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I take great pride in learning more about the spaceship we call Toyota Prius. I especially love writing about how to keep them maintained properly, and what to do when parts need replacing.
A common issue that many Prius owners face all the time is that blasted 12v battery. It always seems that the 12v is going dead, or causing issues with our cars. I want to take a look into why this is and what you best replacement option is when it comes to taking care of the problem.
I have been at Weber State University this week studying with Professor John Kelly who has become a YouTube sensation for his work on hybrid and electric vehicles. I was able to chat with him at length about problems with the 12v system and why people are having issues with them. His responses were astounding.
AGM vs Lead Acid
Absorbed Glass Mat or AGM batteries are in all years of Toyota Prius. The only exception to this is Prius Prime. The reason they are used in our cars over lead acid batteries is because they do not spill. In the even of an accident the battery acid could leak in a regular battery and cause issues with getting acid all over next to the high voltage in your trunk. AGM is also a battery that can take abuse and keep on working, it is also better in extreme climates as well. The downside is one of these can easily run you between $150 to $235 depending where you get it from.
Lead Acid on the other hand is cheaper and still gets the job done, however due to the differences in the makeup of the batteries the charging system on the Prius is designed to charge an AGM battery, not a Lead Acid. This means that even though a Lead Acid may work, your car will not charge it properly and it will fail sooner than you want it too. So while it may seem the LA battery is the cheaper option, you may end up spending more over time vs getting the right battery for the right job.
According to Prof. Kelly, if you want the vehicle to function as designed, use what battery is required for the car.
Choosing The Right AGM
While talking to John, I relayed to him that at my school we have a 2004 Prius with a 12v battery that keeps going dead. I told him we spent quite a bit of money on our yellow top optima. He chuckled and proceeded to tell me that not all AGM batteries are created equal.
The Toyota Prius battery from the dealer can easily run you upwards of $235 dollars. For a battery that hardly does more than power up some computers and allow the high voltage system to come on, this can seem like a lot. In fact, that it just about all it does, really. It does not get used all that much. This is one reason that these batteries fail. They just are not maintained as well as they probably should be.
There is also another side to this story, and it is one I have been dying to tell everyone. The aftermarket batteries we are buying at autozone, walmart or wherever are not being built to the same standards as the Toyota OE ones. This means that the internal resistance of each battery, even though it is for Prius, will not yield the same results as the one you get from the dealer.
Three batteries that I looked at were from Autozone, O'reilly and NAPA. Each one has a 3 year warranty and all cost between $199 and $237 dollars. The Toyota Truestart battery runs between $176 dollars and $237 which is basically the same as aftermarket. It also carries a similar warranty as well. I am sure you can see where I am going with this.
Conclusion
It may seem silly to spend that kind of money on a 12v battery and especially one from your local Toyota dealer. However, if you are a Prius enthusiast like myself, you should be able to see that the right battery for your car is the Toyota Truestart AGM battery. It is designed to charge and discharge at the optimal rate that your Prius monitors with the DC-DC converter.
Just like choosing the right brake pads for your Prius will save you in the long run, the right battery will give you the right results.
I hope that you have enjoyed reading about new Prius Technology. Check out my other story 3 Top Tire Brands You Should Consider For Your Toyota Prius to find even more ways to make that fuel sipper go the extra mile.
Also Watch 5 Things To Know About Toyota Prius Battery Maintain it Well and Click to Subscribe to Torque News Youtube Channel for Daily Toyota Prius and Automotive News.
Peter Neilson is an automotive consultant specializing in electric cars and hybrid battery technologies. He is an automotive technology instructor at Columbia Basin College. He holds a Bachelor of Science in Automotive Service Technology from Weber State University. Peter can be reached on Linkedin and at Certified Consulting.
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Comments
Agree, and it's not like
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In reply to I maintain 10 Gen 2 prii, by Nicholas D Haines (not verified)
Agree, and it's not like Toyota makes the battery anyway... I got an Interstate AGM Group 51 for $150 after rebates at Napa, and wish Costco would carry those as they are cheapest (all my other batterie) and best 6y pro rated warrantee, but thy don't carry Prius ones. I could fit an $80 lead acid Group 51 (or even deeper one), and get mount adapters, but no venting (since the living space, not real trunk like BMW) and acid spill inside compartment made me decide on teh real AGM ones...
Anyone know of anybody,
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Anyone know of anybody, anywhere, that still makes a battery that fits a first generation Prius? The Truestart's aren't made for them anymore, and Optima doesn't appear to be making anything for them either. Thanks
YES, I do, WALMART lawn
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In reply to Anyone know of anybody, by Jim (not verified)
YES, I do, WALMART lawn tractor battery. I still own 2003 Prius. Original 12volt lasted about 5yrs, when it died I did not have $235.00 but I had 40 so off to Walmart I went with a ruler. As I recall the positive terminal needed some modification. Since then, every 4 years (before it fails) 'cause if you wait you wont like the timing. And if you replace it with the car running ( ON ) the car doesn't care, no errors, no problems. And cheap. Also own 2008 Prius and it also has lawn tractor battery. 2008 when 12volt bat dies open hood and apply 12volts DC or at least 10.5vdc to the jumper post and then open rear hatch and again R&R the battery with the car "ON"...
