2017 Prius PHEV battery

[RichSH]

With the Covid-19 lockdown due to get more draconian my car isn’t doing much mileage and that I am doing is almost all on EV alone. When running in EV mode, does this charge the 12v Battery or does the engine need to run to do this?

[Ten Ninety]

I believe the 12v will charge as long as the car is in Ready - EV or HV mode. The ICE does not have to run.

I also read on Priuschat that when you plug the car in to charge, the 12v gets topped up after it's 'filled' the HV Battery. Therefore, even if you're doing very low mileages, as long as you're plugging in regularly the 12v should be fine.

 

[PeteB]

2 hours ago, Ten Ninety said:

I believe the 12v will charge as long as the car is in Ready...

That's correct, for all Toyota Hybrids, not just plug-ins.

I had a minor heart scare just over a year ago and was told not to drive for a month.  Every 10 days I sat in the Prius I had at the time for 20-30 minutes in READY mode and that kept the 12V Battery topped up just fine.

I also believe Jay is right about plug-ins charging the 12V when plugged in as well.

[Ten Ninety]

On 3/22/2020 at 10:03 PM, PeteB said:

I also believe Jay is right about plug-ins charging the 12V when plugged in as well.

Apparently, the original PiP charges the 12v whilst charging the traction Battery, whereas the PHV waits until the traction Battery is full and then charges the 12v. However, that information was from people on Priuschat doing their own measurements and not an official source.

[RichSH]

Like most others,  I’ve been doing some short journeys recently but was safe in the knowledge that having plugged in to charge the traction Battery on returning home all would be well with the 12v one. A couple of weeks ago I disconnected the cable as there didn’t seem much point in having it connected all the time. Went out to the car today to move it and it’s as dead as a dodo: central locking went haywire, alarm went off and, once I got in through the only door which would unlock (n/s front), I was presented with a blank screen when I pressed the start button. This rate of degradation seems ridiculous to me on a two year old car. Nothing had been left on and my wife’s  6 year old Audi, (still on its original battery) which hasn’t moved either, is in rude health!

[FROSTYBALLS]

Also see:

 

[Joseph D]

On 5/4/2020 at 4:41 AM, RichSH said:

Went out to the car today to move it and it’s as dead as a dodo: central locking went haywire, alarm went off and  ...   This rate of degradation seems ridiculous to me on a two year old car.

Yes, something sounds awry. I don't know if I would have unplugged it though, just because it seemed to be doing nothing, doesn't mean it was doing nothing.

Might be a good idea to check to confirm your model does charge up the 12 V Battery in addition to the HV Battery, though.

[RichSH]

Interestingly, the Toyota maintenance blog on how to maintain Battery condition on hybrids doesn’t mention remaining plugged in for PHEVs but simply says turn the car on and into ready- mode for a period each week. That says to me mains charging doesn’t top up the 12v Battery.

I jump started the car to get it going and went for a drive and all seems well for now. Will obviously keep an eye on it but it seems poor to me to be so susceptible to a flat Battery.

[QuantumFireball]

My understanding with the 1st gen PHV is that the 12V Battery is charged while the HV Battery is being charged. This can be observed by checking the 12V voltage when it's charging. However, once HV charging is complete, it seems to do nothing if you leave it plugged in.

I know other EVs and PHEVs will do some maintenance of the 12V Battery if left plugged in, however I don't know about the Gen 2 PHV. 

I got a CTEK smart charger for mine and leave that plugged in, as I'm driving less than about once every two weeks now (and only to the shops).

[Ten Ninety]

I've been putting miles on the Lexus recently as my PHV is well past its service mileage. However, I had to use it yesterday and after being unused but plugged in for nearly a month, it started up fine. Whilst that is hardly definitive proof that leaving it plugged in does charge the 12v, I am still inclined to believe that it does, as suggested by the testing carried out by Priuschat users.

Don't read anything into that Toyota blog not mentioning this - when it comes to the PHV, Toyota UK barely know it exists, let alone how it might actually work.

I think the 12v has long been a bit of a 'weak spot' for most Toyota hybrids. If I'd have left any of my previous Toyota hybrids for a month, they'd have been dead. I don't know if it's because there are more things draining charge (like keyless entry) or just that the Battery is specced lower than a traditional ICE car because it doesn't need to crank a starter. Either way, it doesn't seem to like being left for very long at all, hence Toyota's recommendation of running hybrids in 'Ready' for an hour a week.

[RichSH]

Jay, you’re right. I contacted Toyota GB who confirmed this morning that plugging a PHEV into the mains does indeed charge the 12v system. Hopefully that’s the problem solved.

[QuantumFireball]

I assume that is only confirmed for the 2nd gen PHV? Because I don't believe the 1st gen will do any 12V charging after HV charging is complete - I'm not certain though.

I'd prefer not to keep the HV Battery at a high SOC with all this lack of use anyway, so happy with using my CTEK 12V charger for now, and charging the traction Battery when needed.

[johalareewi]

On 5/6/2020 at 1:03 PM, RichSH said:

Jay, you’re right. I contacted Toyota GB who confirmed this morning that plugging a PHEV into the mains does indeed charge the 12v system. Hopefully that’s the problem solved.

From past experience Toyota GB don't always know thier products that well.  Especially hybrids and plugins.

[Ten Ninety]

4 hours ago, johalareewi said:

From past experience Toyota GB don't always know thier products that well.  Especially hybrids and plugins.

They probably looked up the answer on this forum. 😁

[RichSH]

I’m beginning to wonder. 
I had my car plugged in for several days to make sure the 12v Battery was (theoretically) fully charged. Unplugged in on Tuesday just to see what would happen and by Saturday, checking it with my newly purchased Battery condition device, it Indicated it needed recharging - urgently. I went out for a drive for 45 mins and it then showed the Battery to be charged. If it holds the charge, it means plugging in doesn’t re-charge the 12v battery. If it doesn’t, the battery is duff. 

[noelfix]

My 2017 Plug in would not turn on because of the 12v Battery was flat. The car has been plugged in continuously but not used very much due to lack of running. The 12v Battery DOES NOT charge despite the car being left plugged in.  The 12v Battery only shows 11.2volts after the car has been running, but if left it drops to 10.2v and won't turn on after not being used for 1 week. So I had to use a charger to bring it back to life.  I now turn on the power to keep the battery charged. 

Originally my car would show a range of 66km but now it only shows 53km. The mileage  is only 26000km. 

[Joseph D]

You probably should be thinking of replacing your 12 V Battery.

Given your PiP does not seem to also charge the 12V Battery when plugged in, you should use a separate automatic multistage 12V Battery charger anytime the car will be laid up for 3 days or more.