MG4 Battery Degradation

[Tig170]

To be fair, the old reason why I have a MG4 now is due to the LEAF, as was given it via work to test out.

 

[Macadoodle]

100% charge is better for LFP than 80%, it is not that.

Not sure about that. The flat voltage curve means the BMS likes the data from a full charge to accurately balance the cells but that doesn't necessarily mean they like it up 'em

Pretty sure 100 half cycles interspersed with a few full balance charges would give less degradation than 50 odd full cycles for example.

 

[tsedge]

Not sure about that. The flat voltage curve means the BMS likes the data from a full charge to accurately balance the cells but that doesn't necessarily mean they like it up 'em

Pretty sure 100 half cycles interspersed with a few full balance charges would give less degradation than 50 odd full cycles for example.

I don't think that's so with a modern BMS and the recommendations are to charge the SR to 100% very frequently for the balancing (as you say). For example, Tesla recommend ALWAYS charging to 100%, even daily:

"If your vehicle is equipped with an LFP Battery, Tesla recommends that you keep your charge limit set to 100%, even for daily use, and that you also fully charge to 100% at least once per week. If Model 3 has been parked for longer than a week, Tesla recommends driving as you normally would and charge to 100% at your earliest convenience."

 

[Tig170]

clealry this is an interesting debate (I have an MG4 LFP not a tesla LFP), I've just manually reduced my ohme charger to add charge to around 80% (from 100%)- and ill try to contiune for the next few months.

 

[bowfer]

See above in the edit for evidence. There's a load more articles on this.

That’s just an odd article, a UK website using data from ‘plug in America’ ?‍
Yes the lack of active cooling has caused the leaf issues in hot USA states, but this hasn’t transferred over to here.
Years of UK Leaf forums, battery degradation was rarely even mentioned.

 

[tsedge]

That’s just an odd article, a UK website using data from ‘plug in America’ ?‍
Yes the lack of active cooling has caused the leaf issues in hot USA states, but this hasn’t transferred over to here.
Years of UK Leaf forums, battery degradation was rarely even mentioned.

Believe what you want, I have things to do. x

 

[bowfer]

Believe what you want, I have things to do. x

I believe you have very odd opinions about the Leaf, despite never having driven one.

 

[Tig170]

From work colleauges, is that the lack of active battery management on the early LEAFs kills the ? (at least in the UK), but this is 10 year old technology!

 

[Macadoodle]

clealry this is an interesting debate (I have an MG4 LFP not a tesla LFP), I've just manually reduced my ohme charger to add charge to around 80% (from 100%)- and ill try to contiune for the next few months.

Interesting indeed. From what I can gather though, you won't 'damage' LFP cells by letting them drift a few mv apart through not balance charging for a couple of weeks, done this on mine at least twice.

The pack will be discharged to the first cell to reach the min voltage threshold even though other cells have more energy to release, but this slight imbalance will recover at the next 100% charge.

 

[Tig170]

Interesting indeed. From what I can gather though, you won't 'damage' LFP cells by letting them drift a few mv apart through not balance charging for a couple of weeks, done this on mine at least twice.

The pack will be discharged to the first cell to reach the min voltage threshold even though other cells have more energy to release, but this slight imbalance will recover at the next 100% charge.

Thats what I'm genuinly hoping, in that when i collected our MG4 it was showing 217 miles @100% SOC on 30/09/22, lets hope in the next month when the temp equals Sept 22 again, we will get something similar (yes I have reset the EV trend 'clock' on the dash)

 

[Macadoodle]

I tend not to look at the GOM I must admit, don't find much use for it's optimistic view of the world
I have a cheap inductive power meter counting juice into my charger in the garage and I keep a record of that.
As long as the battery is still accepting 50 + kWh from 10% including charger losses I'll be a happy bunny.
I am finding 50kWh usable (or 45 in practical reality) about the minimum I find comfortable to live with, so I'm really hoping for minimal degradation in the 3 or 4 years I'll likely keep the car .

 

[Tig170]

I tend not to look at the GOM I must admit, don't find much use for it's optimistic view of the world
I have a cheap inductive power meter counting juice into my charger in the garage and I keep a record of that.
As long as the battery is still accepting 50 + kWh from 10% including charger losses I'll be a happy bunny.
I am finding 50kWh usable (or 45 in practical reality) about the minimum I find comfortable to live with, so I'm really hoping for minimal degradation in the 3 or 4 years I'll likely keep the car .

What should we be looking for? - mines on 40% this evening, but should charge to 100% overnight - what figures am i expecting am?

