Toyota Rav4 EV Forum

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Thu Feb 27, 2020 2:39 am 
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Joined: Thu Jan 17, 2013 11:13 pm
Posts: 1828
Location: Los Altos, CA
asavage wrote:
miimura wrote:
Yes. The car has a larger than usual drain on the 12V when parked. This was evident from the start when cars would be dead sitting on dealer lots. This situation also caused many people to have a factory 12V battery that had a short life due to it being drained dead before even being sold.


Thanks for that. I'd only read about the many premature 12v battery failures, hadn't seen this before.

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I run the Odyssey 34R-PC1500T + the Group 34 height spacer to correct the fit. The combo is a bit over $300. I own three of them for some of our vehicles (RAV4 EV, Sienna, another Sienna), they seem OK so far. The oldest one is in the RAV4 EV, and will be three years old in August.

If you drive the car every day or leave it parked for max 2-3 consecutive days, you won't see the problem and the factory battery will last the normal 4-5 years for a starter battery. However, if you regularly leave it parked for a week at a time, the factory battery will only last 2-3 years. This is why people have been recommending deep cycle batteries and higher capacity batteries. I still can't figure out why Toyota put the smaller Group 35 battery in from the factory when the ICE variants like the V6 uses the 24F. Maybe they were stuck in the ICE thinking and the EV doesn't need the cranking amps of the 24F.

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Thu Feb 27, 2020 2:52 pm 
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Joined: Fri Apr 26, 2019 3:06 pm
Posts: 12
Location: MA
Search 'ev vampire drain' & this is a common issue - especially when either things malfunction or settings are chosen that take the normal vampire drain & cause it to be 3-5X.
There's vampire loads on the 12V & on the big battery. Most people complain about the big battery losing (1-3%) range per day. Personally I don't have an issue with a load that maintains big battery or other car features (proximity alert, temperature sweet spot). It's the 12V, just like in an ICE car, that may need to be jumped. The assumption (that there's so much electric capacity in the big battery that they must have designed the EV/PHEV to trickle charge the 12V) is wrong.
So, we have to know what normal vampire loads are & get alerted when they become excessive. Killawatt type meter on Level 1 charger should do this if reset after big battery is full.
Carrying a small paperback book sized jump battery would avoid waiting for AAA. Instead of buying new batteries for the snowblower & lawn tractor, I use it there & elsewhere. $40+ Amazon. Would this work on a dead 12V or just a weak one in the RAV4EV? Once the car's back, I can disconnect & see if mine can. The jump battery may need to sense some minimal voltage to work.
asavage, thanks for the measurements

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 Post subject: Re: ALL POSTS - 12-volt battery replacement
PostPosted: Sun Mar 01, 2020 4:02 am 
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Joined: Mon Apr 01, 2013 11:42 pm
Posts: 314
Location: San Diego, CA, USA
miimura wrote:
If you drive the car every day or leave it parked for max 2-3 consecutive days, you won't see the problem and the factory battery will last the normal 4-5 years for a starter battery. However, if you regularly leave it parked for a week at a time, the factory battery will only last 2-3 years. This is why people have been recommending deep cycle batteries and higher capacity batteries. I still can't figure out why Toyota put the smaller Group 35 battery in from the factory when the ICE variants like the V6 uses the 24F. Maybe they were stuck in the ICE thinking and the EV doesn't need the cranking amps of the 24F.


I don't know why they didn't pay more attention to charging the 12v so this wouldn't happen. Then the smaller battery would have been just ducky. It's not rocket science, they just needed to fire up the DC-DC converter more often.

Anyway the best way to handle it if you know you're going to park it a while is to get an inexpensive battery maintainer.


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