12v battery keeps going flat

[HowdoIdoit]

I've had my 2021 RAV4 plug in hybrid for 9 months and had to have the RAC out 3 times cos of flat 12v Battery.  I'm apparently not doing enough longer journeys to keep it charged up,  Am I alone in this problem?  The dealer never warned me of this quirk, having had RAVs for 25+ years and never ever had this problem before.

[Roy124]

You are not alone. 

Fixes discussed here include :

Toyota advice to put it in Ready mode for an hour a week. 

Using a smart charger to maintain the Battery. 

To use a solar charger if you have no mains power or in a holiday car park for 2 weeks. 

Get a jump starter pack as a backup. 

Badger your dealer for a replacement Battery as yours is dying (literally). 

Save up for a new Battery if your dealer won't exchange it. 

[ernieb]

On the ‘ask a Toyota owner’ forum thingy one of the guys has had his replaced after the dealer did all sorts of tests, charging and discharge tests and fitted a higher storage capacity Battery. As the poster says all that is likely to do is extend the periods between discharges.

[Roy124]

My dealer exchanged my Corolla 35AHr for a 42AHr after 12 months.  Like you I was not told about Ready mode but I bought the car in March 2020 and I think the Ready mode advice was dated April AFAIK. 

To help my case, I measured and recorded the Battery voltage every day the car was not used. 

[Strangely Brown]

32 minutes ago, HowdoIdoit said:

I've had my 2021 RAV4 plug in hybrid for 9 months and had to have the RAC out 3 times cos of flat 12v battery.  I'm apparently not doing enough longer journeys to keep it charged up,  Am I alone in this problem?  The dealer never warned me of this quirk, having had RAVs for 25+ years and never ever had this problem before.

There is a known fault on the Plug-In Hybrid whereby the DCM (Data Communication Module) can fail to shut down when the car is switched off. This drains the 12v Battery.

Fortunately there is a software update that fixes the problem. Have a word with your dealer to see if that update is in place. If not, get it done.

[FROSTYBALLS]

Toyota's advice on Battery maintenance came about due to owners having problems through not using their cars during lockdown in 2020. 

The first lockdown commenced 23rd March 2020. The advice was posted on toyota.mag.co.uk on 3rd April 2020, and on these forums on 9th April 2020.

https://mag.toyota.co.uk/coronavirus-toyota-hybrid-car-maintenance/

 

[Roy124]

Frosty, thank you for confirming my recollection of the advice dates.  I can't remember when I hot the first flat as we really were locked down as I had been incorrectly put on the at risk register. We had friends doing the meds run and others doing the shopping. 

 

[Gray86]

3 hours ago, Roy124 said:

Frosty, thank you for confirming my recollection of the advice dates.  I can't remember when I hot the first flat as we really were locked down as I had been incorrectly put on the at risk register. We had friends doing the meds run and others doing the shopping. 

 

If you have a driveway or garage, a smart charger is a wise investment (particularly as this issue is common across many hybrids and EVs). A trickle charge once a month in winter or every few months in warmer months will keep Battery operating as it should, and importantly - keep the car reliable. Once Battery goes completely flat it loses capacity and will rarely be as good as it should be 

[ernieb]

That’s effectively what I’m doing with my car as I’m able to park on a driveway.

[HowdoIdoit]

On 1/20/2023 at 3:04 PM, Strangely Brown said:

There is a known fault on the Plug-In Hybrid whereby the DCM (Data Communication Module) can fail to shut down when the car is switched off. This drains the 12v battery.

Fortunately there is a software update that fixes the problem. Have a word with your dealer to see if that update is in place. If not, get it done.

Strangely, thanks for the info.  Car booked in at dealer on Thursday for investigation, so forwarned, etc.

[philip42h]

On 1/20/2023 at 2:29 PM, HowdoIdoit said:

I've had my 2021 RAV4 plug in hybrid for 9 months and had to have the RAC out 3 times cos of flat 12v battery.  I'm apparently not doing enough longer journeys to keep it charged up,  Am I alone in this problem?

On average, how many hours a week do you use the car? If you use My Toyota > My Vehicle > Driving Analytics > Year you can see how many hours you have spent driving the car (i.e. in Ready mode) over the past year (or in your case 9 months). Divide that by the number of weeks to get an hours/week figure ...

As above, Toyota advise that you need to have the car in Ready mode for an hour a week to balance out the drain on the auxiliary Battery when the car is off. If you are at or below an hour per week then you probably are not using the car enough and will need to consider ways to top up the auxiliary Battery. If your average is two or more hours per week - mine is two and I never have an issue - then there is almost certainly something else 'wrong'.

[Nick72]

On 1/20/2023 at 2:29 PM, HowdoIdoit said:

I've had my 2021 RAV4 plug in hybrid for 9 months and had to have the RAC out 3 times cos of flat 12v battery.  I'm apparently not doing enough longer journeys to keep it charged up,  Am I alone in this problem?  The dealer never warned me of this quirk, having had RAVs for 25+ years and never ever had this problem before.

Had same problem. Boosting it every other day.

Started only a few months back after a dealer visit. Prior to that I had done loads of short journeys previously and not used the car for weeks too yet had no problems whatsoever.

There's a TSB or fix for it. Telematics module is not shutting down properly when you switch the car off. That drains the 12V Battery. Dealer updated that software and all other software just in case. Not had a problem since and did loads of 1 to 5 minute journeys over 2 weeks at Christmas and then didn't use the car for 5 days. No problems.

What caused this all of a sudden was a repeatedly botched attempt to upload the brake actuator recall software during the first service. Basically they must have rolled back a whole lot of software. It was the only explanation. More to this story that convinced me this was what happened.

