New owner, USB and 12 volt battery query

[JodyS21]

I am of the opinion that the HVAC system uses both the 12 volt battery and the HV battery, as stated by others.
The 12 volt battery will be used for providing power to the blower motor in the unit ( the thing that provides the air though the vents ) and the HV battery provides the power to provide the heat or the cooling.
You can see this divide some what, if you have the car in the “Ready” condition and with the blower motor turned off and the heat control set to no heat or cooling.
Now - Turn on the blower motor only and keep an eye on the GOM and select the power consumption screen, by scoring though the menu’s on the right hand button on the steering wheel.
With the blower motor ONLY pulling a load, the drop on both gauges will be next to nothing, because the demand is coming from the 12 volt battery.
Now - Turn on the demand for heat to Max setting and watch what happens to the range on the GOM and the amp gauge !.
This proves that the power required to heat or cool the car IS coming from the HV battery.
You can see this when you are travelling as well.
With the HVAC turned completely off.
Firstly, check out your remaining mileage on the GOM.
Then turn on the HVAC and ask for Max heat, almost instantly you will see a 8 - 10 reduction in your predicted range straight away.
HVAC systems are a big consumer of stored energy in your HV pack.
This is one of the reasons why your winter range is never as good as your summer range.
Using “Eco” mode lowers the heat & cooling ability of the HVAC system in an attempt to preserve your range a little.
If you are running short of range while on a trip or looking for a charger, then turn off your HVAC to save your remaining range.

It is possible that the HV battery power that you see is going to the DC-DC converter and then to the 12V system.
It doesn't really make any difference to the HV battery usage which way the power actually gets to the heater.

To know for sure, would either need to look at the heater wiring to see if it does connect to 12V system or HV system direct, or could probably tell via the OBD2 data - as that shows 12V load I think.

 

[Cocijo]

I am of the opinion that the HVAC system uses both the 12 volt battery and the HV battery, as stated by others.
The 12 volt battery will be used for providing power to the blower motor in the unit ( the thing that provides the air though the vents ) and the HV battery provides the power to provide the heat or the cooling.
You can see this divide some what, if you have the car in the “Ready” condition and with the blower motor turned off and the heat control set to no heat or cooling.
Now - Turn on the blower motor only and keep an eye on the GOM and select the power consumption screen, by scoring though the menu’s on the right hand button on the steering wheel.
With the blower motor ONLY pulling a load, the drop on both gauges will be next to nothing, because the demand is coming from the 12 volt battery.
Now - Turn on the demand for heat to Max setting and watch what happens to the range on the GOM and the amp gauge !.
This proves that the power required to heat or cool the car IS coming from the HV battery.
You can see this when you are travelling as well.
With the HVAC turned completely off.
Firstly, check out your remaining mileage on the GOM.
Then turn on the HVAC and ask for Max heat, almost instantly you will see a 8 - 10 reduction in your predicted range straight away.
HVAC systems are a big consumer of stored energy in your HV pack.
This is one of the reasons why your winter range is never as good as your summer range.
Using “Eco” mode lowers the heat & cooling ability of the HVAC system in an attempt to preserve your range a little.
If you are running short of range while on a trip or looking for a charger, then turn off your HVAC to save your remaining range.

I find the whole HVAC/range thing can be a bit confusing. Here are my thoughts - no particular order of importance - I would be interested to learn more;
The ZS does not have aircon in the true sense. It has a simple cooling of air function that works when the cold temperature is selected and the cold air button pressed. Using this cold air button with heating on does nothing at all in terms of additional battery load or to the air coming into the car - it does not run any air conditioning function. There seems to be a lot of confusion about using the cold air button and how it affects range.

I doubt that any part of the heating system or cooling function is powered directly by HV. The HV battery simply charges the 12v battery - the more load on the 12v battery the more it needs to charge it. If for example high heating is selected the range prediction adjusts based on the predicted impact on HV battery use to keep the 12v battery topped up.

