Over charging

[Coulomb]

on a Zappi 6.8 amp charger

Did you mean a 6.8 kW "charger"?

 

[IanMG]

So I would argue that with DC charging, the BMS really has full control. If it wanted to, I suspect that you could do balancing with DC charging, but of course that would be a terrible waste of public charging resource. I suspect that's the only reason that balancing doesn't happen on DC charging: that it's unthinkable, not that it's not possible.

I think you are correct in that the DC charge protocol is 'coarser' than AC with the full control by the BMS.
Over two years ago, i.e. before the pandemic, when EVs were still a niche purchase, there were many tales of various DC chargers not handshaking correctly with cars. This was spread evenly across car manufacturers and DC charger manufacturers. ABB were always OK with my I-Pace but there was another make, I can't remember it, that would fail with almost a guaranteed certainty! This seemed to be consistent across the I-Pace fraternity.
As for cell balancing, this can take over an hour once the car has reached full charge, imagine that on a Gridserve charger in the services!!

 

[dickturpin]

I have ordered the MG ZS 2022 model because it has the new LFP battery chemistry which does not suffer from repeatedly charging to 100%.

Am very glad someone has wrote down what I was saying in earlier piece

 

[MichaelJHunt]

Am very glad someone has wrote down what I was saying in earlier piece

The LR does not not suffer adversely from charging to an indicated 100%.

Cannot perceive of an advantage of having a smaller battery, unless range is it not an issue and price is the concern.

 

[Coulomb]

The LR does not not suffer adversely from charging to an indicated 100%.

What makes you say that? High voltage and high temperature are bad for any battery.

Cannot perceive of an advantage of having a smaller battery,

Less weight means slightly better efficiency.

Also if the smaller battery is LFP chemistry, then it is expected to last about 3x as long as NMC etc.

However a smaller capacity battery will experience higher C rates for the same loads, which will tend to slightly reduce the expected life.

Overall, if you need the range, a larger battery is fine. And it's possible that LFP will catch up in energy density in a year or two.

 

[MichaelJHunt]

What makes you say that? High voltage and high temperature are bad for any battery.


Less weight means slightly better efficiency.

Also if the smaller battery is LFP chemistry, then it is expected to last about 3x as long as NMC etc.

However a smaller capacity battery will experience higher C rates for the same loads, which will tend to slightly reduce the expected life.

Overall, if you need the range, a larger battery is fine. And it's possible that LFP will catch up in energy density in a year or two.

The LFP battery in the SR weighs all almost the same as the NMC battery in the LR.

The MG ZS EV, like the vast majority of Modern EVs, is equipped with a thermal management system and BMS that ensured the batteries are well looked after and don’t suffer from overheating during charging.

An NMC battery is typically good for around 2000 cycles to maintain 80% of its capacity. Opportunistic charging of the LR battery can increase the life to 3000 to 5000 cycles - this is not possible in the LFP battery due to it NEEDING to be charged to 100%.

An LFP battery is typically good for around 4000 cycles for the same.

As such the LR battery will maintain 80% of its capacity after around 400,000 miles, and much more with good charging management.

The SR battery will maintain 80% of its capacity after around 600,000 miles.

I think worrying about battery life in either car is not an issue.

The LFP battery also suffers more in cold conditions compared to the NMC battery. As heating the battery, rather than cooling it, uses more energy in the MG ZS EV, this is another win for the LR.

 

[hmadsen]

Also, charging the LR to 80% gives about the same range as charging the SR to 100%.

 

[dickturpin]

What makes you say that? High voltage and high temperature are bad for any battery.


Less weight means slightly better efficiency.

Also if the smaller battery is LFP chemistry, then it is expected to last about 3x as long as NMC etc.

However a smaller capacity battery will experience higher C rates for the same loads, which will tend to slightly reduce the expected life.

Overall, if you need the range, a larger battery is fine. And it's possible that LFP will catch up in energy density in a year or two.

This is for Micheal Hunt because of the chemistry in LFP battery’s you can charge them up to 100% as and when you want to no ifs no buts

 

[Coulomb]

this is not possible in the LFP battery due to it NEEDING to be charged to 100%.

I'd love to know where this myth comes from.

