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Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004, to 2015 & Plug-in

Availability: Usually ships the same business day

Optima+kit  US$270.00  Year: 

If you need a battery for a 2000, 2001, 2002 or 2003 Prius click here.

Save time and work use same battery with smaller connectors Both are in stock! Both come with instructions! We recommend the battery with the Japanese style connectors (what comes on a Prius in North America) because it is less work to install! The only advantage to the battery on this page(D51) is that it has American style top electrical posts. You might need American style electrical post if you want to add a disconnect switch or you have already converted your car to use American style terminals but then you should just order the battery. If you need American electrical posts ok, If you don't click here to save time and money!

Fits all Prius 2004 + including Plug-in.

Also for a Prius 2004 to 2009 without Smart-key and without the Navigation system. If you Prius came without Smart-key and without the Navigation system the Prius comes with a smaller battery, S34B20R or Toyota part number 2880021181 or 2880021180. The battery tray is also smaller and it can be a tight fit. You can make it fight and our instructions tell you how! However,if are NOT installing this battery yourself or want a better fit get the larger tray. We sell the battery and tray together. You are going to end up with 35% more capacity and with a deep discharge battery. (You can leave the lights on etc. more times before battery fails.)

Price includes:

  • Optima D51 (D = Deep discharge, yellow top; 51 = group size) battery(We expect this battery to outlast the Prius because the Optima red top [more crank amps, fewer deep discharges] batteries last 10 years in cars where they have to crank the engine and are exposed to engine heat! The yellow top [deep discharge] should last even longer especially in a Prius! (no engine heat, no engine cranking) We have been selling the batteries for over 5 years and they are going strong in the Prius! [We asked!]) Here is the reply from one customer who bought the battery 8 November 2007: "No problems whatsoever. I have one red Optima that is 10 years old and still works fine!" P.G., Cherry Valley, CA
  • Our installation kit with new connectors and 5 pages of instructions.
  • Free shipping to all 50 states and US territories via ground to color areas of map below or via Priority Mail all other areas in US not colored on map below.
  • Price includes A write up on how to significantly reduce engine oil consumption.

    You should have your battery in 1 to 3 days! (Well, 4 if you order after cut off on Friday)


While you are waiting for your new battery we suggest you turn off smart key; if you have it. (Square switch by drivers right knee labeled Key.)

"Unbelievably good service!!!! I ordered the battery after 4PM and it was sitting on my back porch by 8:30AM the very next morning----just about 16 hours after ordering. WOW!!!!! Installation with the included instruction was a snap.

Thanks. Great to know such service still exists in today's world.
" H. S., Santee, California

"Just to thank you for extra fast delivery, I got it on Wednesday [He ordered on Monday.] - picked up in local post office and replaced old one." R. M., Franklin Park, Illinois

Hobbit talks about his Optima battery in his 2004 Prius. August 2013, after 5 1/4 years of use, Hobbit had this to say: "My yellowtop is still holding up great [despite the pounding and dust it's taking back there] but you know who I'll call if I need another one. Car just turned 200,000 miles!"

In stock.

For customers not in the US or territories we can often get you a battery in one to two days but it can be expensive! Look at our DHL shipping options and decide. You can also buy our installation kit as it is too expensive to ship the battery outside the US. Outside of the US you also may not need the installation kit. The Optima YT S 2,7J (available in Europe, the middle east and parts of Africa) has Japanese electrical posts and will work if you Prius has them. You can tell by looking at the battery. If it has electrical post that are only a little bigger than pencils (Japanese posts) the battery will work without a kit. battery The installation kit will work in Canada or Australia but not in Japan a Prius made for Japan has a battery with American electrical post.

The 12 volt battery provided by Toyota is a pretty ordinary flat plate sealed battery. We hear far too often about it failing within two years. Here is one example: "I'm going thru my 3rd Toyota Aux. battery in 6 years. Toyota replaced the others under warranty... Their/Yuasa batteries still STINK! I even had a "Battery Minder/Tender" on this entire winter to top off the Aux. Bat. It still stinks!" [and fails] K. B., Talent, Oregon The Optima does fail usually within 6 months but only at about at .5% rate and we have been selling this battery since Oct 2007. The batteries are holding up just fine! WE ASKED! We expect the Optima to last longer than 10 years as their batteries last that long when they have to crank the engine and are exposed to engine heat. (Neither of this occurs in the Prius. See chart below)

We have helped Prius owners install this battery in over 700 Prius!

