Squeaky Bum Time!

wattmatters said:
It does also occasionally require this.

Lowest reported SOC I've hit is 5.0%.

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Just new to home assistant: ours is

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I had (I thought) a nicely judged Holyhead to Mid-Wales run last week, estimating 50km to spare at departure. A road closure added 30km extra and a few mountains. At one stage around midnight the GOM showed 30km range, 25km to go.
Regen on the downhill was reassuring. Ended the trip with 20km in the kitty :)
 
securespark said:
It was more that the MG app was happy to state a full charge of 100%, yet Ohme says it still has 7% to go from a starting point of 5%.

Or is my maths up the creek?

Have I misunderstood?
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No your maths are correct but I think the issue is that the car 'knows' its battery state whereas the Ohme estimates based on the car details it has plus how much it has supplied to determine percentage charge added. Also you must allow for measurement accuracies.

To get 88% charge from 56.33kWh the Ohme appears to be using 64kWh maximum charge rather than the usable 61.7kWh. Then you must factor in your battery SOH and the fact that your car looks like it is balancing and will require more energy to complete a full charge.

Another way to look at the numbers is to add 3.1kWh (~5%) to the 56.33kWh to give 59.43kWh which is near enough max battery usable charge. However that implies no losses.

Finally, my Ohme app does not list the car name that's on your Ohme image, with the year 2023. I have only the selection below when I look at the car options.

Screenshot_20250224-091854 (1).png
 
Coulomb said:
Wonderful! Now, if only they were believable.

My guess is that they're not applying the right corrections (scale and offset) to the raw CAN bus data.
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That's odd. About a year ago I poked around trying to find sensible values for the MG4 using car scanner by looking at what was known for other MG's. I found some PIDs which looked plausible for battery pack values:

Post in thread 'OBD Data' OBD Data

The voltages were typically 3.xxxx to a bit over 4 if I remember correctly. Is that in the correct range? If so, I doubt I applied any specific scaling beyond the decoding of the bytes.

As all the values I saw were multiples of 5mV I suspect the decode was just 2 bytes as a 16 bit value, with a scale down of 2000 and an offset of 0. Would the values now available by default in carscanner above, be in range if they were just multiplied by 2?

When I get back off holiday, I'll see if I can find the old phone I did it on, and see what I used.
 
Muffler said:
Deliberately ran mine down last night to see what would happen and with a view to doing a full balancing charge. Got down to 4%. GOM stopped displaying remaining miles at 10% ish and went into turtle mode at 5% and on the hill, I have to travel up to get home, I was gradually losing speed down to 20mph leaving both a squeaky bum and a feeling of total embarrassment. Fortunately there weren't many other cars around at the time but the thought of calling out the AA just 1/4mile from home due to a flat battery wasn't good 🤔😢
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I've been down to 4% a few times and never seen a turtle. The car drove normally the whole way. I was on fast roads and didn't need to cut my speed at all.
 
DixieTGS said:
The voltages were typically 3.xxxx to a bit over 4 if I remember correctly. Is that in the correct range?
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NMC cells have a typical operating range of 3.0 - 4.2 V.

LFP cells have a typical operating range of 2.5 - 3.65 V.

Mostly however you don't take NMC all that much below 3.1 V and LFP much below 2.9 V. There's not a lot of energy left at those voltages.

When my (NMC) car reported 5% SOC the pack voltage was 351 V which is an average cell voltage of 3.375 V (104 cells).
 
Got to 0% and the message ‘low charge, stop safely’ literally as I pulled up opposite the charging station.
Passenger was getting a bit anxious.
I was as calm as ever, as I know my GoM has always been absolutely spot on below 25% charge.
Turtle appeared at 2% charge left with 4 miles remaining.
At 0% it was still showing 1 mile left.
This was taken after plugging in for less than a minute.
 

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fnegroni said:
Got to 0% and the message ‘low charge, stop safely’ literally as I pulled up opposite the charging station.
Passenger was getting a bit anxious.
I was as calm as ever, as I know my GoM has always been absolutely spot on below 25% charge.
Turtle appeared at 2% charge left with 4 miles remaining.
At 0% it was still showing 1 mile left.
This was taken after plugging in for less than a minute.
Click to expand...
You win
 
fnegroni said:
Got to 0% and the message ‘low charge, stop safely’ literally as I pulled up opposite the charging station.
Passenger was getting a bit anxious.
I was as calm as ever, as I know my GoM has always been absolutely spot on below 25% charge.
Turtle appeared at 2% charge left with 4 miles remaining.
At 0% it was still showing 1 mile left.
This was taken after plugging in for less than a minute.
Click to expand...
bloody hell, I would not have been calm (but then when I was young and poor I did run out of petrol a lot)
 

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