12v battery maintenance

[CBphev]

Thanks Ian, I put it on charge with a smart charger but that only has a 4amp output.  After ten hours it was still merrily charging away so Battery was flat rather than voltage dropping due to a load on it.  But I will definitely take your advise for when I check it again at the weekend.

[nlee]

I found this interesting.

The following two screenshots are at the same scale. The first shows the rate of discharge of the Battery a couple of weeks ago. The second shows it now.

I'm the time between, 2 things have taken place. I've given the Battery a treat with a day on the smart charger, and I've had the software update on the DCM. It's quite clear that the rate of discharge while standing is less now.

[IanML]

What is the vertical scale in terms of Volts?

[Dala]

[nlee]

10 minutes ago, Dala said:

Never really looked at he scale on mine before, but surprised to see that it isn't linear with the top and bottom sections covering a range of 2v and the middle 2 covering 1v each. It's a strange way to present data. Glad you pointed that out!

[IanML]

Yes, very odd, but workable once you know.  It looks like the long charge has brought the baseline up to a good level (about 12.6V) and it's holding, which suggests that there is no appreciable parasite drain.  The see-saws were perhaps cured by the update.

What is revealing is that a voltage reading after a charge is only representative after about a day and a half, which I didn't know.  What are you using to monitor the voltage - I'm tempted 😉

[Dala]

https://www.aliexpress.com/item/1005004439206340.html

[Roy124]

Dala, excellent price, less than half that on Amazon.  My only reservation would have been whether it worked or not (at £27), but now I know how it works and at that price.go for it. 

Reviews are correct, the instructions leave a lot to be desired.  I am sure Dala can fill in any gaps. 

The only thing I would say is the SoC/Voltage default is only indicative and can be fine tuned using advice here or from the Internet. 

[nlee]

This is what confuses me over the way the DC-DC invertor works.

The graph below shows the 12v system voltage yesterday. On the way to work the voltage is around 14.3v. Quite normal and as expected. After parking up and settling down the voltage is higher than before the journey, again as you'd expect.

On the way home, I noticed that the usb adapter I have in the 12v socket that shows voltage was only showing 12.3/12.4v. Looking at the graph, this results in the Battery voltage being less after the journey than it was immediately before, i.e. driving the car for 20 mins has put no charge into the 12v Battery.

Both journeys on EV with climate control and lights on so should be comparable.

Note the blip at the end of the journey home. I've mentioned this before but as I pull up outside the house and steer ready to reverse, the voltage jumps up to the normal 14.3v.

It's also noticeable that the rate of discharge while parked and standing between the two journeys is greater than before the 1st journey and after the 2nd.

[philip42h]

1 hour ago, nlee said:

This is what confuses me over the way the DC-DC inverter works ...

I'm not sure that I can add 'clarity' but this is what I see:

• The car sits overnight at around 12.3v. There is no obvious appreciable drop in voltage while standing for this time.
• When you set out, shortly before 8:00, the DC-DC converter switches immediately into 'charge' mode delivering a charging voltage of around 14.5v. This remains the case through the 20 minute journey.
• At the end of the journey there remains a certain amount of 'surface voltage' giving a reading of around 12.6v which settles / dissipates throughout the day. But the Battery is still at around 12.4v when you return at 17:40.
• The DC-DC converter switches into 'supply' mode for the return journey delivering around 12.6v - i.e. at that point it sees no need to recharge the Battery but simply delivers the operating supply that the 12v system needs.
• There is that transient 'blip' towards the end of your journey but the DC-DC converter never actually gets into charge mode.
• At the end of the journey the car settles at around 12.3v as before ...

If you drove for an hour or so in the morning (rather than just 20 minutes) I would expect to see the DC-DC converter switch from 'charge' mode (14.5v) to 'supply' (12.6v) as the state of charge of the Battery is restored ...

[nlee]

7 minutes ago, philip42h said:

There is that transient 'blip' towards the end of your journey but the DC-DC converter never actually gets into charge mode.

It does go up to "charge mode", around 14.3/14.4v but the resolution on that longer term graph is every 2 mins. From what I can work out, it's the average of the 2 min block it plots. 

Like I say, it's only as I steer left to prepare to reverse onto the drive that it jumps up so probably only for 30 seconds-ish before I turn the car off, hence why it doesn't look like it got to max voltage.