"I want to say that the battery, kit, and instructions were excellent. I had no problem performing the installation, and am very satisfied and glad that I took the chance that I'd be able to do this myself rather than paying a Toyota dealership through the nose for an inferior product." D. P., Lafayette, California

What makes this a longer lasting battery?

    7.5x or more deep discharges - Thicker lead plates for deep discharges instead of cranking amps! (see chart below)

    15X Superior vibration resistance! - The tightly wrapped spiral design (see cut away image toward bottom of page.) provides superior vibration resistance so you battery is less effected by pot holes, construction projects, drainage ditches speed bumps and rough roads.

    Pure lead! - Because of the spiral design the lead plates do not have to be strengthened with an alloy and are 99.99% pure. This results in lower voltage drop as the battery discharges and contributes to the longer life of this battery!

    More capacity: 2 ampere hours more capacity and 2 pounds lighter than the larger Toyota (GS) Battery for cars with Smart Key or Navigation.

    Toyota with smart key3629.5
    Toyota with out smart key28 Note: May have to slide tray forward by looseing two bolts and lifting one tab but it will fit!
    Optima D513827.5

The Toyota GS Battery has free liquid acid that is not absorbed in the glass mat. Consequently, it can not be easily shipped to you. So if you wait till your battery is completely dead you might have to go to the Toyota dealer near you and pay whatever price they charge. PLEASE DO NOT WAIT! HOWEVER, WE DO SHIP Ground (Next Bus. Day if you are in CA, Western AR or Western UT) and PRIORITY MAIL so we often can GET A BATTERY TO YOU IN 1 to 2 DAYS!

Also Prius owners have told me the Prius acts very strange when the 12 volt battery gets weak they get error messages like: "P LOCK MALFUNCTION WHEN PARKING, PARK IN FLAT PLACE AND APPLY PARKING BRAKE SECURELY." Your MPG can also deteriorate for reasons we can not explain but this has been reported by several Prius owners.

This is the ideal battery for the Prius. We have sold them for over three years now and the battery has a less than 1% failure rate! On a Prius the 12 volt battery does not start the engine the high voltage battery does. You do not need the RED TOP battery which is configured to provide a lot of starting power. Instead you need a battery that can handle the slow stead drain than occurs when the car is parked from: the clocks, the memory chips, the security system and the remote entry and key less starting system. THIS YELLOW TOP BATTERY IS DESIGNED FOR THE DEEP DISCHARGES THAT THESE SYSTEMS CAUSE WHEN THE CAR HAS BEEN PARKED FOR A WHILE. (See comparison chart below!)

How much work is this to install?
    Normal car:
      You pop hood, disconnect battery terminals, unscrew hold down bracket replace battery and then attach above and close hood.

    Prius 2010 +: it is just two extra bolts plus the vent tube connections.

    Prius 2004 to 2009:

      Open trunk.

      Remove floor and plastic panels.

      You are replacing negative cable. One extra bolt.

      Positive terminal replacement requires removing of one extra bolt to connect a fuse assembly.

      This requires a vise or long handle adjustable wrench and a long handle socket set. The nut is on tight!

      The mounting bracket is a little harder as it requires a socket extender because there is plastic box in front of this.

      You also have to disconnect and reconnect the ventilation hose that connects to the battery but that is not a huge challenge.

      You also have to remove and reinstall a ventilation duct. (two bolts and a little finesse [explained in the instructions])

      So it is more work than a traditional car but very doable if you have the tools!

      Minimum tools needed:
      • Flat screw driver
      • 10 mm wrench or 10mm deep socket
      • 10mm socket
      • socket extender
      • 12mm wrench or socket
      • 1/2 inch wrench or 1/2 deep socket (13mm will do)
      • vise, large adjustable wrench or vice grips
      • tape
      • a small battery or jump start battery to maintain the 12 volts in the Prius so you do not loose any presets. (Optional but recommended!)
Our free shipping is next business day ground (to the California and western Nevada, including: Las Vegas & Reno & Arizona including: Phoenix, Flagstaff & Tucson ) or Priority Mail (2 to 3 days)! If you need the battery as soon as possible let us know in the comments or call us at 818 364 9810. We will do what we can to get it to you as soon as possible!

