Q. I was offered a 2008 Prius for free, but was told the battery had been removed. Would it be worth taking?
answered by Sunny Patel, Senior Software Engineer (2013-present)
First off, this is almost exactly what happened to me. My mom had a 2005 Prius lying in a dealership service parking lot for two years. Since then she’s gotten a 2010 and a 2017 Prius. I just moved back into the state with a growing family and in need of a second car. She let me have it for free, and warned that there was issues with the hybrid battery, to which the stealership was offering $4,000 to replace it.
I took the free car anyway and got it towed over (two hour drive). I tested the 12V accessory battery, which was under three years old, and holding a low charge (about 9V). Got it replaced under the warranty (free, but normally ~$70). I was still getting the red flag of doom from the Hybrid battery, but it was still otherwise drivable. It would only randomly beep and have loss of power to the wheels for tens of seconds at a time.
I did some research and found that the hybrid battery is just an array of ~7.68V cells. Ordered three from Amazon – make sure you get the right generation version. Gen 2 Prius (2003–2009) batteries ran me $40 each (pretty standard price).
Watch the above YouTube video: Prius Gen2 (2004 05 06 07 08 09) Hybrid Battery removal to get to the hybrid battery and remove it completely. You’ll want to do this because replacing a cell requires you to open the harness, and you won’t have space inside the vehicle. You do need to be careful when handling the charged battery (mainly loose objects like tools touching end contacts), because DC voltage is more dangerous at that level (240V total). I didn’t use gloves, but that’s cause I’m a bit mechanically inclined and not clumsy.
Once out, I took a multimeter and tested each cell’s voltage and wrote them down. They should all be about the same. If you find outliers (greater than ~0.3V drop), mark them for replacement. Charge the remaining good cells to about 7.68V (should match your new cell’s voltage) to ensure consistent charge levels and then replace the bad battery. Lucky for me, only one battery was bad. Then put your bad boy of a battery back together and reinstall.
Bam! I had fixed the issue for $40 and saved myself the hassle of a new battery and forking over $2k+. My car has put on 15k miles since and still running great with 170k miles on it.
If your battery is actually missing, I would suggest getting the replacement – refurbished works as well too. I’ve seen a few around for $500–800.
Addendum: Some comments suggest that I will be guaranteed to have to do this in the future. But, for the 28 cells in the battery, you just need to do the math, and choose for yourself. On one hand, you can choose to do this at most 27 more times (if one cell breaks down at a time). It took me three hours the first time (referring to tutorials and picking the right tools), but as I continue to gain muscle memory for the process, I’m sure it can drop down to an average of 1.5 hrs. So that’s almost 40 hrs and $1080 total, in a span of the next 5 years (assuming they all break down by then), but the replacements should last another 10 years or so, so that’s at least a 5 year break. Compare this to dropping $4000 one time (plus labor costs), and you lose your car for a full day at least.
I grew up under a handyman legend where I thrive on fixing things myself, without a big pocket. I gained a lot from this experience; it brought me closer to the car, I won’t get gypped by overpriced mechanics, and I will have the confidence to fix worse things that may happen along the way. And best of all, I can pass this info on to my kids and friends and instill similar values to not always take the easy way out; valuing knowledge, time, money, and patience.
Only you can decide your priorities.