 

[Lovemyev]

I find the whole HVAC/range thing can be a bit confusing. Here are my thoughts - no particular order of importance - I would be interested to learn more;
The ZS does not have aircon in the true sense. It has a simple cooling of air function that works when the cold temperature is selected and the cold air button pressed. Using this cold air button with heating on does nothing at all in terms of additional battery load or to the air coming into the car - it does not run any air conditioning function. There seems to be a lot of confusion about using the cold air button and how it affects range.

I doubt that any part of the heating system or cooling function is powered directly by HV. The HV battery simply charges the 12v battery - the more load on the 12v battery the more it needs to charge it. If for example high heating is selected the range prediction adjusts based on the predicted impact on HV battery use to keep the 12v battery topped up.

I do see your point and are unsure just how the system works with regards to what is powering what, at any one time.
However, the heating side of the unit has such a massive affect / drag on the range when used, I am pretty sure that this level of power is not coming from a 12 volt supply.
The blower motor - yes ( maybe ).
But the heater element drain is to far to heavy surly for the 12 volt to even consider ?.
It would be like trying to power a 2kw electric fire with a dry cell battery .

 

[Cocijo]

I do see your point and are unsure just how the system works with regards to what is powering what, at any one time.
However, the heating side of the unit has such a massive affect / drag on the range when used, I am pretty sure that this level of power is not coming from a 12 volt supply.
The blower motor - yes ( maybe ).
But the heater element drain is to far to heavy surly for the 12 volt to even consider ?.
It would be like trying to power a 2kw electric fire with a dry cell battery .

Yes - good points. i think that the drop in predicted range is just a calculation based on current draw. Don’t forget the prediction is based on using the same amount of draw for the whole usable capacity of the HV battery pack. I’m not sure how much current the heater uses but the 12v should cope as long as it is being charged shouldn’t it? Indeed I think it can also cover heated seats, lights, wipers etc too. I think that the heater still works without the HV battery being engaged (albeit not for long before it needs a charge by the HV pack).

 

[Kithmo]

Mine displayed the "format not supported" message when I plugged a 128Gb stick in, then immediately started playing.

 

[Lovemyev]

I’m not sure how much current the heater uses but the 12v should cope as long as it is being charged shouldn’t it?

You know what, I don’t think it could cope with that level of drain myself.
The heated seats do not demand anything like the power required for the heater.
If you left your head lights on by mistake, it would not be too long before the 12 volt would be completely flat.
I imagine the power required to power the cabin heater would be a lot higher.
All guess work on my part here of course.
A bit more research required on my part now I have the bit between my teeth !.

 

[Chrisjk]

After your car has charged to 100% it will them perform a balancing of the cells in the pack IF left to do it’s on thing.
Some EV companies call this “optimising” also, same thing really.
If you are only charging your pack to say 70% most of the time, because you are only carrying out small trips, then the recommendation is to full charge and balance about once a month.
This helps prevent the cells in the battery becoming too far out of balance.
This is why they refer to it as “Balancing The Pack” I think ?.
The second part of your question about “Full Booting Up The Car” with out your foot on the brake pedal, simply means putting the car into the full “Ready” to drive state.
Not pressing the foot pedal and only pressing the “Start” button avoids powering up any other electrical items, if you are looking to check your voltage in your HV pack after a full charge and balance.
Owners with the latest BMS update have learnt that they should be seeing a voltage of around 448 - 450 volts and a estimated range in the default mode of around 160 - 163 miles.
This gives a rough estimation of the level of imbalance in your pack.
I hope this makes some sense at least Steve !.

