If I do need a new 12V, where have you gotten yours?

Advance Auto Parts may not have them. They didn't have them for Gen 2s, so I suspect they might not for Gen 4s. Got the Gen 2 battery from a Toyota dealer.

Posted via the PriusChat mobile app.

 

I'm not in the States, but I've heard good things about Pep Boys. At least for regular Prius they have a Bosch 12 volt that seems to be "on sale" half the time, for around $145, installed. It's dimensionally/functionally identical to OEM, with slightly better specs IIRC.

You can enter your car data on their site, see what they've got. It is not that intuitive a website, but if you persevere you'll find what you need. Try to soft-pedal the Prius c install factor (under rear seat), until after they've agreed to the install.

 

Ok shape should read 12.5 or higher. A Solar BA5 tester is a good toy to have, good for testing new battery at the store too, though they may have a pro-level tester, and be willing to check it for you, show you the results. With the new battery on a tester, You want to see Cold Cranking Amps higher than spec, likely significantly so. Voltage, if it's been sitting, might have drooped a little, but should at least be 12.5~12.6. 12.8 would be in the pink.

 

A lot of battery retailers will have a pro-level version of the Solar BA5, can do a more in-depth assessment, for free. As you say, you're likely out of the woods for a while, but check them out when it's convenient.

Or if your pockets are deep enough, google Solar BA5 or Solar BA7. The latter has more (useless to Prius?) features, but is apparently a bit cheaper now, on Amazon. Maybe due to supply factors.

A smart charger is another good thing to have; the Owner's Manual will have a guideline regarding max amperage.

 

I recently bought a larger/better quality mobility battery - which should be better at withstanding low discharge than the original battery.

I've heard people say that after three weeks of standing, the original battery can be flat enough to not start the car. I reckon I should get a couple of months now!

I bought a 55aH Lucas LSLC55-12 Its dimensions are bigger than the original, but it fits like a glove! I had to modify the battery clamp as it is 12mm taller, and a fair bit longer.

If I hadn't wanted the higher capacity, I would have gone for a 35 aH battery such as the YUASA REC36-12 which is slightly less high than the original.

Both batteries are much heavier than the original, so must contain more lead, and should last at least ten years with any luck.

They both have 6 mm screw fittings instead of the normal SAE or JIS posts, but were easy to adapt.

BTW I must give credit to Britprius for the idea!