12V battery group size

It should not need to be checked often, I would think. I have 15K miles on my year-old 2017 and have not checked the battery levels yet. I think the general level can be checked by looking through an area of the casing.

 

I would check it monthly......until you get an idea how much loss there is.

My guess: 6 months since you aren't in a really HOT climate.
Even if there isn't evidence of much or any loss, I'd still check it at least once between oil changes.
Use only distilled water to fill.

 

What we think is not always right.
NOW would be a good time to do that.

 

I have a copy of my owners manual for a US built and European copy and the European has battery electrolyte level listed and the US does not. I am saying the same thing you are.

I have about ten 12 V batteries, on the average I buy one a year and have two cars that need batteries.

 

I would check once a year, MINIMUM.

Add DISTILLED water ONLY. Refill using a syringe or a battery syringe filler; a few dollars.

You can buy a Hydrometer Tester, and test each of the six cells, to see which one is weak; a few dollars.

 

My 2 cents, for a conventional battery, with accessible caps: once, mid-way through a battery's life, say 2~3 year mark? That always seems like a good time to pull the battery right out, clean the posts, check the levels in a good light. Hopefully the case isn't solidly opaque black...

 

I have one of these
SOLAR BA7 100-1200 CCA Electronic Battery and System Tester
I don't have to go to the dealer or the parts stores to have my batteries tested.

http://www.amazon.com/gp/product/B0015PI7A4/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

 

Not nearly often enough.
It can be empty by then.....and damaged beyond repair.

 

If your battery is using up all its electrolyte in 2 years then your charging system is overcharging.
I've not had a battery, on any of the cars I've had in the last 10 years or so, use any electrolyte within 3 - 4 years.

 

Overcharging is possible.
But if your battery is in the engine bay, simple evaporation from heat will cause some loss.
You have been lucky.
Not good to advise others to take that chance.

 

Not wishing to step on anyone's toes, but I believe the answer lies somewhere in between the two extremes already mentioned. Nobody's right and nobody's wrong either, because the are too many variable conditions to predict a specific outcome with a lead acid battery.

 

Has anyone considered a lawn tractor battery for their Prius? I have seen some that have over the 325 CCA that my 2017 OEM battery has.

 

The PRIUS battery doesn't need consideration of CCA - as it doesn't crank, let alone in the cold.

I suspect that TOYOTA has chosen a battery based on other "credentials".

 

CCA doesn't need to higher than the stock battery. On the other hand, measured CCA is a good barometer of a battery's health? The electronic load testers test actual CCA, compare to spec, and pass judgement based on that.

 

For a Gen2, a vent tube is required for safety. Liquid sulfuric acid from a wet/maintenance free battery is not a good thing esp in a collision back there. Thus the use of an AGM battery; pretty much insignificant amount of sulfuric acid in a liquid form.

CCA is meaningless for the ALL Prius, as the 12V battery does NOT crank the engine. The HV Battery cranks the engine; this provides some serious CCA over any 12V battery.

You could start your Prius w/ a 12V alarm SLA (Sealed Lead Acid) back-up battery, found in home alarms and UPS (Uninterruptable Power Supplies) for computers! This type of battery won't start a traditional car obviously, but is sufficient for a Prius. The ECUs need a 12V source to power the computers, which in turn tells the various mechanical devices what to do, such as start the engine using the HV battery as a power source. Now you should begin to see the insignifigance of CCA for the Prius.

For the Gen2, the 12V battery in the Prius is a primary power supply for the brake accumulator. Should the 12V charging system fail, the accumulator will be powered by the 12V batteryry until it runs this down. An AGM battery has endurance to be run down longer than a traditional wet cell/mantenance free battery that is intended for cranking. When the 12V battery gets depleted to the point of NOT being able to power the accumulator any more, the capacitors in the accumulator, will provide power to the accumulator for an hour I believe (thus the failsafe). Obviously, there will be warning lights when the 12V battery is not getting charged. I believe the accumulator will also sound an annoying audible alarm when it begins to run off the 12V battery only. You will have to be blind, deaf, and dumb, to continue driving the vehicle in such a state, where the 12V battery is not getting charged by the vehicle, beacuse the dash will likley be lit up and the annoying audible sound from the accumulator.

 

True, that's a good measure - but actually getting cranky isn't one of it's tasks. Lead acid battery technology has many different types for many different purposes.

I used to have a chart, but can't find it - of batteries for different purposes. It was VERRRY old, when I had a '77 VW Microbus and was setting up a secondary battery only to run the fridge & radio and maybe a little ventilation fan when we camped in it. I ended up with an identical sized battery (physically) because it was easy to mount - there was a place the opposite side from the main battery in the engine compartment, but the fridge battery was quite different construction, designed to be more sympathetic to occasionally going closer to "flat" than a normal battery would appreciate.

 

You make a good point about the battery not being used to crank the engine, but keep in mind that a battery’s CCA rating (also called the low-temperature test current) is also a proxy for other important characteristics.

Besides its role in bootstrapping the hybrid system, the 12-volt battery on the Prius also provides a reserve to meet brief demands for current greater than the 100 A than the DC-DC converter can provide. Toyota doesn’t publish an electrical load analysis, so we don’t know the load, diversity, or demand factors, but a glance at the ratings of the fuses shown in the Electrical Wiring Diagram gives an idea of how one might need more than 100 A under some conditions.

The 12-volt battery also needs enough capacity to power the parasitic load without being drained, even if the car is parked for a while, since the hybrid vehicle battery is isolated when the car is off. One parameter of interest here is the nominal capacity (K₂₀ or Ah₂₀), marked as 45 Ah on the factory-installed battery. Bosch Automotive Electrics and Automotive Electronics (5th ed., p. 421) explains:

The nominal capacity K₂₀ is the battery’s rated electrical charge in ampere hours (Ah). According to EN 50 342, this is the electrical charge that can be taken from the battery within 20 h at a fixed discharge current of I₂₀ until the specified cutoff voltage of 10.5 V at (25 ±2) °C is reached. The discharge current I₂₀ is the current that is allocated to the nominal capacity, and must be delivered by the battery during the total discharge period: I₂₀ = K₂₀/20 h.​

I imagine Toyota’s engineers selected the smallest (i.e., least costly) battery they could, considering all of the requirements, including many not known to us. I wouldn’t be comfortable replacing it with a smaller one, except temporarily in an emergency.

 

I measured a 30A initial surge, using a clamp on induction ammeter, when jump starting SWMBO's Gen 2 from an external battery, so if using a small back up battery, make sure it's capable of taking a 30A surge without exploding.

 

So I read all 7 pages of the whole thread and did not find a solid answer on which battery to get as a replacement. I have a 2016 Prius Four. Long story short, battery is smashed so it needs a replacement. Not sure if there is an alternative to a Toyota Dealership's battery.

 

Nothing wrong with the dealership battery, and $186 isn't bad:

12V battery group size | Page 2 | PriusChat

How's your's "smashed"? Make an insurance claim?