Gen 4 12 Volt battery.

NAPA had a direct replacement? I believe it is Japanese size.

 

Can you post the battery's identifier stats, name, part number or whatever? Thanks.

 

It’s a Japanese adaptation of a European size. As @padroo pointed out in post #1 of this thread, BCI now has a group number, 140R, with the same 207 mm × 175 mm × 190 mm case size and terminal arrangement.

From the photos @KeanuMok kindly shared, I believe it’s the NAPA BAT 75140R.

 

That’s what @Elektroingenieur is saying. It has been sorted out by a new size designation. 140R.

 

Part of the problem has been that there are multiple designations and designation systems, some of which have only recently been used to describe batteries available in the U.S. aftermarket, and not all of which are used consistently by sellers. Toyota didn’t help matters with their “no size listing” statement, either, though the 2017 edition of their battery application guide (PDF) mentions the “H4” designation.

The case size (207 × 175 × 190 mm) and terminal layout came from the European EN 50342-2 standard (successor of EN 60095-2), which also defines other sizes; that one is known as size “LN 1.” That standard was adapted for Japanese use, as previously described. BCI subsequently assigned 140R as their group number.

At this point, I think it’s safe to say that any LN 1, 140R, or H4 battery would fit physically in a fourth-generation Prius or Prius Prime car, and most would also be suitable electrically, considering the relatively undemanding requirements. Since the battery is under the hood, a flooded (wet cell) lead acid battery, as Toyota installs, will do; an AGM battery is required only for previous models that have the battery in the passenger compartment.

We also had a report of a successful replacement with a battery having the BCI group number 26R. This group has a similar case size, 208 × 173 × 197 mm, and could be a reasonable second choice if an LN 1, 140R, or H4 battery isn’t available.

 

I can't see why MPG would be different with 12v battery - it should be unrelated.

When you sat in the parking lot charging your phone, did you have your car running, or just on Auxiliary?

 

There have been reports of mpg affected by bad 12 volt. Likely the inverter is using extra energy from the traction battery trying to charge the bad 12 volt battery.

 

It's like a flashlight using batteries that are drained and need to be replaced. You can still turn on the flashlight and it'll have enough charge to throw out some light, but not as bright as if the batteries are new. Likewise, a discharged 12v battery will still allow the car to turn on and run, but not as efficiently as a new fully charged battery.

SM-T820 ?

 

I can understand that the inverter will be sending some power to the 12v battery to charge it. As long as there's enough in the 12v to START the Hybrid system you'll get going - and the inverter will gradually charge the 12v battery. The relatively low powered 12v battery is using only a small fraction compared with the charge in the hybrid battery and the other electrical systems going on. I can't see how it will make a difference to MPG. A hybrid battery with only 2 bars will use more MPG as it charges.

 

The engine needs to run more to replace the extra electricity used from the traction battery trying to charge a 12 volt battery that never gets fully charged.

 

But it's not going to be much. It's like I wonder why race-cars drive with headlights on - but I was told that it's just a drop in the ocean compared with the amount of power driving the car itself.

 

Does anyone know whether you need to add distilled water once in a while to our battery? I tried to search myself and cannot seem to figure out to try and add or not.

 

@Elektroingenieur what does the service docs say?

I believe you can check & add water as needed but I do not think it should be needed.

 

The caps look to be readily accessible, no sticker over them. The case is completely black/opaque, or is that just the top? A translucent case affords a much easier view of the electrolyte levels.

My past experience: removing a battery, about mid-way through it's "life span", I'll see electrolyte levels starting to drop. The case side walls were usually translucent, and IIRC there was a reference line showing the top-up level. I topped the cells up with distilled water, then hooked the battery up to a charger. Then cleaned the posts and clamps and reinstalled.

 

It is just the top & the bracket. They even mark a Lower level.
Why are we doing the work for those too lazy to check? There are shadows in the photo so you cannot see my battery level.

?

 

Good to know @Prodigyplace

 

I thought the sides were clear but I just went outside & checked..
I know you do not have a Gen 4 so I looked for you.

Apparently that is too difficult for some people here.