Charging under lockdown

[JAYT22]

My wife just received the following from a Mitsubishi email address. Are there any actual lithium battery experts on the forum that can comment on it?

"Don’t leave your PHEV plugged in longer than necessary. While you’re not driving it, aim to keep the charge at around the 30% mark and leave it unplugged."

As there is frustratingly no numeric indicators on a 2018 Outlander PHEV, it's difficult to judge 30% by eyeball. Or maybe they mean the 30% the car retains when the electric gauge is zero.

Some of the other information on this forum appears to be wrong about memory effect for lithium batteries. NiCads have a pronounced memory effect but two generations on, lithium ion degradation is due to crystal growth within the batteries, there is little memory effect. In fact if there was, the advice above would make it worse.

Does anyone know the facts, or is the information from Mitsubishi's marketing department unreliable. (I know they put out something a while ago that was in fact not how the vehicle works, so I'm going to unplug my car for now, but don't know what to trust. )

 

[AlexBorro]

The information is correct. The best voltage to store Li-Ion cells is 3.86V. Of course you don't need to be spot on this. Just avoid full charged or discharged battery.
If you do not plan to use the car for a few days (that is the target customer for the email you received), charge/discharge the battery to half (around 50% on the display gauge) and let it there.

Li-ion does not have memory effect, but storing it at full charge or depleted speed up the degradation process.

Cheers.

Alex.

 

[STS134]

Best to put the car in READY mode for at least 15-20 minutes every 2 weeks to allow the system to charge the 12V battery. The 12V battery seems to lose about 0.2V/week and it's best to keep it above 50% SoC, but the system WILL NOT charge the 12V battery if you don't use the WiFi remote control. You have to put the car in READY mode and only then will it apply 14.7V to the battery for 10 minutes to charge it, before dropping to 14.3V and continuing to charge at a lower rate. I've found that about 20-30 minutes is enough to get the voltage of the 12V battery up from around 12.3V (which is where it typically is if you let the car sit for 2 weeks) to around 12.7V.

 

[michael8554]

I measured mine at 12.1V, so I trickle charged for a couple of hours and it went to 13.0V straight off the charger, I didn't measure it again after letting it rest

 

[STS134]

Correction, voltage after 2 weeks is around 12.54V, not 12.30V. Turns out, even with all lights in the car off, that display in the instrument cluster draws enough power from the battery that the voltage sags by about 0.14V. I did another test where I shut all of the doors and the hatch and waited long enough for the voltage to stabilize, then measured it. So I'm guessing that after 2 weeks, the battery still has around 70-80% SoC left, assuming it was charged to 100% before you let it sit for 2 weeks and do NOT use the WiFi.

 

[ChrisMiller]

Won't the WiFi always be on, continually broadcasting (10 times a second) the car's SSID? The power draw should only be a few watts.

 

[ThudnBlundr]

The have been posts on the UK FB page that the WiFi goes off after some days without use. That would make sense for cars being transported or in storage. Pressing 'Start' will turn it back on.

 

[STS134]

Won't the WiFi always be on, continually broadcasting (10 times a second) the car's SSID? The power draw should only be a few watts.

No, it will not. There is actually a procedure to enable the WiFi (turning on the hazard lights and pressing two buttons on the remote alternately 5 times in a row, 10 button presses total). This causes the vehicle to start sending 802.11 beacon frames every 100ms or so and that's what causes it to become detectable. The vehicle keeps track of how many devices are "registered"; if there are 1 or more devices registered, then it will send out 802.11 beacon frames (and I'm guessing it also keeps a small computer running at all times). However if you press the keys alternately 10 times in a row (20 presses total), then this deletes all registered devices and disables the WiFi and any associated power draw.

https://www.mitsubishi-motors.com/en/products/outlander_phev/app/remote/registrationinitialization.html

There does not appear to be any security on the system beyond the WPA2 PSK of the WiFi and perhaps MAC address filtering (to identify individual devices) which can easily be bypassed by sniffing WLAN packets and spoofing the MAC. So I see the WiFi as a security issue since Mitsubishi never issues updates/patches for this system. That's another reason (in addition to the vampire power drain issue) that I just want that system switched off at all times.

 

[ChrisMiller]

It's conceivable there are differences in the UK implementation, but the multiple key presses you describe instructs the car's computer to accept a new connection, and (as far as I can tell) WiFi is always on even before this procedure has been done (though I obviously can't go back in time to check). That the car continues to broadcast its SSID can be easily seen by observation. It may be it ceases to do this after a few days, as ThudnBlundr suggests, but I haven't noticed this happening after 4 or 5 days.