Installed an Optima yellow
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Installed an Optima yellow top in a 2011 Prius in the spring of 2014. The car is driven infrequently (after 9 years has 36K miles). The Optima has never failed. Thinking about connecting a trickle charger anytime the car isn’t started for more than two weeks. Other recommendations? Thanks
Take a jump box with you. Can
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Take a jump box with you. Can save you cussing out the world with a dead battery for whatever reason. My father in law is 'cheap' to nearly the extreme. He has been jumping his 2014 Prius for many months now. Half the problem is he doesn't run it often enough. Anyway, it works for him, takes a few minutes for the system to come up from 'deader than a door nail' but he's happy.
I left my low mileage 2014
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I left my low mileage 2014 Prius C3 sitting in the Florida sun with a friend taking a drive every few weeks. The 12volt battery apparently died and AAA will not come replace it. Any suggestions?
The main article by Peter
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The main article by Peter Neilson is pure long-winded hog-wash. Why would you push a Toyota product, hmmmm ... makes one wonder.
I thought this exact thing.
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In reply to The main article by Peter by panjurli bhoota (not verified)
I thought this exact thing.
My 2016 Prius 2 has an OEM
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My 2016 Prius 2 has an OEM lead acid battery.
GS YUASU 345LN1-MF
My 2020 Toyota Corolla Hybrid
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In reply to My 2016 Prius 2 has an OEM by Duane Bryant (not verified)
My 2020 Toyota Corolla Hybrid basically has the heart of the Prius transplanted literally just underneath the hood and also the power train also as well. Even the OEM lead acid battery is the same right down to the same Toyota OEM proprietary GS Yuasu 345LN1-MF also as well.
Long winded sales pitch for
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Long winded sales pitch for Toyota. How much is the commision? I use an AGM battery made from a chain auto parts store. Going 2 years strong with no issues.
Just bought 2013 Prius from
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Just bought 2013 Prius from my work. Car sat for 8 months. 12 v battery was dead I jumped it and was able to start the car and drive home. Once I shut it down would not start again. Attempting to charge battery now took out of circuit to charge.
Hoping that does trick.
Should I be worried with the drive batteries setting so long?
I have an 05 Prius with 310
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In reply to Just bought 2013 Prius from by Brian (not verified)
I have an 05 Prius with 310,000 miles I have owned since 2007. The original 12V battery lasted six years. The Optima batteries certainly look impressive, but my last two lasted 36 and 38 months, and my mechanic picked up an OEM battery from the local Toyota dealer this time. I doubt it would do any worse than my last two Optimas. My experience seems to be similar to the author's impression.
I am beginning to suspect
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I am beginning to suspect based on the wording of this article that it’s a shill. AGM is AGM. the only thing that matters is quality. Generally speaking, you want the battery in any vehicle to have as low of internal resistance as possible so it charges as efficiently and quickly as possible.
Yes the actual AGM battery
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In reply to I am beginning to suspect by Carly (not verified)
Yes the actual AGM battery design product quality matters a great deal; as that tends to promote AGM battery desired longevity and reliability characteristics; I would generally be ok with using a group 35 sized AGM battery ordered from RockAuto; after I checked that the specifications were first satisfactory and actually met the expected specification; currently that AGM battery is about $165; while the Toyota OEM is considerably much more costly but it will last for the full six year expected OEM specification; the gamble here is the RockAuto AGM battery example would have to last a minimum of at least four years to break even; which it probably easily be able to actually do in real life. Then there are those consumers who actually want the full expected OEM specified six years AGM battery design life and are willing to pay about $85 extra for that premium to get that full extra two years.
Now I would personally try both options; so long as the potential risk was acceptable to the potential end user AGM battery customer naturally of course; and then decide to go with the better perceived option depending on ones actual positive or negative perceived potential outcome. Now your actual opinion or preference may vary of course naturally on this important matter also of course so please decide accordingly to what one may perceive as the best value received for the price paid for both AGM product choices hopefully.
My son has an infrequently
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My son has an infrequently driven 2013 Prius. Can a NOCO Genius 5 charger maintainer be used on the 12V accessory batter 24/7 to keep it in top condition?
