51 or 64KW

[Bodie70]

Hi, I am considering buying an EV for the first time, so please excuse my ignorance! The 51KW battery is LFP and, from what I have gleaned from other posts, this can be regularly charged to 100%. The 64KW does not have an LFP battery and so it is recommended to only regularly charge to 80%. So, unless I am missing something, 100% of the 64KW usable range is not far from 100% usable range of the 51KW. Is this correct?

 

[siteguru]

Lots of threads already on this subject ... you can charge the LR battery to 100%, it's simply not recommended to charge to 100% and then leave it for a few days. Regular charge to 80% with occasional charge to 100% is perfectly fine.

 

[MoDolph]

I've seen this argument a few times lately but I don't get it.

If you are needing 200 miles + every day then yes, you will be charging the LR to 100% which isn't ideal but still ok. The same journey with an SR will likely require rapid charging every time making it unsuitable.

If your not driving 200 miles every day then what's the issue with charging the LR to 80% instead?

We do 10 miles per day with the occasional 200 mile + journey so will likely charge our LR to 60% every couple of days but when we need it we can charge to 100% and enjoy the extra range and rapid charging speed.

 

[Oberoy]

Hi, I am considering buying an EV for the first time, so please excuse my ignorance! The 51KW battery is LFP and, from what I have gleaned from other posts, this can be regularly charged to 100%. The 64KW does not have an LFP battery and so it is recommended to only regularly charge to 80%. So, unless I am missing something, 100% of the 64KW usable range is not far from 100% usable range of the 51KW. Is this correct?

As @siteguru states it's fine to charge to 100% on the occasional basis e.g. before you are doing a long journey/need the range. The rest of the time you set the charge limit to the recommended 80%, and charge when you need.
You just want to avoid leaving it at 100% for days (or below 10% for that matter).
Another key point relates to efficiency, not that the regenerative braking will not be able to store any charge if you charge to 100% regardless of battery chemistry, I think this needs 5-10% from the top capacity to function.

 

[Kithmo]

I'm waiting for the 73kWh.

 

[siteguru]

Bear in mind that the 64kWh battery is 61.7kWh usable. (The 51kWh one is 50.8kWh usable).

 

[MoDolph]

Bear in mind that the 64kWh battery is 61.7kWh usable. (The 51kWh one is 50.8kWh usable).

Meaning 100% in the LR is more like a real 90% However, the advice regarding degradation at high SOC still holds. LFP is, in my opinion, superior to the ternary chemistry of the LR if, and this is the thing, that the range was equal.

Over our expected ownership period of 10 years I expect the range at the end to be very similar between the two variants, maybe even in favour of the SR. Had the trophy been available in LFP guise then we would have been tempted. Yet, we still believe that the value in having the extra range initially is worth something.

 

[BugEyed]

Not directly related to the battery chemistry, but to the specification provided in the UK by MG, there are a few other differences:

• the motors offered with each battery are different - broadly 150 BHP with the smaller battery and 200 with the larger
• the gearing is different with lower gearing for the smaller battery resulting in faster acceleration (despite the lower power) but less efficiency at higher (but UK legal) speeds
• the larger battery has the "active grille" which is partly responsible for the higher efficiency and subjectively looks better if like me you are nerdy enough to notice
• the larger battery rapid charges slightly faster both in % terms and hence in kW terms
• the Trophy is only available with the larger battery

My takes on all of this is that the SR is better for around town and for back road blasts, but the LR is better on the motorway even if you are not going to need the extra range. There's also the fact that the Trophy is only available with the larger battery.

 

[siteguru]

168 BHP not 150.

 

[Stan1970]

the larger battery rapid charges slightly faster both in % terms and hence in kW terms

i have seen much slower charging speeds for the LFP battery, the LR gets up to 140kw but the LFP charged even with half an hour "pre-warming" the battery only at 80kw max.
So.. if you prefer long range travel then pick the LR battery rather than the SR battery

 

[MoDolph]

Since this is the active thread on the subject of differences. Does anybody know the nominal pack voltages of each version?

This is important for charging speeds on chargers that are current limited, such as older 50kW chargers.

 

[siteguru]

Not sure what you mean by "nominal pack voltage" ... I think both are 400V systems.

 

[Bodie70]

I've seen this argument a few times lately but I don't get it.

If you are needing 200 miles + every day then yes, you will be charging the LR to 100% which isn't ideal but still ok. The same journey with an SR will likely require rapid charging every time making it unsuitable.

If your not driving 200 miles every day then what's the issue with charging the LR to 80% instead?

We do 10 miles per day with the occasional 200 mile + journey so will likely charge our LR to 60% every couple of days but when we need it we can charge to 100% and enjoy the extra range and rapid charging speed.

