Weird stuff happening? MPGs dropping? Test The Battery

i like the new oem, and they have a good track record if not drained. optima has been iffy, but most of the problems are receiving a battery with a low charge and not charging it up before installing. i haven't read anything about the bosch. there is also a duracell at batterie plus stores. some of these batteries are made by the same factory.

 

with those numbers I'd keep the old battery and spend the money on a CTEK 3300 (

) and charge it up a couple of times a year.

If you end up getting a higher capacity battery the Prius won't charge it fully either and you'll still want the CTEK to charge the new battery.

 

The readings above indicate that you are on the verge of battery failure.

You also need to test the voltage in the "ready" mode; ON and ready to drive.
Assuming that comes out to be above 13 volts, then you just need a new battery.

Your drive time should be plenty to keep a healthy battery up......if you start out with it fully charged.

As for battery selection, IF the Bosh really is a direct fit AND it is an AGM type, I'd go with that.
There have been some problems with the Optimas and the OEMs are way over priced (no surprise there).

Listen, I really don't want to start an argument here but all of that is wrong.

Those numbers plainly indicate a battery that no longer can take and hold a full charge.
It is likely that no charger on the face of the earth can fix that; certainly not used only a couple of times a year.

The Prius charging system is fully capable of charging any battery you can fit into the space.
My guess is up to twice the capacity of the OEM. That assumes the standard, stock 12 V load on the car.

While the Ctek looks to be a fine charger, a perfectly adequate one can be had for about $20 less at WalMart or auto parts stores.

P.S. Do not confuse the CTEK chargers with the cheap junk they sell at Harbor Freight called CEN-TECH. I got a large 2/10/100 charger from them and it is a joke.

 

Once in ready mode, the number is almost always 13.9V.

 

Then the charging system (inverter) is just fine and you just need a new battery.

 

No all of that is hard fought knowledge documented here on Priuschat. Take a good look at my posts in New Optima Battery DOA (almost); And Getting Worse | PriusChat I put the meter to the battery and I've charged the battery outside the car and recharged it inside the car.

I had an OEM battery that would still start the car below 11 volts and I used the CTEK on it before I got the optima. I can tell you from memory that somewhere around 10.7 volts it wouldn't start the car but I'm not going to bother to search for the exact numbers. They probably exist on this forum and on my home PC but ignore the OEM battery for a bit, and look at my posts on the optima

No matter how far I drive the optima never read as fully charged after I put it in my Gen II 2005 Prius. You might say the inverter is doing a great job with your 2013 Prius c but I'm saying there are hundreds of thousands of older Prius that don't charge the 12v aggressively enough and nothing short of an external charger is going to bring those batteries to a full charge.

 

and if you think just knowing the inverter puts out 13.x to 14.x volts is good enough to charge the battery no matter how often you drive or how far you drive or what kind of battery is in the car you have a lot to learn.

 

I did not say that now did I.

It is not necessary to have an absolutely full charge all the time.
90-95% is plenty.
That last 10% is not necessary to ensure long battery life.
It does take away some of your "reserve" though.

You can nurse a weak battery for a LONG time by charging every night.......or every few nights......but it will catch up to you eventually and that's not likely to be very long.

And finally........maybe those "older Prius" also have "older" batteries that won't take a charge like they should. The number of electrical problems due to batteries versus due to insufficient charging is probably a thousand to one.......or more.

The person who most recently asked for help in this thread NEEDS A NEW BATTERY.
Encouraging him to "nurse it along" is not doing him any favors.

 

All,

I am the person asking about the battery. I decided to go with a Bosch battery that I found at Pep Boys. I used an online coupon code (SECRET35) and ended up paying $131 out the door for the battery, with installation included! I am attaching a picture of the battery, as well as a picture of my receipt. I had them show me the charge beforehand (it was 12.7V) and they hooked it up to a trickle charger for a while as I waited for an opening in service. I know Pep Boys isn't always the best, but in this case they were super helpful, and the price was amazing.

I will post pictures of my tests before and after the battery is replaced. At any rate, there is a 48 month full replacement on this battery, so at the end of the day, there isn't much risk here.

 

Old battery with IG ON and headlights ON (11.3V):




New battery with IG ON and headlights ON (12.0V):

 

you say "Old battery with IG ON and headlights ON (11.3V):" but the picture says 12.3V

Hmm, after replying it looks like you attached multiple pictures and somehow only one shows near the 11.3V statement

 

Sorry. I have a bunch of pictures on my phone and was trying to sort it all out when my phone died. They should be good now!

 

yeah the old battery was well ready to be replaced 11.3 is getting into the funky behavior levels.

Notice how your new battery tested 12.7v outside the car and drops to 12.0V in the car. Testing under load and with different test equipment (handheld vs cars internal diags) both make a difference.

I'd still suggest charging the battery with something other than the car several times a year. Up to you how often you want to bother but you know how to get a reading so you can charge to full and set your own baseline.

 

Driving 45 minutes to and from work every day is plenty to charge the battery if the charging system is OK and your tests with the prior battery show changing at the normal level.

