12V battery replaced with wrong polarity

Hi Jenny,

Wow, this is a great "happy ending" story.

I wish you took some photos of the disassembled relay/fuse box. I am very glad that your car is back in service!

 

Crowbar protection is exactly what you want for this sort of circuit.

Tom

 

Happy to hear you had the best-case scenario happen. As a FYI, whenever you get a new battery for a Prius, fully charge it before putting it in. That saves a lot of troubleshooting if the battery is almost dead and your Prius isn't behaving any better than before the battery replacement

 

+1

 

Since the DOME and ETCS fuses also popped without any apparent damage caused to those circuits, perhaps the ECUs drawing power from those fuses have crowbar diode protection.

 

SWEET!!!

Yes you were lucky, but, good for you!!!

73 de Pat KK6PD

 

I'm amazed that Toyota in Phoenix does not stock that 100 Amp fuse, I guess I'll ask my local dealer.

 

Sounds like everyone who hooks up the batt backwards blows that 100A fuse everytime so you already have your crowbar up & running. But when I think crowbar I think electronic soft shut down. Nothing gets blown. It detects a problem and disconnects. Blowing fuses is well..... blowing fuses.... not crowbarring. I have never put my peeps on the wiring schematic of this vehicle's boot up circuit. Is that 100A fuse protecting the boot cpu circuit? Does the boot circuit pull that much power? How could it with such a small boot battery? Or is it protecting the main B+ line from the hybrid pack to the inverter? If it is protecting the main inverter B+ line how is the processor operating correctly enough to close the hybrid main power relay with its run voltage reversed.
Maybe the processor must latch up with the reverse volt pulse and latch the hybrid relay momentarily but since the reverse voltage problem resides on the CPU boot side it doesn't damage the hybrid pack but maybe then the cpu is sending wrong pulse/data commands to the inverter damaging it by pulling excessive B+ current from the pack.
There's an elegant electronic solution for this reverse polarity problem by building a voltage comparator into the cpu circuit. Wrong pol or low main boot B+ to CPU and its brain dead by not allowing a relay to close for CPU power. This protection circuit would of course be kept alive by an onboard CPU keep alive cell.Thats an easy circuit. C'mon Toyota get with it. Don't they know Americans can't tell the difference between + and - signs?

 

Jenny, you got lucky!

The really sad thing, however, is there really isn't any reason that Toyota shouldn't have designed the Prius to simply ignore a reversed battery.

Anything that is electrical and not electronic (such as incandescent lighting with mechanical switches) inherently won't care.

Any computerish electronics could easily have a built-in polarity protection diode. This goes for the audio, the MDF, all of the various control computers and the like.

Any LED based lighting can tolerate reverse biasing if it's a red or a green LED. If it's a blue or white one, it would be a simple matter to put in a polarity protection diode.

The only thing left is the power inverter feeding power into the battery. That could easily be protected by a relay or better computer control and monitoring of the voltage of the line attached to the battery (if it's negative polarity, don't even try to pump current into the battery).

I guess when you're making millions of things, every penny counts, but adding polarity protection to EVERYTHING electronic in the car would add maybe $5 - $10 to the parts cost.

sigh.

 

1. Yes
2. Yes. That fusible link box is not easy to change, by the way. Post#19 here is the only description I have seen regarding how to perform that procedure.
3. When compared to a battery sitting by itself, the power from a donor battery where the donor vehicle is running has a greater likelihood of causing damage to the Prius inverter in a reverse-polarity situation. The voltage may be ~2+V higher and both the battery and the car's alternator can contribute current flow towards damaging the inverter.

 

Jenny,
I been following this thread and hoping everything would come out fine. I know what you mean on the 12v polarity issues as I just replaced my 12v battery too. Once I disconnected the + side, I wrapped in with electrical tape so I know which is which on cable reinstallation. I work on enough vehicles to know the Prius electrical battery layout is not the greatest. Any way, it sounds like a very happy ending.

Good for you!

DBCassidy

 

.

 

exactly.

 

Can someone please tell me what happened in this thread. Was it "bumped" and then the bumping post deleted or something? Jenny's long gone isn't she?

 

Kimbrie in post #30 resurrected this thread because she apparently has a similar issue with her Prius. Her questions are embedded within that post.

 

Oh... It would help if Kimbrie would fix her post or somehow differentiate her questions/changes. Whenever I see posts like that, I skip them. It can be too difficult to sift out the changes and sometimes there are none.

 

Ok I see now. Questions were embedded inside of quote. Yeah like cwerdna did, I skipped over that that. Thanks guys.

 

Thanks

 

pleasure.