It's really all about the vehicle cost. I would rather buy the cheaper version with the smaller 51KW battery but I am concerned about having enough charge to last the day, taking into consideration real-world driving, battery degradation and the use of heating or air conditioning. I do mainly multiple, short trips. I don't usually know how many daily trips I will make in advance, so I wouldn't know when to charge to 80% or 100%.
I was basing my figures on only charging the different batteries to 80% but then I read that the LFP battery could be charged to 100% daily, making the usable range very similar to the 64KW at 80%. This made me wonder if there was any point in buying the more expensive car. I hope this makes sense!

 

[5teep]

Kinda pointless buying the bigger battery if you can only charge to 80% as you say. I suspect this 80% thing might be an internetism based on 2nd hand possibly faulty info.
80% on DC I can understand because of the different charging rate but 100% on AC at 7kwph should not harm the battery at all.

 

[siteguru]

As has been said many times ... it's not the charge to 100% that is the problem (at least not with an overnight home charge); it's the leaving it at 100% for a few days that may be the problem - the NMC battery in the LR versions doesn't particularly like that.

If you're going to use (most of) the charge the next day then go for it.

 

[MoDolph]

It's really all about the vehicle cost. I would rather buy the cheaper version with the smaller 51KW battery but I am concerned about having enough charge to last the day, taking into consideration real-world driving, battery degradation and the use of heating or air conditioning. I do mainly multiple, short trips. I don't usually know how many daily trips I will make in advance, so I wouldn't know when to charge to 80% or 100%.
I was basing my figures on only charging the different batteries to 80% but then I read that the LFP battery could be charged to 100% daily, making the usable range very similar to the 64KW at 80%. This made me wonder if there was any point in buying the more expensive car. I hope this makes sense!

That does make sense. Provided there is no rush to order then I would suggest measuring and keeping a log of your daily mileage for a few weeks regardless of which version you order. Usually people overestimate the number of miles they do.

If you are doing more than 150 miles regularly then I would lean towards the LR, and if it is less than 150 then the SR would be a good choice instead.

People seem to be placing too much importance on the whole charging to 80% thing. It will not invalidate your warranty by charging to 100% every day so if you need the range I wouldn't worry about it.

 

[siteguru]

Bear in mind that even 3.2 miles per kWh will give 160 miles for 50kWh of charge. (Although it's not recommended to go much below 10% charge remaining, so 45kWh would give 144 miles. 3.5 mpkWh would give 157 miles for 45kWh).

 

[Macadoodle]

Not directly related to the battery chemistry, but to the specification provided in the UK by MG, there are a few other differences:

• the motors offered with each battery are different - broadly 150 BHP with the smaller battery and 200 with the larger
• the gearing is different with lower gearing for the smaller battery resulting in faster acceleration (despite the lower power) but less efficiency at higher (but UK legal) speeds
• the larger battery has the "active grille" which is partly responsible for the higher efficiency and subjectively looks better if like me you are nerdy enough to notice
• the larger battery rapid charges slightly faster both in % terms and hence in kW terms
• the Trophy is only available with the larger battery

My takes on all of this is that the SR is better for around town and for back road blasts, but the LR is better on the motorway even if you are not going to need the extra range. There's also the fact that the Trophy is only available with the larger battery.

That's interesting regarding the gearing, would explain the slightly better 0-60 with fewer horses to muster.
I'm almost ready to place an order and have decided LFP would make most sense for my usage pattern but was worried the missing 30 bhp would be noticeable, even though torque is apparently the same.

To be honest, the thing that made the 2 hour test drive fun for me was the way the traction control let the rear end step out a couple of feet on the wet (fairly deserted) roads I tried it on, having owned a first gen leaf for four years it was a bloody revelation !

Sounds like the LFP will suit my B road lifestyle then ! Woohoo

 

[Les burrows]

Bear in mind that even 3.2 miles per kWh will give 160 miles for 50kWh of charge. (Although it's not recommended to go much below 10% charge remaining, so 45kWh would give 144 miles. 3.5 mpkWh would give 157 miles for 45kWh).

That’s about as far as I can go without a LOO these days so the SR is fine for me, I have been driving my MG 5 SR about 18 months now getting on for 18000 miles and never had a problem with charging, I try never to let the range drop below 40/50 miles and when on a journey I plan the journey and charging points before I set off and it works, plus if something does go wrong like a charger not working or a few queuing for a charge point when I get there I always try to have a plan B as well.

So which ever battery size you go for if you read your handbooks it tells you that it is good practice and needed to do a full charge and balance charge around every 4/6 weeks to keep the battery in good condition and stable.
Les

 

[Bodie70]

Many thanks for all the useful and informative replies!