Cannot figure out what is wrong....electrical issue...

Good

Ok, that's actually the "accessories mode" reading. This is basically the minimum power draw that you can have while still having the display powered on so that you can take the readings.

This is the real telling reading, this one is called "Ig-On mode". Here most of the prius systems are powered on, so there is a fair bit of current drain on the battery. This is the test that sorts the wheat from the chaff.

A battery in good condition will remain above 12 volts during this test and a battery which is marginal will generally be around 11.5 to 11.9 volts. At 10.4 volts your battery is undoubtedly toast.

This reading shows that the DC-DC converter is working hard to recharge your sick battery. The battery has a higher than normal internal resistance (bad) which can actually cause a weak battery to sometimes have a higher voltage than normal here. Most people with a healthy battery only report about 13.9 to 14.2 at this test.

In summary, it definitely sounds like your battery is sick. However you might want to test the connections to the battery terminals (as well as the pig-tail from the negative terminal to the car body) just to rule out those as a possibility. If no problem is found there, then it's almost 100% certain that your 12V battery is the issue.

great analysis uart, should be a sticky, thank you!

If a small current load as you did with ACC mode drops the voltage by a significant amount (as it did) either:

• The battery is toast so get a new one or
• There is a bad connection in the electrical path to the battery in either the positive supply line or the negative connection to the car body.

A good battery and electrical wiring will NEVER charge the 12v battery at a voltage over 14 volts as that would quickly ruin a good AGM battery. They should not be charged at a rate much above 2 amps and never above 4 amps.

Take the good advice given you in this discussion and first check the wiring, and if that doesn't help, get a new battery.

JeffD

But why does this drain the 12V when very hot only? Would the pack cooling fan come on [with ignition off] and drain the 12v. But I don't think that would effect the 12V! Heat does not effect a 12v does it? H

It may not be draining the 12v when hot as temperature variation could be a factor if there is a bad connection in the 12v circuit. This could cause the 12v charging process to be inhibited and then the battery charge would get low.

No, the HV cooling fan cannot come on when a Prius is off (It is controlled by an ECU which is inactive when off), but the radiator cooling fans in many cars can activate when the car is off, but I doubt that that is the problem. There are also some pumps which do operate in a Gen2 Prius when it is off (mainly the Thermos pump), but it operates only for a short period and since it is a bit noisy one would notice that it is running when it shouldn't.

JeffD

I'm thinking loose connection as well, maybe it was disconnected during the body repair and not reconnected properly?

How close to Hollywood? Is 91042 close enough? If so I might be able to help.

These readings suck! You NEED a new battery..... You can wish all you want, your post showed clearly, the old battery is SHOT!!!
Please buy an Optima!

Well there you go. You can't even think about going further hot or not without replacing the battery as its obviously toast.
If the OP comes back for further discussion about this battery then we know he's a troll for sure.

heat will definitly effect an failing 12V battery. Why do you think so many car batteries get sold in August?

10.6V under load, and despite all of the issues that the OP experienced because of that, nevertheless the OP demonstrated more commitment to his failed 12V battery than some individuals demonstrate to their spouse.

However the time has come to let go. Don't waste time with a battery from a salvage yard. Someone else already had the good sense to dispose of that.

Buy a new battery and be done with this drama.

Used battery $50
New battery $200
Ruling out your problem is just a battery by installing a NEW battery, priceless.

Yep. OP seems to have a pattern of misdiagnosing things e.g. from HELP!!! Prius sometimes won't start, will after I fidget with it. | PriusChat

It has nothing to do with overheating. The bulbs were failing, a well known issue w/the D4R bulbs that shipped w/06-09 Priuses and the subject of Toyota Prius Class Action Lawsuit | Toyota Headlight Lawsuit | Girard Gibbs LLP.

Nothing guys?

So those readings mean nothing? They are basically normal.

Those readings mean your battery needs to be replaced. I just tested mine (7 years old) and it was at 11.3V with the headlights and A/C fan on. I know it is time to replace mine as I am experiencing all the common problems associated with a bad battery. I have not replaced it because I am waiting to see how long it will last until it leaves me stranded, however, I may soon decide to give that up as I figure having my baby back to normal would be nice.

Everyone here is telling you you need a NEW battery. Please take our advise before continuing. The used one might work, however, if you choose to go that direction and you still have problems, we will tell you to get a NEW one. You might as well do that in the first place.

I'm done telling this guy to change his 12 volt. I suspect his voltages looked even worse than what was already bad after the car was started in the morning (left sitting from 5:15 pm until sometime after 7 am, instead of his 2 am test).

BTW, if he keeps wanting to test it, one can save the wear/tear on the HID headlights (cycling them is bad for them) by only going between on/off the parking light and off position, instead of all the way on.

You are a brave fellow

Thanks for the help guys....clearly, it's the battery after the readings. Why this chat has 2 pages, I have no clue, but that's why I posted those last two replies...I hadn't seen the replies. And seriously, some people need to drink a little less coffee and take this chat a tad less seriously. Thanks!

When you put in the NEW battery be sure and come back on the forum and confirm the results for us, that is part of the feedback loop. Some folks are very passionate about the Prius so don't be surprised when their patience seems to run thin, particularily when they perceive someone isn't maintaining a Prii with the same level of devotion. Appreciate this devotion and take full advantage of it.

$200 is a lot for a car battery, if you get the Optima (which I recommend). The Gen II Prii are getting old enough that just about all of them will have their original 12V battery fail soon. Unfortunatly the symptoms of a failing 12V in a Prii are not the same as a normal car that uses the 12V to crank start the engine. On top of having "strange electrical problems", the mpg will lower and eventually you will want to jump start the Prii with jumper cables. Improperly jump starting a Gen II Prius can be the kiss of death, a $4000 repair for a 5-6 year old car is hard to justify, especially for an actor wrestling with the $200 for a battery replacement.