RAV4 PHEV 12 volt battery maintenance

[varastevens]

From various forums maintenance of the the 12 Volt Battery is an issue.

1. Can you disconnect the Battery in the rear location in order to charge it to isolate it from the electrics to ensure there is no damage to the  ECU and systems?

2.Who is the Battery manufacturer? Model and cost.

3. Battery capacity and with car parked and locked battery drain {mA)

  

[philip42h]

There's a pinned thread on exactly this topic ...

There's a jump start / charge point under the bonnet - you can top-up / recharge the Battery from there ... there's no need to disconnect anything.

If you use the car for an hour a week you'll never have a problem (OK, never is a long time); if you leave the car idle for over a month you are quite likely to need a jump start / recharge the auxiliary Battery before you can get going again.

But it really isn't an issue ... 😉

[ernieb]

I always figure it’s never a good idea to disconnect the 12v Battery, use the charge points under the bonnet if needed.  Some people connect a n extension cable and socket directly to the 12V Battery in the boot and just plug a trickle charger into that.

As has been said, if the car is used regulator;s not likely to be an issue.

[Catlover]

I am sure Devon Aygo once said NOT to use the under bonnet points to charge the 12v Battery.  They are there for jump starting.            
I also emailed a Toyota customer service and asked the question… Can I use under bonnet connections to charge a 12v Battery in the boot…. And their answer backed up Devon Aygo. No, use to jump start only.

[IanML]

One reason I can think of for not using them for charging is if they were out of circuit with the ignition off, i.e. disconnected from the Battery.  Easily checked - just put a voltmeter across them with the ignition off.

Another is if the Battery were gassing hydrogen - not a good idea with the boot and cabin closed.

[ernieb]

11 hours ago, Catlover said:

I am sure Devon Aygo once said NOT to use the under bonnet points to charge the 12v battery.  They are there for jump starting.            
I also emailed a Toyota customer service and asked the question… Can I use under bonnet connections to charge a 12v battery in the boot…. And their answer backed up Devon Aygo. No, use to jump start only.

Thanks, you learn something every day.

[philip42h]

That sounds like paranoia to me. I can't see any material difference between "jump starting" and "Battery charging". Specifically, the handbook instructions for jump starting require the donor vehicle to be wired to the "exclusive jump start point" and be left with engine running for 5 minutes in order to recharge the auxiliary Battery before attempting to start the car. Personally, I'd much rather do this with a purpose designed smart charger than the dodgy alternator of a donor vehicle.

The gassing question could be relevant but it's worth noting that the Battery in the boot will be charged as you drive along anyway. A good smart charger won't cause any more 'gassing' than the onboard charger.

Personally, I'd rather trickle charge the auxiliary battery via the "exclusive jump start point" to maintain the charge state than risk flattening the battery and requiring a "jump start" and accompanying reset (and I do) - but each to his own ...

[Catlover]

Well, in my mind I was querying what Lee, Devon Aygo, was informing us of, and that’s why I contacted Toyota customer services. It was initially a general question, but they came back saying the technical dept was asking for specifics so I had to give registration number and I used the wife’s Auris hybrid, Battery in the boot, as that was what my question about (Gen4 Prius Battery under the bonnet). There was not a lot of detail in the reply ie they didn’t say not to do it because……..
Maybe Lee can enlighten us a bit more.

[philip42h]

22 hours ago, varastevens said:

2.Who is the battery manufacturer? Model and cost.

3. Battery capacity and with car parked and locked battery drain {mA)

Toyota 'hide' the Battery details quite well but information is given in the Owners Manual under What to do in an emergency; Restarting the Hybrid System (buried in the text). In mine it says:

Use a 12-volt Battery that conforms to European regulations.

• Use a 12-volt Battery that the case size is same as the previous one (LN1), 20 hours rate capacity (20HR) is equivalent (45Ah) or greater, and performance rating (CCA) is equivalent (285A) or greater.
• If the sizes differ, the 12-volt battery cannot be properly secured.
• If the 20 hour rate capacity is low, even if the time period where the vehicle is not used is a short time, the 12-volt battery may discharge and hybrid system may not be able to start.
• Use a ventilation type calcium battery
• Use a 12-volt battery with a handle. If a 12-volt battery without a handle is used, removal is more difficult.

I'd guess that the PHEV would be the same but stranger thigs have happened and owners should probably check their own manual ... 😉

[ernieb]

With the PHEV it might well be just as easy to switch the car into the READY mode and leave it for 20 mins.  The traction Battery will then charge the 12v Battery.

[philip42h]

43 minutes ago, ernieb said:

With the PHEV it might well be just as easy to switch the car into the READY mode and leave it for 20 mins.  The traction battery will then charge the 12v battery.

