12v battery maintenance, issues, etc.

[Roy124]

Or is it possible that the DCC (?) is also limited in how much it can transfer?  Ie the power drain exceeds the charge rate? 

The biggest power drains could be the rear screen heater, seat heaters, wheel heater, then wiper motors. Aircon might obviate the need for the additional heaters and intermittent wipe cut that drain too. 

But what is the most efficient way to operate the aircon when the high energy demand is greatest? 

 

[ernieb]

I can only speak to the PHEV RAV which has a heat exchanger that runs from the traction Battery, so little other than control drain from the 12v system. Interestingly if you run the PHEV in EV mode even with a full traction Battery and switch on the front screen heaters the ICE will fire up even though this runs off the traction Battery (I think?)

[Nick72]

4 hours ago, Roy124 said:

Or is it possible that the DCC (?) is also limited in how much it can transfer?  Ie the power drain exceeds the charge rate? 

The biggest power drains could be the rear screen heater, seat heaters, wheel heater, then wiper motors. Aircon might obviate the need for the additional heaters and intermittent wipe cut that drain too. 

But what is the most efficient way to operate the aircon when the high energy demand is greatest? 

 

Stereo on loud.

[Nick72]

4 hours ago, ernieb said:

I can only speak to the PHEV RAV which has a heat exchanger that runs from the traction battery, so little other than control drain from the 12v system. Interestingly if you run the PHEV in EV mode even with a full traction battery and switch on the front screen heaters the ICE will fire up even though this runs off the traction battery (I think?)

I had assumed, but possibly wrongly, that the front screen demisters requires ICE start because the heat for it is sourced from the engine output and that the only thing that required electrical power was the fan to drive the hit air through and the valves to control temp. Both of which I assumed were driven from the 12V?

This is probably the most efficient way of doing it from an energy perspective.

[IanML]

It may be both - a 12V heater to get it going until the ICE coolant is hot enough to take over.

That would be similar to my KIA SoulEV - it has a PTC heater to get things going, and a heat pump to take over when fired up and delivering.

[ernieb]

My guess is that it’s a PTC heater for the front windows in the RAV. This could be 12v or run off the higher voltage of the Heat Pump, I’d guess not the 12v system.

[Nick72]

What confuses me then is why the ICE needs to start right away. Why not start it later. I mean if the PTC heater is running it probably does the job in a few minutes in most circumstances and then the user switches it off. Having the ICE warming up was unnecessary. Surely the best option would be to delay start of the ICE (for the case of an anticipated prolonged use of the demister and which can be predicted based upon outside air temperature). That would make a lot more sense? Pretty simple logic but I could be missing something.

[Cyker]

It depends on how powerful the PTC/resistive heater is, but I suspect it's either quite weedy (just enough to stop you freezing but not output anywhere near enough heat to make the cabin actually warm), or it'll be so powerful it'd drain the traction Battery very quickly; Either way I suspect the engine has to cut in to do the heavy lifting, so to speak.

This is one of the biggest problems EVs have - The heat ICE cars get 'for free' is actually a huge amount of energy which the EVs don't really have to spare; The reason they're trying to moving to heat pumps is because it needs a lot less energy to 'move' the heat from somewhere else into the car than to actually make it. At the end of the day, burning stuff for heat is far more efficient than burning stuff to make electricity to make heat.

 

[ernieb]

8 hours ago, Nick72 said:

What confuses me then is why the ICE needs to start right away. Why not start it later. I mean if the PTC heater is running it probably does the job in a few minutes in most circumstances and then the user switches it off. Having the ICE warming up was unnecessary. Surely the best option would be to delay start of the ICE (for the case of an anticipated prolonged use of the demister and which can be predicted based upon outside air temperature). That would make a lot more sense? Pretty simple logic but I could be missing something.

Agreed, but you know from your own experience that once you touch that font window heater the ICE kicks in. Just the same when you brake heavily going down hill, especially when the traction Battery is full, the ICE kicks in. They must have solved the issue in the full EV car?

[nlee]

If this video is anything to go by, it's decided it needs more heat than the heat pump alone can generate, so use heat from the ICE.

 

It's near the end where this is discussed, but it only tells you how, rather than why.

I haven't used the demister since last winter but I wonder if you just turn the heat and fan up and direct it to the screen in manual, it just uses the Battery as normal. It gets plenty warm enough  normally and quickly in EV mode.

[ernieb]

I’ve followed the guy in the video for some time, his explanations are usually spot on.

Never had a combination where selecting the screen heater in the car did not fire up the ICE.

[IanML]

3 hours ago, ernieb said:

 They must have solved the issue in the full EV car?

In a full EV car, you draw in the traction Battery either for the PTC, or for the heat pump if it has one.  The heat pump is much more efficient, becase it is only shifting heat from the electronics and propulsion, where it is unwanted and wasted.

[ernieb]

24 minutes ago, IanML said:

In a full EV car, you draw in the traction battery either for the PTC, or for the heat pump if it has one.  The heat pump is much more efficient, becase it is only shifting heat from the electronics and propulsion, where it is unwanted and wasted.

That’s what happens in the PHEV as it has, even when depleted, round 6k/Wh of energy left for the cars services and to operate in HEV mode. But even when the traction Battery is full, 18.1k/Wh the ICE will kick in under certain circumstances as discussed above.

[Rav4 Hybrid]

I hope everyone knows, what EV mode does to your Battery. Hybrid Battery that is, not the 12v one.

Using EV mode button, lets the hybrid Battery to deep discard, instead of discarding only to 50% like batterys are safe to do, in order to still recharge to 100%.

