12 Volt battery for 2012 Prius -maintenance free?

To my knowledge, Gen II and III 12V auxiliary batteries are sealed and externally vented. Read some Gen II posts about guys prying up the seals and adding distilled water, but with an AGM (absorbed glass mat) battery how would you know how much water to add. Yes, maintenance free for 5-6 years (assuming you don't deep discharge it) and then replaced.

 

yes.

 

No. The battery really needs to have water added after a few years. BUT it's "maintenance impossible". You can't add water as it's sealed.

You -can- check the terminals/connections for oxidation and to ensure they are tight.

I was one of those guys Arwxguy mentioned. On the GII battery. The GIII battery is glued together so I didn't bother. I just replaced it.

 

The 4th gen battery looks to be conventional, larger, regular post size, back in the engine bay, with accessible caps and translucent sidewalls with level markings.

 

mine is now 5 years old. no idea where the water level is, but it is still very strong, the posts require no cleaning or tightening, and i expect it to last 10 years, maintenance free.
but i have never abused it in any way, other than letting it sit every winter for 5 weeks with sks on.