Which 12V OEM battery is better for Prius 2nd Gen?

How are you venting this battery?

 

VRLA means there's a vent port on the battery if it has to vent so you can connect to that... But truth is VW and many other auto makers have had batteries inside the cabin of their vehicles for 80 years without a vent. There's only one time on New Jersey turnpike when cause of death couldn't exclude the battery, but it could not prove it either.

 

I have a 2003 Prius and have been using the Optima Yellow Top 51R batteries (after installing the kit several years ago to adapt to this battery) but have found that they are not good batteries and die right after their warranty runs out (just after 3 yrs) and also need constant charging in the winter (in Vermont) when it is cold or if we haven't driven in over a week. They are also very expensive (over $300). I would like to get the one that you recommend (12 Volt (12V) 55 Amp (55Ah) VRLA AGM Sealed Lead Acid Battery 55 AMPS HIGH CAP), and just add longer bolts and washers, but do you (PriusCamper) or anyone else know I will have any unforeseen issues with it? Thank you!!

 

Nobody could say for sure, but if you are confident the size of this battery will fit in the battery compartment without any issues, then a 55Ah AGM battery should in theory be superior to a 35/36 Ah standard flooded lead/Acid battery.

 

Not to hijack this thread, but has anyone put a LiFePO4 battery in their car as 12v replacement? They're getting cheap! 50ah like $120. My only fear is maximum amp draw tripping the bms (usually 1c/50amp). Anyone have any idea what maximum amp draw/charge to the 12v system?

 

Toyota Prius Gen2 Inverter - openinverter.org wiki

says up to 100A at 12V from the inverter.

I would worry though that the LFP "12V" is not close enough in voltage characteristics to the expected AGM voltages to work properly. For instance, and just making these numbers up, if the LFP is nominally 13.5V fully charged and 13.2V fully discharged then the car will see 13.2V and think it is a fully charged AGM, when it is instead a completely discharged LFP.

If you want a cheaper 12V AGM than the OEM one look at the Walmart battery.

 

I've only seen bms cutoff at around 11.6v for LifePO4, but LiFePO4 is 13.5 resting fully charged. I could see a scenario where one could deep-discharge the battery often, and have it not recharge quickly enough by the DC-DC converter. Or worse, have the BMS cut voltage and you're dead in the water. Much to think about!

I think there are other members who have replaced their AGM with LiFePO4 as well perhaps they can chime in.

I may experiment with a 50ah LiFePO4 to test, my only worry is charge/discharge rate. I know the DC-DC converter can go 60-70 amps on a low-voltage AGM for a few minutes from another member at Prius 12 volt charging current | PriusChat

 

I have the Duracell AGM battery which you can buy in Batteries Plus stores. I recovered the battery when I bought my Prius used (totally dead) took me 2 days to fully charged it. It's like 2+ years old now without any issues.

 

Hit the local UPullandPay. They sell batteries cheap.

 

I have looked at the local LKQ on several occasions and there has never been a Prius 12V on the shelf. Not saying one cannot be found eventually, but at least in my area it is not a reliable way of obtaining a Prius 12V.