MG ZS EV Long Range - Rapid Charging Test - 76kW Peak?

[MichaelJHunt]

Speed seems to bomb out at around 85% SOC on the graph, so I guess 85% is the optimal cut off.

Yes. At around 83% SOC the charge rate dropped to 27kW. I would stop a Rapid Charge when it gets to this point unless you really need the extra range and are not holding up anyone else who wants to charge.

 

[BarryH]

It's LFP: Lithium Ferrous Phosphate, sometimes called Lithium Iron or LiFePO₄. It's a type of lithium ion battery. You can see why they switched to "ferrous" in the name; lithium iron sounds too much like lithium ion.

The LR and Mark 1 models use NMC (lithium Nickel Manganese Cobalt oxide) cells, which are also a type of lithium ion cell.

So the term "lithium ion" doesn't distinguish between the LR and SR chemistries.

Yes, it is true that they both "contain" Lithium in them and in each charge and discharge cycle Lithium ions move from one electrode to the other and there are also 'free' Lithium ions in the electrolyte between the Anode and Cathode. However, whereas in what is generally known as a regular Li-ion cell there are also other exotic metals (i.e. Nickel and Cobalt) to enable those ions to move to and fro and to provide a home for those "Li" ions, the LEP has Iron (fe) and Phosphorous (P) instead of Nickel (Ni) and Cobalt (Co) and consequentially a less flammable electrolyte into the bargain.

Whilst there is a constant development to modify the structure and Li-ion chemistry, the Li-ion battery remains essentially the same and uses Ni and Co and continues to be referred to as Li-ion since its cell characteristics and voltage range etc. is defined by that Li-Ni-Co chemistry. There are variants of this chemistry which have very low Cobalt content or even Colbalt free, however, they still exhibit the Li-ion characteristics. Whereas an LEP cell, with Li-fePo4 derived chemistry, will have distinctly lower cell voltages and different charge/discharge profiles.

Hence the LEP deserves to be characterised as different just as an ICE driver needs to know whether they are driving a Petrol or Diesel fueled car before refuelling so the EV driver/owner ought to be told about the battery tech since they need to be treated differently for optimum performance and longevity of the most expensive part of their investment.

 

[drmcw]

@BarryH I think you're missing the point that the battery is pronounced/spelt LFP (Ell Eff Pee) NOT LEP (Ell Eee Pee) as you keep writing.

 

[BruceT]

Yes. At around 83% SOC the charge rate dropped to 27kW. I would stop a Rapid Charge when it gets to this point unless you really need the extra range and are not holding up anyone else who wants to charge.

You REALLY start getting glared at by everybody even if there's nobody waiting, sometimes you just have got to take those extra 10 - 15 miles

 

[Coulomb]

However, whereas in what is generally known as a regular Li-ion cell there are also other exotic metals (i.e. Nickel and Cobalt)

That's becoming the colloquial usage, it seems. Yet LFP is a subset of all Lithium Ion battery types. In Battery University, LFP appears on the same page as other Lithium Ion types, and there is a comment in the LFP section stating "one of the safest li-ions".

BU-205: Types of Lithium-ion

Become familiar with the many different types of lithium-ion batteries: Lithium Cobalt Oxide, Lithium Manganese Oxide, Lithium Iron Phosphate and more.

batteryuniversity.com

I think it's clearer if you nominate the type of lithium ion chemistry you mean, if you mean "non-LFP". For our cars, that's generally NMC. [ Edit: Though I've recently heard the terms "ternary chemistry" or "ternary battery" to indicate chemistries with three main oxides at the cathide, e.g. NMC or NCA. ]

I'll agree that LFP is distinctly different to the other lithium ion battery types, and it's probably worth the owner knowing about that.

 

[BarryH]

@BarryH I think you're missing the point that the battery is pronounced/spelt LFP (Ell Eff Pee) NOT LEP (Ell Eee Pee) as you keep writing.

@Coulomb Point taken my mistake, I stand corrected. Being dyslectic, I should have avoided the shorthand and kept to the longer form of Li-fePo4

 

[MichaelJHunt]

@Coulomb Point taken my mistake, being dyslectic I should have kept to the longer form of Li-fePo4

LFP is the simplest way of referring to it

 

[Dranov]

True, but if the battery heater uses 7kW to heat the cells, then you won't get much charge actually making it into the battery on a home AC charger.

