My turn for a new 12v battery?

It's plausible but not certain that the problem is a bad battery. The 13.6V you saw while the car was ON was the output of the car's own charging system. 12.1V is acceptable for a battery if it never drops any lower than that, but one should let the car sit OFF for an hour before checking the resting battery voltage. Try the built-in selftest procedure, which contains a load test, and see what you get:
PriusOnline.com • View topic - how to put 12V battery in sleeping mode?

Another simple possibility is a loose or lightly corroded connection at the battery terminals or at the connection between the negative cable and the car wall. Definitely inspect that before buying a new battery.

By The Way, there is no known drop-in replacement aftermarket battery for the Prius. Every battery will require some modification to the cables and vent tube and perhaps the holddown clamps to make it fit. It also must be a vented battery. The surest thing is to buy the same one from Toyota, and the easiest replacement is to have a dealer do it.

When mine died a year ago I bought an Optima yellowtop and adaptor kit from eLearnaid. They have very thorough instructions. It took about an hour including installation of the new cables. Reading others' posts it appears that swapping in a new Toyota battery takes about 1/2 hour. The box thingy is the traction battery exhaust duct. Removing it is not difficult and it makes access to the 12V battery much easier. Note carefully how it fits as you remove it. At every point *be alert* to loose bolts and hardware!

 

Hmm,,

My car is at 11.8 volts after sitting not being used since Friday. When I put the load on, it dropped to 11 volts when the button was pressed, and came up to 14.0 volts when the inverter was started.

I guess it would be prudent to the battery before winter. I can't think that the battery at 0 F, is going to be up above the 10 volts needed to start the car.

 

Hi Jim,

It does sound like the 12V battery is marginal. The rectangular black box in the foreground of your picture is the brake emergency power supply. It contains a large number of electrolytic capacitors and its purpose is to keep the brake system energized for a brief period if the DC to DC converter fails and the 12V battery is weak.

You'll find that the battery replacement task is easier if you remove the rectangular box to gain access to the battery. You may also have to remove the traction battery vent duct which is above the battery.

When removing the battery cables you'll probably find that it is easier to remove the negative cable where it attaches to the vehicle body (rather than try to remove the cable connector on the battery.) When working on the positive terminal, you may find that it is very hard to remove the red plastic cover from the fuse block. Just bend the cover up to gain access to the terminal nut.

Be careful not to drop any hardware into the fender well where the battery sits.

 

Hi All,

For some reason my outgoing email is perona-non-grata with Yahoo/Att (Not again !!). So, I could not send Elearnaid an order. Out of frustration, I figured out which Optima battery they sell, and found that Advance Auto stocks it, although the one closest to my residence (about 1 mile away) had a battery that was 3 years old. The next furtherst out (about 8 miles) had one made in June. So off I went. I had already bought the adapter kit last year. So, I went ahead and did the modifications. Nothing too it althought it was allot of wrenching. You will need a vice to disasemble the connector from the lug. A cresent wrench and/or vice grips were just not good enough for my bolt. It was really on there! Even got a $12 core charge back from Advanced Auto - almost pays for the adapter kit! And the lousy internet service providers I have do not get there chunck either!

Doing the battery test and I get 12.6 v unloaded, 12.1 volt starting load, and 14.0 volt with inverter on now.

 

On a somewhat related note...I'm wondering what the failure profile is for this type of battery. I ask this because I have a home security system that has had periodic battery problems lately. It's a small 12V, 4AH sealed, lead-acid that seems to be held at some sort of charge voltage constantly similar to how a car operates.

What's weird is that the system started saying the battery has trouble (nasty alarm at about 4 am.) Reset things all was well for about 12 hours. I checked the voltage and it was in the mid-to-high 12's with wires disconnected. Reconnect and after about 12 hours get more warnings. After a few days of this I had time to jack with it.

So I decided to unplug the alarm and see what happened. The first time I did this the battery powered it with no problems. So I left it like that for several hours, running off the battery. Then I plugged it back in. No more problems for a month.

Then about a week ago it did it again. Same high voltage on the battery. Tried to let it run the alarm. This time, it couldn't seem to take the load. Pulled the battery down, voltage is okay.

Now it gets interesting: I hooked the battery up to large electronics fan (at least 120 mm) on my telescope mirror. This is the same basic draw as the security system. The fan starts, everything is okay...except the fan is cycling up and down in rpm. The voltage is dipping down to about 8V then rising back up to 12V. It did this for several minutes, then smoothed out. I ran it for several hours until the battery voltage fell to about 12.1 V under load. It was a very smooth progression except for the first few minutes when it acted like it had forgotten how to discharge at all.

At that point I disconnected it and put it back in the security system. It has been fine since then. Of course, I'm expecting a repeat in a few weeks.

 

must be bad battery season... on my SPM, also a 2006 which has nearly identical stats to yours. the battery died this morning.

now, i know why it did. spent day washing and cleaning both cars yesterday. kid was playing in SPM told SO that battery will die if she lets him flip lights on and off, etc. she said ok, but life goes on.

sure enough, this morning, she is going somewhere ( i was at work so its all 2nd hand knowledge here) she starts car, it moves forward a few feet and stops, dash lights up. car turns off. she tries to restart, nothing.

i come home, try it, it seems to power up ok, but after a few seconds, engine does not run, i put it into drive, and it wont move. oh, well. knew what it was. brought out little DC power supply. hook it up, car starts immediately, no issues, run it around the block, and everything a-ok.

