You Can Fix Your Own Prius Battery (or not)
Can I fix my own Prius battery?
(Yes, but be smart and careful as you do it)
This is the question I asked myself when the repair shop said it would cost $1800 to $2800 to have them replace it. But let's back up a bit.
Somewhere around 11-01-18, on the dashboard of my 2007 Prius, the check engine light came on, followed by the VSC warning light, then the dreaded "red triangle of death" (as I call it) with a beautiful grand finally of the red caution symbol on the center console display. It was a progressive light show that grew one after another over a series of maybe a couple days. It felt like a small success because pretty much every light that could come on, was on.
To help you understand my next steps, you need to know that I bought my Prius used from a taxi cab company 4 years ago in Las Vegas and it has over 560,000 miles on it. So warning lights are no stranger to me and sometimes they just go away after a bit and we move on (yes I know they actually mean something but ignorance is bliss).
That was not the case this time and things just got progressively worse. The car starting losing more power each day, the engine was randomly revving really high and finally when the battery fan kicked on and stayed on, my wife said, "I think I smell smoke." I am not sure she really did smell it but I headed straight for my Prius repair guy and the car really started limping to get there, just barely made it.
It was 11-08-18 when the shop pulled the codes and said I have a bad battery pack, specifically cell #10. I could replace it with an aftermarket pack for $1800 installed or an OEM pack for $2800 installed (which is cheap compared to what I have read in other places).
Well I had just dumped $1700 into this car for suspension and other odds and ends, so I was not excited to dump thousands more into a car with this high of miles. So I asked if they could just replace the the bad cell and they would not, nor would they recommend someone who could or even sell one to me to do it myself. "It is too time consuming to be worthwhile for a shop to do just one cell and too dangerous for you to do it."
Although they were willing to clear the codes for me so I could try and drive it back to my work and take time to decide. It drove fine for two blocks before the light show began again and it had to crawl along for the reaming ten blocks.
Long story short, after lots of research and YouTube videos I decided these were my options:
1. Let them do the job for $1800
2. By my own refurbished replacement pack for someone like these guys and put it in myself, saving a few hundred dollars.
3. Get rid of the car all together
4. Attempt to replace the one bad cell myself, despite all the DANGER warnings on the internet and on the pack itself.
I chose option 4, primarily because I am fairly handy and I know how to use a volt meter, which is basically all the skills needed. Although, a basic knowledge of what you can and can not touch when working with electrical is crucial.
I also chose option 4 becuase after watching the videos, I couldn't imagine it was as hard as my shop tred to make it sound. So I pulled the battery pack out on 11-10-18 following the guidance of first this guy and then this guy who both did an excellent job of breaking the project down step by step and how to remain safe.
A strong back could have gotten it out alone but I opted for help from a friend, lifting it out on to a rolling cart when disconnected. You can also see my rubber gloves above that I used during the whole process (yes, basic kitchen cleaning gloves).
Once it was out and on wheels, it was time to find which cell was the bad one. So I followed the advice I read and watched in videos, disassembling the entire battery pack and then voltage testing each individual cell.
Every cell tested out to 7.9 or 8 volts, all except cell #8, which tested out at 6.7 volts. AHA!!! I had my culprit and now I knew I needed to just replace one bad cell. So I hopped online, looked at all my options and after reading several good reviews I decided to buy it from 2ndLifeBattery on eBay, for $29.95.
You can see that a good amount of dirt and oxidation came off in the vinegar, after which I decided to use my Dremel with a course attachment to buff each piece back to shiny.
The replacement cell arrived and on 11-19-18 I installed it according to the videos I mentioned above. Here are some key tips that might help you in this process.
1. Make sure you number the cells w/ Sharpie before pulling them off, so that you can keep them in order when they go back on. It might also help to write down each cell's tested voltage on it so if you have to go back, you will have a reference point of what it used to be.
2.When pulling the cells off of the battery pack tray, be careful of the wires connected under some of the cells, especially the very first one to come off.
3. Finally, here is something I lost about an hour on trying to troubleshoot. Once I had the battery back put back together and installed in my Prius again, bolted in place and everything reconnected but the two primary wires that connect to the vehicle, something confusing happened. I was replacing what I would call the orange breaker (watch this part of the video to really understand what he calls the "battery interlock"). This is one of the first things you need to remove when starting the project and one of the last things to go back in, for obvious safety reasons.
My issue was not getting it back in, but rather the fact that once I put the breaker back in, my volt meter would read no voltage on the two main leads that are supposed to connect back to the vehicle. I had about 220 volts before I pulled the breaker out at the very beginning of the project. Logic would assume that when I put the breaker back in, I would get 220 volts again, but alas I was getting no voltage at all. I took my battery back apart to double check my work and saw no issues with anything. Voltage was everywhere it should be but at the final two points at the end.