 

[Macadoodle]

What should we be looking for? - mines on 40% this evening, but should charge to 100% overnight - what figures am i expecting am?

Figures on the GOM ? Dunno, mine usually suggests 200 miles after a balance but I get nervous after 160 or so and tend to pay it no heed.

 

[Tig170]

Figures on the GOM ? Dunno, mine usually suggests 200 miles after a balance but I get nervous after 160 or so and tend to pay it no heed.

I assume GOM = GuessOMeter ? - but i still do have ABRP of 2.7% degredation

A shout out to OHME / MG / EDF - as its appearing to handle BST / GMT seamlessly - in that it appears to be only chaging in my off peak time?

 

[Ayoull]

This morning:
MG4 SE SR
1.9% degredation
2779mi

 

[Macadoodle]

This morning:
MG4 SE SR
1.9% degredation
2779mi

Weird, I have almost 1000 miles more and I'm just not seeing any noticeable difference in energy in with my battery, I wonder if these scans are accurate.
All will have some degradation, no doubt, cells degrade a chunk in the initial period of use, but I think I would notice a full kWh lost

Oh well, tis what it is I guess, more important things to fret about .

 

[Ayoull]

Weird, I have almost 1000 miles more and I'm just not seeing any noticeable difference in energy in with my battery, I wonder if these scans are accurate.
All will have some degradation, no doubt, cells degrade a chunk in the initial period of use, but I think I would notice a full kWh lost

Oh well, tis what it is I guess, more important things to fret about .

The readout on missus MG ZS EV MK1 is the same via odb2 as what MG provide on their service paperwork.

And you wouldn't notice 1kWh missing unless you did the WLTP tests as, too many variables in your day to day driving to notice

 

[Macadoodle]

And you wouldn't notice 1kWh missing unless you did the WLTP tests as, too many variables in your day to day driving to notice

51 kWh plus or minus a couple of hundred wh from 10% measured from inductive loop on line in to my wall charger, has not varied by any noticeable amount since day 1, that's what I'm basing it on.
As I've only a 4mm SWA feeding my garage I limit my charger to 20 amps, has never been DC charged, battery coolant pump has never been heard to run .
My battery gets treated like a baby, mainly because I'm too tight to pay for DC charging and can't be arsed running a bigger cable to the garage.
So it's just possible that my pack is in particularly good health, but I won't lose any sleep over it.

 

[Ayoull]

51 kWh plus or minus a couple of hundred wh from 10% measured from inductive loop on line in to my wall charger, has not varied by any noticeable amount since day 1, that's what I'm basing it on.
As I've only a 4mm SWA feeding my garage I limit my charger to 20 amps, has never been DC charged, battery coolant pump has never been heard to run .
My battery gets treated like a baby, mainly because I'm too tight to pay for DC charging and can't be arsed running a bigger cable to the garage.
So it's just possible that my pack is in particularly good health, but I won't lose any sleep over it.

What class is your meter? And what class is the CT? As even the most accurate metering equipment for a utility company will have between 0.2-0.75% accuracy discrepancy as well as a minimum burden amount before they reach that level of accuracy.

Many domestic electricity meters that are whole metered current have 0.5-1.0% accuracy discrepancy depending on the age of the meter.

Many 3rd party meters are class 1 permitting upto a 1% discrepancy in accuracy.

So there is easily the possibility of missing a full kWh when you're also trying to account for losses that are dependent on the temperature of everything in the circuit.

 

[Macadoodle]

What class is your meter? And what class is the CT? As even the most accurate metering equipment for a utility company will have between 0.2-0.75% accuracy discrepancy as well as a minimum burden amount before they reach that level of accuracy.

Many domestic electricity meters that are whole metered current have 0.5-1.0% accuracy discrepancy depending on the age of the meter.

Many 3rd party meters are class 1 permitting upto a 1% discrepancy in accuracy.

So there is easily the possibility of missing a full kWh when you're also trying to account for losses that are dependent on the temperature of everything in the circuit.

My point is that my readings have been oddly similar throughout my ownership.
When I take one, I park the car near 10%, then sit with the heater on to bleed it to exactly10%.
It's then charged to the point where it finishes by itself, so my method is consistent.
The meter I'm using is just some crapper that was rattling around in a drawer, no specs on it.
The accuracy or class of what I'm using is irrelevant though IMO, its the trend I'm experiencing, and that trend is largely flat so far, and does match the promised capacity of the pack.
I'm under no illusion that this will continue indefinitely