P0ADB Hybrid Battery Positive Contractor Control Circuit Low

Well, been befuddling over my 2009 Prius (115,000 mi) for 3 weeks now and need help!
It quit on me driving through town - just error coded and drifted off to the roadside....
Thought the aux. battery was to blame as I had to replace it 2 years ago. Towed it into the Walmart parking lot right there, took the aux battery home and charged it on my shop charger. Was able to drive Prius 6 miles to within a few feet of my driveway the next day. Went worse from there with more and more difficulty getting into ready mode let alone drive. So the scangauge says problem is DTC code P0ADB which means "Hybrid Battery Positive Contractor Control Circuit Low". Because charging the aux battery seemed to help a lot the first time, I claimed it was bad to my battery supplier (being in the solar biz, I have a whsl acct with them) and they replaced it "no charge". That didn't help though. Was able to verify that when I could get the car "on" the diagnostics showed the aux battery coming up to 14 volts so it is charging, and sometimes can even get the engine going and even move a bit, but generally the least bit of effort from it causes it to kick off. Anyway - not the famous sensitive aux battery syndrome. So I have an o-scope and in looking at the circuit driving the "positive main battery contactor's circuit" it goes through kind of a dance when the start is pressed as the relays are turned on in sequence to carefully engage the high voltage from the battery. First the low relay engages, then the precharge positive relay (has a power resistor in series to carefully bring up the volts and quash any arcing during shutoff), then finally the main positive contactor engages. During the time this happens the drive signal from the hybrid ECU goes a little nuts and is a series of pulses maybe 10msec long which doesn't make sense to me as a way to treat a contactor. So figured this might be the actual problem and went ahead and found a used replacement set of contactors and ECU (just try and find new ECUs). After learning about the wonderful world of computerized cars and getting the replacement ECU and old key to play nice with each other, I actually got my Prius into ready mode for the first time in a couple weeks. Engine came on, main batt started to charge up (was down to 1 bar) - but when tried to go, it kicked off very easily and my old friend DTC P0ADB came back.
Now, it seems like if I just let it sit for awhile it tries to work, then as I try repetitively to make it work it just gets worse until can't get into ready at all. But let it sit for a couple hours and it seems a lot better. Could all this be a symptom of the main battery failing? From what I read, the usual code for a failing battery is P0A80 and this P0ADB code is unheard of. I figured replacing everything to do with the contactors would solve this but of course, who really knows what this error code really means? Maybe something wrong with the wire going between the ECU and contactor - but that is hard to believe. Guess I'll take the battery cover off and measure batt cells to see if any are amiss.
Anyway, I'm wide open for suggestions if anyone has a clue as to what is going on here.
I'm a long way from a Toyota dealer and I'm dubious as to how much help they are going to be.
I always seem to get the unusual, hard problems.....
I love my Prius, but am dismayed at how much complexity it takes to gain some efficiency!

 

Disconnecting the battery doesn't change anything. Still can only drive a little bit before it kicks off. Like as if the main batt is so weak or the contactor won't stay closed.
The car did suffer a head-on with a piece of rail-road tie over a year ago that a stupid landscape contractor was using to hold down his cargo tarp with. Came up over a little hill and there it was right in the lane. Hit it straight on and jammed under the transaxle - tore out the plastic underneath and even broke off a bit of flange. Could of been a lot worse. He bitched about paying the $1500 of body work but should be glad we weren't hurt. The dealer could not find any mechanical damage, but it has developed a creaking noise when accelerating though which no one has been able to locate. I doubt that this has anything to do with the present problem though.
Even if I get to the bottom of this problem and fix it for sure, I'll no doubt always be afraid of "some little detail" in the complex inner workings of this car going kafluey - however, you can say that about just about anything these days. Windows 8 - don't get me started! It's why I love driving my tractor - Ahhh, simple is beautiful! You want to talk complex? I used to be in the commercial avionics business and can tell you that I fly as little as I possibly can.....

 

Today was able to force the engine to run while parking brake was on and get the main batt charged up to normal. Then removed the battery cover and measured all the battery modules - all between 7.7 and 7.8Vdc. I'm thinking the battery is ok. The car actually drives now and feels like it should, however when I tried to go up a small hill - it kicked off. And then heard the contactors making a lot of wild clicking noise until could pull over and shut off. Same P0ADB code of course. It just feels like the contactors aren't staying on well and when stressed, they give out? But they've been replaced and the Hybrid ECU has been replaced. ????

 

OK, a follow up to this problem....
Got the mini-VCI and it confirmed the DTC code of P0ADB with same description as the scangauge but the Toyota TIS does have nice info on the details of the circuit. No other Toyota history of this problem though.
Spent some time driving around with the mini-VIS and an O-scope connected to the Contactor control signals and concluded that there is an unacceptable amount of noise on these wires. I don't know what's in the ECU circuit driving the coils on these contactors, or in the contactors for that matter, but I suspect there is no snubbing circuit on these coil drives. The ECU is in the front and the contactors are in the rear so there is plenty of potential for the coil drive to get out of control. It could be that there is an electronic noise problem in the car or poor grounding and this contactor circuit is just susceptible to it as this whole thing seems to be a rare problem. Anyway, after putting a 0.1uF filter capacitor on each relay coil, have had no more problems. (If anyone wants to do a little preventive insurance - put any nice, film type capacitor, about 0.1uF between the yellow wire and the convenient chassis ground right there and another one between the black wire and ground)

Had a problem similar to this years ago on a Toyota van where the EFI computer died when the fuel pump got weak. As the pressure went lower, the EFI had to work harder firing more to make up for it and the output circuit blew. I dug into that circuit and - no snubbing diodes or anything. Just a transistor directly connected to the injector coil. When the transistor turns off, the coil tries to keep the current flowing and kicks back reverse voltage to the drive. A reverse biased diode is standard procedure with coil drives or at least a capacitor. I'm surprised that a Toyota circuit designer would make that kind of mistake. Probably figured that their circuit worked when tested new, but didn't figure in an aging fuel pump.

Sorry Toyota, not impressed with your circuit designers again, and not wasting money with your dealer service either.....