Prius with 193K miles and repeatedly dying 12V: repair or donate?

I actually don't think you have any parasitic draw, if your car is completely stock without modifications.

I suspect the batteries you installed are not getting a good connection, not fully charged when you installed, corroded terminals, etc thus causing charging problems......and battery dying a premature death.

But you can simply check your voltages and see if it is indeed losing charge.......that's simple if you use the front jump points to check

 

Most batteries come with a 2 year warranty now.....it's not even prorated, it's a straight out replacement.

You can also try charging it at 4amp overnight and it should do the trick. If you've been charging it at higher than 4 amps (I think optima will take 10 amps), then you can damage the battery

Do you see corrosion at the terminals? Is the negative cable tight against the body of the car?I'm wondering if your constant charging of the battery would kill it. Maybe you should just try and let the car charge it as you drive....nothing more.

How long is your drive?

 

Why haven't you claimed the warranty on the batteries? It doesn't get cheaper than free under warranty.

I was thinking the 12v charging system might be bad and you haven't noticed it is because you charge the battery manually all the time. BUT, I'm not sure how you can make a 380 mile drive with a bad charging system.

I would go somewhere and get the car scanned for codes......it could very well be your charging system and you just can't tell because you charge your 12v manually

 

I believe I read you can connect 2 batteries together in a series (you should double check this series or parallel stuff lol), that will help your charger charge up the batteries that are really dead.

Here's a video

 

what you have to do is get an ammeter, put it between the positive cable and the positive post on the battery. roll a window down so you don't lock yourself out of the car, shut everything completely off and lock the car. what you will be measuring is the "quiescent current draw". after 5 or 10 minutes when all the control units are supposed to have gone to sleep, the current draw should be < 20 mA or something very low-- I'm not sure what Toyota's spec is. if its drawing like 120mA after 30 minutes, you have a draw-- usually its because a control unit has an internal problem. if you do have a draw, you have to remove fuses 1 at a time until the draw goes away. its a real PITA, but that's what we did at the Benz dealer all the time because that junk had a lot of problems with killing batteries due to bad control units.
if you don't have a draw, perhaps something with the key must be waking it up and killing the battery.

 

I think in a (gen2) Prius it’s easiest to measure the current by disconnecting the ground cable where it attaches to body. And while doing this you’ll also see if cable has good connection there.

If there isn’t parasitic draw then check the battery voltage from battery terminals with multimeter while Prius is in ready. Voltage should be 13.6…14.4V. If voltage is fine drive it for some time and then check it again (without turning the Prius off in between).

 

just mount a switch by the rear passenger door to the battery..no need to open the hatch, Toyota might replace the battery free once than you will be out the money...you have a short and the labor to rip the car apart to find it exceeds its value unless you do it yourself ..did you call Luscious Garage | Hybrid Specialists ? they are near you and know what they are doing..if you want cheap buy the switch and wire ..you don't have a lot of options when its an electrical issue

 

Your car logs so many miles daily, that normally the 12V battery should enjoy a very long life.

Use your multimeter and determine what is the voltage when the car is READY, and when it is IG-OFF after the car has been idle several hours. Measure the voltage either at the battery or at the dedicated jumpstart terminal to body ground.

As previously suggested, make sure that the battery cables and connections are clean and tight, especially the negative cable where it bolts to the body. To remove corrosion, you can use an auto battery terminal cleaning tool (which is basically like a wire brush for the terminal) and you can use fine sandpaper on the metal lug that attaches to the body ground.

You asked how to test the amount of current going into the 12V battery when the car is READY. This is easy: just connect your digital ammeter between one of the battery cables and the corresponding battery terminal. However, you need to be aware of the maximum current rating of your meter (usually 10A for a decent digital multimeter) and if the current flow exceeds that, the meter's fuse will blow.

My method to test quiescent current draw is to open the hood, find the dedicated jumpstart terminal located in the main relay/fuse box next to the inverter, then use a 10 mm socket to remove the nut nearby. After the nut is removed, use long-nose pliers to pull up on the wire that is attached to the threaded stud.

Now the 12V battery is disconnected from the fuse box. To measure quiescent current, attach your digital ammeter between the removed wire terminal, and the stud. Lock all doors and the hatch and keep the Smart fob well away from the car (more than 15 feet away). It is OK if the hood is up (at least with my 2004, that was the case.)

Let the car's electronics settle down. The quiescent current draw should be ~ 0.02A (20 mA). If it is much more, then start pulling fuses to determine where the problem is. DOME would be the first fuse to pull.

You may need to purchase jumper wires with alligator clips to make it easier to connect your digital multimeter to the car (Radio Shack is one potential source.)

You can obtain the electrical wiring diagram for your model year at techinfo.toyota.com and that would be highly useful to give you a clue about what fuses are likely to try, during this process. This will also help if you want to assess the likelihood of removing a fuse as a way of deactivating a circuit because you don't use that feature.

