I suspect it's really doing a CA test, unless you have a 0 ℉ freezer to keep the battery in for a while before testing, or you make sure to use it on winter days that happen to be 0 ℉, which would match an official CCA test. Or maybe the reduction in CA with decreasing temperature has a known formula, and the tester measures the ambient temperature and corrects it to 0 ℉ with math. I don't know if that's practical.
It has several other options, including CA (Crsnking Amps) though I’m not sure my battery specs that. Would there be a general factor applicable to CCA that would ballpark the CA? that said, testers of that ilk typically offer CCA measurement; they employ some method to make measurements at other than zero?
I wonder why you care about crank amps for a Prius? The 12V does not crank anything, it just powers up the ECU… Yuasa is the best I have tried, but I also use ctek attachment and recond them 12V every quarter year regardless. Dead aux batteries are the worst.
That's not the first time that's been wondered in this thread. Seems like every time it gets wondered, someone has to say again "because there are common tools that let you compare a battery's present cranking amps to the cranking amps on its label, and that's an easy way to get an indication of the battery's present condition". Doesn't need to have anything to do with 'cranking' needs of the car.
Agreed, but then I also have to wonder what do a Prius actually need in A (sustainable for five seconds?) to boot the system? (CA value is defined on need to be able to (repeatedly) crank an engine. That is a highly irrelevant value for the Prius.)
The banal ballpark test for any battery sustainability/capacity - apart from for Prius irrelevant CA - may be to know the exact A input charge, then measure the amount of time in H it takes to get that battery to full - if initially almost empty. It’s fairly obvious if a ie 45Ah battery charges very fast (under 2 hours on 5A charge) from empty/low, it’s a loss/toss. Even CTEK can’t fix those and it will not hold for any kind of weeks.
That same condition may also show up quickly on the local auto shop's CA tester, as a value much lower than what's on the label, and that's a convenient test you don't have to wait 2 hours for. As far as I know, that's the only reason PriusChat people give for caring what CA your battery's label says. Even the lowest commercially-available car battery CA ratings are several times what it takes to make a Prius READY. There are threads in this forum where graphs of amp draw during the few seconds of going READY have been posted. I seem to remember the area under the graph being about 90 amp seconds, over a stretch of 2 or 3 seconds, so an average of 30 amps or so, but the graph is more spiky than steady.