In the end I decided maybe the car has to start up in order for something to trigger the battery pack to engage voltage again (just a guess) and so I put it all back together and started it. It started fine, no warning lights and all was good. What I think I might have concluded is that what I call the orange breaker actually has a capacitor (or something similar) in it that needs to charge up before it will pas signal through to the main leads.
4. Above I say it "started fine" once the battery was back in but actually I had to jump the auxiliary battery to get it to start. This reminded me that I read somewhere that when the primary larger battery has issues it can start pulling too much voltage from the smaller auxiliary battery (or just cause it to over work) and actually damage the auxiliary battery. In my case the auxiliary battery was already pretty old and I think it did destroy it because it would not accept a charge from that point on. Swapped out that battery and all is well.
Okay, let's wrap this up. I am writing this blog because I got a lot of help from others who took the time to document their process but none of them did follow ups to let people know if the repair lasted any length of time. As my repair guy said, "if you only replace one cell and not the whole battery pack, you will have to replace another in a few weeks and then another a few weeks after that etc."
Well, we are going to find out. I will keep updating this to let you know how it goes. Oh BTW, total time working on this project was about 6 hours and could have been 4-5 hours if I had the tips I mentioned above.
Updates:
11-24-18 After nearly a week of good driving (I say good because it does have 560k miles on it and it is back to driving as good as it did before) the check engine light came back on. No other lights yet and it still feels like it is driving fine, so it could be something else totally unrelated. I will add another update when I have time to go get the codes pulled.
11-27-18 On my way over to O'reilly's Auto Parts, to get the check engine code scanned last night, and the check engine light went off. I still had them try to scan it but their OBD scanner couldn't sync with the Prius computer. They suggested I check the fuse for my OBD port to make sure it is working and off I went. Haven't had time to check that yet.
12/1/18 This just in! A day after my last post we were driving home from work, everything driving great with no lights on and we pulled up to a light. I then heard a "click" sound and every dash light came on again and the car would not move at all. I turned it off and let it sit for about 30s and then started it again. Now it would drive but without any battery so we limped it back to work. That is where it has sat for the last few days as we discuss what our next move is.
05/17/19 Shortly after the last post we decided to sell it for parts when Boulder Hybrids contacted us and said they would take it off our hands to put towards a trade in on a different car, we agreed. That trade in went towards the 2013 Nissan Leaf we are now happily driving.
Conclusion: Maybe you can fix your own Prius batteries... but I couldn't.
(Yes, but be smart and careful as you do it)
This is the question I asked myself when the repair shop said it would cost $1800 to $2800 to have them replace it. But let's back up a bit.
Somewhere around 11-01-18, on the dashboard of my 2007 Prius, the check engine light came on, followed by the VSC warning light, then the dreaded "red triangle of death" (as I call it) with a beautiful grand finally of the red caution symbol on the center console display. It was a progressive light show that grew one after another over a series of maybe a couple days. It felt like a small success because pretty much every light that could come on, was on.
To help you understand my next steps, you need to know that I bought my Prius used from a taxi cab company 4 years ago in Las Vegas and it has over 560,000 miles on it. So warning lights are no stranger to me and sometimes they just go away after a bit and we move on (yes I know they actually mean something but ignorance is bliss).
That was not the case this time and things just got progressively worse. The car starting losing more power each day, the engine was randomly revving really high and finally when the battery fan kicked on and stayed on, my wife said, "I think I smell smoke." I am not sure she really did smell it but I headed straight for my Prius repair guy and the car really started limping to get there, just barely made it.
It was 11-08-18 when the shop pulled the codes and said I have a bad battery pack, specifically cell #10. I could replace it with an aftermarket pack for $1800 installed or an OEM pack for $2800 installed (which is cheap compared to what I have read in other places).
Although they were willing to clear the codes for me so I could try and drive it back to my work and take time to decide. It drove fine for two blocks before the light show began again and it had to crawl along for the reaming ten blocks.
Long story short, after lots of research and YouTube videos I decided these were my options:
1. Let them do the job for $1800
2. By my own refurbished replacement pack for someone like these guys and put it in myself, saving a few hundred dollars.
3. Get rid of the car all together
4. Attempt to replace the one bad cell myself, despite all the DANGER warnings on the internet and on the pack itself.
I chose option 4, primarily because I am fairly handy and I know how to use a volt meter, which is basically all the skills needed. Although, a basic knowledge of what you can and can not touch when working with electrical is crucial.
