Only charged my Leapmotor C10 as a trial really, charged from 80 to 100% at a Tesla charger capable of 250 kW.

I know my cars max charge is pretty low at 86kw, but the highest I saw was 33kW, majority of the charge was around 27kW.

Just wondering if it might be because the battery was already at 80%. Or is there another explanation?

Thanks

Starting at 80% is the reason, most cars slow down on DC chargers once the battery gets full. Some at 80%, others higher or lower depending on the design.

So 20-80 looks like your sweet spot.

 

Does this drop off occur when AC charging at home?

 

it might be because the battery was already at 80%.

That's it.
Most EV charging rates are roughly as advertised up to 50% state of charge, then drop off with increasing SoC to almost nil at 100%.
80% is where many people stop charging, because it's so slow that you'll reach your destination faster by carrying on and charging again later if you have to.

 

Only charged my Leapmotor C10 as a trial really, charged from 80 to 100% at a Tesla charger capable of 250 kW.

I know my cars max charge is pretty low at 86kw, but the highest I saw was 33kW, majority of the charge was around 27kW.

Just wondering if it might be because the battery was already at 80%. Or is there another explanation?

Thanks

Pretty standard that. The explanation that I was given was to look at filling a builder's bucket without spilling over, using a fire hose. The first few seconds will fill it quickly, but you then have to choke the valve off more and more to fill the last 20% without spilling and then the last few drops with the water flow really slow.

The same thing with a battery without 'spilling' over. First 80% will fill quickly and the last 20% will take as long as the first 80%.

 

Yep, Autoexpress recently did a rapid charge test of several cars, results here Electric car charging mega test: do EVs really charge as quickly as they say? | Auto Express, the magazine article had the actual charge curves, but they give you the 80-100% charge time for each EV (and time to add 60%)

 

Yep, Autoexpress recently did a rapid charge test of several cars, results here Electric car charging mega test: do EVs really charge as quickly as they say? | Auto Express, the magazine article had the actual charge curves, but they give you the 80-100% charge time for each EV (and time to add 60%)

That was an interesting read.
My MG5 charge rate start to drop off at 82% and I normally stop charging on a DC CCS charger when rate drops away at about 87%

 

Thanks for the replies, thought as much but nice to have it confirmed.

 

Rapid charging is like trying to fill a bucket with a powerwasher.
The only way you will get it filled as fast as possible without overfilling it (kaboom) is by starting off at full tilt and then dialing the flow back as you get close to briming it.
The fuller it gets, the slower it goes.

 

Autoexpress interesting. It is a shame they didn't have another 800v car - an HMG car.
Pre-conditioning to get the battery up to temp??
What temp is the battery getting to??
How is this achieved?? I assume either by reducing the battery cooling or by active heating or a mix of the 2 depending on ambient temp and how much power is being drawn from the pack.

 

Autoexpress:
"
none of the cars were preconditioned before charging; not all models provide the option to do this manually, so it was the fairest way. Besides, it’s something many of us often forget to do, anyway.
"
Such a lazy test and a stupid reason. If some cars don't provided this option, then those cars should be tested as it is.
But if the cars do this automatically, then the forget argument is out of the window.

It's like blaming premature engine failure/wear but never warm up the engine before driving flat out on a race track. Hopefully that's a language those ICE car people can understand.

 

@SteveG9 - Forgive me if you’re already aware of this, but most EV manufacturers’ advice to owners is not to charge above 80% on a regular basis. And some manufacturers, plus forum advice, is that it’s OK to charge to 100% occasionally, as long as you plan to travel within 12 hours or so of completion.

 

Answering my own question from chatgpt:

Yes — the same principle applies with AC charging, but it looks a little different compared to DC fast charging.

Here’s why:

• Battery charging taper (physics of lithium-ion batteries):
  Regardless of the power source, lithium-ion batteries can only accept high charging currents up to a point. As the state of charge (SoC) rises (around 70–80% and higher), the internal resistance increases. To prevent overheating and damage, the Battery Management System (BMS) gradually reduces the charging current. This taper is universal for all lithium-ion batteries.
• DC fast charging:
  On a DC charger, the charger itself delivers current directly into the battery under the control of the BMS. That’s why you see the very obvious “cliff” after ~80% — the charger power output is actively throttled down to protect the pack.
• AC charging:
  With AC, the current first goes into the car’s onboard charger (a rectifier and power electronics module), which then feeds DC to the battery. The onboard charger is typically limited (e.g. 7 kW, 11 kW, or 22 kW), which is far less than DC fast charging. Because the charging rate is already modest, the taper above 80% is much less noticeable — but it still happens. The onboard charger + BMS will start to reduce the current as the battery nears full.
• Effect in practice:
  On AC, you might still get close to the rated onboard charger power up to ~95% or more, depending on the car, but the last 5–10% often slows significantly (sometimes dropping to just a few hundred watts). That’s why an “AC full charge” can take disproportionately long compared to reaching 90%.

🔑 Summary:
Yes, EVs also slow charging above ~80–90% on AC charging — but it’s far less dramatic than on DC fast charging, since the starting power levels are much lower.

 

Note that it's vehicle-dependent. Some cars, like certain Audi e-tron's, can charge pretty quick up to 100%, about 70kW still at 95% and 50kW at 100%. Meanwhile my ID.3, I will be lucky to be getting 15kW at that point. So the Audi owner might not feel too bad staying on till 100%, but in my case it's always better to move on above 80%.

 

Only charged my Leapmotor C10 as a trial really, charged from 80 to 100% at a Tesla charger capable of 250 kW.

I know my cars max charge is pretty low at 86kw, but the highest I saw was 33kW, majority of the charge was around 27kW.

Just wondering if it might be because the battery was already at 80%. Or is there another explanation?

Thanks

First, see the charging curve, for example here

Then realise that ALL chargers are spec'd as 'up to'. The EV, depending on SoC, temperature, architecture (400V vs 800V), etc, decides how much power it will take from what's available (which is another issue).

If you want to delve deeper, then look at the initial constant current charging which then becomes constant voltage as the battery voltage rises.