My i3 has been losing about 3% soc each night after being charged completely even though I'm still plugged in. It did not do this before and has been happening regularly now. I'm using l1 charging. When I wake up in the morning it's charging itself even though it was already at 100% 8-10 hours earlier. Does anyone else experience this problem?
Losing charge while plugged in
- Thread starter Pixelpro
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alohart
Well-known member
If you are preconditioning the cabin and/or battery pack, the preconditioning might be requiring more power than your L1 EVSE can provide thus taking the additional power needed from your battery pack.
Pixelpro said:
Exactly the same here. Car is charged up to 100% (32 Amps) in the evening, remains plugged in. In the morning, around 30 mins before the end of precon (departure time 8:30am) the charge is at 97% and the car is charging.
My guess was that it is obviously related to the preconditioning and battery prep.
I'm just wondering what to do once my Economy-7 meter has been installed in 2-3 weeks time, as I was planning to charge that car during the cheaper overnight period. The battery prep cycle would obviously fall into the costlier morning rate.
I know Jim posted a graph of charge the car takes before/during the battery prep cycle, but can't find the old post.
Anyone got any experience with this?
jadnashuanh
Well-known member
It's frequently colder in the morning than in the evening. I do not know if that is part of the equation. It is for max range calculations.
Do you leave the car locked or unlocked? Do you have comfort access? How far away is the car from the living spaces where you may have the fob in your pocket? Each time the fob gets closer to the vehicle, certain things happen. That could be happening numerous times over the time the car is sitting there.
Do you leave the car locked or unlocked? Do you have comfort access? How far away is the car from the living spaces where you may have the fob in your pocket? Each time the fob gets closer to the vehicle, certain things happen. That could be happening numerous times over the time the car is sitting there.
NormanF
Active member
Could it be from charging the low voltage battery?
jadnashuanh
Well-known member
All batteries lose some capacity as temperature drops, but LiOn are much better than most types. But, the car may be responding to a slight voltage drop based on it being cooler, and subsequently trying to recharge it. This is a guess.
jadnashuanh said:
I alwaya lock the car when it is charging and the key fob stays in the same place, which is not close to the car.
This issue didn't happen until recently and is a daily occurrence at around the same time each morning. It has actually been much warmer rather than colder in he mornings the last several days as well. This leads me to believe it is not related to the weather. I leave the car charging at work outside during the day on the l1 charger and do not notice this issue.
RJSATLBA
Well-known member
I mentioned this behaviour in my 27 Feb post re discrepancy between SoC per car and per iRemote.
This isn't just a discrepancy between the iremote app and the actual soc. I witnessed the car drop three percent charge this morning and the charger kicked back on. The iremote indicated 100 percent then wirhin two minutes dropped to 97 percent and began charging the car. This isn't a cold weather problem from what I can tell either. Something is definitely wrong.
jadnashuanh
Well-known member
Many of the modules in BMW vehicles rely on the computer to tell them when to turn off via the CANBUS. If a module fails to either receive that message, or is defective, it could stay on when it should not be, and could be discharging the vehicle. Very few of the things in the car are controlled directly like a real switch...there's a little circuit card in there and a connection to the computer. FOr example, the light control switch for the headlights does not switch power to the vehicle lights! The connection to is has 3-4 very small wires in a miniature connector that in no way could switch the current required to control them; it sends a signal as to where it is, and the computer sends out another signal to tell the things to turn on/off, or switch modes. This allows the wiring to be much lighter, the connectors smaller, the switches to use low power contacts, and overall, saves weight and costs. My other BMW is the same way, so it is not unique to the i3. But, as I said, if a module is flaky (more likely a connection in the wiring is) it could prevent things from seeing that the car is actually off, and continue to try to talk on the bus, wasting power.
I checked again this morning and at 7:50am the car was still at 100% charge, from the night before. At 8:04am precon & battery prep started and app reported 97% and car charging. At 8:09 it was back at 100% and stayed that way. I guess precondition and battery prep continued until departure time at 8:30am.
My relatively uneducated guesses are:
a) there's a difference in SOC since the outside temp dropped overnight and needs briefly topping off in the morning. As morning temperatures rise in the year, this will occur less.
b) at the start of precon, some power is drawn from the batteries (or the prep heating has some effect)
My relatively uneducated guesses are:
a) there's a difference in SOC since the outside temp dropped overnight and needs briefly topping off in the morning. As morning temperatures rise in the year, this will occur less.
b) at the start of precon, some power is drawn from the batteries (or the prep heating has some effect)
RJSATLBA
Well-known member
It has to be telling porkies because the rate of charge when so close to 100% couldn't possibly be enough to charge from 97% to100% in the 5 minutes to 8:09.psquare said:
RJSATLBA
Well-known member
psquare said:
Nor me, just curious.
jadnashuanh
Well-known member
Estimating battery capacity, especially when nearly full, is tricky. A slight voltage change can occur by a slight temperature change, and I doubt the vehicle has more than a few (if that) sensors in the battery compartment. So, once you start to draw power from it or recharge it, it tends to warm itself up, which can change the voltage, and that can change how 'full' it thinks it is. The battery SOC is much more reliable when operating rather than while just sitting there. The vehicle could get a feel for how full it is by noting the input voltage and the amount of current being used during charging, but, the voltage always drops when you stop charging and you must be using more than the pack can make itself to push electrons in (you need that electrical pressure), so monitoring how much and how fast the voltage drops off when stopping the charge can also give an idea of how full it is. If a cell is 'low' some of the power could move around internally, and then show up as the whole being less than full after balancing things...I think this is one reason why the car cycles the EVSE when near the end of the charge cycle. Not every cell accepts a charge at exactly the same rate - IOW, there are (usually minor, but measurable) differences between them, so balancing helps maximize the overall capacity.
