What Brand of Battery do you like ? (Auxiliary)

Maybe a loose connection? Check ground connection at battery first, the low-hanging fruit.

 

Even when connected to battery directly the charger complained and did some reconditioning for few minutes. After that it charged ok. Ground connection in battery is very good, everything shines. Cannot say same about engine compartment..

 

An electronic load tester can confirm battery condition, something like Solar BA9. Retailers selling batteries will often have pro version of such testers, will test for free.

 

Sounds like you might have a shorted battery. Warranty?
But, if it's not an agm, you should replace it with one. You'll have toxic fumes from the acid
in the battery getting into the cabin that you and your passengers would be breathing....

 

I agree. We must use AGM when it is inside the car for mainly safety reason, not just reliability. I also think the OEM original Yuasa battery is still the best for Prius. They last 8 years even in hot FL when I drive it regularly.

 

I now have a new Toyota AGM battery. Car is driven more than ever (some 400km per week and mostly highway) but guess what: battery was almost empty one morning. My son had to use jump pack to get car started. Drainage somewhere or charging problems. I have camera and bluetooth tether connected to cigaret lighter sockets but those are not giving out anything when is off and locked? Or do they..?

 

Yes, the 12-v sockets are off then the the car is shut down. The most common cause of such battery "drainage" is a door or hatch not fully latched. That will fully drain the battery in a couple of days, even if no interior lights are on. Your old battery might have been ok for a while longer, if simply recharged promptly.

 

If something not fully latched and i lock the car (from the keyless button in door handle) car does not give any feedback? It just locks the doors that are latched and blinks bye bye as usual?

Car worked fine for a month and couple thousand kilometers. There may have been very obvious drain but since car was actively driven it just managed to top up battery during driving

 

You could have a defective 12v battery. It happens. But if it's drained completely
to the point of death, it won't last long. You could give it a 12 hour charge at 4 amps or less
and hopefully it has survived and will give you a few more years of life.
But you should start saving for a new one and keep a jump pack in the car.

 

I had problems with previous battery which was just 2years old. It was regular (flooded type) and was empty few times a year so i bough new Toyota AGM. However, the AGM stamp said June 2021 but their sales said there is no need to worry. Full warranty etc so i did not return. I actually believe there is nothing wrong in the battery, probably that flooded one is ok as well (holding 12.7v charge in my storage no problem). But yesterday when i tried to charge that AGM with 4A either my charger, or car or the battery acted weirdly: first 12.8v but with just few minutes of charging it went up to 14.4V. Almost like car had power on but it was off. I only opened door to open hood and brake booster did its thing as usual. But i assume that car go off right after the brake booster buzz. Or does it..?

i bought a jump pack when the battery circus started. It has been used once and it surely saved that day. It is no big deal to use it e.g. once a month but would be nice to get this battery circus stopped.

 

The overpriced ones that Toyota and auto parts stores recommend are only 38 amp-hours, yet industry standard for the space available for 12v is 55 amp-hours. What's more if you go around the gauntlet of hybrid car price gouging you can get one online for a little over $100. Here's the one that I recommend: https://www.ebay.com/itm/141206981871

 

FYI, Walmart now sells the AGM battery for a Gen 3 Prius. I live in PA and can buy one locally for $160 plus tax. Walmart started selling them about 2 months ago.

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