which one is more efficient? charging just after a journey..

[DocRush]

Hi

I really doubt if one should charge his/her i3 just after a journey or wait for a period till the battery gets cool(?)

In terms of efficiency which one is more rational?


BTW, I am aware of the hint which recommends charging a BEV just before the start of a journey maximises the energy efficiency (with or without preconditioning).

( PS: Our i3 had no relation with the KLE issue thanks to its fortunate production date. )

 

[alohart]

If one's battery pack and charging electronics are hot enough to require active cooling while charging, the overall efficiency would be significantly lower compared with charging without cooling. It's easy to hear the heat pump compressor, so I terminate charging and wait till later if I hear the compressor.

If the battery pack and charging electronics aren't hot enough to require cooling, I don't know whether charging immediately after driving is more or less efficient than charging later. For best battery pack longevity, it's probably slightly better to charge just before departing so the battery pack doesn't sit as long at a high charge level, but that's not always possible.

 

[DocRush]

Dear Art,

Our i3 unfortunately devoids of heat pump; so, I can never hear the heat pump compressor. :roll:
But our parking area under the condo is chilly enough to cool the high voltage battery in an hour.

After an hour long journey (=commute) should I connect the i3 to our EVSE or wait (e.g. 1 or 2 hours) for the sake of efficiency and/or high voltage battery's long-term health :?:

 

[alohart]

Our i3 unfortunately devoid of heat pump; so, I can never hear the heat pump compressor. :roll:

I would be surprised if Turkish i3's do not include air conditioning (i.e., air cooling). If yours has air conditioning, it has a heat pump. Unlike with the BEV, your heat pump doesn't pump heat into your car, only out of your car. The cold refrigerant created by the heat pump cools the battery pack and charging electronics when they're too hot.

But our parking area under the condo is chilly enough to cool the high voltage battery in an hour.

The heat capacity of the battery pack is quite high. Its temperature would likely drop a bit sitting in your cool parking space for an hour, but it might not drop enough to avoid needing cooling while charging immediately after driving, especially in warm weather.

After an hour long journey (=commute) should I connect the i3 to our EVSE or wait (e.g. 1 or 2 hours) for the sake of efficiency and/or high voltage battery's long-term health :?:

If it's not too difficult to return to your parking space (ours is ~100 meters away!), I would wait which is what I do. But I also stop charging at ~80% unless I'm about to depart and need more range. But I don't know whether charging a warm battery pack is more or less efficient unless the cooling system turns on while charging which would definitely be less efficient.

 

[jadnashuanh]

Up to a point, a warmer battery pack will hold more energy (or at least be able to discharge it during use). Even while driving, if the battery pack needs to be cooled, it will be, so the pack probably should never be too far from within its desired temperature range. The thing weighs about 450# (maybe about 210Kg), and once hot, it will take awhile to cool off (and conversely, once cold, awhile to heat up!). The logic is fairly robust, I"d just charge it up and not worry about it. The EVSE will be shut off once the car is happy with its battery, so it does not just sit there under charge forever. The hysteresis and parasitic power drains are small enough, so that the EVSE doesn't cycle very often, either. I do not know what warranty BMW has on the battery pack outside of the USA, but if it's similar to ours, 100,000-miles, or 8-years, and if it doesn't hold at least 70%, it will be replaced. IOW, the car is designed to handle it, and if there's a glitch, you're covered.

 

[DocRush]

Dear Art
In Turkey our unique importer had established some idiosyncratic treaty with BMW AG implying below specifications:
* vehicles possess both 4U7 and 4U8 (fast charge gadget)
* vehicles devoid Heat Pump
* vehicles devoid Sun Protection Glass
etc.

( PS: Here we fortunately are allowed to benefit from air conditioning . )


As a result,
I owe gratitude both of you for friendly replies and/or comments.