Aux 12 volt battery replacement - upgrade the tray - for non smart key

Our '06 prius is the model without the smart key and without navigation. Since I am replacing the 12 volt auxilary AGM battery anyway, it seemed prudent to update to the same battery that came for models with a smart key. That way, I'm getting a bit more amp hours 36 AH vs 28 AH. Some are as high as 46 AH. I'm finding that the larger battery is much more common to find, while the smaller battery is only available as Toyota OEM. It appears that the only item to change is the battery tray, right?

Upgraded Tray: Toyota Part No.: 74440-47020 (about $15)
"Smart Key" upgraded Battery: S46B24R
Original battery for reference: S34B20R

The battery bracket, hold down, carrier, cables and vent tube appear to be identical between the two different battery versions when I look at the parts on toyotapartsdeal.com

 

Excellent. Thanks for the update on the AH as well.


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Results:
I purchased a Duracell SLI51PAGM / S46B24R battery (larger 46AH version for Prius models with the smart key). 48 month warranty; $50 less than Toyota; better battery specs. I also swapped out the battery tray with the larger one mentioned above. An annoyance with the tray is that Toyota decided to have one of the mounting bolts be a 9.5 MM head, despite being the same thread diameter as the 10 MM head version next to it. They do the same thing on the negative battery lead where it attaches to the chassis ground. I was unable to find a 9.5 MM socket locally and had to carefully use vice grips to extract the bolt. I'm sure this behavior by Toyota was on purpose to encourage replacement at a dealer. Sorry Toyota, I foiled your dastardly plans.

To keep all memory on the car's computer and radio I used my CTek7002 8 stage smart charger that has a 12V supply mode, connecting it to the jumper wire in the fuse box under the hood. This charger also has an AGM mode. I used it to top off the battery overnight after install. The existing battery read 12.71V after removal; the new was 12.84V prior to install. The Duracell was manufactured in April; purchased in July. I know from having AGMs in an RV that they typically lose about 1% of charge per month when not connected to any parasitic draws. (Conventional flooded cell batteries can lose up to 10% per month). After install I did a final road test to confirm no surprises.


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The battery was last replaced in 2008. There was a trouble code by the prior owner in the log from April 2008 that indicated a possible relationship to an aging auxiliary battery. It tested out ok in a recent inspection, but the ASE mechanic who has owned several Gen 2 Prius suggested also to consider replacing. Thus, I went ahead and replaced it due to age / preventive maintenance as it is my wife's car and wanting to minimize a potential reliability liability.


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Indeed!


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April 2018 trouble code date above, not 2008. The battery replaced was from 2008.


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That's right. The 1st battery was replaced after 2 years old by the original owner on 5/31/2008 at 12,888 miles. Service record: "Customer states that vehicle won't start. Replaced battery. In 2008, the battery was $138.70 and the owner was charged $20 to install it. Kinda sad that it wasn't considered a warranty item at the time. Now the battery from a local Toyota dealer was $228.74 for this smaller battery. I'd say the price has gone up some! I was happy to upgrade to the higher AH model that I paid less for and got a 48 month free-exchange warranty.