Off Peak Charging - i3 120Ah BEV

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Hengus

Well-known member
Joined
Jan 6, 2015
Messages
85
Location
Uk - Worcestershire
A question for those who use 'off peak' charging. I am finding that setting the car up for 'off -peak' charging can be a bit hit and miss.

My 'off- peak' window is 0030 to 0430am. It's a new i3 so I have access to The Digital Charging Service but no Wallbox. I can set the car up to charge via the App and I can see the settings in the car. The car starts and then pauses the charge. So far: so good.

Yesterday, I did all the above when I returned home at 10.52am. The car has charged to 100% SOC and the amount of charge needed (about 18kWhs) was well within the off-peak window but a quick calculation on cost suggests that charging started at about 11pm last night.

My question is this. Is it possible that there is a bug (or design) in the software that turns a paused charger on after a pause of 12 hours irrespective of the settings in the car? Am I missing something?
 
The charging starts at a time that asures the car is fully charged at the set departure time. The time needed is calculated; the calculation however generally is to pestimistic. This means that often the charge cycle will start earlier than the start of the off-peak hours.
 
If only. I have a 7.4kW charger. I set delayed charging with a departure time of 0430 am. The car required 17.3kWhs to charge to 100% according to the DCS log. Charging appears to have started at about 11pm last night. My off-peak period starts at 0030am. All the charging should have been within the off-peak window. Charging was set to max rate and my smart meter consumption shows that most of the charging was not off-peak and that it finished about 3 hours early.
 
I've not used that feature. From reading the posts here over the years, many people have found it to be unreliable. The most reliable way to accomplish this is with a smart EVSE or a suitable timer that can control the power to the EVSE. Note, not all EVSE devices can work properly from a power off/on cycle...a few require the plug to be inserted only after power has been applied to the EVSE and it has rebooted.

THere's a bit of hidden logic in the car, too. The batteries can be damaged if they are really cold with a low charge. And, while recharging them will warm them up, it may also require heating them a bit. The warming could occur as soon as you plug in to ensure they are not likely to be damaged and it will recharge them to a safe level prior to then switching to wait for the off-peak time window. Same thing with excess heat...damage can occur if they are allowed to get too hot, so if you tried to start while there were already near max, then tried to recharge them, it may delay to cool things off first. If you've set a departure time, the final charging may occur during the battery preconditioning time. Also note that conversion process from line voltage to DC is not perfect, it uses some that is mostly lost as heat.

I don't have time-of-use billing capability, so I never really looked into it in more detail.
 
Thanks Jim. I would seem that owners are getting more consistent off-peak charging by using the settings in the car rather than the App. As of 1 July this year, all new EV chargers in the UK have to be smart enabled which gets around having to set anything but 'charge immediately' in the car. Sadly, I have an old dumb charger and I am not keen to spend £00s to save a few pence. BMW's Digital Charging Service appears to anything but intelligent when working with a third-party EV charger.
 
Update:

By a process of elimination, I seem to have discovered a bug in the charging software (or it may be by design). I have deleted all my Home information from the BMW Digital Charging Service, and I have reverted to setting off-peak/delayed charging in the car. When I came to set it up last night, I noticed that the off-peak time settings in the car for the previous night's charge were different from the ones that I had previously set. I set 00.30 to 04.30 but the car was showing an off-peak start time of 22.51. Why would anyone set 22.51?

The simple answer appears to be that 22.51 was 12 hours from the time that I set up delayed charging on the previous day. That is, the maximum permitted delay can only be 12 hours. I may of course be wide of the mark but having set delayed charging last night, it would seem from my electricity usage graph that all charging was done in the off-peak period.

Qn: Am I brave enough to re-set the Digital Charging Service as it does provide download and cost information?
 
We have also realised that the off peak tariff times we set are being changed apparently randomly by our i3.

At around 18:00 we reset the tariff times in the car to 1:00-6:00 and connected to the charging cable but then needed to use the car 30 minutes later, before the charging had started. But we noticed the times had changed to 09:28-10:15 or so when I re-parked a little later.

We have now turned off connected services and deleted our phone apps to see if that helps. Fingers crossed.
 
After turning off Connected Services and the mobile apps our i3 has been stable and so far retained its off-peak tariff times.

Looks like the issue may not be the car after all
 
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