... and the same is true of the HEV, of course, but the ICE will run as well ... 😉

[Firecycle]

Ok here's a question, when I collect my new RAV in a week or so I will be installing a dash cam with park mode and it need to be hardwired. Whilst I can install myself, the camera via the settings provides protection so as not to discharge the 12v Battery that it wont bring the car into life.

My question is what is the minimum charge level the Battery will engage the system into a ready state?

The app provides various protection levels i.e. 12v, 12.1v, 12.2v, 12.3v and so on.

[philip42h]

I've not seen any minimum charge level stated. Normal practice is to wire the dash cam to the switched side - so it doesn't drain the auxiliary Battery when not in Ready mode. If you need additional park mode functionality I understand that folk install an additional dash cam Battery that recharges when the ignition is on ...

[Cyker]

Agreed - If you want to run it 24/7, get a lithium Battery pack that can power the Dashcam while the car is off, and be charged while the car is running, that way you don't risk the 12v Battery drain problems that people seem to be having! There are some recommendations on the dashcamtalk forum, as most power banks don't let you charge them while they are powering something.

If you're just running it while the car is on like I do, no need to bother with setting a protection level.

 

7 hours ago, Catlover said:

Well, in my mind I was querying what Lee, Devon Aygo, was informing us of, and that’s why I contacted Toyota customer services. It was initially a general question, but they came back saying the technical dept was asking for specifics so I had to give registration number and I used the wife’s Auris hybrid, battery in the boot, as that was what my question about (Gen4 Prius battery under the bonnet). There was not a lot of detail in the reply ie they didn’t say not to do it because……..
Maybe Lee can enlighten us a bit more.

Yeah I was wondering that too but DevonAygo did post a followup later - I think he said something like the +ve point in the fusebox is not connected to the Battery directly, but is connected via the DC-DC system, so putting loads of amps through it could blow something which is why he was saying any battery chargers should be connected directly to the battery.

You can get away with it for 'jump starting' as the 12v system doesn't need much power to turn the computer on and activate the traction battery relays, nowhere near as much as cranking an engine - I've heard of people claiming to have 'jump-started' their hybrid with 8 AA batteries, although not sure how true that is  

 

[Roy124]

16 minutes ago, Cyker said:

- I've heard of people claiming to have 'jump-started' their hybrid with 8 AA batteries, although not sure how true that is  

What do you think is in these mini Battery packs?  That or similar. 

[Catlover]

Just now, Roy124 said:

What do you think is in these mini battery packs?  That or similar. 

But some of these packs can jump start a 3 litre diesel or a 5 litre petrol, much is needed then firing up a hybrid system, and they still only the size of a smart phone.

[ernieb]

Don’t the dash cams with a live feed have an inbuilt trigger to disable the function if the Battery gets low?

[Cyker]

Unlikely - I don't know of any Dashcam that pulls 12v from the car directly; Virtually all of them take a 5v USB supply, so they have no way of knowing if the 12v Battery voltage has dropped below a critical level as all they see is 5v.

Usually that setting is on the hard-wired 12v->5v DC-DC converter like the one I spliced into my lighter socket.

 

[philip42h]

12 minutes ago, Roy124 said:

What do you think is in these mini battery packs?  That or similar. 

Small lithium ion 'jump start' packs will do the job perfectly - and for a hybrid you don't need anything particularly powerful since you don't have a traditional starter motor to turn.

[philip42h]

9 minutes ago, ernieb said:

Don’t the dash cams with a live feed have an inbuilt trigger to disable the function if the battery gets low?

Even if they do, and it works perfectly, I still would want to rely on such a thing. OK, so it switches of the dash cam well before the auxiliary Battery gets too low to start the car. But the car's electronics carry on drawing power for the next few days ensuring that the car won't start anyway!

The 'problem' such as it is is that the auxiliary Battery is of relatively low capacity since it doesn't need to turn over a starter motor, while the car's electronic systems place a non-trivial load on the system. I wouldn't want to add to that load by permanently wiring any accessory to the live side of the system that wasn't originally fitted by Toyota.

[Roy124]

7 hours ago, ernieb said:

With the PHEV it might well be just as easy to switch the car into the READY mode and leave it for 20 mins.  The traction battery will then charge the 12v battery.

Chicken and egg.  Ready mode will indeed allow the traction Battery to charge the 12v Battery provided the 12v Battery has sufficient charge to energise Ready mode. 

[Roger_N]

56 minutes ago, Cyker said:

Unlikely - I don't know of any dashcam that pulls 12v from the car directly; Virtually all of them take a 5v USB supply, so they have no way of knowing if the 12v battery voltage has dropped below a critical level as all they see is 5v.

Usually that setting is on the hard-wired 12v->5v DC-DC converter like the one I spliced into my lighter socket.

 

These appear to be 12V: https://thinkwaredashcam.eu/product/q800pro/

Just for info.