12V battery group size

OK, Pearl's "sealed" AGM battery started to exhibit signs of dying at 3 years of age. I removed it and discovered I could access the fill caps. Popped them off and saw some cells with liquid over the mat and some that were drying out. So I filled them all to the same level with distilled water and got another two years of use on that battery.
Pearl S' "sealed" AGM battery did the same thing, only in this case the manufacturer glued the cover on over the caps. I gave up and re-installed the battery, and it failed the next year (four year life). Pearl S is now running a Canadian Tire Ultra AGM (Exide) battery with a 5 year pro-rated warranty. I'm not holding my breath as to the value of this warranty, because I know when I return it they will charge the battery and immediately load test it. It will work in this test. It will not hold the charge overnight. But they won't test that.
Anyway, on a per year cost, the Canadian Tire battery is the best option. It cost $170 Canadian, less the $20 for the dead stock battery, and also less the $50 gift certificate I got when I bought it. For a total cost of $100, and IF it lasts five years that's $20 per year.

-ALL- lead acid batteries loose some water from hydrolysis, INCLUDING AGM types. If they don't vent that gas or convert it back to water somehow, the pressure in the battery will build and the battery would explode. This required venting is loss of water. If you can't replace that water this loss of water will likely be the life determining factor. When the tops of the cells start to dry out the plates corrode by several processes and can swell and short.

There are many reasons for battery failure, including cell shorts from plate failure, plate shorts from "debris" accumulating in the bottom of the cell chamber (common), loss of water, and of course, abuse. I've seen them all over the years. I've been working with lead acid and other types of batteries for 50 years, for a living.

 

Unfortunately, we do not have a good large automotive chain that concentrates on having good, affordable items with their own brand. I truly miss Canadian Tire. I shopped there quite often when I lived in Canada. I still have some of their tools, over 30 years later. I also have some from the original T. Eaton Co. TECOMaster brand.

The closest we had was Sears, but they are slowly dying and closing stores in many areas.

 

It is my understanding that a well designed AGM does exactly that......with most or all of the H and O that is produced.
Is that not true ?
If you claim not, a reference would be appreciated.

Absorbent Glass Mat (AGM) Battery Information - Battery University

 

Best solution would be to get a second power supply. Keep the 12V Prius computer/accessory battery separate from a dash cam 12V battery. A second battery would not cost that much more, and it would not be a cause of draining the 12V Prius computer/accessory battery.

Blackvue makes an ideal set-up. BlackVue Power Magic Battery Pack (B-112) - Parking Mode Made Easy You, or a hired installer, can conceal its location.

A more robust solution could be a 12V SLA (of your choice; larger gives you more run time) and an isolated DC charger like this; higher charge rate when the car is READY, to recharge the dash cam SLA. 12V input lead acid battery charger for 12V batteries; fully
isolated taper-style DC Input 12V Battery Chargers useful for charging electric
golf trolley in cars from PowerStream

 

So am I the guinea pig or has someone successfully fit another 12volt battery in a gen4??
12 Volt for 16 Prius 2 | PriusChat

 

I doubt is.
The only other high mileage 2016 I remember. they traded at about 90K miles for a VW Diesel because they preferred the diesel and basically considered the Prius an interim car until VW got its act together. They did tires but I do not remember any mention of battery.

 

I think you are the first with the generation 4

 

I've read every Gen 4 post for 2+ years since Gen 4 came out - and can only recall 2 dying 12volt post yet. From memory, the first one was someone wanting to run some life-support system while camping, an this current thread relating to a Dash Cam.

I would expect most of us would expect our 12volt batteries to last many years. I haven't replaced a 12 volt battery in any car since 2003 - I've kept cars for 3-4½ years, and each battery was still going strong.

 

The battery in my 2016 Prius is a conventional battery not an AGM.

Apparently Toyota does not use the Group standards for size that we do in the US.

 

Gen4 12V battery located in the engine compartment?

 

Yup, but apparently still a somewhat odd-ball size, or hard to find?

 

Really ?? One with easily removable caps so that you can check and add water ??
I didn't think that ANY car came with a conventional battery anymore.

 

I believe it is a Japanese size.

 

I saw no mention about any type of service to battery. I don't see the battery mentioned at all in list of dealer serviced items.

 

In the U.S., neither the Owner’s Manual nor the Warranty and Maintenance Guide says to check the battery electrolyte or add water. In Europe, however—where the Prius gets the same battery—the Owner’s Manual does include this procedure in the “Do-it-yourself maintenance” section. As I mentioned in post #81, it’s also in all versions of the Repair Manual.

 

Thanks - I never realised that - my manual has the same:

 

Yes, much easier to access than when in the trunk.

 

Thanks, Alan.
Earlier when I posted a photo of my 2017 battery somebody said it looked like it could be topped up. This thread is the first I remember confirming that.

 

That does not answer the question.

"Production" may have decided to change the battery type without notifying the people writing the manuals.

IF.....it really is a conventional type with easily removable caps that are vented, then it WILL lose some water and it needs to be checked.

 

OK I will check it, how often should I do it? Check it by months, mileage or what? I have 2000 miles on the car, will it make it to the first oil change?