Topradio
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Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 7:31 am

I am going away and will be leaving my PHEV on the drive for a week. Would it be best practice to leave it discharged (which is the state it's currently in) or plug it in and leave it to charge up, or doesn't it matter?

I will have plenty of time to charge it when I return before I will need to drive it.

Bladevane
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 8:49 am

Can't see that it matters. I've left mine at airport parking for 2 weeks and there has never been a problem. Equally I leave it plugged in at home, with a padlock on the cable, just in case.....
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ps44
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 9:26 am

Doesn't really matter for just a week.
Best practice for battery life for longer storage is, I believe, to leave them at about 70 % charge, which equates to about 50% on the gauge.

Kesto
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 10:43 am

Make sure you reset all timers on MMCS , otherwise battery will discharge. People forget ,park the car and off to the terminal to get off on holiday.

jaapv
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 11:10 am

Basically 50-70% charge is the best state to keep Li-ion batteries for longer periods. However, as the car will recharge the 12V battery from time to time and will have the WiFi active, it is wiser to store it fully charged.
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STS134
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 12:57 pm

I disagree. The 12V battery is like a glass of water and the drive battery is like a barrel. It's not good to keep the drive battery fully charged for any length of time especially during hot weather -- ideally, you charge it up no more than an hour before you drive it. In the case of leaving the car for a week, there would be plenty of drive battery energy to replenish the 12V battery even at just 1 bar. But you also have to remember that the 12V battery itself was designed to last at least 30 days during storage, so keep it discharged during your absence.

jaapv
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 5:01 pm

You are forgetting that a "fully charged" battery will never be fully charged. The safety margin you refer to is built into the car firmware.
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Re: Leaving vehicle for a week - charged or uncharged?

Sat Sep 28, 2019 5:27 pm

jaapv wrote:You are forgetting that a "fully charged" battery will never be fully charged. The safety margin you refer to is built into the car firmware.
Keep in mind that this "safety margin" was set by the engineers from the same company who claim that the ICE has "modifications" that allow it to immediately start producing power after a cold start (i.e. if you floor it and the ICE is cold). Yet these same engineers also actually designed the system to specifically NOT put more than ~3 kW load on the ICE until 48 seconds after it starts, if the driver does not demand more than 60 kW of total power. :roll:

jaapv
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Re: Leaving vehicle for a week - charged or uncharged?

Sun Sep 29, 2019 1:28 am

Umm - isn't the delay part of the modifications? It shows that it has been carefully thought through.
The engine starts for charging during driving are magnitudes more frequent than the ones for high power demand.
As there have been zero reports of worn ICEs - indeed, any ICE trouble- with plenty of cars around that have done hundreds of thousands of kms, they clearly did an excellent job.
I fail to see what this mechanical thing has to do with the state of charge of the battery, come to think of it, I am sure that the engineers who worked on the electrics are not the same engineers that worked on the mechanical part.
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Re: Leaving vehicle for a week - charged or uncharged?

Sun Sep 29, 2019 7:36 am

jaapv wrote:Umm - isn't the delay part of the modifications? It shows that it has been carefully thought through.
The engine starts for charging during driving are magnitudes more frequent than the ones for high power demand.
As there have been zero reports of worn ICEs - indeed, any ICE trouble- with plenty of cars around that have done hundreds of thousands of kms, they clearly did an excellent job.
I fail to see what this mechanical thing has to do with the state of charge of the battery, come to think of it, I am sure that the engineers who worked on the electrics are not the same engineers that worked on the mechanical part.
The whole point is, I don't trust statements from those engineers. There is clearly something that isn't good about loading the ICE less than 48 seconds after a cold start, and they try to avoid this scenario, yet they allow it to happen if you suddenly demand power.

What is known about Li-ion batteries is that leaving them at a high SoC and at high temperatures for long periods of time causes extra degradation. OP has already stated the following: "I will have plenty of time to charge it when I return before I will need to drive it." As such, there is absolutely no reason why the OP should leave it charged. It can only hurt, it cannot help. As I've already said, the best policy for your battery is to charge it up such that it finishes charging less than 1-2 hours before you drive it. Over long periods of time, this lowers the average SoC and thus the total amount of degradation, and the effect is cumulative. It won't matter much what the OP does for this specific trip either way, but you don't want to make a habit of leaving the vehicle plugged in and fully charged all the time.

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