Could be a bad 12V battery...

Hello All!

Well, I may have a bad 12VDC battery on my hands. Both yesterday and today, I drove my Prius for about 10 minutes to the store, went in and came right back out to find my Prius C would not enter the ready state.

Some background: I bought my Prius new in 2013 and I have 131k miles on it. I have never left the lights on it (inside or out) or drained the battery in any other way. I think it's just time. Some interesting observations:

When this happened, I was able to open the doors with the remote.

I put the key in and the entire dashboard stayed dark - no display of the car zooming by, no status lights of TPMS, airbag, etc.

It wouldn't do anything. I got out of the car, closed the door and checked under the hood. I saw nothing out of place - no fuses blown.

I checked the battery terminals - they are tight and the battery is secure.

I checked the voltage. I saw 12.4VDC on the multimeter - a little low, but it had been sitting overnight and it was cold (40 d F).

Both times, after exiting and entering the car, I put the key in, turned it and low and behold I got the normal start up screen. It then entered the ready state and I could drive it.

After each time, the car has not had any further problems for the day. Just once - the first trip out for the day about 15 minutes.

I run my car an hour 1 way to work each day, so I think it would have plenty of opportunity to charge. I am thinking I could have a battery that has a bad cell. I did not see any lose connections on the battery posts.

What do you think? At 12.38 VDC after 8 hours of sitting, would you consider that acceptable? I do have a battery minder with desulfation and the 4 stage processor controlled charge scheme. I could hook it up and see if it increases the voltage...

Thoughts? Thanks for reading this...

 

Hello all. Thanks for the speedy replies. I did check the negative to body cable - it's tight. I will take the terminal connections off, clean them and reinstall the clamps. Sam, I think you're right - 12.38 V is not that great. It may be on it's way out. The odd thing is I searched a local OEM parts web page and the Prius C without smart key battery is no longer available...

Battery - Toyota (28800-21181) | Conicelli

I have had good luck with Odyessey batteries, but they make mention of having to install their offering on it's backside (not sure what they mean)...


buy online
Year: 2013
Make: Toyota
Model: Prius C
Engine: 1.5 Liters 91 CID L4
Model #: PC925MJT
BCI #: S34B20R
Install Notes: Installation requires battery to be placed on its back side to fit dimensionally

Never mind. I see what they mean... I don't think mounting it on it's side is bad - the battery would be fine, but the way some have run auxiliary cables to the positive and negative terminals isn't for me.

There is this offering:

Replacement Battery for Toyota Prius - Battery Warehouse

But it doesn't list my model (which is a C without the smart key). But it should fit...

Does anyone have an updated part number for the Prius C 12V battery? 2880021181 seems to be no longer available...

Thanks again!

 

Hello! Thanks for the reply. Yes, it's true the battery is above 12V, but not by much. I think it's odd that this has happened for the last two days - only once at the first trip of the day. If it is a connection, I bet it will be joys finding it. I'll start with the terminals on the battery and see what happens. Bisco suggested checking trouble codes. I guess I'll bust out the Techstream and see if I can find anything out.

 

OK. So, no check engine light = no trouble codes. I was kind of wrestling with the idea of replacing the battery if that is not the problem, but as you said, it WILL need replaced in the not so distant future IF it doesn't need to be replaced now. Thinking about it in those terms is a little more palatable.

@bisco - I mistook the "always have the trouble codes read, before going to all the hassle of testing the 12v health." as a suggestion that I should check for codes. I think it's a good idea regardless. Sometimes there are codes that are stored and the check engine light is not on.

But, I can check the connections, clean them, try to follow connections and see if anything looks amiss and go from there. It is odd that after several minutes I can get the ready state on. I am curious what the amperage demand is on the 12V battery when booting the control units during start up. I haven't found evidence to support that a smart key Prius C battery (which is said to have more capacity) will fit in a non smart key Prius C. Can anyone confirm if this is true?

I found an OEM Toyota parts dealer in PA that lists the battery Conicelli shows as no longer available (in the first post link). If I can fit the larger battery, and it is a stocked part, I'll most likely go that route.


Toyota Prius c Vehicle Battery. HAZMAT. NOT AVAILABLE TO SHIP. PICKUP ONLY - 2880021181 | Diamond Toyota, Lebanon PA


Thanks for the replies and suggestions.

 

Hello. Thanks for the replies. I am about to take the Prius out for a 10 minute trip. If it is going to do it, it will most likely do it then. I mean, of course, exhibit the dead display screen symptoms it has for the last two days (referred to as "it"). I find it curious that it has happened on two consecutive days only once. The last time it happened, I noticed that the lock/unlock button on the door would not actuate the door locks; however, I did gain initial entry into the vehicle with the remote - the door unlocked. When I tried the lock unlock on the remote fob, I could hear a relay click under the dash, but it would not actuate the locks either. The display screen that shows a pictorial of the car with the door open was not present, but as the situation unfolded, the graphic did appear, but flashed and seemed dim. After checking all the obvious (fuses, loose terminal on the battery, etc.), I was thinking that perhaps I had a loose connection somewhere in the car. I am including this detail so if anyone else has the same sorts of symptoms, it may aid them with diagnosis.

I think I will get a new, fully charged battery and replace the old with the new and see what happens.