Shawn; sounds like you might have a bad cell. the cells within a lead acid battery can reverse its polarity if charge is brought down too low.

just read an interesting article on failing lead acid batteries in a bank (like in my Zenn) and how they react as they start to fail. instead of all the cells discharging evenly, you will have one discharge much deeper than the rest. the battery will then push the weak cell beyond its chemical equilibrium causing its polarity to reverse.

now as long as the battery is fully charged it will act relatively normal, but as soon as the charge on the good cells is dissipated slightly, the bad cell will start to show up. unfortunately, a battery is only as good as its weakest cell. once the cell flips polarity one time, its a goner

 

Dave,

I'm aware of the polarity flip failure mode, but what is weird is that it is reading a high voltage, not low. And then when I start to discharge it acts like a cell is flipping polarity...then promptly flips back...then starts again...then after a few minutes it acts normal and runs fine for hours. It's the oddest thing I've every seen with a lead-acid battery. It's like it wants to be taken out for a walk...a long discharge now and again.

 

well as i understand it, wild voltage readings are normal... the cell voltage will start out ok when battery is fully charged but voltage will start to drop (i had a battery die on me. it would basically discharge to 8-9 volts while the rest of the pack was low 12's or high 11's) on the bad cell much quicker until it just dives very suddenly.

when mine finally died (i have paktrker to monitor voltage) i saw it go from 8 volts to 25 volts and back to 9 to 15 to 8 and finally stayed at 8. apparently when the polarity starts to flip, it seems to have minimal resistance at the point causing the voltage to swing way high and kinda like slingshot over. it was really weird. i thought the battery was going to blow up or something but it was all rather benign... didnt even get the slightest bit warm

 

With my 2004 Prius, I also never saw any corrosion. Until I backed out the bolt that holds the ground wire to the unitbody, that bolt had *heavy* corrosion. I got in the habit of backing out and snugging up the ground bolt, every fall and spring

A battery that is getting sulfated will act like your battery, or like the security alarm battery Shawn has. Although something like a VDC Battery Minder *might* be able to bring it back, given the age of the battery its doubtful

I wired a VDC Battery Minder harness directly to my Prius battery, and left it plugged in overnight. After 5 years, the battery was still strong.

Since I only drive the FJ a couple of times a week, it also sits plugged into a Battery Minder. As with the Prius, the ground cable on my FJ, the bolt at the fender also had heavy corrosion after the first winter. I backed it out, smeared electrical contact grease on it, and snugged it back up

 

I don't think it is necessarily your 12V battery. I have had problems with mine (now replaced under warranty). My battery would drop into the low 8V area, not enough even to allow the MFD to work, yet it would still allow the car to start. As far as I can remember I only had the red triangle icon when this happened.

 

I had my 12V replaced in June. Symptom as described by the OP. No longer than 1/2 hour to replace if you're using the original Toyota battery.

What I noticed (as a way of diagnosing) is to check the speed of the power windows. When my battery was on its way out, the power windows was much slower under accessory power than it was when the car was in Ready mode. It's a cheap non-mechanic way of load testing the battery.

My battery got to a point where I couldn't start the car unless I had all accessories off and the headlight turned to parking lights (to bypass the DRL modification I had to do to import to Canada), so the battery was definitely toast.

FWIW.

 

Must be that time of year. The 05 12v would no longer stay up, my fault been ignoring it and only driving the 2010. Found info on this group about eLearnAid after checking here in Tucson they where only $2 to $10 more then the Toyota dealers and $40 less then all the Optima dealer her and that was with the kit.

Ended up swaping between the 2010 & 2005 the only PITA I found was removing the screw for the battery air vent (could not find my 10mm socket) Over all an easy change out had them both done in 2 hours with out the right tool.

tony l

 

I strongly recommend you wire in a VDC Battery Minder

BatteryMINDer® Plus 12 Volt 1.33 Amp Charger-Maintainer-Conditioner (Desulfator) :: All :: Battery Chargers by BatteryMINDers.com

Directly to the 12vdc battery





like I did. Problem solved

 

Thanks Jayman

I should have added that I also added my older BMW MC battery tender and a 5 w solar panel under the glass on the rear hatch both diode isolated, I was pleased to see the solar reading 13V in none direct lite under the window.

tony l

 

My airbag light came on and I also got a weird code about the transmission when I brought it to the dealer. The first was the airbag which was B1908. I found a link online here that says its a "SHORT IN P/T SQUIB (P SEAT SIDE) CIRCUIT (TO B+)".
They also pulled another code dealing with the transmission. It is code C2318 with more info on it found here. This error says "LOW VOLTAGE ERROR (POWER SUPPLY MALFUNCTION)". I don't have any engine lights on except for airbag light. I have never seen the red exclamation point. Someone here on PC mentioned to check the battery voltage which might be the culprit. I put the car into accessory mode (power button twice with no break press) and did the maintenance self check. It was at 9.9V-9.8V steady and dropped down to 9.7V if I held down the brake. When I put the car into ready mode, the ICE would kick on and it would stay at a constant 14.0V. I haven't driven the car around yet to test what the voltage is while driving a considerable distance, nor have I tried the above test after driving for about 30 mins. Not sure if my results are low because of the latter, but is 9.8~9.9V for a colt acc start too low? Any help would be appreciated. Thanks!

 

You need a new battery. The low battery can cause the error codes you mentioned. Replace the battery, clear the codes, and see if they reoccur.

 

DP sry

 

So is the Accessory voltage of 9.8-9.9 definitely enough reason (what is acceptable range for cold battery check in Accessory mode) or is the low voltage error simply confirmation that I need a new battery? If so, what is the price and what would toyota dealer probably charge for installation + labor? (Guessing I can't install it myself). I bought car used (05) and have no idea if its original battery. Car fax never showed if it was replaced. Thanks!