Update battery thread: is the Optima Yellow Top still the preferred choice?

This makes it obvious to me this company failed to comply with specs, as OE now seem to be Yuasa AGM.

 

For a Gen 5? Not in my '26, lol. Flooded.

 

Ah, but this is a G3 forum, that’s my reference. It’s the same form factor for G2 and G3. I have so far no other relevant experience.

An interesting possible reason for placing the battery in the trunk is that small Ah batteries do not cope well with extreme temperature changes, as is the case when placed in the engine bay (engine is hooooot).

 

doubtful. space, maybe weight. I had a BMW once, a 3 series coupe, I believe, with the battery in the trunk.

 

Are you saying you see problems with the Gen 4 battery under the hood? There was no unusual problem for a flooded battery when I had mine.

 

There are so many considerations when placing components for production as an engineer. 12V batteries are still using lead/acid. That tech is from 1920. Extreme heat or cold are equally bad.

The engine bay on G2 and G3 could easily handle this form factor if this would have been prioritized. Many cars, including Volvo S80 2001 placed 12V in the trunk.

 

Not at all, just curious/talkative about general engineering decisions. The heat from the engine is actually good for 12V health in my climate, but not so much in other climates.

 

I was not aware they moved this, I have only G2 and G3.

This info actually makes me a little bit more inclined to also get a G4.

Any odd/special issues to look for, according to your experience @Prodigyplace (or any other G4 DIY reading this)?

 

My OEM battery lasted about as could be expected for a flooded battery. I notice my 2025 Camry had a flooded maintenance-free battery in the trunk area. There is a jump start point under the hood though.

When I took my 2017 in for the first check in late 2016, the tech supposedly did not check the battery because "Prius us different" even though the battery had been under the hood for over a year by that time.That is one of many reasons why I do not trust my local dealership. I drove over 2 hours to a good one to have the wiring harness recall performed.

 

So, there's no tube leading to the outside?

 

I just checked. It is vented, likely because the rear seats fold down, making it part of the cabin area. See the rectangle below

 

You would need an awful lot of abnormal hydrogen release from the battery to even consider this being an issue, wherever the battery is placed.

With a SMF battery, I find it rather funny they have a vent.

 

Interesting. The battery on my Gen5 Prius is LN1 size. There was a recent thread where a LN3 was stuffed in there. Haven't heard back from the original poster on that yet.

 

It DOES make me wonder how plentiful a replacement will be.

 

(I just assume with full prejudice, that the concept of caring about this issue is based on fearbased regulation rather than science.

 

The Camry has a larger engine. Mine is the XLE with a lot of options too.

 

Plentiful? As in..?

That vent seem to comply with some outdated regulation. Very few SMF/flooded batteries and even fever agm have this concept.

 

Never heard about LNx…. Please link source.

Where is ISO / EU regulation when any battery can be any dimensions? Who benefits from this?

It’s just such a waste of resources, and in my mind this is what happens when you let companies create their own standards.. CHAOS for everyone,

 

So it will likely be difficulty to find a replacement with a vent when a replacement is needed.