I also chose option 4 becuase after watching the videos, I couldn't imagine it was as hard as my shop tred to make it sound. So I pulled the battery pack out on 11-10-18 following the guidance of first this guy and then this guy who both did an excellent job of breaking the project down step by step and how to remain safe.
A strong back could have gotten it out alone but I opted for help from a friend, lifting it out on to a rolling cart when disconnected. You can also see my rubber gloves above that I used during the whole process (yes, basic kitchen cleaning gloves).
Once it was out and on wheels, it was time to find which cell was the bad one. So I followed the advice I read and watched in videos, disassembling the entire battery pack and then voltage testing each individual cell.
Every cell tested out to 7.9 or 8 volts, all except cell #8, which tested out at 6.7 volts. AHA!!! I had my culprit and now I knew I needed to just replace one bad cell. So I hopped online, looked at all my options and after reading several good reviews I decided to buy it from 2ndLifeBattery on eBay, for $29.95.
It would be about a week before arrival so why not use that time wisely and follow the cleaning advice recommended in this article!? I removed all the of the copper connectors and nuts from each cell and soaked them in a bath of vinegar for about half an hour.
 |
| dirty connectors |
 |
| connectors and bolts bathing in bucket |
 |
| dirty vinegar |
You can see that a good amount of dirt and oxidation came off in the vinegar, after which I decided to use my Dremel with a course attachment to buff each piece back to shiny.
 |
| Before and after |
 |
| All done and drying |
The replacement cell arrived and on 11-19-18 I installed it according to the videos I mentioned above. Here are some key tips that might help you in this process.
1. Make sure you number the cells w/ Sharpie before pulling them off, so that you can keep them in order when they go back on. It might also help to write down each cell's tested voltage on it so if you have to go back, you will have a reference point of what it used to be.
2.When pulling the cells off of the battery pack tray, be careful of the wires connected under some of the cells, especially the very first one to come off.
My issue was not getting it back in, but rather the fact that once I put the breaker back in, my volt meter would read no voltage on the two main leads that are supposed to connect back to the vehicle. I had about 220 volts before I pulled the breaker out at the very beginning of the project. Logic would assume that when I put the breaker back in, I would get 220 volts again, but alas I was getting no voltage at all. I took my battery back apart to double check my work and saw no issues with anything. Voltage was everywhere it should be but at the final two points at the end.
In the end I decided maybe the car has to start up in order for something to trigger the battery pack to engage voltage again (just a guess) and so I put it all back together and started it. It started fine, no warning lights and all was good. What I think I might have concluded is that what I call the orange breaker actually has a capacitor (or something similar) in it that needs to charge up before it will pas signal through to the main leads.
4. Above I say it "started fine" once the battery was back in but actually I had to jump the auxiliary battery to get it to start. This reminded me that I read somewhere that when the primary larger battery has issues it can start pulling too much voltage from the smaller auxiliary battery (or just cause it to over work) and actually damage the auxiliary battery. In my case the auxiliary battery was already pretty old and I think it did destroy it because it would not accept a charge from that point on. Swapped out that battery and all is well.
Okay, let's wrap this up. I am writing this blog because I got a lot of help from others who took the time to document their process but none of them did follow ups to let people know if the repair lasted any length of time. As my repair guy said, "if you only replace one cell and not the whole battery pack, you will have to replace another in a few weeks and then another a few weeks after that etc."
Well, we are going to find out. I will keep updating this to let you know how it goes. Oh BTW, total time working on this project was about 6 hours and could have been 4-5 hours if I had the tips I mentioned above.
Updates:
11-24-18 After nearly a week of good driving (I say good because it does have 560k miles on it and it is back to driving as good as it did before) the check engine light came back on. No other lights yet and it still feels like it is driving fine, so it could be something else totally unrelated. I will add another update when I have time to go get the codes pulled.
11-27-18 On my way over to O'reilly's Auto Parts, to get the check engine code scanned last night, and the check engine light went off. I still had them try to scan it but their OBD scanner couldn't sync with the Prius computer. They suggested I check the fuse for my OBD port to make sure it is working and off I went. Haven't had time to check that yet.
12/1/18 This just in! A day after my last post we were driving home from work, everything driving great with no lights on and we pulled up to a light. I then heard a "click" sound and every dash light came on again and the car would not move at all. I turned it off and let it sit for about 30s and then started it again. Now it would drive but without any battery so we limped it back to work. That is where it has sat for the last few days as we discuss what our next move is.
05/17/19 Shortly after the last post we decided to sell it for parts when Boulder Hybrids contacted us and said they would take it off our hands to put towards a trade in on a different car, we agreed. That trade in went towards the 2013 Nissan Leaf we are now happily driving.
Conclusion: Maybe you can fix your own Prius batteries... but I couldn't.
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