MG 5 Battery Pre Heat ?

timmpo said:

But interesting is that i can clearly hear the feeding-pump when i start the heating but i have never hear it when i connect the charger.

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The battery heater has it's own small circulation pump

timmpo said:

the service manual does only mention that the BMS starts the PTC heater in the case of fast charging.

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Actually the manual mentions the battery heater in the context of both rapid and fast charging (see edits in post 39)

I have now confirmed that the BMS lets the battery charge in below zero temperature. There is no wait for the battery to heat up before charging.
I can charge at 10kW when the battery temp is -4°C and the heater will start at the same time the charging starts.
If the heater draws 4kW then the battery receives 6kW and its around 15 amps DC and if the cells are around 120 Ah the charge rate is around 0.125C if my poor math is correct.
Charge rate over 0.1C can destroy a LFP battery, google says...
I hope the BMS limits the current when charging at higher levels than that, I have not yet tested.

This calculation is very loose and I may be wrong, but I have not seen any indication that the car will limit the charge current but I have not tested at higher charge rate than 10kW.

If my math is wrong and the c rating is at 0.1 or less there is no problem at -4°C battery temperature.

timmpo said:

I have now confirmed that the bms lets the battery charge in below subzero temperature. no wait for the battery to heating up before charging.

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Thanks for confirming

timmpo said:

I can charge at 10kw when the battery temp is -4c and the heater will start at the same time the charging starts.
If the heater draws 4kw then the battery receives 6kw and its around 15 amps and if the cells is around 120ah the charge rate is around 0.125C if my poorly math is correct. Charge rate over 0.1C can destroy a lfp battery, google says...

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Nothing wrong with your maths per say:

According to the manual

• LFP cell capacity 131Ah (120 cells)
• max CCU HV output 9.9kW
• battery heater rated power 3.5kW
• total battery voltage range 300-438V i.e 2.5-3.65V per cell ??**

**curious what your actual battery voltage is @10/100% SoC

Assuming a low SoC cell voltage of 3.2V, a charging power of 5.5kW into the battery, (3.5kW for the heater) would result in a current of 14.5A or about 0.11c.

The interesting question is how long does it take for the cells to warm up sufficiently, do you have any data?

timmpo said:

I hope the bms limits the current when charging at higher levels than that, i have not yet tested.

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You can't achieve higher rates using AC charging with an active heater.

Unless you have a CCS station at home, one needs to drive to do a rapid charge and unless it's just down the road, the cells will have 'naturally' warmed up by the time you arrive..

MickeySw said:

Unless you have a CCS station at home, one needs to drive to do a rapid charge and unless it's just down the road, the cells will have 'naturally' warmed up by the time you arrive..

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I suspect that it takes a lot longer than "just down the road" to warm a typical EV battery with normal driving.

Coulomb said:

I suspect that it takes a lot longer than "just down the road" to warm a typical EV battery with normal driving.

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Best to turn on the MG5’s ‘battery heating while driving’, set regen to KERS1 and monitor cell temperature with OBD to be on the safe side.

Coulomb said:

I suspect that it takes a lot longer than "just down the road" to warm a typical EV battery with normal driving.

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In my experience at zero degrees C the first 6-10 miles are very poor consumption wise, but after that it picks up the economy to almost normallish.

See my post from a while ago...(you need to click on it to go to the post to see the end)

Gomev said:

In my experience at zero degrees C the first 6-10 miles are very poor consumption wise, but after that it picks up the economy to almost normallish.

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Yes, that’s probably the time it takes to get the cell temperature up to ‘nominal’ 10 deg C in winter time.

Would be interested to know how quickly the cells reach this level in standstill with the battery and cabin heater at full blast?

I tested 15 min drive in the city with max 50kmh roads and logged the lowest battery cell temperature starting at 3°C and finished at 3.5°C.
I used OBD car scanner on Android.
No preheat engaged in this test, next time I should activate the pre heat, good to know how fast it will increase the temperature.

timmpo said:

I tested 15 min drive in the city with max 50kmh roads and logged the lowest battery cell temperature starting at 3c and finished at 3.5c.
I used odb car scanner on android.
No preheat engaged in this test, next time i should activate the pre heat, god to know how fast it will increase the temperature.

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LFP cells have a lower internal resistance (vs NMC), the theory is that this results in very little thermal output.

Looks like your quick test seems to confirm that…