The three main contributors of premature battery failure are:

  1. Vibration which causes distortions in the plates and eventually shorts.
      This battery is made by sandwiching the acid filled mat and the lead together and then tightly wrapping them in a spiral. This reduces vibration by 15X as a cause of battery failure.

  2. Repeated deep Discharges
      This Yellow Top battery is also thicker lead plates to handle repeated deep discharges not huge starting currents. Leaving the lights on a few times will not kill this battery! My battery in a 2001 Prius is over 5 years old and still going strong after leaving the lights on twice!

  3. Heat!
      Yes batteries have less output when cold but they also last longer. In a Prius that is partly handled because the battery is in the trunk not the engine compartment!

If you want a battery that lasts longer. This is it! You will pay about the same at a Toyota Dealer but this is a better battery! We offer free shipping on this battery via UPS to the Southwest and or Priority Mail to the rest of the 50 states Hawaii, Puerto Rico and other US territories! You should have your battery in 1 to 4 days!"

_____ is Optima red top battery _____ is Optima yellow top battery

soc-% state of charge ocv - open circuit voltage for deep cycle

soc ocv
100 13.18
90 13.01 The 2004-2009 Prius has a drain of approximately 12 milliamps with smart key turned off (Thanks hobbit). After two weeks the battery would still be at 95% soc and the battery good for 10,000 cycles. However, age and heat also effects batteries.
80 12.83
70 12.65
60 12.46
50 12.28
40 12.08
30 11.89
20 11.68
10 11.48
0 11.27 Look at the graph! A battery with thicker lead plates to take deep discharges (yellow top) has 7.5x(300/40) the life compared to the red top!

The US Prius models come with batteries with Japanese size electrical posts. We provide an installation kit with new electrical connectors and a connector and plug to allow you to connect the vent holes in this battery to the vent tube in the Prius. This Optima battery can replace the Toyota 12 volt battery for the Prius with Smartkey or navigation system Toyota part number 28800-21170, now 28800-21171 (GS Battery # S46B24R) or for a Prius without the Smartkey or navigation system Toyota part number 280021050.

Comments from customers who have used this battery in the Prius for over a year!

"The battery has performed absolutely flawlessly and is one of the best improvements you can make to a Prius . Easy to install, everything is included.

In general, I am totally sold on Optima batteries; I use them for my cars and boat, my oldest one is about 10 years old and still works.

Toyota puts so much emphasis on how the Pruis main battery lasts the life of the car; but what they don't tell you is that the accessory battery is a cheap ass lead acid that, even in a best case scenario, will be dead after 5 years. The Optima should correct this issue and bring the accessory electrical system to the level of the rest of the car.

My factory battery died when one cell failed; the car was 1 year old at the time. As you know, Prius, with all its electronics does NOT have a simple circuit to shut down the interior light! It is therefore only a matter of time until one does not shut the door all the way and the next morning the battery is completely dead. This is what happened to me twice. When I charged the factory battery for the second time it failed. The symptoms were somewhat strange as it would still run but after sitting a few days it would not.

It is good to know that with the Optima kit the chances of recovery are much better . And I don't think I'll ever have to worry about having to replace it due to age.


P. G., Cherry Valley, California

"I just wanted to let you know that the Optima battery in my '04 Prius has been great. We had a few sub-zero mornings last week -- the kind that in the past, with the OEM battery, had me running a long extension cord and portable charger out to where my car is parked overnight to get it started. I had been taking to turning off the keyless entry system to try and avoid a cold-morning dead battery. I found the OEM battery to be the car's achilles heel, because when it is weak, you have to resort to the physical key to get in the car, and even then you can't get the back hatch open to access the battery.

But this winter with the Optima battery in place, not an issue. No matter the temperature, the car 'boots' properly, so all other systems, including the gas engine, start up without problem. I've always been a fan of Optima batteries, and adding one to my Prius brings up the 12V traditional electrics up to a quality level commensurate with the rest of the car.

Thanks for a great kit to install the battery.