NOCO Genius 5 is the best
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In reply to My son has an infrequently by Henry Tupis (not verified)
NOCO Genius 5 is the best charger on the market today. It is very safe and have really good reliability compared to CTEK fragile capacitors and diodes. I used it and it works really well without going overcharged. My battery is 6 years old and after 4 hours of drive, the maximum voltage is still only 12.5V. NOCO 5 is able to charge it within 2 hours to that level and stay there even after I leave it overnight. A cheaper Unknown brand Chinese battery charger often keeps charging at a small current and degrade the battery over time. Other alternatives are BOSCH C3, ALDI, and LIDL charger, it is really good but will not continue charging after an outage.
I wish someone would just be
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I wish someone would just be straight forward and just say what battery is best to use for our Prius'? Give the top 3 besides the Original yellow top AGM OEM please!
Rockauto which always has
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In reply to I wish someone would just be by J (not verified)
Rockauto which always has generic decent quality agm batteries for sale to pick from that are under $200 simply just look up ones specific prius model and year make vehicle and look at the specific agm batteries for sale and decide accordingly.
How can you tell if the
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How can you tell if the battery is chargeable and needs to be replaced? Can one charge the Toyota Prius 2008 battery with a battery charger ? The battery ran down because I did not use the car for a few weeks.and probably left the light on.
One can invest and buy(for
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In reply to How can you tell if the by Shri Kulkarni (not verified)
One can invest and buy(for about $75 on amazon) what is called an automotive battery trans conductance tester; it will indicate among other things one actual battery reserve capacity to hold a charge; this is quite handy piece of information to actually have as it will tell one well in advance before ones automotive battery fails without warning.
This is very important and useful information to have so that one is not suddenly stranded out in the middle of nowhere during cold weather in particular. Life is good when one can avoid unforeseen bad circumstances from happening down the line; so its a good thing to invest ones money in a potential automotive battery trans conductance tester.
Recently there have been a
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Recently there have been a number of YouTube videos describing the virtue of car camping or outright living out of a Prius. Two assertions which were made several times seemed interesting.
While parked with the air-conditioning on, the Hybrid battery will run the AC until it discharges sufficiently, then the engine will auto start and recharge the Hybrid battery to some point then shut down. After an amount of time the Hybrid discharge and engine recharge cycle would repeat. I have a 2014 Prius V with 75,000 mi on it. I tested the assertion and sure enough in a closed up car on a warm day, with the AC on, monitoring the Hybrid battery on the energy display, the battery would discharge down to two bars out of eight then the engine would start and recharge up to three bars then shut off. I let this go 4.5 hours like that. I had noted the range left in the tank at the beginning and it was 171mi. After the test it displayed 167mi. So, if that was correct, I used 4 mi worth of gas. I average 40 MPG so that was 1/10 of a gallon. One YouTuber claimed Uber and taxi drivers sometimes left their car on for over a month at a time.
The second “tip” given by a car-camping person was that in stead of using a Coleman stove or propane stove he used a microwave oven plugged into a 1500W inverter which was connected to the 12V Prius battery. He stated that it would work the same way, with the engine recharging the 12V battery. I didn’t want to buy a large inverter to test this.
So I have a couple of questions. Is the constantly discharge/recharge of the hybrid battery causing any problems? And what is the truth about the 12V being recharged while in park. If the 12V is recharged automatically, what is the effect of an inverter hooked to the stock battery?
Not at all; the constant
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In reply to Recently there have been a by Dave H. (not verified)
Not at all; the constant recharging and discharging is not a critical aspect of operating ones car accessories even ones air conditioning. All one has to be careful and be aware to notice or observe is to never put ones car in neutral when one has their air conditioning accessory on; as one will then allow the depletion of ones 12V battery.
Yes for example it is preferable to connect ones portable air compressor to ones battery leads since then does not have to worry about overloading and interfering with ones current draw on ones air compressor for example.
Thanks Daniel58. Good point
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In reply to Not at all; the constant by daniel58 (not verified)
Thanks Daniel58. Good point about being in Park. That addresses the AC question. My other question has to do with hooking up an inverter to the 12V. 1. Does the auto recharge from the engine work the same way with the 12V when parked as it does when you’re driving? And 2. How tolerant is the stock 12V to having a high capacity (say 1500W) inverter installed possibly increasing the number of discharge/recharge cycles?
Does the vehicle recharge
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In reply to Thanks Daniel58. Good point by Dave H. (not verified)
Does the vehicle recharge from the engine work the same way with the 12V when parked as it does when driving?
The good news it does recharge the 12V battery from the hybrid battery which is recharged by the engine directly.
How tolerant is the stock 12V battery to having a high capacity inverter installed possibly increasing the number of discharge/recharge cycles?
I have a Toyota Corolla Hybrid vehicle which is basically a Toyota Prius engine with a Toyota Corolla vehicle body.
The 12V battery if drained by high enough capacity inverter, would then be recharged from the Toyota hybrid battery which is then recharged by the engine directly.
Edit suggestion: your car
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Edit suggestion: your car will not charge it properly and it will fail sooner than you want it *yo*.