Dead battery after 2.5 weeks

This is OK. When your car is ACC-ON, then the battery voltage is going to drop down since the battery is under some load, with the MFD and a few other systems on.

If you have a digital multimeter it would be interesting to measure battery voltage after the car has been IG-OFF for an hour or more. Open circuit voltage should be around 12.6V if the battery is fully charged.

 

OK, with Acc mode that's about right, a little anemic for a new battery, when you go to ready, does the signal check show about 14.1 ? That's charge voltage. I think after buying and before installing you did not give it a bench charge? ( 24 hour ) You can still do this, if you like, no need to remove battery just connect charger to positive terminal under main fuse box. Do a search and find recommended type charger for the newly installed battery. ( important ). As Pat said a multimeter will provide back-up info.

 

The Prius "12V" battery, like most "12V" car batteries is a lead-acid battery with six cells. The basic chemistry of the design is such that with no load the voltage should be in the range of 12.6V to 12.8V. They would more accurately (and less misleadingly) be called "12.6V to 12.8V" batteries, but of course no one would be that pedantic... If such a battery reads 12.0V with no load then it is getting so weak that it is near failure.

For lots more detail see among other places
http://en.wikipedia.org/wiki/Lead-acid_battery

 

When avocadoman says "static mode" he means ACC-ON, and the battery is under some load in that operating mode.

 

Argghhh...! thanks for the correction.

A completely unloaded "12V" battery reading much less than 12.6V is cause for concern. Seeing that requires a voltmeter.

 

Patrick Wong is correct. that 12.0 reading is with ACC-ON.
in all likelihood...if i had a tester, my new Optima Yellow Top would register as richard schumacher states while in static mode/without ACC-ON.

 

OK...one more time:

i tested several times in last two days.
1) after driving 30 minutes or more, then stopping and testing via the display, it registered anywhere from 11.9 - 12.4 during a 2-4 minute test
2) while driving and using the display to test voltage output while in route, it registered no higher than 14.2 and eventually reduced no lower than 13.4

 

OK! I finally did it.

I should have read the instructions. I only had to reset the clock. Old battery measures 10.5 on the bench. Everything went back together very easily. Delivered the day after I ordered.Took less than an hour.

Thanks Prius Chat! THE place to get information about these amazing contraptions.

 

I have this problem off and on for weeks with my Prius (2006 with 50k miles). They have repeatedly tested the battery and never found anything. Until today the mechanic at my local dealer kept it for a few hours and was able to determine that it was just loose terminals on the 12 v battery and a new battery wasn't needed.

Try finding a different dealer to look at your problem.

 

Sounds perfect to me:rockon:

 

Jay: The nice thing aout the display mode, signal chaeck is: first you can get the Acc mode readings, with increasing loads And then put it in ready and monitor the change and the charging voltage. And this is all thru the dynamic circuit using the computer. A fluke of course is accurate, but cannot internally check the circuitry in the various dynamic modes and loads. Plus it's extremely convenient, do it any time, for instance, while driving.

 

how do i "turn-off" the signal check and get monitor to display normal information?
that is, currently i place into signal check, and it remains in that mode until turn off vehicle, which in turn re-sets the display upon restart.
is that the only way to do it?

 

Unfortunately, you have to power down and then power up again, If I'm driving I wait until a light has just turned red.

 

My Fluke can take basic recordings. I have access to an AEMC power quality analyser that can be used for detailed, long term power quality analysis

I really don't care about voltages at the inverter or front of the car. I'm concerned about voltages at the rear of the car, where the 12 vdc battery is. I think it's pretty conclusive with the lower charge voltage in Ready, and the distance to the back of the car, once the aux battery gets discharged, it *must* be manually charged

My first winter with my Prius, 15 minute city commutes, with headlights on, max heat, electric rear defrost, at -40, the aux battery slowly lost its charge. It got to the point in the undergrond parking at my old condo, when I would power on, the auto headlights would dim to a yellow glow as the coolant transfer pump ran.

I knew I had to go away for about a month on a business trip. I got a VDC Battery Minder, took the battery out of the Prius, and left it in my suite with the Battery Minder hooked up. When I took the battery out, my Fluke claimed 12.2 vdc, call it almost dead

I returned after about 2.5 weeks, and the Prius behaved much better. With the freshly charged battery in, the auto headlights barely flickered when I powered on. I used the VDC supplied ring terminals to make a permanent connection to the aux battery, and got in the habit of plugging in the Prius overnight

It's going on 5 years now, the battery is still very strong

 

Hello Jay, True there could be a slight difference between the voltage readings under the fuse box and at the bat itself. But, they should be electrically the same with only a slight drop. I do also check with a meter. I'm sure your fluke does a better job.:cheer2: I also had problems with my first battery, but got The dealer to give me a new one, no problems since. Am experimenting now with a another Panasonic from a Honda RAV. I want to see if it can maintain min charge. In the meantime I'm also keeping the OEM Bat on a float charger. I keep a 7AH gel in the car for emergencies, that also works fine. In changing bats I did experience one of those 5/50 amp surges, ( a very minor spark) my trickle chargers produce more spark from the capacitor after I finish with them. From what I have read a surge current is not a major problem as it is temporary, ( 1-5 seconds) These boot-up bats seem to be a perpetual subject.

 

Or hold the [Display] MFD button for about three (3) seconds.

 

As the AEMC Power Quality Analyzer can accept two channels, I think a test is in order: record the voltage at the aux bat, and at the underhood jump point

I would guess for the vast majority of Prius owners, leaving the car for 2-4 weeks shouldn't be a problem. In bitter cold arctic temps, with frequent short trips and constant use of headlights and electric defrost, there is a problem

Of course, a lot of city driver cars have battery problems after only 3 years, at least they do up here

I have a 700 amp jump start box from Canadian Tire in my Prius. Not just to have a boost if the Prius is dead, but more importantly to offer assistance to stranded motorists.

I've used the jump start box 6 times now over the past 4 years to offer assistance. It has always worked well. I charge it once a month, and immediately after each use

Otherwise, there is no way I'd offer my Prius to boost a dead pickup at an intersection

 

I had to go out and try that! Works! Thanks much.

 

worked for me too! seemed like about a 4-5 second hold...

 

Maybe British seconds are more economical than American seconds