Granted, MG makes it harder to charge the LFP battery to 80%, but it's no harder than with the Mk 1. I really think that MG made a mistake not allowing the LFP battery to be charged to less than 100%, especially since all the logic is there, they just need to not disable it!

 

[MichaelJHunt]

I'd love to know where this myth comes from.

Granted, MG makes it harder to charge the LFP battery to 80%, but it's no harder than with the Mk 1. I really think that MG made a mistake not allowing the LFP battery to be charged to less than 100%, especially since all the logic is there, they just need to not disable it!

In this case I would be happy to take the advice of Tesla….

 

[N2STY]

Yep tesla learnt the hard way having to replace batterys so changed the advice on changing so if a warranty claim comes in the will download charging history I can't see them owners charging to 80% after teslas update get a battery swop?
I am only taking LFP here

 

[Coulomb]

So Tesla recommends that you leave the charge limit at 100%, but still gives you the option of leaving it lower. And they recommend charging to 100% once a week, a fair bit more often than the once a month recommended by MG.

But I don't see how this translates to "LFP must be charged to 100% every charge". Though I can't quickly find that statement now, perhaps I'm misremembering.

 

[MichaelJHunt]

So Tesla recommends that you leave the charge limit at 100%, but still gives you the option of leaving it lower. And they recommend charging to 100% once a week, a fair bit more often than the once a month recommended by MG.

But I don't see how this translates to "LFP must be charged to 100% every charge". Though I can't quickly find that statement now, perhaps I'm misremembering.

So those with LFP batteries should follow the advice of a moderator on this site rather than the largest manufacturer of BEVs in the World?

Fortunately, LFP owners of the ZS EV are forgiven this because MG has rightly decided to remove this choice.

Of course owners can use their own prerogative and turn off charging from the incar screen or at the charger and ignore MG and Tesla advice.

 

[N2STY]

Some say it's the flat voltage Curve that's the problem with LFP the guess o meter has no idea of range left as same voltage at 30% to 80% this is why sort range owners say I parked up with 50% battery and came back after work/shopping iand car now says 30% the truth is unless charged to 100% the bms has no idea of state of charge only if full or almost empty so this it's the reason to charge to 100% for more accurate range

 

[N2STY]

I do think this is why tesla where getting so many warranty claims the BMS had no idea of state of charge until full.
So LFP batteries are good but not really the best battery for cars as its hard to determine state of charge and range which gets a lot worse in winter? But they're a lot cheaper and we will probably see a lot more of them.

 

[MichaelJHunt]

Some say it's the flat voltage Curve that's the problem with LFP the guess o meter has no idea of range left as same voltage at 30% to 80% this is why sort range owners say I parked up with 50% battery and came back after work/shopping iand car now says 30% the truth is unless charged to 100% the bms has no idea of state of charge only if full or almost empty so this it's the reason to charge to 100% for more accurate range View attachment 9878

It is very important for the health of the battery pack that the BMS knows its SOC, hence TESLA recommending charging to 100%. A single LFP battery in an electrical device is not an issue. 360kg of LFP batteries in car is a completely different issue.

Anyway, everyone has the choice to manage the batteries in their car the way they see fit and ignore the advice of the manufacturer.

 

[Elec Car Aust]

Hi Does anybody have any thought on the best way to charge my MG Zs? I don’t want to over charge it and ruin the battery life. Thing like is it ok to charge it up to 100% every time? How low should I leave it before I charge again? Or is this all a bit trail and error. Thank in advance from a first timer EV

I have done a number of YouTube videos on my Aussie EV Channel (Electric Car Australia) related to charging our ZS EV. Check these out they might help. Short answer though generally run battery between 20-80% in normal around town use and you wont have any probs.

 

[MichaelJHunt]

I have done a number of YouTube videos on my Aussie EV Channel (Electric Car Australia) related to charging our ZS EV. Check these out they might help. Short answer though generally run battery between 20-80% in normal around town use and you wont have any probs.

The problem with the SR is that the BMS doesn’t know accurately where 80% is unless you regularly charge to 100%, This is clearly an issue if you can only Rapid Charge.

If you don’t regularly charge to 100% with SR the GOM can give wildly varying and confusing range and SOC figures.