Thanks for all that
just completed a slow charge.
est miles on N v= 184 and voltage only 431

 

[Chrisjk]

After your car has charged to 100% it will them perform a balancing of the cells in the pack IF left to do it’s on thing.
Some EV companies call this “optimising” also, same thing really.
If you are only charging your pack to say 70% most of the time, because you are only carrying out small trips, then the recommendation is to full charge and balance about once a month.
This helps prevent the cells in the battery becoming too far out of balance.
This is why they refer to it as “Balancing The Pack” I think ?.
The second part of your question about “Full Booting Up The Car” with out your foot on the brake pedal, simply means putting the car into the full “Ready” to drive state.
Not pressing the foot pedal and only pressing the “Start” button avoids powering up any other electrical items, if you are looking to check your voltage in your HV pack after a full charge and balance.
Owners with the latest BMS update have learnt that they should be seeing a voltage of around 448 - 450 volts and a estimated range in the default mode of around 160 - 163 miles.
This gives a rough estimation of the level of imbalance in your pack.
I hope this makes some sense at least Steve !.

Thanks for all that
just completed a full slow charge
est mileage 184 voltage 431
it always give a high estimate for mileage, once it was 203 but then about 30 miles disappeared over about 5 miles actual driving

 

[Gomev]

Thanks for all that
just completed a full slow charge
est mileage 184 voltage 431
it always give a high estimate for mileage, once it was 203 but then about 30 miles disappeared over about 5 miles actual driving

431v is low, as mentioned previously/elsewhere, old BMS should be c. 455v and new should be c.449v

 

[Mark Holmes]

Thanks for all that
just completed a full slow charge
est mileage 184 voltage 431
it always give a high estimate for mileage, once it was 203 but then about 30 miles disappeared over about 5 miles actual driving

Glad you’ve got your car booked in for check as I suspect you’ve the doggy BMS, the sooner it’s corrected the better.

 

[Lovemyev]

Glad you’ve got your car booked in for check as I suspect you’ve the doggy BMS, the sooner it’s corrected the better.

I think both Mark and myself both had a gut feeling early doors, that your car had been bitten by the “Buggy” software.
Your lower voltage is a red flag.
If you where charging by using rapid chargers, you will increase the imbalance in your pack even more.
I am a little surprised that the dealer did not update the software before you collected the car ?.
But then again, I am not THAT shocked to be totally truthful.
Pretty standard level of service - POOR !.
I mean, this not a “Nice To Have” update, it will reduce the range to a level that makes the car almost unusable.
So, not that important really is it ?.
I am currently shaking my head in disbelief here .
The dealer has the opportunity here to update the software and then help restore the pack to a more reasonable level.
Let them know that MG has issued this option as part of a service bulletin.
You will be without the car for a while, so you will need a replacement vehicle while they do the work.
Or the alternative is you can let them update the software and then you can perform the rebalance at home on your wall box or Granny.
Not on a rapid though !.
It is going to take a few slow charges now to recover your pack, so it’s not a five minute job.
MG are offering a voucher to get your next service done for free for the inconvenience is my understanding.
Don’t worry, your battery will recover.
Other owners on the forum have been in the the same situation.
I think you will see a much better / consultant range when your battery is back in a good state.
When sorted, you should see a one to one situation between miles used from the GOM to the distance covered in these weather conditions.
That quick drop in range after only covering a few miles, is another warning sign that the software is a little screwed up.
The use of range to distance covered should be more linear.
Get done ASAP or the recovery time on your HV battery is just increasing with every charge you make.
Remember to check your voltage and predicted range when the car is returned.
You should be seeing a voltage of around 448 - 450 volts and a predicted range of around 160 - 163 miles.
If you are in this all park, you are good to go !.
Good luck !.

 

[Chrisjk]