Yes, the Toyota dealer in principle should be able to do this, but the reality is that if a DTC is not logged, you may be asking too much for the auto tech (not trained as an electronics technician) to do this successfully. They'll probably charge you for two hours of labor and say "no trouble found".

So it is up to you to gear up with the necessary information so you can DIY, if you are serious about keeping the car. It sounds like you have the needed equipment on hand.

And if you decide your DIY skills are not up to the task, you can try Luscious Garage in SF as previously suggested.

 

I've recently learned from this forum that there is more than one level of charging the 12V from the inverter. You've mentioned measuring the 14+ volt mode. It sounds like there is also a lower voltage mode. Maybe others could answer if it's possible your car is constantly overcharging the battery?

I agree with the suggestion to temporarily disable the solar charger. And to get a Toyota battery and start fresh--give it one more shot. The difference in mpg vs. the Camry, with the mileage you drive, could make it worthwhile.

It sounds like SKS has been ruled out, but check that the SKS indicator light on the dash does not flash when the SKS switch is off and the car is off.

I'd use two tools to clean the Prius ground cable--a flat file on the cable terminal and a wire brush on the body to get to clean metal. The attachment point is just a few inches away from the battery and as always, be careful when working around the positive terminal. But by this time you've probably put that issue to bed.

Whenever I solve this kind of unusual problem after hours of looking (I'm a retired EE and a life-long amateur mechanic), I wonder how long it would have taken your average mechanic to find it, if at all. So often it's a matter of poring over a wiring diagram, finding pin-out diagrams and function tables, tediously checking continuity and device functions and outputs. (And in the last decade or so, spending time on the forums.) I look at it as good hobby and it's rewarding when you fix it. Good luck with this problem.

 

my wife's '05 has an alarm on the hood. if you do your current test under the hood (thanks for the tip, Pat) you will need to close the hood latch-- unless there's a separate hood switch somewhere which I didn't see-- or the microswitch in the latch might keep a control unit awake and set off the alarm.

 

One thing I see no one has suggested thus far.

Go to the 12 V battery compartment in the rear of the car and remove the red protector cap that is over the +ve terminal. It has three clips -- LHS, top and RHS towards the back of it holding it in place. These just lever outward on the left and right sides and then the cap swings up and away.

You should see a white harness clip that you can just press in on the locking tab and remove the plug. (This will reset your radio stations and a couple of other things (Clock) and probably reset some DTS's). Check both the socket and plug for corrosion and/or loose connections and clean or fix as necessary.

If it looks clean and tight, push it in and then remove it a couple more times, then on the final push make sure it is in good and tight and locked in place. Replace the red cap, it just clicks on. Let us know if that helps.

If you have a clamp-on meter that has a DC current setting then that will make life easy. Set it for 200 Amps and just clip it over the big black lead (-ve) coming off the battery on the right, as you look at it. Check, also, that the other end of that black wire is attached firmly to the car body and looks clean and free of corrosion. Try and orient the display of the meter so you can see it from outside the car.

Set your Voltmeter to the 20 or 200 V scale, doesn't really matter, use the one that gives you the reading that looks right to you. Place this also in a position where you can see the display from outside the car. Connect the red lead of the Voltmeter to the +ve (red) battery terminal and the black lead to the -ve (black) terminal of the battery. You may need to use a couple of short leads with alligator clips on both ends to ensure the Volt meter leads are firmly attached to both the Voltmeter and the 12 V battery. Also make sure no part of the Voltmeter probes or clips have any exposed metal that is able to contact any other metal part -- it is a good idea to use a small rag or such like to wrap around any exposed parts of the Voltmeter leads to insulate them.

Make sue that both meters read something (you may need to switch on ;-)) and then close up the car. Next, look through the window note down the date/time on a piece of paper and the voltage and current that you are reading.

If the battery is good you should may be get 12,7 V or better (ideally up to 13.1 V) and the other meter should show some -100+ mA (I think, but don't quote me on that, it might be more). Your current readings will be negative as you are reading the current as it leaves the battery.

After about 20-30 mins you should hear a couple of relays click in the front end under the hood. At is time you should observe the current reduce on the Ammeter to something like -20 mA (or about -50 mA, if the SKS is on).

Let us know if that provided any answers.

Hope that helps.

 

1) So it was completely dead and then you touched some wires and it worked for a moment? This means that you just have bad connection somewhere. Instrument panel lights flashing as you connect the battery are normal.

2) You shouldn’t have to tighten the screw very tight to get the terminal tight on battery post. So probably something is broken. Probably this is the same thing that causes your charging problem.

3) Voltage is good. It’s probably good enough for Prius.

I think that if you just get the cables connected good it will work fine. When you get this working please post us your fix.

 

maybe there's something wrong with the threads, you really shouldn't need to torque the clamp onto the post. you should be able to snug it down tightly without damaging anything. are the battery posts the correct size?

the battery sounds like it's good, so reinstall it, check your voltage every morning for awhile, and keep an eye on the connections.yes, buy the mini vci on amazon, it's the best prius diagnostic tool and only $25. look around here for many threads and info.