Content by MickeySw in February, 2026

The 12V aux does not serve any purpose (all low voltage power is provided by the CCU) when the car is READY, you could actually remove it?? The fact that the car started just fine using the 12V aux means it's OK. Disconnecting/reconnecting the aux does a full HW reset, which ‘fixed’ the...

Might have something to do with high frequency sound waves of the electric motor only the dog can hear? We have two cats, every time I turn on the air fryer the the kitten legs it out the door, the old fellow couldn’t be bothered but then his hearing isn’t the best??

LFP cells have a very low internal resistance therefore less heat is generated by the current flowing through them. The MG5’s heating circuit is also used to cool the cells while driving, hence cruising will not heat to battery to the 30-40 deg C required for optimal LFP charge rates.

As you have noticed CarScanner doesn’t display all PIDs correctly (CMU min/max voltages, Battery cells' data). I wonder if ‘Battery temperature average’ is to be trusted? It could well be that the OEM MG diagnostic tool shows different values? I see roughly the same slow 40-50kW in winter on...

Sorry, I misunderstood, are you’re saying that after the latest upgrade your NMC battery now thinks the average cell temperature is 10deg lower than actual? That’s obviously very concerning, anyone else experiencing the same issue?

I’m guessing you have LFP cells, if that’s correct, then what you see is as good as it gets, unfortunately.. The MG5 is designed to keep the battery at 10deg C or ambient temperature, whichever is higher while driving. It’s therefore a common misconception that cruising at motorway speeds is...

Afaik LFP SR FL models were never sold in the UK market therefore there doesn't seem to be much 1st hand experience available on this forum. But according to European colleagues LFP charge rates (especially in winter) are disappointing to say the least..

Afaik Pre-FL MG5's were only sold in the UK & Ireland, the rest of Europe got the FL models later on. SR versions were always equipped with LFP batteries, LR stayed NMC.

I think @5teep is referring to the NMC (pre-FL) SR version (49kWh usable) when stating range. If that’s the case, expect less range from LFP models (46kWh) especially in winter. https://ev-database.org/car/1646/MG-MG5-Electric-Standard-Range

You can check charging losses by comparing your wall box power (energy going into the car) vs iSmart/console values (energy going into the HV battery)?

If your battery is really LFP then frequent DC charging should not cause such a low SoH, however leaving it fully charged for an extended period of time (weeks) is known to cause excessive degradation. I gather nobody has managed to increase a low SoH by re-calibrating the BMS on an MG5? The...

How far you get on a full charge is definitely influenced by your right foot, however the ‘shrinking’ of your ‘tank’ due to seasonal changes in battery performance cannot be avoided presently (the future seems brighter though).

It does indeed, but who reads manuals? In order for the heating to work the car needs to be READY, same applies to access the Energy Management tab in FL models, (manually start/stop the charging process)?

I have never felt the need to do ‘forced balancing’ as I trust the BMS to take care of it if required, looks like I was right, after 3 years the min/max difference on our MG5 is just 13mV? Actually there is another ‘theory’ that by deep discharging one can trigger a ‘proper balancing’ which...

Maybe SoH is only changed if there is a significant difference? Another reason to deep discharge is to force ‘proper’ balancing (according to some opinions) any chance you did look at min/max cell voltages after charging/balancing was finished?

Slowing down however, will significantly decrease air resistance by about 27% (velocity squared). Lower drag means less energy required, resulting in an increase in range

Lowering speed is the easiest way to increase range? Try 60mph next time.

Looks like 20min wasn't enough, as stated before, one needs to monitor the battery temperature via OBD to get this right, i.e. have the cells at optimum temperature just as you plug into the rapid charger. Apparently the MG4 has a better solution for this, you just select a rapid charger from...

Forgive me for stating the obvious, what do your tyres look like, pressure OK?

Don’t think a SoC of 46% is low enough to re-calibrate the BMS, hence SoH did not change?

Can’t remember if one can monitor battery current on a pre-FL? If possible, you can check if the heating activates: start the car, take a note of the battery current, manually turn on the battery heater, current should increase by 10-15A

99% SoH after 3years and 27k miles is a tad bit optimistic imho, I would not be surprised if they mistook SoC for SoH?

No surprise Your battery will most likely be at 10deg when arriving at the Rapid Charger. At this stage the heating should automatically activate but that doesn’t seem to be happening? The resulting low charge current alone won’t heat the cells significantly, especially if they are LFP..

Pre-heating on an MG5 doesn’t work as one would think, i.e. that I heats the battery and keeps it at that level. It only starts heating if the cell temperature is below ca 10deg C. Once it reaches set temperature (around 30degC) the heater simply turns off. Only when the cells have cooled...

Showing 12.6V after being charged is a good start, question though is how long will it last? Common consensus is that ‘sulfation’ can cause irreversible damage to a 12V aux with just one deep discharge ( < 10.5V)?!

The main function of the 12V aux is to get the car to start, once in READY (or charging) the DC/DC converts the HV battery voltage to around 14V. (You could actually disconnect the 12V battery, the car will keep running). As long as the DC/DC is working, the 12V battery is charging. Once you...

This was discussed a few years back: https://www.mgevs.com/threads/video-doing-the-rounds-to-update-climate-control.3561/

Might have something to do with how accurately one can measure actual fuel consumption in an ICE car? On the other hand the Coulomb counting method (integrating current over time) used in EV’s is very accurate?

Not of you know what you’re doing 😉, as @siteguru correctly pointed out, it’s a quick way to determine battery degradation without a diagnostic tool, e.g. if the GOM shows 230 instead of 250 miles (WLTP), your SoH has reduced to 92%. If you do a BMS calibration charge and the range doesn’t...

Nice work, how do you accurately estimate efficiency though? Ambient temperature is just one factor; others like speed, no of passengers, terrain, weather, driving style etc can have a big effect aslo?

https://www.mgevs.com/threads/making-my-dumb-rolec-charger-a-smart-one-for-under-%C2%A320.4051/

Future range is calculated using the current capacity (SoC x SoH) and rolling average of (past) consumption. Battery capacity looks OK, therefore the cause of dismal range seems to be efficiency (which does go down a bit in winter). What was your accumulated miles/kwh before you reset trip...

.. or follow instructions in post #14. It’s just one of these MG5 ‘quirks’, no need to loose sleep over it..

No surprise here: SoH 95.33%