What type of battery is our 12 V accessory?

Yes, I'm using a CTEK 3300. I've had it for maybe a decade, and always elected to use the "middle" charging rate (auto symbol), not the "snowflake and Optima" symbol. The charger's instructions on AGM charging are a little vague, so I've opted to err on caution:



I'm still not sure if that means I'm charging less than optimum; just suspect the AGM batteries with the cylindrical 6-pack configuration are the special category. The Solar BA5 charger has two categories of charger type: describing them as flat case (which I selected) and spiral wound, which I think means Optima Yellow Top and the like.

So anyway, last night right after charging, the tester indicated voltage 12.75 and 354 cranking amps (EN setting). This morning voltage was 12.63 (surface charge bled off?) and the 350 cranking amps. In both cases just the green LED showing.



The battery is coming up on 5 years now. OTOH, it has had a pretty easy life. It was installed fresh the day we bought the car, due to the one originally in there being completely dead, from sitting around on the dealership lot. I've had one accidental draining, leaving the driver's door for about 18 hours, ran the voltage down to 11.9, about 6 months back.

BTW, speaking of hijacking threads, guess that's what I've done.

 

Just to confuse matters, Chinese manufacturers have started calling most of their aftermarket batteries "AGM." It is unlikely that they actually are real AGM batteries - more likely they just changed production slightly, maybe by adding some fiberglass matting. I don't know if the same is true with Japanese manufacturers like Yuasa...

 

I think the Yuasa battery should comply properly with the AGM spec, since Toyota chose it.

 

I don't know why CCA matters in the Prius except that it can be an indicator of battery health. The Prius has very low peak amp demands.

When my battery gets low, I'm replacing it with a LiFePO4 since they are more efficient and will likely last the life of the vehicle, not to mention Toyota charges a fortune for their small OEM battery. If I had to buy now, I'd probably get 4 of these for $140 total.

I have briefly tested a small LiFePO4 battery in the Prius with no issues.

 

Just for the record, I recently polled two local dealerships, for the Yuasa battery: they both said $273, ouch. I was considering replacing, I mean it's coming up on 5 years. But with the glowing endorsement from this new meter, I'm going to hang in there. Hopefully my optimism is not misplaced.