M. A., Fort Collins, Colorado

"I've had no problems since I replaced the battery. The sound system sounds great. I haven't let the battery discharge deeply (I've learned to turn off the wireless key when I'm on vacation), but I trust the yellow optima is the right battery for a deeper discharge and a good choice for this application."

J. G., Monte Sereno, California

From the manufacture:

optima spiral technology

The unique design of the SPIRALCELL TECHNOLOGY. provides many features not available in ordinary batteries. The following is a summary

SPIRALCELL TECHNOLOGY PROVIDES: More plate surface, closer plate spacing, ability to use high purity lead. RESULTING IN: Low internal resistance. This low internal resistance gives you more power in a smaller box, ability to recharge much faster and higher cleaner voltage characteristics during discharge

Immobilised plates (locked in place). RESULTING IN: Improved vibration resistance, no shedding of active paste material, lower gradual loss of power and capacity as the battery ages. This gives you a battery that lasts longer and performs better throughout its life.

  • Voltage 12 (12v or 12 volts)
  • Amp Hour 38
  • CCA* 450 (Cold Cranking Amps)
  • Shipped fully charged ready to install
  • Maintenance-Free
  • Valve-regulated absorbed glass mat (AGM) eliminates acid spills and terminal corrosion.
  • Vent hose holes for emergencies in case the battery is heavily overcharged. (You need a connector and plug that we provide with our installation kit)
  • More than 15 times the vibration resistance of an ordinary battery.
  • Last up to twice as long
  • Length 8.9" and 9.15" at top cover
  • Width 4.5" and 4.9" at top cover
  • Height 9" including posts
  • Weight 28lbs
  • Warranty: 3 year exchange, excludes damage due to misuse or neglect, improper charging or improper application of battery
  • Free shipping to all 50 states and territories: Ships the same business day you order via UPS ground or Priority Mail! Just select the shipping method "Free to 48 states for $50 order"

The Federal Magnuson-Moss Warranty Act of 1975 prohibits a manufacture from curtailing warranty coverage due to after market parts unless it can be demonstrated that they caused the problem. (For more information look for "Federal Magnuson-Moss Warranty Act Tie-In Sales" Provisions.)

This sealed battery has little free liquid electrolyte because it is absorbed into the glass mat. Consequently, there is little acid that can spill into the trunk even if the case cracks. It also has attachments for a vent hose so any gases are vented outside of the car. The battery does not normally emit gases but can do so with heavy over charging with pressure building up and the valves in the batteries releasing. This should not normally never occur because the Prius high voltage to low voltage converter puts out around 13.8 volts. 13.8 volts is the voltage the battery puts out at no load and at that voltage the battery can not be overcharged and it is the maintenance voltage for the battery. However if one cell shorts out or the voltage unexpected goes high gassing can occur.

The 12 volt battery is not used to crank the gasoline engine in the Prius but it does supply all the 12 volts circuitry which includes all of the computers in your car. If this battery fails, the computers will not start and the Prius will not start. A weak battery can also pull the 12 volts power down to a lower voltage. This can cause problems with all of the computers that control your car. (When I had a problem with my car the first thing the dealer insisted I do was replace the battery. The problem was caused by something else but the battery was weak.)

Since the 12 volt battery does not start the gasoline engine you can still use the car with a very weak battery. So much so that at least three Classic Prius users have told me that their Prius now gets better mileage with the new battery. I am now starting to get these stories from 2004 + owners also for example:

"The MPG skyrocketed in my car after the battery replacement. I was getting 37mpg on the freeway and now its over 48mpg. Thank God!"

So if your 12 volt battery is very weak and your MPG has deteriorated a weak battery could also be affecting your gas mileage.

If in doubt check the voltage after the car is started. (see procedure below) If it is at 13.8 volts or higher then the high voltage to 12 volt converter is operating and charging the battery and it is probably not the battery that is causing lower MPG. Click here for more information on other things to check for.

Has your 12 volt battery failed? Prius battery test procedure for 2004 to 2012+ Prius Cars

Prius not starting?

The traditional load test is for 12 volt batteries test your battery ability to crank the engine. The 12 volt battery on the Prius never does this. The high voltage battery does. (So you might be able to get a few more years use out of a battery that fails the load test. However, the less capacity your battery has the shorter the period that you can leave your car parked before you need a jump. It can also affect mileage.) The 12 volt battery only has to maintain the electronics in the car (security system and remote sensors) while the car is parked and then have enough juice to start all the computers and all the 12 volt systems in the car on start up. Once you have started the car a high voltage to 12 volt converter takes over and charges the battery.