[IanML]

One possibility is that the power steering is powered electrically (rather than belt drive from the ICE on an ICE car), and the extra demand when you steer left prior to reversing onto the drive, takes the 12V system load into the region that requires "charge" to resume.

[Cyker]

Plausible, I could hear the engine load increase if I tried to turn against full lock in my old cars! 

[Nick72]

Just an update, since the DCM software update (failure to shut down issue) I've had zero 12V problems. I can go for over a week so far without car use and then just a few short 1.5mile short trips in-between. Not had a problem. Same prior to taking it into its first service (when the problem started from I think a bodged attempt at software updates by the dealer). I went 2 to 3 weeks at a time without using the car and then just the odd very short trip. Never a problem.

[spicyhotone]

Had my alarm go off a few times - always around 9pm. Nothing happening around car. Given it a good spray of fly spray, thinking it was a moth waking up and trying to reach a nearby streetlight, but still get the same. Then measured 12v Battery, and it's 11.8v, not good, assuming that's most likely the cause.
I've got a Battery charger somewhere, but a little worried charging this as it's in the car's interior rather than the better ventilated engine bay like most cars - is it safe to just leave on charge for a few days with all the doors closed, don't really want a recreation of the Hindenberg on my driveway!
Not sure if it's rescuable or if such a low voltage indicates permanent damage to the Battery. Had a longer run over the weekend, a couple of 1+hr drives, and still seeing low voltage after a day or so, so I'm a little concerned.
Off on a driving holiday across Europe in a couple of weeks, so probably not time to book it into the dealer before we go. Is there a way of seeing if the DCM update has been done on my car (would this be done routinely at service?). Am assuming as the car is less than 3 years old, any DCM updates would be done under warranty - but what about a 12v battery replacement if it is knackered?

[TonyHSD]

21 minutes ago, spicyhotone said:

Had my alarm go off a few times - always around 9pm. Nothing happening around car. Given it a good spray of fly spray, thinking it was a moth waking up and trying to reach a nearby streetlight, but still get the same. Then measured 12v battery, and it's 11.8v, not good, assuming that's most likely the cause.
I've got a battery charger somewhere, but a little worried charging this as it's in the car's interior rather than the better ventilated engine bay like most cars - is it safe to just leave on charge for a few days with all the doors closed, don't really want a recreation of the Hindenberg on my driveway!
Not sure if it's rescuable or if such a low voltage indicates permanent damage to the battery. Had a longer run over the weekend, a couple of 1+hr drives, and still seeing low voltage after a day or so, so I'm a little concerned.
Off on a driving holiday across Europe in a couple of weeks, so probably not time to book it into the dealer before we go. Is there a way of seeing if the DCM update has been done on my car (would this be done routinely at service?). Am assuming as the car is less than 3 years old, any DCM updates would be done under warranty - but what about a 12v battery replacement if it is knackered?

Hi Paul, 

if your Battery is located inside the car will have a vent hose and any gases will escape out. No problem leaving it charging overnight. Smart charger will do it . Not sure though if the Battery drops below 12v in two days of inactivity means most likely you have parasitic drain or Battery is on its last days. You can run your regular number on dvla site for recalls or Toyota website directly and see if there are any outstanding recalls, if yes you can call your local dealer and ask to confirm. You can also ask them to check your battery and if bad May push your luck for under warranty replacement. You can argue that the car has premature dead battery or inheritance bad battery problem., all that can be accepted unless you only do 2000 miles per year. Worth noting to try your luck. 👍

[ernieb]

I have a NOCO genius 5 smart changer and I’m happy to leave that overnight as it mangers the charge, temperature itself. I’d have thought that even a dumb charger if you started the charge during the day time would be OK so that the higher current has reduced.

Before the DCM update I regularly saw 11.8v when I switched on the car and after the various pumps had stopped but the car would always go into READY mode.

You could leave the car in READY mode and that would charge the 12v from the traction Battery.

From you description I’d say you probably have not had the DCM update, I got a letter telling me that this was needed and my car is also a ‘21 PHEV. 

[philip42h]

18 minutes ago, spicyhotone said:

I've got a battery charger somewhere, but

I recognise the concern, but wouldn't personally have an issue with using a modern smart charger to top-up the Battery. I wouldn't use an ancient dumb charger that I happened to have 'somewhere' ... 😉

I assume from what you have written that the car goes into Ready mode happily? If it does, I wouldn't be too concerned about the state of the auxiliary Battery - and would be looking for an alternative cause for the false alarms.