I think both Mark and myself both had a gut feeling early doors, that your car had been bitten by the “Buggy” software.
Your lower voltage is a red flag.
If you where charging by using rapid chargers, you will increase the imbalance in your pack even more.
I am a little surprised that the dealer did not update the software before you collected the car ?.
But then again, I am not THAT shocked to be totally truthful.
Pretty standard level of service - POOR !.
I mean, this not a “Nice To Have” update, it will reduce the range to a level that makes the car almost unusable.
So, not that important really is it ?.
I am currently shaking my head in disbelief here .
The dealer has the opportunity here to update the software and then help restore the pack to a more reasonable level.
Let them know that MG has issued this option as part of a service bulletin.
You will be without the car for a while, so you will need a replacement vehicle while they do the work.
Or the alternative is you can let them update the software and then you can perform the rebalance at home on your wall box or Granny.
Not on a rapid though !.
It is going to take a few slow charges now to recover your pack, so it’s not a five minute job.
MG are offering a voucher to get your next service done for free for the inconvenience is my understanding.
Don’t worry, your battery will recover.
Other owners on the forum have been in the the same situation.
I think you will see a much better / consultant range when your battery is back in a good state.
When sorted, you should see a one to one situation between miles used from the GOM to the distance covered in these weather conditions.
That quick drop in range after only covering a few miles, is another warning sign that the software is a little screwed up.
The use of range to distance covered should be more linear.
Get done ASAP or the recovery time on your HV battery is just increasing with every charge you make.
Remember to check your voltage and predicted range when the car is returned.
You should be seeing a voltage of around 448 - 450 volts and a predicted range of around 160 - 163 miles.
If you are in this all park, you are good to go !.
Good luck !.

Thanks, reassuring that a lot of others have had this problem

 

[Lovemyev]

A bit more research required on my part now I have the bit between my teeth !.

Just had a quick look at how the majority of EV's are heated and I came across this video.
If you advance the video along to the 6 minute point, then watch until the 7 minute mark, it gives a good explanation of an instant heat resistive heater, then quotes a figure of 2 to 3 kw of energy is being consumed from this type of heater system, to provide heat to the cabin of the car.
It also explains that in much colder conditions, the demand / loss of energy from the HV pack can be further increased.
Also stating that this extra energy demand is therefore lost from the traction battery and effectively shortens the range even more.
Given that a heavy load of 2 to 3 kw's of power is required / consumed by the resistive heater when used flat out in the winter, then it must be safe to assume this load is NOT being supplied by the 12 volt lead acid battery of the car ???.
So, therefore it has to be supplied by the main traction battery of the car then surely ?.
The very small blower motor maybe driven by the 12 volt battery though.
Just like in the case of the heated seats, wipers, lights etc etc.
So the instant ( predicted ) range reduction we see on the GOM when you light up the heater to Max, has a fairly close connection to the extra 2 to 3 kw's of demand you have just placed on the energy stored in the HV battery.
Okay, the GOM is "A Prediction" figure granted, but we have all witnessed the 8 - 10 miles of range lost instantly, when cranking up the heater in the winter time.
My money is still on the energy IS coming from the traction battery to provide heat / A/C cooling then.

 

[JodyS21]

Just had a quick look at how the majority of EV's are heated and I came across this video.
If you advance the video along to the 6 minute point, then watch until the 7 minute mark, it gives a good explanation of an instant heat resistive heater, then quotes a figure of 2 to 3 kw of energy is being consumed from this type of heater system, to provide heat to the cabin of the car.
It also explains that in much colder conditions, the demand / loss of energy from the HV pack can be further increased.
Also stating that this extra energy demand is therefore lost from the traction battery and effectively shortens the range even more.
Given that a heavy load of 2 to 3 kw's of power is required / consumed by the resistive heater when used flat out in the winter, then it must be safe to assume this load is NOT being supplied by the 12 volt lead acid battery of the car ???.
So, therefore it has to be supplied by the main traction battery of the car then surely ?.
The very small blower motor maybe driven by the 12 volt battery though.
Just like in the case of the heated seats, wipers, lights etc etc.
So the instant ( predicted ) range reduction we see on the GOM when you light up the heater to Max, has a fairly close connection to the extra 2 to 3 kw's of demand you have just placed on the energy stored in the HV battery.
Okay, the GOM is "A Prediction" figure granted, but we have all witnessed the 8 - 10 miles of range lost instantly, when cranking up the heater in the winter time.
My money is still on the energy IS coming from the traction battery to provide heat / A/C cooling then.

Video link?

My thoughts:
A fan heater that you may have at home is what a max of 2kWatt. Surely the one in the car isn't going to need to be/is higher than that to heat up a small volume of air inside a car (compared to a room in a house).

