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OK, so you rock up at an ultra-rapid charger, it says it can deliver upto 150kW and the car says it can use upto 100kW, so that’s easy, it’ll charge at 100kW right?
The charger & the car manufacturer are using ideal figures where all the conditions are met to get that fast charge rate, so no, it’s unlikely you’ll see that rate of charge for very long & only if many other conditions are right.
Chargers may limit the amount they can deliver at certain times of the day when electricity is super expensive (4-7pm). The BP Pulse ultra-rapids have a battery inside the adjoining cabinets that charges up when cars aren’t pulling too much so that they can discharge & privide a boost to the charging speed when needed. Late in the daytime these chargers batteries are getting depleted.
The EVs demand only a certain current from the chargers, this is the usual limitation that gets you less than the 100kW & it’s the car’s Battery Management System (BMS) that only wants so much so that it can heat up/cool down the battery, balance the battery at slower speeds & high states of charge.
Some cars “Rapidgate”, that means the battery gets too hot & the BMS limits the charging rate to stop the heat damaging the battery.
Some cars “Coldgate”, that means they don’t maintain enough temperature in the battery to charge optimally.
Then there are charge curves & profiles that every EV has, they all slow down as they reach a higher state of charge (the reason why BEV drivers only take 80% charge before heading for the next charger 100 miles on into their journey, it’s simply to spend less time charging overall).
We have coping strategies to deal with these problems, such as driving fast to the first 50kW rapid charger rather than an ultra-rapid as we know the battery is cold, charging there then heading to use ultra-rapids for the next legs of the journey & ride the 25C wave & the faster charging it allows. Another is to pulse the battery by speeding up & slowing down a few times (yo-yo-ing) before reaching a charger to increase the temperature, or driving more slowly if you want to decrease the temperature.
It’s early days for EVs & in time these problems will be solved by better battery technology, but until that time, the above hints could save you as much as 4 minutes at a charger, so sip your coffee & just charge as you want & wonder why some of us spend more than 4 minutes writing about it.
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Very informative read – thank you.
Informative (as gothitjulie’s posts generally are) but depressing that this is the reality we are being forced to confront.
Informative (as gothitjulie’s posts generally are) but depressing that this is the reality we are being forced to confront.
Agreed, but a couple of mitigating factors here, the first is that battery technology is improving & is already far better than it was a few years ago as manufacturers introduce active heating & cooling to their battery pack & adjust the cobalt ratio. The second is that for many people, rapid & ultra-rapid charging isn’t something they need to do very often as they charge using AC chargers at home/supermarket/street lamp etc.
When I’ve charged outside my home at -5C this winter I’ve seen no slowdown in the 7kW charging speed until it reaches 98% when it slows as the BMS balances the battery, it does this at any temperature & it needs to be done about once a month to maintain battery health over the long term.
Hint: If you balance charge to 100% then don’t leave it sitting at 100% for a length of time as it degrades the battery. Driving it the next day to reduce it from 100% is absolutely fine.
Not sure if anyone remembers going to foreign climes & leaving the car sitting for two weeks, well, ideally leave it sat at around 70% charge, although anywhere between 20-80% will be fine. Same with a fossil, in hot weather the fuel will expand so you’d not leave it with a full tank.
My car (and I get I’m lucky) takes 6 seconds to charge. I park on the drive at night, plug the lead in and have a full charge in the morning..a little tongue in cheek but works perfectly for me. Much nicer than visiting a petrol station.
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