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Toyota Prius Leaking Hybrid Battery Mystery

Should the possibility of a leaking hybrid battery be part of your vehicle maintenance checks? Here’s a Prius with a possible leaking hybrid battery mystery you need to see.

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Batteries Leak

Whether it’s from your kid’s toys, your flashlight, your remote control, or anything else battery powered with an electrolyte whether it be liquid or semi-solid, there is always the possibility of a battery cell degrading and winding with at the very least a mess and at worse a health hazard.

Do Prius Batteries Ever Leak?

That was the take-away message from a recent Toyota Maintenance YouTube channel episode where the host does a “show and tell” of a 2015 Prius with 103,000 miles on it of which the customer complained of a suspicious looking potential hybrid battery leak he discovered while taking the spare tire out of the trunk.

The oddity of what looks like a clear case of “If it looks like a ducks, walks like a duck, and quacks like a duck---it must be a duck” scenario, is that why were there no check engine light, or check battery light warnings on the dash, or even a scan tool code letting you know that something is less than optimal with your car’s hybrid battery? It’s a mystery.

Related article: The Truth About Owning a Prius and Its Battery

A search on the Internet reveals very little about Prius models ever having any leaking battery issues save for some earlier batteries where the terminals were observed to leak at their connections and cause corrosion.

Hints on the Mystery

During the demonstration by the host we are left with the following hints as to what might be happening:

  • The car has been to the beach as evidenced by sand on the trunk floor, therefore saltwater exposure could be a culprit.
  • There is no evidence of spillage from a soft drink or other family-related mess accident.
  • The corrosion appears to be only on the lowermost part of the hybrid battery and not at the high voltage terminal connections.
  • The corrosion you do see is a combination of reddish metal oxidation corrosion and the typical battery terminal yellowish white crystalline mess you find with leaking batteries.
  • The hybrid battery is at or very near its expected lifespan.

Actions the Host Took

Quite rightly, the host stopped his investigation after removing the hybrid battery panels and is advising the car owner to take his Prius in for an inspection by the Toyota dealership garage. Primarily because this could be a defective hybrid battery and there might be some compensation despite the fact that the vehicle’s warranty coverage has just passed the 100,000-mile mark, Doh!

There’s another good reason for this inaction action: the battery poses a potential health hazard that may affect the owner and his family’s health. By not disassembling the battery further, this prevents clouding of the battery issue should there be a lawsuit and Toyota claims someone else handling the battery is the cause of whatever damage may be found.

Watch the Video and Make a Guess

Follow along with the host in the video and see if you can come up with other sources or causes that could explain the hybrid battery mystery.

My Best Guess

From an earlier article about Prius hybrid batteries we have learned that corrosion can occur under the battery bus bar cover in a Prius battery over the years, presumably from wet, humid conditions over time.

And, since there is what looks like beach sand in the trunk it is not unconceivable that the Prius could have been parked on a beach near enough to the water to have been exposed to actual water entering the trunk or enough salt spray in the air to cause a corrosion problem.

However, I would like to pose an alternative theory: rodents. Rodents like parked cars because they are a good source of crumbs. And, if you have ever seen the effects of rodent urine on metal, what you see in the video looks suspiciously similar.

While the mystery appears to be unsolved as of yet, be sure to watch for a follow-up video of this Prius problem. If there is an answer, the host will likely share that in a future video for his followers.

For additional articles related to Prius hybrid batteries, here are a few for your consideration:

Timothy Boyer is an automotive reporter based in Cincinnati. Experienced with early car restorations, he regularly restores older vehicles with engine modifications for improved performance. Follow Tim on  “Zen and the Art of DIY Car Repair” website, the Zen Mechanic blog and on Twitter at @TimBoyerWrites  and Facebook for daily news and topics related to new and used cars and trucks.

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