12v battery (hybrid) runs low after sitting for a week

[MustardTiger]

@TacoFreak I gave up checking the underwood boost point a long time ago. Instead I removed the clips holding the rear seat cushion down and go straight to the battery. I figured in the event that it does go dead on me, I’d rather not have to figure out how to get the seat up in the heat of the moment. Here’s what I’d do…next time you come come from a drive somewhere…turn off the switches for interior and cargo lights, leave the rear drivers side door open, lock the truck and walk away for a bit. Come back, and test at the battery terminals. This would be your true resting voltage of the battery. You could do the same thing at the boost point under the hood…but you’d have to wait for the instrument cluster to blank out. It’ll stay dimly lit with a hood ajar warning for idk 30 mins? It does go out. I’ve left my hood open all night.

Obviously do this with it parked in the garage lol

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[franx]

I was talking with my dealer about the battery levels and what could cause the battery drain...he said the truck sometimes does a test called Evaporative Emission Control (EVAP) test that the system performs a self-test to check for fuel vapor. He also mentioned that the key fob communicates with the truck if its close enough to the truck, in addition I know my Toyota app communicates too because its always reminding me of open doors when its parked in my garage unlocked. I force close the app to stop that to prevent any drain. They claim it shouldnt impact the battery, but I am not convinced. I have another 13months on warranty if it kills another battery its on Toyota again to replace.

The dealer also claimed what I am seeing on the battery voltage gauge sounded normal. Now I keep watching this gauge every time I drive it and making me a bit OCD

 

[TacoFreak]

I force close the app to stop that to prevent any drain. They claim it shouldnt impact the battery, but I am not convinced.

That is interesting, because Toyota and Lexus need to get their dealer BS stories lined up. The 12 volt in my wife's Lexus electric SUV went so low that it wouldn't turn on or even open the doors. It had just been driven the day before and I charged the battery to where it would start.

The dealer contacted Lexus who told them that the app was causing that, that it was a known problem, and that there was no fix. Their suggestion was to always sign out of the app, and almost two years later there is still no fix. It uses a similar DC/DC converter to charge the 12 volt and it is always really low too, but it has not gone stone dead again.

 

[franx]

In another month the "Free" Toyota Connect expires and I will not renew that subscription, therefore I wont need to force close the app anymore ;)

Its a rip off at $15/mo besides I dont care for the app in general and what you get for it. I cant stand these companies that want subscriptions for everything to keep the money flowing in even after the sale.

 

[gpburdell]

He also mentioned that the key fob communicates with the truck if its close enough to the truck, in addition I know my Toyota app communicates too because its always reminding me of open doors when its parked in my garage unlocked. I force close the app to stop that to prevent any drain. They claim it shouldnt impact the battery, but I am not convinced.

couple of data points for you.

Beginning in 2024, the key fob goes to sleep after a few minutes automatically. Granted, the truck is always listening for a key fob, but so has my 2017 for the last 9 1/2 years. That’s not going to impact the 12 V battery in the short term.

Additionally, I have a third-party app/LTE remote start with app on my phone. It’s gone as much as two+ sitting unused well we’ve been traveling, with no trouble starting afterwards.

My point is it seems Toyota‘s got something wrong with these, and doesn’t seem to want to admit it.

 

[TacoFreak]

My point is it seems Toyota‘s got something wrong with these, and doesn’t seem to want to admit it.

Exactly. If Toyota admits there is a problem with their vehicles still under warranty they have to fix them. But instead they just say that trucks killing their 12 volts or not starting after sitting is normal. My dealer said it was my fault because I don't drive my truck enough. Some trucks do this and some seem to be fine and I have no idea what the difference is.

My 14 year old Tundra was used exactly the same way and it would still start after sitting for weeks, so I don't buy their story. But I also don't know what we can do as long as they keep saying that these vehicles are working as intended.

 

[StreeTaco]

This is pretty cool.
https://presale.alwaystart.com/?v=A

 

[gpburdell]

I also don't know what we can do as long as they keep saying that these vehicles are working as intended.

If it were me, I’d seek out an independent mechanic to attest to the 12V charging system being faulty and initiate a lemon law case. Of course that’s easy for me to say since I’ve not yet bought a 4th gen.

Sort of that I’d blow up Toyot’s socials making others aware of the issue. Would it accomplish anything? Maybe not, but if it cost Toyota a couple sales it’d make me feel a little better.

 

[trailhunger]

https://prioritystart.com/product/12v-promax-h-d/

Or get a battery disconnect switch (best defense against a CAN-BUS attack, although kills the alarm system too / but doesn’t protect the battery if you’re running accessories after turning of the engine, so use generator ‘ready’ mode as much as possible especially if you’re milling about the truck with the fob not in a faraday bag)

Or get this if you have a solar panel on your rig like I do:
https://www.homedepot.com/p/Grape-Solar-PWM-10A-IP68-Charge-Controller-GS-PWM-10A-IP68/334393733

A weak cell that’s going bad, you so much as use the powered tailgate a few times out in the boondocks pray your jump pack is fully charged…

 

[trailhunger]

If you’re driving a hybrid and your OE aux/starter battery is acting up/requires a jump periodically…get that batt load-tested. A fresh replacement will improve your MPGs full stop

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