So perform this test after the car has been parked for as long as it would be normally parked to see how the battery holds up under the drain from the security system, clock, memory chips etc. Ideally first fully charge your battery with a charger for sealed lead acid batteries then let the Prius sit parked. (If the Prius is not driven much the charging is very important.)

  • The transmission should be in Park with the ignition off.
  • Engage the parking brake
  • Push in the power button. (if not already on)
  • Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times.
  • Push on Menu in upper right of display screen.
  • Push on Display Check
  • Push on Vehicle Signal Check
  • You will see the 12 volt voltage displayed. In accessory mode the voltage should be 12.6
  • With no electrical accessories on including lights the voltage should be fluctuate between 12.6 and 11.9. The lower the voltage, the less of a charge your battery currently has. If the voltage is low do not proceed as the load test might totally discharge your battery. (If you see a voltage around 13.8 you are seeing voltage from the high voltage battery being converted to around 13.8 in an attempt to recharge your battery. This normally does not occur till after you start the engine but might occur earlier if the battery is very drained.)

  • You can also test the battery by turning on the headlights, rear window heater and the heater fan. For a new battery the voltage would be around 11.3. If the voltage drops below 10.2 it should definitely be replaced. For voltages in between the lower the voltage, the lower current charge of your battery.
  • Push on the brake pedal and push start. You should see Ready in the Speed display. The voltage should now read between 13.8 to 14.2 and higher in winter. This is the charging voltage!

2004 to 2009 Prius Customer comments:

"The new battery is perfect. Thanks for the kit. Installation was easy. On the OEM battery when I'd close the windows after shutting off the Power switch the battery voltage would drop to 11.8 or less. The new Optima only dips to 12.4 volts.

Also the shipping was perfect. The cardboard container is very cleverly designed. Thank you for sending such a heavy item without charging and arm and leg for shipping." C. M., Bainbridge Island, Washington

"I installed your Optima battery kit tonight in my '04 Prius. Shame on Toyota for making battery replacement so hard, and Kudos to you for making a nice replacement kit and good instructions!

J. H., Minneapolis, MN

Please Note: California Proposition 65 Warning Battery posts, terminal, and related accessories contain lead and lead compounds, chemicals known to the State of California to cause cancer and reproductive harm. Wash hands after handling.

Save money and less work to install use same battery with smaller connectors Both are in stock! We recommend the battery with the smaller connectors because it is less work to install! The only advantage to the battery on this page(D51) is that it has stronger larger connectors (thumb size versus pencil size). As long as you do not over tighten the connectors you do not need this advantage. Both come with instructions!

Availability: Usually ships the same business day

Toyota Prius 12 Volt Auxiliary Battery with install kit for 2004, to 2015 & Plug-in Optima+kit  US$270.00  Year: 

Air Filter for Prius 2004 to 2009 - extend the life of your hybrid battery
Air Filter for Prius 2004 to 2009 - extend the life of your hybrid battery

Prius 2004-2009 did not come with a filter for the hybrid battery cooling air.
Prevent premature failure from overheating!
Keep your fan and the top of your battery from clogging up!

Air Filter for Prius 2010 to 2015 - extend the life of your hybrid battery
Air Filter for Prius 2010 to 2015 - extend the life of your hybrid battery

The cooling air intake is about 6 inches above the seat bench so a lot of dirt can get sucked in in when the fan is running. Plus the fan blows straight in to the bottom of the pack. About 1/4 of the dirt sucked in ends up in the cooling passages between the modules. YOU CAN PREVENT THIS WITH A FILTER THAT JUST NEEDS TO BE VACUUMED OCCASIONALLY!

Ev (Electric Vehicle) Mode switch for Prius 2004 - 2009
Ev (Electric Vehicle) Mode switch for Prius 2004 - 2009

List price: US$50.00
Sale price: US$30.00
New hybrid Batteries and recharge rather than replacing!
New hybrid Batteries and recharge rather than replacing!

Repair the Prius hybrid battery and save!

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