Just viewed this video and apparently charging the first 50% of an electric car is quicker than charging the remaining 50%. They made an analogy of pouring a pint.
Can any of you lads confirm whether this is a myth or fact? I've never noticed this with phones, laptops, etc.
I only ever put half a tank in my petrol car anyway. I'd probably do the same with an electric. The weight of a full battery will hurt your MPG won't it.
>>4848 Completely true. When I go to the supercharger with a very low battery it storms the way to about 50% in 5- 10 minutes, but the last 20% or so takes about 20 minutes more.
A lot of manufacturers recommend you charge them to 80% most of the time to prolong the life of the battery, unless I'm driving to France and back I hardly ever charge to 100%.
Supercharging is awesome, but most people don't know where they or how plentiful they are (they're in a lot of strange places tbh). Whatever EV I had, I would use the Tesla charging network forever, they are everywhere.
It's broadly true, although the specifics depend on the chemistry and pack design. It's also true for phones with fast charging, but not for devices that charge at a more modest rate.
In the pint analogy, the bubbles mostly represent heat in the battery pack. Charging a battery isn't perfectly efficient, so some of the energy you put into the battery is wasted as heat. You might have noticed that your phone gets reasonably warm when you charge it. There's a double whammy as you approach full capacity - the charging process becomes less efficient the closer you get to 100%, and the battery is already warm from all the previous charging. Excessive heat will damage the chemistry of the battery and reduce the capacity over time.
EV manufacturers have tried to mitigate this issue by designing battery packs with liquid cooling. That was the key technology that enabled rapid charging, but there's still a limit to how much heat you can suck out of a huge slab of batteries.
Concorde would use paraffin as coolant by pumping it around the aircraft this had the added advantage of preheating it for the engine. Maybe they should try that? The paraffin could also be used to power the car!
> I've never noticed this with phones, laptops, etc.
Batteries are complex, along with heat that's already been mentioned they are also a bunch of chemistry. Small devices like laptops, tablets or phones have become increasingly good at compensating for all that palaver and pretending that the battery is a linear thing. This improves the UX for the vast majority of people who don't care about any of this, 100-80% should mean the same as 30-10%. In practice, the device fibs the charge state into a number that lets people predict when they need to recharge. For "small" applications like portable devices this works really well.
Cars are not "small" devices so reality kicks back in until, maybe, it's being abstracted away again.
If the battery is very cold, the chemistry slows right down and both the charging and discharging rate will reduce considerably. The sweet spot is about 20°C, but the issue only becomes really noticeable below about 0°C. In severe cold, most EVs will run their battery cooling system in reverse to warm up the battery. Most EVs can do this predictively, so (for example) if you usually leave the house at 8:30am on a weekday, it'll start warming up at 8am while it's still plugged into the wall.
Also, when you're near full, that battery management system has to avoid overcharging any individual cell, because they're not identical. It does this by shunting charging current around, and that can't be done at anywhere the same currents as just shoving charge into all cells identically, as you do when there's plenty of capacity left.
Lithium cells of all chemistries are damaged (and risky) when overcharged. Auto manufacturers are risk averse and don't really charge cells to 100%, but they still have to back off as they get near full.
>Most EVs can do this predictively, so (for example) if you usually leave the house at 8:30am on a weekday, it'll start warming up at 8am while it's still plugged into the wall.
Bit of a tangent here but this reminds me of the one thing that I see as probably the single biggest obstacle to EV usage in our country. We are a very dense population in many places, huge numbers of people live on terraced streets where parking is just a matter of where there's space, or flats with communal car parks, or what have you.
From what I understand home charging is a lot cheaper than using the "pumps", and if the fundamental issues of range and capacity with battery tech don't drastically change, home charging will be the only really long term viable prospect to actually make them attractive to owners. So what do we do about that, and is anyone even looking to address that part of the problem?
>>4854 The opposite. When I tell the car I am going to a supercharger, it actually starts warming the battery.
>>4858 Yes one the fundamental issues with EVs is that you need off-street parking to charge them at home. The pricing difference is enormous - 300 miles of range at a supercharger costs me 20something quid - a full tank at home is nearer 6 quid.
Cheap EVs have a range of about 150 miles and mid-priced ones can do 250+ miles. A large proportion of people can quite happily get through a week's motoring with half an hour on a rapid charger while they're at the supermarket, particularly people who live in cities. One charger per car is ideal, but it really isn't necessary for the overwhelming majority of motorists.
Flats with communal car parks are easy to solve if the government is serious about it. They already provide a grant to landlords for installing EV chargers, but we really need to make it mandatory for landlords to install a charger if the tenant requests it.
A few councils have started installing EV chargers in lamp posts and bollards. Lamp posts are ideal because they're already wired up, so it's fairly cheap to convert them. For really tricky installations, there are retractable bollards that hide away completely when not in use.
For people who park on the street outside their house, there's a fairly cheap and simple solution - a little rubber gulley for your charging cable.
There's no one magic solution, but none of this is rocket science either. There are seven million street lamps in the UK, but once upon a time that number was zero; installing an EV charger is no harder than installing a lamp post. The vast majority of people could have easy access to EV charging if there's the political will to make it happen.
To make a broader point: as a society, we've sort of forgotten that we can just do things. When the car arrived as a technology, there weren't any petrol stations or car parks. When we switched from coal fires to gas heating, someone had to dig up all the roads to put in gas mains. Over the last couple of decades, we've ripped out the entire phone network and replaced all of the copper cables with optical fibres. We can do huge infrastructure projects, we've just completely lost confidence in our capabilities. Projects that run late or over-budget or just fail completely should be a learning opportunity, but they've become a justification for not even trying.