So in simple terms : You deep discard your hybrid battery to way under 50% in EV mode, EV button pressed that is.

Result is that your hybrid battery will never again charge back to 100%. This is for the PHEV rav4 model, with iron phosbate battery. Plug-in model battery is different.

 

Think it as this way: Gel battery can discard to 0% and still able to recharge to 100%, while AMG and older/worse types are only able to discard to 50%, in order to still recharge to 100%. Discard AMG battery to below 50% and it will never fill to 100% anymore, ever. Not even if youd stood on your head.

 

PHEV rav4, using EV button, end up replacing the hybrid battery in 3-5 years (100 000- 160 000km) (10 years warranty wont count as its used like ment to be used, battery just wont last if using EV button too much (at all basicly) replace and pay the costs).

Never use EV button in self-recharging rav4, and your hybrid battery will last 10-15 years (350 000km).

 

Above is just about the EV button, not the EV-mode, wich is often use if driven normally, or un-normally. Button does the damage, normal usage does not.

With button pressed hybrid battery deep discards, without button on normal use only discards to 50%.

 

But everyone uses how they like.

Personally 12v battery here hasnt ever ran out yet.

Currently car has sitted on -20c for a week now in Finland, and starts up like from under the palm on summer day. 2019 model, so battery is now 3, almost 4 years old, original one.

🙂

[nlee]

17 hours ago, Rav4 Hybrid said:

This is for the PHEV rav4 model, with iron phosbate battery. Plug-in model battery is different.

I'm sure this is just in the translation and I'll credit you that your English is far better than my Finnish!

But the PHEV is the plug-in version. 

I admit, I don't know for sure, but I'd be surprised if the system allowed the Battery to be fully discharged. It might show zero on the display but likely it is protected to reserve 10-20% of the Battery to prevent long term damage.

[ernieb]

@nlee, correct the traction Battery has around 30% when the SOC shows zero. So that the claimed performance can be maintained, acceleration etc. but also so that the HEV mode is fully supported. 

[nlee]

17 minutes ago, ernieb said:

@nlee, correct the traction battery has around 30% when the SOC shows zero. So that the claimed performance can be maintained, acceleration etc. but also so that the HEV mode is fully supported. 

Yes, I know it's a bit confusing but I believe he's taking about the HEV and squeezing as much as possible out of the hybrid Battery by forcing it to EV. It probably doesn't reserve as much as our PHEVs but I'm sure it'll keep something back for charge protection.

[Nick72]

6 hours ago, ernieb said:

@nlee, correct the traction battery has around 30% when the SOC shows zero. So that the claimed performance can be maintained, acceleration etc. but also so that the HEV mode is fully supported. 

Ernie is right here. And it is virtually impossible to use up all of that 30pc despite hard up hill extreme frequent acceleration. Had it almost true 0 and I was really hammering the car. But the moment you are not accelerating then the excess power is now going into topping up the reserve in the traction Battery. So it it soon restored. Max 306hp DIN only used in hard acceleration, and probably high constant speed towing up hill!

[robo1]

Not sure if people have seen this USA Tech Tip regarding damaging the ECU when jump starting the 12v Battery. If you use the ECU mounting nuts as your neutral return it can frazzle your ECU. Problem is the Battery packs have too short a negative lead to reach the official ground point.

[ROCKETRON]

When I have needed to use a boost I have used the nuts at the top of the strut for my earth. Seemed to work ok.

[robo1]

That’s the ones I used but wasn’t aware of the potential pitfalls. I wouldn’t think you would get a replacement ECU under warranty. Perhaps Toyota should fit plastic nut covers and update the manual if they have not done so already. 

[Strangely Brown]

There is no pitfall using the nuts on top of the strut. In fact, AMD (Care Care Nut) has shown that to be a good place in one of his videos.

There is, on the other hand, and pretty obvious risk if you were to use the ECU mounting bracket nuts as shown in that document.

[CBphev]

I checked my 12V Battery yesterday on my Rav4 PHEV and was a bit shocked to see it at 11.5V considering it is used every day for 2 x 20min commutes and on a weekend for 2-3hrs.  Does anyone know the power of the DC-DC charger?  I did check the voltage in "Ready" and it rose to 14V so it is charging, just wondering if the charger just isnt quite man enough

Thanks

Chris

[ernieb]

Mine shows 14.4v initially when charging and then drops to 14.2v pretty quickly. I use an accessory socket digital voltmeter which seems accurate enough when compared to the direct Battery reading. It’s easier to monitor the Battery in various conditions.

I don’t know the answer to your question about the inverter charge capacity but so far in all the discussions this has not appeared to be the issue.

[IanML]

The Battery terminal volts depend heavily on the load presented at any time.  If you unlock the car and measure it immediately, it will be lower than when the car has been left open with nothing on for (say) 30 minutes.  That is because various items are woken-up when the car is unlocked, and they go back to sleep after a period if nothing happens.

Try opening the bonnet and leaving the car with nothing on for half an hour, and then measure.

If it's still low, disconnect the earth terminal and measure again.  If that's still low, charge the Battery with a modern charger (eg CTEK or NOCO), and repeat the checks a day or two later.  In your case, after the weekend would be ideal.  If the problem has persisted, the Battery may have a partial internal short-circuit, which is slowly discharging it.  Alternatively, there may be an excessive current draw from a defect in the car wiring.  This can be checked with a sensitive ammeter connected between the battery negative terminal (when disconnected from the car) and the earth connector, observing the half hour wait from when the ammeter was placed in circuit. It should be less than about 20 mA, but on a new car I would expect better then 10 mA.