Sudden 12V battery failure

Went to my prius about an hour ago and tried to unlock her...nothing. bum bum buuum!!

Tried using the key...nothing. Phone Toyota road-side assistance:"It's easter weekend we cannot help you".Okeey.

Tried the key again. You have to twist REALLY hard. I then opened the bonnet and jumped the car with a small 12V battery I had. Once I had the trunk open I shut everything down again. After removing the 12V battery I tested it with a multimeter. It read 11.96V. I opened the battery (it's not sealed) and checked the water level. One cell was dry and 3 others were low. I topped them up and its' happily charging now.

This failure was very sudden. I'm pretty sure I didn't leave anything open or on. I have noticed sluggish boot-ups for the past two weeks, but I thought I was imagining it. The battery is about 18-24 months old now.

MUST I use the Toyota GS battery or is their a cheaper alternative?

There are alternatives, but it takes a little handy work for mounting. I recall that the terminals are different too, so you need an adapter. A quick search will fill you in on the details.

Tom

What's the typical lifespan of these 12V batteries?

looks like 2 year are normal for failure!

I'm glad it happened with the car at home and not at work or in a mall parking lot. I'm gonna start keeping a small "jumper" battery in the car.

People, keep a small 12V battery in your car for jumping.

mine failed after 2 years to
i now have a solar charger to keep it charged when standing still

I'm still running 4 years on mine with no problems. It's possible that you depleted the battery at some time and now it will not take a full charge.

Some of the cells were dry. How could this happen? I had a look and there are a number of locally made equivalents for the 12V battery. Not identical, but they should work.

I agree with you. Here is my back-up arrangement. "EMERGENCY BATTERY PICTURES"

Could you please post photos of the top & side of your GS battery? It is supposed to be absorbent glass mat which means that it should not have free liquid in any of the six cells.

When you opened the battery to look at the cells, did the lead plates look like a normal battery or did you see anything strange (like the fuzzy white mats that are between the plates in an AGM battery)?

I posted photos of the GS battery from my 2004 equipped with SE/SS, which is AGM since no sloshing sound is made when the battery was shaken. #1 shows the 2004 battery at the bottom of the photo, compared to the battery from my 2001. #2 shows the side view of the 2004 battery.

If you can find a vented AGM battery that is rated 31-32AH or better, that fits the available space with the correct terminal polarity, and has the correct size terminals, then you are good to go. A regular lead acid battery is not recommended for safety reasons - if your Prius is hit in the right-rear fender, you probably don't want liquid acid everywhere.

It says S46B24R on it. But it is flooded. One can clearly see the liquid in some of the cells while the others are bone dry.There's matting between the plates.

hot weather increases the chance for water to evaporate from cells.

it is a good idea to check the cells before hot weather arrives.

BTW, filling the cells in with distilled water is lot better than using regular water that contains extra minerals (regular water).

other reasons for evaporation of water from cells could be due to overcharge, but i seriously doubt that this is the case, as prius has a very sophisticated battery charge/management system.

BTW, i liked that term "boot up"
how appropriate for a hybrid!

as far as spare backup "boot up" battery goes, maybe it is not a bad idea to build a NiCad pack of say10 to 15 A capacity, just for situation like that.
I am thinking of building one such batt pack, to carry as a spare, just in case, and it would help with troubleshooting of components as well.

I'll probably end up replacing the battery with a locally built sealed lead-calcium.

Now that you've added water, is the battery holding a charge?

Does your battery look like the one in my photos?
Thanks.

distilled water is not better then normal water
distilled water is the only water you can put in

Yes, it's identical to the larger one in your photo. It is holding a charge too.

Don't mess about, just put a new battery in it.
Also I don't believe there is such a thing as a maintenance free lead acid battery.

I'm going to replace the battery.Just wanted to get it running. Everything is closed till Tuesday anyways.

You really want deionized water. Distilled is the closest you can get to deionized from a normal store, but a technical person would feel compelled to point out that distilled water is not deionized water.

Tom

I was referring to your bolded text. At the first sign of battery failure, replace the battery rather than mess about with jump start batteries.
It is also a good idea to check the electrolyte levels every 6 months or so. Keep the levels right extends battery life. A battery cell low on electrolyte is more likely to get hot and boil off the remaining electrolyte causing cell failure.