You should have had a recall letter before the DCM update was done. And I might expect to see evidence in the Service History - though other owners can advise better.

Your usage pattern really should be sufficient to keep the Battery topped up. Touring around Europe should certainly do it. But I would invest in a Jump start pack (and have invested) to get you going again just in case.

Also, while others may I don't get too excited by a nominal 11.8V on the battery - this is a reading with the battery connected and powering the car's systems when off. You shouldn't necessarily expect over 12V as you might get if the battery were disconnected from the car.

[Rigsby]

As above replies, the DCM recall addresses a number of issues including those relating to the 12volt Battery, if you haven’t had a recall letter contact your dealer.

There are some very good smart chargers available, my advice is to buy one of the more reputable brands (CTEK, NOCO etc) rather than a cheap one, I have a CTEK MSX 5.0 that I used with my Jaguar whose Battery was located under the spare wheel in the boot, a real PITA to get to so I fitted a CTEK remote charging socket in the boot.

 

[ernieb]

Hot of the press:

Just called a local dealer to get them to have a look at the charger door cover which has started to sag and they said that there was a new recall my car needed which is to replace the DC/DC inverter. I asked which one it was and he said the 375v to 12v.

I’d give your local dealer a ring and ask if there are any outstanding recalls on you car.

(I did say the car had had the DCM software updated and the 12v system stayed charged now and he said OK but that inverted needs changing, he’s getting the parts delivered overnight for me to go in tomorrow at 10am)

[ernieb]

Toyota RAV4 (2019 – 2022)

Published on 24. 07. 2023

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Problem description:

The DC-DC converter may be faulty, which can cause the current from the 12V Battery to continue to flow, generating heat and increasing the risk of a vehicle fire.

The Toyota RAV4 vehicles affected by this recall were manufactured between 26 November 2019 and 26 May 2022.

Toyota recall code: 23SD-075
Affected models: Passenger car, equipped with plug-in hybrid engine. Model code: NX450h+: AAZH26; RAV4 PHEV: AXAP54; model year: 2021-2022.
Vehicle numbers (worldwide): 47,000

[spicyhotone]

Ordered myself a noco charger. Is it safe to charge the Battery with it still connected to the vehicle - given this is more than a trickle charger, so will be doing fancy stuff to the current/voltage to try and fix the Battery, is there any danger of it frying any of the car's own circuits? Wondering what happens if the car is powered on whilst the charger is connected?

I've ordered a permanent wired connector/socket so I can easily plug/unplug the charger from the Battery, but now wondering if that isn't such a good idea, as it means having the battery connected to the vehicle whilst charging.

I've never received any letter concerning the DCM update, or so far about the DC-DC converter recall - purchased my car in August 2021, so am guessing I will be affected by that one. The only recall so far has been the one concerning the braking system, which was applied at my last service in April. Although, it's not explicitly listed in my online service history - is that normal?

[philip42h]

31 minutes ago, spicyhotone said:

Ordered myself a noco charger. Is it safe to charge the battery with it still connected to the vehicle

Personally, I use the jump start point in the fuse box under the bonnet to charge the Battery as needed.

This approach strikes me as perfectly safe and effective. The Noco (or any smart charger) will simply charge the Battery using a constant current approach at the outset, converting to a constant voltage as the Battery approaches full charge and intermittent top-ups to maintain the battery once full charge is achieved.

I wouldn't dream of running any repair mode while the battery is still connected to the car but for a standard battery top-up the smart charger isn't doing anything that the DC-DC converter wouldn't - the DC-DC converter is simply a smart charger anyway.

I wouldn't try to go into Ready mode with a charger connected. I doubt that it would do any harm but you'd have two chargers connected at the same time and they might just argue one with the other. And there would be absolutely no need to do so.

Just a personal view (and practice) - others may disagree.

[ernieb]

I have fitted a connector to the Battery so I just plug the charger into the socket when needed. I’ve used it a few times now and nit had any issues.

[Wrighty69]

I have been in contact with Toyota and they said "get a solar charger that plugs into the DL3 diagnostic socket and that will charge the Battery with the ignition off".

Now I just need to locate the DL3 Diagnostic Socket and a suitable solar charger.