see it happening...

certainly they "could" use other things (MG?) to act as a Load Cell - but the additional complexity would also increase the risk of failure..

Re: 12 Volt Battery
 

I once read that the traction battery contains a small computer that scans the groups of cells in it. If any or weak or have a single dead cell, it then reports this information to the ECU to provide a trouble code.

Re: 12 Volt Battery
 

I wouldn't worry about the traction battery simply on the basis of it not showing a full charge. Not having the energy screens in my NAV display (Canadian version:() I can't say what the battery readings are typically supposed to be there. HOwever, using the MFD on the dashboard, the battery almost never will show full, unless you've just gone down a very long very steep hill (ie. in the mountains). My battery display typically fills up to the minus sign in the picture, with the top area left empty.

Re: 12 Volt Battery
 

:D:D
Due to the desighn the system will never show 100% full or less than 1/4 empty. this is for maximum battery life of 8-15 years on the traction. full charge or full discharge would be early retirement for this battery.

Re: 12 Volt Battery
 

The top area of your battery display is the 20% left for braking. Braking down a 16% mountain or using the brake position on the selector. I have found using the braking selection works better at slower speeds like 35 mph or slower. It in many cases it adds in the brakes which adds wear if you going faster.

Re: 12 Volt Battery
 

Agreed. I understand that the battery is never totally charged or discharged - I was just clarifying that on the display, it will typically never show full (which really means 80%) unless you've used up all of your regenerative braking to do so.