Of course, as with any modern car, even when it's 'off' there will be several computers churning away, doing 'stuff'.

The security weaknesses in the WiFi implementation were partially addressed by software updates a few years ago, but (like all too many 'Internet of Things' implementations) it's still not very strong. But since the worst that an attacker can achieve using the WiFi is to turn the heating or headlights on, I don't lose too much sleep about it.
https://www.pentestpartners.com/security-blog/hacking-the-mitsubishi-outlander-phev-hybrid-suv/

 

[STS134]

It's conceivable there are differences in the UK implementation, but the multiple key presses you describe instructs the car's computer to accept a new connection, and (as far as I can tell) WiFi is always on even before this procedure has been done (though I obviously can't go back in time to check). That the car continues to broadcast its SSID can be easily seen by observation. It may be it ceases to do this after a few days, as ThudnBlundr suggests, but I haven't noticed this happening after 4 or 5 days.

10 presses causes the vehicle to start accepting new connections and enables beaconing. If no device registers, then it should stop beaconing. If a device registers, then WiFi is enabled, and it should continue beaconing. It's roughly equivalent to pressing the button on a garage door opener. 20 presses is for clearing all registered devices, similar to a long hold of the button on a garage door opener. If you do that, it will disable the WiFi.

Of course, as with any modern car, even when it's 'off' there will be several computers churning away, doing 'stuff'.

The security weaknesses in the WiFi implementation were partially addressed by software updates a few years ago, but (like all too many 'Internet of Things' implementations) it's still not very strong. But since the worst that an attacker can achieve using the WiFi is to turn the heating or headlights on, I don't lose too much sleep about it.
https://www.pentestpartners.com/security-blog/hacking-the-mitsubishi-outlander-phev-hybrid-suv/

And disabling the theft alarm, according to that article. And if they connected the WiFi system to other systems, you could in theory take over more parts of the vehicle, potentially even disabling or reprogramming safety systems.

 

[ChrisMiller]

All I can say is that my PHEV is still broadcasting its SSID after 4 days without use (and it's been 3 years since I did the 'multiple presses' to connect a new device). I've no plans to disable the useful WiFi app to save a couple of Watt power drain.

 

[STS134]

All I can say is that my PHEV is still broadcasting its SSID after 4 days without use (and it's been 3 years since I did the 'multiple presses' to connect a new device). I've no plans to disable the useful WiFi app to save a couple of Watt power drain.

Have you been able to determine what the power draw of the WiFi is (i.e. by putting an ammeter in line with the battery terminals)? If it is indeed a "couple of watts", then that's 166 mA of current. The Yuasa s46b24l(s) is rated at 45 Ah in the 20 hour test. Assuming we use the same total amount of charge available, that makes it a 271 hour battery, i.e. the WiFi would discharge the entire battery on its own in about 11 days.

I've determined, experimentally, that without WiFi on, the battery loses about 15% of SoC a week, or 30% every two weeks. That means that even at 2W, the WiFi is drawing down the battery at about 9%/day, as opposed to the entire rest of the vehicle which draws it down at around 2%/day. That's a ton of useless cycling, and is probably why these batteries have been reported to be failing in some people's cars. When I drive my car almost every day (as is the case when there's not a pandemic), the battery probably spends most of its time between 98-100% capacity.

 

[AlexBorro]

I'm trying to understand how this post turned out to be about the 12V battery..

Anyway, absolutely under no circumstances a Wifi module will take 2W of power.

A regular wifi module with a 32 bits microcontroller will draw around 200mW in idle with the WiFi powered on.

 

[STS134]

I'm trying to understand how this post turned out to be about the 12V battery..

Anyway, absolutely under no circumstances a Wifi module will take 2W of power.

A regular wifi module with a 32 bits microcontroller will draw around 200mW in idle with the WiFi powered on.

Do you have reason to believe it's just a 32 bit microcontroller? I think Mitsu didn't really take power budget into account and is running something much more power hungry along with the WiFi. Except unlike Tesla (which regularly issues OTA software updates and my friend with one says that his "vampire drain" has decreased from 15% per week when he got it to around 1-2% now), Mitsu doesn't ever issue software updates.

 

[AndyInOz]

... Mitsu doesn't ever issue software updates.

:roll:

I guess that explains why Mitsubishi have updated the software on my car many times, including updating the wifi software three times.

 

[jaapv]

... Mitsu doesn't ever issue software updates.

:roll:

I guess that explains why Mitsubishi have updated the software on my car many times, including updating the wifi software three times.

:lol: