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

Thanks, everyone. I am expecting my various parts, cleaning brushes, etc. to arrive tomorrow. As I recall the things that surround and clamp to the battery posts are soft, like lead, and visibly distorted upon being tightened. I feared it might crack. I will take close-up pictures of my work and my Prius' various parts tomorrow and will post the pix here. If stuff needs to be replaced I can certainly buy it. My wife's family purchased this car used with about 40k miles on it, and it is possible that the previous owner modified some aspects of the vehicle.

I'm curious if anyone has thought to wire a volt meter to the 12V accessory battery and mounted the display somewhere in the rear of the car. I wonder if it is possible to do this in a way that wouldn't kill the battery. It would be nice if there were a convenient way to see the battery's level of charge at a glance, every time you opened the hatch.There's a Mini VCI cable and software headed my way from Hong Kong. Doubt I'll need it to resolve this particular issue, but I'm sure I'll find uses for it in time.

 

disregard this post

 

My work in progress. Here's a photo of the positive terminal for the battery, discussed earlier in this thread. Note the distortion of the soft metal. Is this the stock battery connection that comes with the Prius?


Photos of negative ground wire and screw, pre-cleaning:


Items sanded, wire-brushed, and cleaned with an anti-corrosion battery cleaner product:


Photos of some of the wiring. Note the electrical tape. Don't know if that's an after-purchase mod by the previous owner of the car:


Battery post cleaned, sanded, and sprayed with a Pemtex anti-corrosion product. I've also sprayed the pos and negative terminal wires, and the negative wire's connection to the car battery.


Let me know if any of this looks out of sorts.

 

It fits OK, the angle on the last photo was a little unclear. See here:

 

Thanks. Battery is back in the car and I am going to attempt parasitic draw tests now; hopefully I don't kill the fuse in my multitesters. Battery reads 12.89V this morning outside of the car (after being off the charger for 2 days) and reads 12.85 at the jump point under the hood now that the battery is installed in the car. Answering your questions and offering a bit more information:



You can see that I've winched down the positive clamp pretty much as tightly as it will go in an effort to insure a good connection. The clamp is snug and does not move if I attempt to twist it with my hand.

1. Yes, the positive terminal has the red plastic cover.
2) Not sure, see my second photo in this post. I did follow online instructions for dissasembly/reassembly.
3) I'm pretty sure I've tightened the positive terminal adequately as described earlier in this message.
4) I had completed the work when I read your post, so I didn't follow your sensible instructions. However, I don't seem to have screwed anything up yet.

I want to proceed with the parasitic draw tests. People have described a method where you test at the jump point at the front of the car, and another method where you hook the meter up directly to the 12V battery. Any input on which would be better? I don't want to blow my meter by opening a door whilst measuring milleamperes, and as it is approaching 100 degrees here I don't think I want to stick myself in the back of the Prius for 10 or 15 minutes, so the under-the-hood method would seem better if it is sufficiently accurate.

If I need to start pulling fuses, are all the fuses under the hood, or are there fuses in the cabin as is typical with other Toyota models?

I do have the Prius wiring diagrams and service manuals to consult if necessary.

 

dolj posted something in message #36 suggesting that I use a multimeter measuring volts and a clamp-on multimeter measuring milliamperes. I have several clamp-on multimeters, and I even ordered the alligator clip leads he suggested I might need . His method seems by far the easiest, I will give it a try.

 

ah, rats, I just figured out that my clamp multimeters do not measure DC amperage (as near as I can tell; this was actually the first time I was going to have a use for these meters,which I bought quite cheaply at Harbor Freight). I'm going to have to get my measurement another way.

 

Quick results: the car appears to be drawing between 28 ma and 33 ma at rest, but it would be wise to have someone with actual experience check my method and work. Details and photos follow.

I McGuyvered up a parastic draw test using the method of disassembling the positive jump terminal under the hood and inserting the meter between the cable part and the stud part via some alligator clip leads. I am vaguely aware of some risks to the car by playing around on the positive terminal, and after taking the pictures below, I wrapped the various contacts up in cloth.



(the blue thing in the picture above is the insulative handle of a pair of needlenose pliers -- I'm using it to make sure the stud and the wire don't connect. Alligator clips lead away and connect to the multitester's leads.)





Assuming I'm using the meter correctly and have wired this appropriately, it bounces around between 28 ma and 33 ma. This is after leaving the car undisturbed for 10-15 minutes. I will test again in an hour. Curiously, when I first turn the meter on, it reads "OL" for a few seconds before beginning to read appropriate values.

I do not have an electronics background so leave the possibility open in your minds that I might have done something completely wacky: you might want to check the scale and settings on the multimeter readout, for instance.

Thoughts? ~30ma is a bit higher than the 20 ma or below that people suggest should be the normal draw. Can people suggest next steps?

 

Thanks very much, Patrick. We left the Prius alone for some hours and upon returning the meter continues to read between 27 and 31 ma. You mentioned testing at the battery itself. One concern: if I open the hatch or a door to place the meter, and turn it on so that I can see the value when the hatch is closed, don't I run a risk of blowing the fuse in the meter while the hatch is open?

I am guessing this latest spate of problems were related to the extremely loose connection I discovered at the positive terminal: as I mentioned earlier, I was able to pull it off without even loosening the nut. Since I now know how to easily test the voltage on the battery, and to test the quiescent current draw, I should be able to keep a close eye on this over coming months. I am hoping the careful work I did to make sure all connections are clean and tight will resolve this issue.

 

Thanks. One other question: does anyone have experience with clamp-on multimeters capable of measuring milliampere DC currents? Are they sensitive enough for the kind of work I'm trying to do here?

I notice that Amazon.com offers "cheap" DC-capable clamp-on multimeters that measure milliamperes for between $100 and $150 (e.g. the GTC CM100 1 mA to 100 Amps AC/DC Low Current Clamp Meter or the ESI 687 80 Amps DC/AC Low Current Probe/DMM). The fine folks at Fluke also offer a low-current DC-capable meter for $700.

Seven hundred bucks is too rich for my blood but I would be happy to pay $100-$150 for a meter that helped me keep an eye on issues of the sort I've been working through. Reading through Amazon's reviews, it wasn't clear to me whether the lower-cost clamp-on low-current meters were sufficiently accurate for my needs.