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Why have a 2 stage start button? First stage drains the 12v battery

Cocijo

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If you get time I would be interested to get your views on what value the 2 stage start button adds. I can’t see any value in using purely the 12v battery in the accessories part of this and I’ve spoken to a few people who’ve started to drain their 12v batteries in this setting. What’s the purpose of even having it? Thank you.
 
When sitting in my MG5 I was having a coffee and you have to switch the car on to listen to the radio every 10 mins or so if you have it on the first setting
 
When sitting in my MG5 I was having a coffee and you have to switch the car on to listen to the radio every 10 mins or so if you have it on the first setting
Why not just have it on ‘ready’?
 
I presumed like a ICE car it was better just to have it in the unready mode so as not to use up more energy than I needed...I presume that mode is there for a reason ?
 
I don’t know what the reason is. Like you - I can’t understand why it’s there. In ‘ready’ you engage the HV battery so it keeps the 12v. battery topped up.
 
When sitting in my MG5 I was having a coffee and you have to switch the car on to listen to the radio every 10 mins or so if you have it on the first setting
Same on the ZS EV.
I think it is there to protect the 12 volt battery from being run down to low, which has been done.
Remember, if your 12 volt battery drops to low, having a full HV battery under your seat will not save you !.
If you need any 12 volt items like the radio on any longer than the 10 mins, boot the car into READY mode.
The main HV traction battery only provides a charge to the small 12 volt battery, when the car is in READY mode.
 
Completely agree - but why have two options at all? What is the value in just having the 12v on?
 
It it just gives you quick way to access / activate the items the 12 volt system, without fully booting up the car.
Say, you just wanted to roll down one of the windows, wipe the windows a few times, or even open the sun roof while parked up.
This is a quick solution I guess ?.
 
Possibly. My car boots into ready in about 2-3seconds though - it’s very quick. I also think that by having the 12v option it just leads to owners unnecessary anxiety over low 12v battery voltages. in fact I would remove the button completely and just have the brake pedal push to get the car to ready state with the key present.
 
It it just gives you quick way to access / activate the items the 12 volt system, without fully booting up the car.
Say, you just wanted to roll down one of the windows, wipe the windows a few times, or even open the sun roof while parked up.
This is a quick solution I guess ?.
I agree, but there’s no point as to turn it off you need to go through the 2nd setting to turn it off again anyway.
 
Hey - I have no idea why they did it this way ?.
Maybe they should increase the time line for how long the radio remains active.
On my previous VW's it would do a similar thing, but it would leave the radio active for a much longer time period.
The radio should stay active until you open the drivers door, then shut it down in my opinion.
But it will be still pulling juice from the 12 volt battery and receiving nothing back in the way of charge from the HV pack.
If in doubt, fully boot it up - would be my best advice.
 
If all it does is protect the 12v battery from the radio then I think it would take a whole day of radio use to drain a 12v battery...not 10 mins
 
Back in the ICE days, ignition switches were simple(ish). You inserted the key, wiggled the steering wheel to release the steering lock (sometimes after much swearing because it would often get stuck!) and then you had four key positions to choose from:

0 or OFF -- everything off, steering unlocked if you're lucky, parking lights/side lights and hazard lights still live if you needed them, headlights live on some cars, clock, alarm, immobiliser, etc...
I or ACC -- as above, plus radio on, cigarette lighter on, not much else
II or ON -- as above, plus all electrics on, including blowers, heated rear window, engine management system, all circuitry needed to allow the spark plugs to fire, electric fuel pump, and so on...
III or START -- engage starter motor

Position II, if the engine was not running, would drain the battery fairly quickly. Position I would drain the battery slowly. This is the position that was most useful if parked up and you didn't want to idle the engine. With a healthy battery, you were generally okay, with care, to park up for a few hours with the radio on, sidelights too if legally necessary, and still have enough charge in the battery left to start the engine.

Then along came more sophisticated cars, still ICE, but with a START/STOP ENGINE button. The button simply emulated the original ignition key switch, one push for position I, another for position II, but push with footbrake and/or clutch down and it would go straight to a full engine start.

Fast forward to our super-futuristic electric cars.

Not much has changed, they've kept the existing switch logic and adapted it for an EV. The positions do similar things, except now, we find there's really little need in having positions I or II. However, as a nod to the old days, they still exist. Perhaps they do have some uses, although I agree, the need to park up and use just the 12 volt battery in isolation is probably limited.

I've been tending to treat these extra button positions as being there because they're historical. They've always been there. They had a use in the past. But, in reality, I've not yet found a need for them. If I'm parked up and I want the car on, I leave it in READY mode.
 
Are there any other items powered up in the accessory mode ?.
I say this because while making a few visits to the hospital last year.
I had a long wait of over an hour in the car park.
At first, I had the car in the accessory position and listening to the radio.
But after a while it would shut down, a brief push on the button again would reactivate the radio again.
But as time passed by I could see the 12 volt battery gauge slowly dropping section by section.
When the gauge hit the mid way 12 volt point, it sent out the yellow 12 volt battery warning.
You would not expect this to happen if it was just powering up the radio ?.
 
Are there any other items powered up in the accessory mode ?.
I say this because while making a few visits to the hospital last year.
I had a long wait of over an hour in the car park.
At first, I had the car in the accessory position and listening to the radio.
But after a while it would shut down, a brief push on the button again would reactivate the radio again.
But as time passed by I could see the 12 volt battery gauge slowly dropping section by section.
When the gauge hit the mid way 12 volt point, it sent out the yellow 12 volt battery warning.
You would not expect this to happen if it was just powering up the radio ?.
That’s interesting. Can I ask why you chose not to just engage ready for your wait in the car?
 
That’s interesting. Can I ask why you chose not to just engage ready for your wait in the car?
Yes of course - This is my first full EV - I had a PHEV for four years before this.
So, I was trying to figure out the differences.
When you have your very first EV - you tend to treat it like any other car you have ever owned.
Quickly you start to grasp that they are a completely different beast in many respects.
I have learned a lot, but still have a LOT more to learn.
Unfortunately, so are some of the people we trust with fixing or cars it appears.
This was the point when I found out about the need to have the car in READY mode if you intend to sit for a long time while parked up.
I tend to boot up to READY mode now regardless.
In the summer time it can be a little more forgiving because a lot less equipment is running and therefore less likely to pull on the 12 volt system.
But in the winter, sitting in the car with everything turned OFF is no joke at all.
Many EV drivers of different makes and models have been caught out with under powered 12 volt batteries.
A lot of EV's have larger info units that rely on a computer to run them, look at the size of the unit in a Tesla for example.
The power these things can pull can not be compared to juice needed to keep your normal run of the mill radio found in older type cars powered.
They could fit larger 12 volt batteries of course, but this add's cost and weight.
Therefore, they install a battery that is just about large enough in normal day to day situations.
Ask more demand from this 12 volt battery, without it receiving a charge from the traction battery ( in ready mode ) and it is likely to drain more quickly than you would like or expect.
 
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