[Nick72]

On 1/20/2023 at 3:04 PM, Strangely Brown said:

There is a known fault on the Plug-In Hybrid whereby the DCM (Data Communication Module) can fail to shut down when the car is switched off. This drains the 12v battery.

Fortunately there is a software update that fixes the problem. Have a word with your dealer to see if that update is in place. If not, get it done.

This worked for me. DCM. Telematics.

[Nick72]

On 1/22/2023 at 11:03 AM, HowdoIdoit said:

Strangely, thanks for the info.  Car booked in at dealer on Thursday for investigation, so forwarned, etc.

You got to insist they do this otherwise they won't be ubikd.

[Hayzee]

10 hours ago, Nick72 said:

You got to insist they do this otherwise they won't be ubikd.

Nick is there a Toyota technical reference for this update?

[Strangely Brown]

I think this is the relevant TSB. It says US market but it is the same problem.

T-SB-0095-20.pdf

[TabbyBoy]

On 1/20/2023 at 2:29 PM, HowdoIdoit said:

I've had my 2021 RAV4 plug in hybrid for 9 months and had to have the RAC out 3 times cos of flat 12v Battery.  I'm apparently not doing enough longer journeys to keep it charged up,  Am I alone in this problem?  The dealer never warned me of this quirk, having had RAVs for 25+ years and never ever had this problem before.

You're far from alone! This is a VERY common issue with the RAV hybrid (mild and plug-in) in the UK affecting a lot of low mileage drivers. My 12v Battery would always go flat (below 8v) after 5 days of not driving. No software update would fix it and Toyota UK didn't seem to care. In the end I had to take my dealership to court so that I could formally reject this PoS. In the end I got a full refund and compensation. Fight them and reject it, as THERE IS NO FIX !!!

I can see this soon escalating into a class action lawsuit like the VW diesel fiasco. Toyota have simply released a vehicle that isn't fit for purpose and could leave you stranded in an emergency.

5 years have passed, where's the recall?

This was my first and last Toyota!

[Roy124]

James, you obviously got the result you wanted,  but I have a question. 

Did you buy new or second hand?

I think there is a potential issue for second owners.  Second owners have no idea how the original owner treated their Battery.

If the car had had Battery issues and not had a replacement Battery fitted then there will be potential problems.   Clearly the original owner is not going to tell the garage when he trades in.

[philip42h]

33 minutes ago, Roy124 said:

I think there is a potential issue for second owners.  Second owners have no idea how the original owner treated their battery.

In the grand scheme of things, a replacement auxiliary Battery doesn't cost that much in comparison to the cost of a secondhand RAV4 hybrid. So what if the auxiliary Battery is shot - simply replace it! It's a 'consumable' item anyway ...

[Nick72]

1 hour ago, TabbyBoy said:

You're far from alone! This is a VERY common issue with the RAV hybrid (mild and plug-in) in the UK affecting a lot of low mileage drivers. My 12v battery would always go flat (below 8v) after 5 days of not driving. No software update would fix it and Toyota UK didn't seem to care. In the end I had to take my dealership to court so that I could formally reject this PoS. In the end I got a full refund and compensation. Fight them and reject it, as THERE IS NO FIX !!!

I can see this soon escalating into a class action lawsuit like the VW diesel fiasco. Toyota have simply released a vehicle that isn't fit for purpose and could leave you stranded in an emergency.

5 years have passed, where's the recall?

This was my first and last Toyota!

It's a software issue on the Digital connectivity module are whatever it's called. It doesn't shutdown as it should and drains the 12V.

I was having issues after a couple of days of not driving the car even after very long drives previously.

Went in for a few months. Constantly using the booster pack I had to buy. After the Comms module software update it was completely fine. I ve done very short trips for weeks then not driven the car for 4 weeks and it starts first time no problem. Not had an issue since the update which was about a year ago I think.

This is not a 12V Battery issue at all. It's software and failure of subsystems to shutdown. There's a service bulletin on it.

 

[Roy124]

1 hour ago, philip42h said:

In the grand scheme of things, a replacement auxiliary battery doesn't cost that much in comparison to the cost of a secondhand RAV4 hybrid. So what if the auxiliary battery is shot - simply replace it! It's a 'consumable' item anyway ...

You are right, but a second owner can get bitten sooner than they expect.

[Nick72]

23 hours ago, Nick72 said:

It's a software issue on the Digital connectivity module are whatever it's called. It doesn't shutdown as it should and drains the 12V.

I was having issues after a couple of days of not driving the car even after very long drives previously.

Went in for a few months. Constantly using the booster pack I had to buy. After the Comms module software update it was completely fine. I ve done very short trips for weeks then not driven the car for 4 weeks and it starts first time no problem. Not had an issue since the update which was about a year ago I think.

This is not a 12V battery issue at all. It's software and failure of subsystems to shutdown. There's a service bulletin on it.

 

Apologies for the typos. Unable to edit to correct them.

[FROSTYBALLS]

33 minutes ago, Nick72 said:

Apologies for the typos. Unable to edit to correct them.

Members only have a limited time from first posting in which to edit posts. 

If you want corrections made after this time has elapsed, you can pm a moderator outlining what amendments you wish made.

[Nick72]

6 minutes ago, FROSTYBALLS said:

Members only have a limited time from first posting in which to edit posts. 

If you want corrections made after this time has elapsed, you can pm a moderator outlining what amendments you wish made.

Thanks Frosty. Good advice.

I'm literally a dyslexic typing fast with an AI keyboard. What's the worst that could happen. 😂

[Hadrian1]

During lockdown the 12v Battery on my Lexus hybrid went flat.

It wouldn't hold a charge so had to replace it. They aren't that expensive.