Okay. Who HASN'T had a 12V battery issue with their 2023-24 Prime?

Although the TrueStart replacement is noticeably bigger in capacity to the OEM. I think it's 470 CCA for the TrueStart vs something like 320-370 for the OEM.

OEM might even be below 300, but I'm not certain about that(the OEM is not rated using the same method as the replacement, so I can't do an easy apples to apples spec comparison).

 

Not sure where you are getting that from, but no, the TrueStart H4 is a 45-Ah battery—same as the OEM GS Yuasa LN1/H4/140R. My Uplus LN1/H4/140R battery is 50-Ah (80 RC). I have not seen any battery with higher than 50 Ah in this group size. I think yours is 74 RC, so 45 Ah.

Yes, the CCA difference is only due to different measuring standards. You can’t have a high CCA with a flooded cell. Mine is very high (570 CCA) because it is AGM.

 

Looking back at the photos of my old battery, I must have gotten the idea from the label where it says: "CCA 285A". I suppose it might mean something else, but that seems pretty clear.

 

Again, that's a different (EN to be exact) testing standard.

It only says 74 RC for the capacity. Mine is 80 RC/50 Ah. Now, the problem is that the RC specs are somewhat unreliable. So, your 20-hour Ah spec is perhaps 50 Ah or, perhaps, 45 Ah.

 

It seems adhered to the battery in some way - I’ll call dealership on Monday and ask direct questions at this point. It certainly no attempt to place something surreptitiously - my quick-connector for my tender is in the same general space.

 

Perhaps just an inventory tracking device they forgot to remove? Perhaps it proves their system is not working well.

 

OK, I have verified that the Toyota TrueStart H4 battery is rated 50 Ah for C/20 (20-hour) discharge. The “50” in the part number indicates the C/20 Ah capacity. Therefore, it is higher than the 45 Ah for the OEM GS Yuasa. 50 Ah is as high as it gets for the EN LN1/DIN H4/BCI 140R group size. It is still a flooded cell like the OEM though.

https://www.toyotapartsandservice.com/wp-content/uploads/2023/09/03_Batteries2023_hi.pdf

As for the CCA, you can’t compare apples to oranges. GS Yuasa clearly labels the rated CCA as 285 A (EN). TrueStart CCA is not EN but likely SAE. For example, the approximate conversion between DIN and SAE is that SAE CCA = (DIN CCA) × 1.5 + 40; so, 285 A would be equivalent to 470 A according to that formula. Moreover, for a given battery type and size, CCA and Ah are inversely correlated, as you need to choose between the power-battery (high-CCA) or energy-battery (high-capacity) architectures.

Guide to understanding battery specifications

 

After the battery went flat on my 2023 Prius Prime for the second time I read the service manager the riot act and told them to keep the car as long as it took to figure out what was causing the problem because it's neither 'normal' nor acceptable. They kept the car for 4 days (gave me a loaner) and ran tests that regional told them to do. The final verdict was a software bug that kept the car's computer constantly pinging Toyota's server. Somehow, this was running down the 12V battery. They replaced the battery and told me to update the phone app because they thought it might re-introduce the software bug. (Funny, because I had deleted the app months earlier). Do I actually believe what they told me? I'm very dubious, because if it's true then they should issue a publicly announced recall for the car and update the firmware on every car, which obviously they haven't. If it happens again to me I will definitely invoke the lemon law here in CA and ask for a refund or replacement.

 

The lemon law will not get you anywhere. Besides, the replacement would be identical.

It is not a software bug. It is the nature of the 12-V-battery management system (BMS). Get a Noco Genius ASAP and recharge the battery now, not later, and recharge it every few months or if the car is not driven for more than a few days. This will eliminate all battery problems.

 

I totally disagree with you. The dealer (and by implication Toyota) has already acknowledged that the problem I had was indeed a defect and they HOPE they have corrected it. And that's EXCACTLY what the lemon law was designed to address.

 

That's not what the lemon law covers. There are far less reliable cars than Prius. Having two battery drains in two years or even in one year is hardly a reliability issue.

Good luck!

 

Even though I got a new Toyota Everstart Battery when they delivered my car (the one in the car on the lot was dead) what a difference after leaving on the Noco Genius 2 for 4 days.
J

 

Yep, there are (mainly) two reasons why the Prius batteries fail: (1) They come with a low SOC from the dealer when you buy the car and/or (2) the car is driven for less than 40 minutes a day.

The solution for both reasons is the same: Use a Noco Genius or similar battery maintainer to recharge the battery. Every new Prius owner should recharge their battery with a Noco Genius immediately after they purchase the car. This should be the first thing they should do as a new owner. That is because the Prius 12-V-battery management system (BMS) is miserly and will not fully recharge a battery with a low SOC.

It is not a software bug. It is not because you got a lemon. It is not telematics. It is not because you leave the car plugged in. (Don’t leave it plugged in unnecessarily though.)

 

When you're street parked charging is nigh impossible. Then maybe a 12 volt disconnect. That messes up the trip meters and sundry though. With our 3rd gen it also means the next few start-ups are "different", odd rev-up, think it's recalibrating something. A pretty funky adaptation, too bad they can't permanently store more of the volatile memories, say with some sort of flash drive.

 

If you don’t have a garage, you definitely want to demand the dealer to fully recharge the 12-V battery before delivering the car. In fact, this is part of the predelivery checklist, but which dealer follows it?