12V battery replaced with wrong polarity

Hi Jenny,

Yes, you will need to carefully check every fuse (suggest you remove each one in turn, using long-nose pliers to remove and reinstall), and I suggest you make note of the names of every popped fuse. Note that there is a fuse box under the dashboard near the steering column, as well as the fuses in the relay/fuse box near the inverter. Also check the fuses in the fuse block attached to the positive battery terminal.

It is likely that the DC to DC converter in the inverter was destroyed, which will be a four-digit repair bill at your dealer. If you can buy a salvage part and can find a hybrid-trained independent mechanic to replace the inverter, that will save quite a bit of money.

 

I'm hoping it was just a few blown fuses, but you had better prepare yourself for a very huge repair bill

The Achilles Heel of the Prius is either jumpstarting with the jumper cables reversed, or hooking up the battery reversed. It can prove fatal to the car

 

The OP's situation is the worst of all possible cases, because the new battery was installed backwards. In that scenario, the 12V bus had 12V applied to it with reverse polarity.

If the problem was reversed jump cables, at least the installed battery would short out the voltage provided by the jump cables, so the voltage on the 12V bus would be negative but substantially lower than 12V (depending upon the internal resistance of the installed battery). And the huge spark created should be good warning that a problem exists.

 

WOW, don't we hope Toyota thought of that and placed a steering diode in line with the + side to prevent this from being really bad!!

If you smelled any burnt electrical smoke kinda smell, well Egon, Thats BAAAAD!

On the other hand, if you did not notice any smell, well keep yer fingers crossed!!!

I repair electronics every day, well excluding weekends unless I am on overtime, I have seen the results of backwards power. Made me a lots of money fixing the results!!

Please post a follow up, I would like to hear a Positive ending to this!!

A little electrical humor there hehe!!

Good Luck
73 de Pat KK6PD

 

Pat you are right and it has been said before. Because Prius never takes big amps from the 12 v battery (normal ops), there is a golden opportunity to polarity protect the car. At the same time Prius has more than average # of ECUs and the worst case scenario here would be hard to out-do.

Toyota, please while you are working on the Lithium suitcase and the aggressive youthful trendy hood design, how about some polarity protection?

 

Hi Jenny,

Thanks for the update. What are the names of the two smaller fuses that popped?

I am surprised that you saw no spark upon connecting the battery. If enough current flowed to pop a 100A fuse, there should have been a very big spark.

If the car becomes READY, then you are good to go.

If the inverter is blown, then the car will not become READY and you will see warning lights appear (probably the red triangle master warning light, the hybrid vehicle icon in the MFD, and maybe the check engine light in the combination meter assembly). Unfortunately, I believe that this scenario is the more likely of the two.

The various ECUs are diode-protected against this reverse-polarity problem. However the DC to DC converter is not. This is probably because 1) lots of current potentially can flow through that system and 2) a silicon diode introduces 0.7V drop. That drop combined with potentially 100A of current flow results in a pretty big power loss.

EDIT: Actually, the way to protect the DC to DC converter without introducing a power loss would be to connect a diode rated at >100A current to the 12V input to the DC to DC converter, cathode to that input and anode to ground. The diode would do nothing under normal use. In the event that negative voltage was applied to the 12V bus, then the diode would conduct and allow the DC/DC 100A fuse to pop.

 

I too got an "American" 12V Car Battery, but I got a Japanese to American conversion Kit from someone on the internet to convert my 2004 Prius to use a 2004 Mazda Maita battery. Only had slight problems using this battery, but this battery is 2x times better than the Toyota Japanese battery.

The cost of the battery was under $90, and not the $250 quoted from my local Toyota parts dept.

But, when I got home for the first time with this Mazda battery I saw that to install correctly the "+" and "-" the battery had to be turned 90 deg, and that would put the connections out of reach of the Prius connectors. The reason for the search for the KIT.

Lets hope that the American Battery Mfg. see the light and start making a battery for our 2001-2003 and 2004-2008 Prii. When and if they do... I might change out

later

 

Hi Jenny,

I assume that you are talking about the 100A DC/DC fuse. Is it your understanding that the little fuse link can be replaced individually; or must the entire 5" long grey/clear plastic assembly that contains all of the fuse links be replaced?

If the entire assembly must be replaced, then it looks to me that removal will entail removing the nut on the dedicated jumpstart terminal and removing another nut on the side of the assembly. Then it can probably be pried out of the relay/fuse box. My repair manual is silent on this question.

What are the names of the other two fuses that had popped?

Hi Perry,

The Mazda Miata battery works better with Classic, since the battery terminal polarity is correct for that car (the Classic battery is located in the left rear fender.) When the Miata battery is used with 2G, it is necessary to install the battery so that the terminals are next to the fender. If that fender is hit in an accident, then you have a greater risk of creating a big electric spark.

 

:fish2:


Jenny,
We're all rooting for you.

 

Thanks, Jenny. Are you planning to try to remove the old fuse link assembly now? (In case something breaks, you can call your friendly parts guy and order a new relay/fuse box, thus saving another trip to the dealer!)

Thanks also for the info on the other two fuses. The DOME fuse provides power to keep the combination meter memory powered up at all times. The ETCS is for the electronic throttle control and provides power to the engine ECM. Not sure why those fuses would have popped if the ECUs were protected by diodes. I guess you will find out soon enough if there's any damage there.

 

EDIT: Actually, the way to protect the DC to DC converter without introducing a power loss would be to connect a diode rated at >100A current to the 12V input to the DC to DC converter, cathode to that input and anode to ground. The diode would do nothing under normal use. In the event that negative voltage was applied to the 12V bus, then the diode would conduct and allow the DC/DC 100A fuse to pop.[/quote]


Uh..no. You don't want anything to conduct. Proper reverse voltage protection is usually done with the diode connected in series on the negative side cathode connected to negative terminal. Proper forward bias conduction with proper polarity. No conduction reversed.

 

Hi Ed,

Your statement would be true if you have a circuit that draws relatively little power under normal operating conditions, such as an ECU. In that case, the 0.7V drop of the series silicon diode is of minimal importance as long as you account for that voltage drop when designing the circuit receiving the power.

With a high power device like the DC to DC converter which is fuse protected at 100A, if you have a silicon diode in series then you will have the 0.7V drop of the diode to contend with. At 100A current flow, this is a power loss of 70W.

My suggested protection uses the diode as a "crowbar" which will force an electrical short upon polarity reversal, and blow the 100A DC/DC fusible link before the inverter can be destroyed. From the manufacturer's point of view, the blown fusible link can serve as a "tell-tale" that is evidence of a screwed up jump start, while the diode prevents serious damage to the inverter.

 

Glad that worked out for you. You must have dome a good Karma thing in the past.