Car batteries can easily output 60+Amps (for brief periods), so battery cables rated for this are not unusual, 60 Amps at 12volts = 720Watts.
The main HV cables used in the car are rated for well over 100 Amps - based on the rapid charging rate we know it supports/and discharge rates seen when flooring it.

Say via the DC-DC converter it's supplying 100Amps at 12v, that's 1.2kW. That is perfectly doable with the cable sizes used within the car.

So, who knows. Who's going to take their car apart to find out.......lol

 

[pjmuk]

I thought it was called HVAC as it's High Voltage Air Conditioning!

 

[Chrisjk]

Just had a quick look at how the majority of EV's are heated and I came across this video.
If you advance the video along to the 6 minute point, then watch until the 7 minute mark, it gives a good explanation of an instant heat resistive heater, then quotes a figure of 2 to 3 kw of energy is being consumed from this type of heater system, to provide heat to the cabin of the car.
It also explains that in much colder conditions, the demand / loss of energy from the HV pack can be further increased.
Also stating that this extra energy demand is therefore lost from the traction battery and effectively shortens the range even more.
Given that a heavy load of 2 to 3 kw's of power is required / consumed by the resistive heater when used flat out in the winter, then it must be safe to assume this load is NOT being supplied by the 12 volt lead acid battery of the car ???.
So, therefore it has to be supplied by the main traction battery of the car then surely ?.
The very small blower motor maybe driven by the 12 volt battery though.
Just like in the case of the heated seats, wipers, lights etc etc.
So the instant ( predicted ) range reduction we see on the GOM when you light up the heater to Max, has a fairly close connection to the extra 2 to 3 kw's of demand you have just placed on the energy stored in the HV battery.
Okay, the GOM is "A Prediction" figure granted, but we have all witnessed the 8 - 10 miles of range lost instantly, when cranking up the heater in the winter time.
My money is still on the energy IS coming from the traction battery to provide heat / A/C cooling then.

Fascinating. Where’s the video link please

 

[Steptoe]

I run a Fiat diesel van and am certain (but unfortunately now can't find a link to confirm this) that the cab heating/demisting system includes a electric element to boost the heat output in the early part of any journey before the engine has had a chance to warm the coolant up.

This must be powered by the battery and/or the alternator and it is likely that for the MG the DC/DC converter is acting as the 'alternator?

I'd be a bit nervous with a 400v element anywhere near my legs.....

 

[SteveP]

After your car has charged to 100% it will them perform a balancing of the cells in the pack IF left to do it’s on thing.
Some EV companies call this “optimising” also, same thing really.
If you are only charging your pack to say 70% most of the time, because you are only carrying out small trips, then the recommendation is to full charge and balance about once a month.
This helps prevent the cells in the battery becoming too far out of balance.
This is why they refer to it as “Balancing The Pack” I think ?.
The second part of your question about “Full Booting Up The Car” with out your foot on the brake pedal, simply means putting the car into the full “Ready” to drive state.
Not pressing the foot pedal and only pressing the “Start” button avoids powering up any other electrical items, if you are looking to check your voltage in your HV pack after a full charge and balance.
Owners with the latest BMS update have learnt that they should be seeing a voltage of around 448 - 450 volts and a estimated range in the default mode of around 160 - 163 miles.
This gives a rough estimation of the level of imbalance in your pack.
I hope this makes some sense at least Steve !.

Thanks for all the information

 

[Lovemyev]

Fascinating. Where’s the video link please

Sorry folks - My post did not capture the link for some reason ?.
Here you go !.
As a side note, I have just finished watching a video posted by James of "James & Kate " fame.
He was changing the cabin filters on a Tesla model 3.
In the video, it clearly shows the orange HV cables that is supplying power to the heater in the cabin.

 

[Lovemyev]

I thought it was called HVAC as it's High Voltage Air Conditioning!

HVAC - Heating / Ventilation / Air Conditioning.