I wonder if, for a long trip during cold days, I can charge my LR Trophy up to 100% during the night and use the hour before leaving to pre-heat the battery. As the motorway is next to my home, I wonder if the battery will remain hot (>30°C) during the trip to have te best charging power. I will test it. The first thing is to get the battery temperature with my OBD and TorquePro.
I anyone already tried this ...

 

[MichaelJHunt]

I turn the battery heater on in my car, but with the battery at around 20degC it does nothing to heat the battery. Don’t know what temperature control point is used.

 

[Miles Roberts CG]

I turn the battery heater on in my car, but with the battery at around 20degC it does nothing to heat the battery. Don’t know what temperature control point is used.

Believe it only comes in if ambient temp is below 10degC

 

[BarryH]

I wonder if, for a long trip during cold days, I can charge my LR Trophy up to 100% during the night and use the hour before leaving to pre-heat the battery. As the motorway is next to my home, I wonder if the battery will remain hot (>30°C) during the trip to have te best charging power. I will test it. The first thing is to get the battery temperature with my OBD and TorquePro.
I anyone already tried this ...

I use "EV Watchdog (Free)" with my "KONNWEI" OBD2 Dongle and it reports battery temperature just fine.

 

[BarryH]

I turn the battery heater on in my car, but with the battery at around 20degC it does nothing to heat the battery. Don’t know what temperature control point is used.

There is a battery pre-conditioning to warm the pack before driving which some EVs have (I believe for example the BMW i3 has it) which is a different feature to the MG ZS battery conditioning before charging to get the battery to an optimum temperature before charging. Some like Tesla will automatically start the battery conditioning before reaching a Supercharging site if it is in the planned route which takes the guesswork out of it. Of course if you drive a 40 kWh Nissan LEAF 2.0 you don't have to worry because the pack has only passive cooling as you drive and so if you try Rapid charging after driving too quick (ie above 55-60mph) in anything other than artic conditions your battery will be too hot to take more than a moderate charge rate AKA "Rapidgate"

 

[BarryH]

Yes, it is true that they both "contain" Lithium in them and in each charge and discharge cycle Lithium ions move from one electrode to the other and there are also 'free' Lithium ions in the electrolyte between the Anode and Cathode. However, whereas in what is generally known as a regular Li-ion cell there are also other exotic metals (i.e. Nickel and Cobalt) to enable those ions to move to and fro and to provide a home for those "Li" ions, the LEP has Iron (fe) and Phosphorous (P) instead of Nickel (Ni) and Cobalt (Co) and consequentially a less flammable electrolyte into the bargain.

Whilst there is a constant development to modify the structure and Li-ion chemistry, the Li-ion battery remains essentially the same and uses Ni and Co and continues to be referred to as Li-ion since its cell characteristics and voltage range etc. is defined by that Li-Ni-Co chemistry. There are variants of this chemistry which have very low Cobalt content or even Colbalt free, however, they still exhibit the Li-ion characteristics. Whereas an LEP cell, with Li-fePo4 derived chemistry, will have distinctly lower cell voltages and different charge/discharge profiles.

Hence the LEP deserves to be characterised as different just as an ICE driver needs to know whether they are driving a Petrol or Diesel fueled car before refuelling so the EV driver/owner ought to be told about the battery tech since they need to be treated differently for optimum performance and longevity of the most expensive part of their investment.

Having been doing a little more research into LFP I also got a good explanation as to why charging Li-Ion to 100% is not a good thing. Essentially, as the cell is charged Lithium Ions move from Li-Metal Oxides at the Cathode across the membrane to the Lithium Metal/Carbon Anode. At high SOC, the Li-Metal Oxides structure is degraded and weakened because the Lithium Ions (essentially Lithium atoms) have been stripped out of the structure and physically moved to the Anode. The Cathode is therefore unstable. Discharging returns the Ions but over time the structure can no longer accommodate these ions and the battery capacity reduces. The Lithium doesn't go away but atoms bond to each other and become deposited as a layer of Lithium metal on the surface of the Cathode and so further reducing the cell's capacity to accept a charge. (see image courtesy of iStock)

 

[N2STY]

But the BMS need you to charge to 100% to look after the battery the best it can and to work out range properly so with LFP it is a bit Catch-22

 

[IanMG]

As the battery has a top 'buffer' you can't charge to 100% for exactly this reason.
LG and the other battery manufacturers are continually testing batteries to find what degrades a battery and what doesn't!
On my Jaguar I-Pace we got an 'extra' few KWs because LG found that it wasn't necessary to limit the charge quite so much. Nice to have an 'extra' 5 miles or so to play with.
There is of course a 'buffer' at the other end and it is impossible to 'flat' the battery!
The battery manufacturers have got our wellbeing at heart, hence battery degradation is remarkably low in EVs.

