I'm Considering Buying a 2015 Prius With 68k Miles. At The Dealership, I Insisted That The Service Staff Check On The Battery Fan Filter. It Was Pretty Dirty. The Owner Hadn't Cleaned It In 10 Years. Is This a Red Flag In a 2015 Prius?

A post in the Reddit r/carbuying forum asks for help on whether or not an original owner's failure to ever change the hybrid battery air filter could have led to damage to the battery from possible overheating.

This is a good question that demonstrates that the potential buyer is examining how well the original Prius owner may have maintained his vehicle's cooling system.

Related article: Don't Fall for This Potential Prius Scam by Used Car Dealers

The Importance of Toyota Prius Hybrid Battery Maintenance

The hybrid battery in a Prius generates heat during operation, and the cooling system helps regulate its temperature to maintain efficiency and longevity.

The battery air filter protects the hybrid battery by preventing dust, dirt, and debris from entering and blocking the battery cooling fan and ducts.

A blocked system could put the hybrid battery under heat stress, reducing its charging capacity and life.

As such, with the recommended maintenance of checking and cleaning the battery air filter every 5,000 to 10,000 miles and replacing it as needed, the Prius the OP is looking at is significantly behind schedule for a vital battery maintenance check.

A Very Helpful Response to The Prius Question

From the forum thread on the OP's query, we find a very helpful response from ThatDudeSky, who points the OP to some facts about what he is looking at with this Prius for sale:

1. A dirty filter by itself does not mean the filter is not doing its job. Because the point of the filter is to keep detritus from clogging up the fan that helps cool the hybrid battery.
2. Toyota does have a maintenance warning programmed into the Prius. If it were affecting battery cooling, which the sensors would note by way of an irregularly high battery temperature, an indicator on the instrument panel would say that maintenance would be required for battery cooling.
3. Minnesota may have cold winters, but it is not the frigid expanse of Antarctica, so during the warm months, if the filter had never been cleaned in 10 years, the vehicle still likely would have signaled the owners to check for a problem.
4. If you would like extra peace of mind, see if the dealership will allow you to get a pre-purchase inspection with a certified hybrid tech at a Toyota dealership so that they can test the hybrid battery for charging capacity and battery strength.

DIY Test Your Prius Hybrid Battery

If you are the DIY type, you do not have to take your Prius to a car dealership for a battery health check.

Armed with only an $89.95 OBDLink LX OBD2 Bluetooth Scanner from Amazon, that plugs into your car's OBD2 port and the software apps― Hybrid Assistant/Dr. Prius―on your smartphone or tablet, you will have access to real-time data and diagnostics that you can use to determine just how much life remains in that hybrid battery.

Here is an informative YouTube video from the H-EV Tech channel demonstrating how to DIY test your Prius' hybrid battery.

How To Test Prius Battery Health

For more Prius-focused articles, here are a few for your consideration:

1. I Bought a 2017 Toyota Prius with 69k Miles For $14,500, It Was an Exceptionally Good Bargain, But There Ended Up Being A Catch
2. Replace the Hybrid Battery in Your Prius with an Upgraded Battery
3. Toyota Prius Hybrid Battery Replacement Warning

Timothy Boyer is an automotive reporter based in Cincinnati who currently researches and works on restoring older vehicles with engine modifications for improved performance. He also reports on modern cars (including EVs) with a focus on DIY mechanics, buying and using tools, and other related topical automotive repair news. Follow Tim on Twitter at @TimBoyerWrites as well as on Facebook and his automotive blog "Zen and the Art of DIY Car Repair" for useful daily news and topics related to new and used cars and trucks.

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