I've used a ctec on an Optima but only during the winter when the car was in multi-week hibernation. It wasn't a charger, just a maintainer. Never ever in 5 years did I ever have to use a charger when the car was in constant use. 7 years now and the Optima is still in the car.

My bet the OP will find he is now fine. Just drive it.

 

And especially right now. The first charge is important and the 12.7 reading could mean that it's only 80% charged since it's an AGM.

I think you made a good choice.

 

I think I have experienced one of the "Weird stuff" scenarios due to a weak battery today, but I'm not sure if something else might be behind it.

I bought my 2008 NHW20 I-Tech about a month ago, with 113000km on the clock. No problems until today, except that the dealer had to jump-start the car via the 12V access point under the bonnet to start the test drive.

Today, the car did not start after it had been standing for almost 3 days since the last drive, with the keyless entry system turned on.
(I'm not entirely certain if I turned the car on very briefly yesterday after replacing the air filter and cleaning the MAF sensor and butterfly valve).

The situation seems to be just right for a weak 12V battery to be the cause, but the details baffle me.

I think maybe some other problem or short could be behind it.

Sequence of events today:
1) I opened the hatch from the outside, took some stuff out and left it open.
2) Tied a surfboard to the roof with hatch still open.
3) Closed hatch.
4) Tried to open hatch again to put something else in, it did not open.
5) Tried to start car, nothing happens, with or without keyless start enabled. Only sign of life in the car was that the "P" button light was blinking slowly.
6) I opened the hatch by crawling in and releasing the mechanical lever.
7) Measured voltage with DMM at 12V battery as about 5V DC.
8) Connected CTEK (5A) charger to 12V battery, this increased battery voltage to 5.7VDC, fluctuating by just a few millivolts.
At this point I thought something must be still drawing current of 5A to keep the battery voltage so low despite the CTEK charging.
9) Found the fuse box under the steering wheel (what a stupid place for it!)
10) I removed a fuse at a time, while someone else was watching the DMM at the 12V battery to see if the voltage would rise. The only fuse that had an effect was the fuse Nr 30: "7.5A 30 IGN"
Removing this fuse caused the voltage to rise from 5.5V to about 8V, and a clicking sound to occur under the steering wheel somewhere (still under 5A charge from the CTEK).
11) Then I replaced the 7.5A IGN fuse and checked the fuses under the bonnet. There was a quiet humming noise coming from the fuse box area. I again removed the fuses one at a time. When removing fuse "15A AM2", the voltage increased to somewhere above 10V (CTEK still charging).
12) I put the "15A AM2" fuse back in, and the voltage dropped a tiny bit but stayed above 10V.
13) I removed the "7.5A 30 IGN" fuse from under the steering wheel again, but it had no clear effect on the voltage.
14) With all the fuses back in their places and the CTEK charge still charging, I pressed the start button and the engine fired up. The engine stuttered a bit for a few seconds, then all was back to normal.

Questions:

A) What was drawing so much power that the CTEK charger could not recharge the battery?

B) How much charge current (how strong a charger or jump start system) is required to overcome this current draw without pulling out fuses?

C) What happens if I disconnect the negative battery terminal? The trip A and trip B counters did not lose their info this time around, and the radio stations are still set. On my NHW10 Prii I always installed a 100A resettable fuse at the negative 12V terminal, so I could just turn it off when parking the car for a while, or to charge the battery fully with an external charger without taking it out.

Thanks for any help with this.

Mik

 

Regarding above post: I checked the handbook and both these fuses are related to the ignition system.
Buggered if I know why it draws 5A or more when the 12V battery gets too low!

It appears that the Prius had been trying to warn me of the impending low-12V battery issue for the last 2 days: It kept beeping at me when I opened the driver door and I could not find a reason for it. I did not drive it, just got stuff out and did some servicing, so the problem worsened until the failure occurred today.

 

Mr Google found this for me from Patrick Wong:

The 15A AM2 fuse powers several circuits, including:

Engine Control
Ignition
Interior Light
Push Button Start System and Hybrid Vehicle Immobilizer System
Shift Control System
TOYOTA Hybrid System

(Source: p. 372, 2004 Toyota Prius Wiring Manual. That page also shows the six pages that you would look at to see the circuits powered by that fuse.) See techinfo.toyota.com if you wish to access this.

The circuit diagrams you are referring to apparently show only partial circuits. Good luck finding the short.
2005 Prius wiring diagram discrepancy | PriusChat

 

Looks like a quick disconnect might already be present in the NHW20:

I have a 2010. The dealer said that the battery will die after TEN DAYS of non-use. I said Wth! It is true. He showed me a service bulletin which showed how to pull the "short pin" in the fuse box if the car will not be driven for 10 days. Very Bad Engineering.
See: 12 volt battery | Page 4 | PriusChat

Does anyone know more details about how to pull the pin on the 12V battery?

 

Hi folks, I've done this test on my battery. It first reads 12.4v then I hit power button without break and it drops to 12.1. When I turn the headlights on it drops to 11.5v. Running it's at 14v. Time for a new battery? It's only two and half years old, but it has been abused (left to run down a few times) It's never not started for me though...