 

[BarryH]

But the BMS need you to charge to 100% to look after the battery the best it can and to work out range properly so with LFP it is a bit Catch-22

LFP you can charge to a true 100% because the chemistry is different and you can move the Lithium ions across the membrane and the residual Cathode material is stable.

Balance or Equalisation charging is is important for Li-Ion battery packs and should be a scheduled charging for a specific purpose and typically only once a month. It is done at a low charge rate after charging and hence at low current to minimise the potential for damaging cells in the pack with higher voltages. Balance charge only balances the voltage of cells in the pack so that when they are Charged and Discharged in their series configuration they all charge and discharge together. Otherwise there can be internal drain as the higher voltage cells discharge into the lower voltage cells when HV batter connects and the load is light thereby reducing available range

However, since LFP cells prefer daily 100% charges Balance charging is arguably an unessesarily operation and in some BMS systems it is disabled for LFP packs. I'm not sure what approach MG have taken with the ZS and MG4 51 kWh BMS to be honest but but certainly for small packs it seems to be a redubdent feature for the BMS to balance cells.

 

[Coulomb]

since LFP cells prefer daily 100% charges Balance charging is arguably an unessesarily operation and in some BMS systems it is disabled for LFP packs.

I don’t follow that logic. Sure, if you charge regularly to 100% you will need to spend less time on average balancing, but surely the total amount of time needed for balancing doesn't change based on whether you usually charge to 100% or not.

 

[ID Korean MG]

Believe it only comes in if ambient temp is below 10degC

Hi Miles, so if ambient temperature is above 10 the battery heater won't heat up the battery to optimal charging temperature (hoping between 20-30)?

Also any consumption figures for LR ZS in winter and others. Which OBD dongle will work with LR ZS to keep an eye on battery temp? Thanks

 

[ID Korean MG]

I use "EV Watchdog (Free)" with my "KONNWEI" OBD2 Dongle and it reports battery temperature just fine.

Any other Bluetooth dongle will work on LR ZS? Just fine as in text and no figure?

 

[BarryH]

I don’t follow that logic. Sure, if you charge regularly to 100% you will need to spend less time on average balancing, but surely the total amount of time needed for balancing doesn't change based on whether you usually charge to 100% or not.

I think you are missing the point ert LFP regularly charging to 100%. It's in the chemistry as I understand it and the difference between how LFP and older Li-Ion respond to being charged to 100%.

LFP cells in a pack when fully charged just stop charging without harm and other cells in the pack carry on absorbing charge, so naturally, when charging the pack to 100% the pack is balanced. On the other hand, Li-Ion Packs you have to stop charging the pack when the BMS sees the highest cells in the pack reach max voltage, since to continue"Charging", would be damaging to the highest charged cells. Balancing is a process which starts after the main charging session finishes and is a selective low rate charge focused on the cells in the pack or groups of cells in the pack quite often that had been left behind as it were and have a lower voltage/SOC. It is necessary for Li-Ion packs because repeated charging cycles without balancing will increase the SOC differential between the best and the rest. its impact on the range is that the BMS reports Empty when the cells with the lowest SOC reach their lowest discharge point and not when the majority of cells do. To continue to discharge a cell beyond will cause terminate damage to that cell.

So what I'm saying is that the LFP pack probably doesn't really benefit from any extended time connected after the pack reaches 100% unlike Li-Ion. This is why if you build a DIY Pack with LFP individual cells you can disable the balance charge when configuring the BMS.

Supplementary Note:
"3. Equalize Charge:

No equalize charge is required for the LiFePO4 battery. If equalize stage cannot be disabled from your charge controller," ( DIY LiFePO4 Battery Pack )