ev battery swapping

[Rod Speed]

That's not the problem. The problem is getting the EV vehicle manufacturers to agree on a few standard batterys.

Not going to happen.

[alan_m]

The car is much cheaper because its sold without a battery. However the battery will not come for free - the consumer will pay for it in the rental so it not just the cost of the electricity.

[alan_m]

But isn't that just spin? From all I've read constantly fast charging considerably shortens the battery life.

[Rod Speed]

Mark Carver [e-mail] wrote

Very different situation in the sense of the number of changes per day needed.

[Rod Speed]

Not necessarily if you plan to battery swap to charge it.

But most won't be battery swapping, they will be charging at home or work or both. That is the very fundamental problem with battery swappable EVs, most won't be battery swapping routinely.

But it is far from clear that there is enough of a market to sustain battery swapping, let alone getting the industry to argee to a few standard battery configs that would be necessary for viable availability of a charged spare when you need one.

[Andrew]

except that at the moment batteries are almost integral to the vehicle and not designed for easy replacement. The electric London Black cab was the subject of a program part of the 'how do they make them' series on TV a few years ago and I got the impression that the battery was never going to be replaced.

[Rod Speed]

Not when being fast charged they don't.

[Rod Speed]

But makes it a lot harder to have a machine that swaps the batterys when a stupid driver shows up for a battery swap.

Very different with the time taken to charge the batterys and not f*ck up the life of the battery in the process.

But then you need a lot of batterys at each swap site.

But you need lots more batterys being charged.

But then you have the problem that most would charge at home or work and fast charge most of the time because when the battery is f***ed by all that fast charging, you just swap for another good battery.

[Rod Speed]

The obvious alternative is to add charging to the current on street parking.

But is less clear that there are enough of those to provide a viable market for the EV vehicle manufacturers.

[Rod Speed]

But the cost of a machine than can do all that is vastly higher than the cost of a petrol pump at the servo.

[Theo]

It only makes a marked difference on vehicles without decent thermal management. If the vehicle can keep the battery cool while it charges via liquid cooling, the battery temperature doesn't become elevated which is what reduces cycle life. Every vehicle has an air conditioning system and that cooling becomes a critical part of the battery management (at least, in hotter weather where the radiator won't suffice).

Some of the early ones didn't have good cooling (hello air-cooled Nissan Leaf) and the number of fast charges is a good proxy for battery degradation. But things have moved on a *lot* since then.

Theo

[Bob Eager]

My new car apparently has (I haven't seen it yet) a separate cooling system and radiator for the battery.

[SteveW]

At the moment. But with standardised battery packs and swapping stations, that would soon change for longer range vehicles (there may be no need to do so for short-range city runabouts).

That is typically the case now. It does not have to remain the case for future designs.

[Rod Speed]

Doesn't explain why Tesla limits the number of fast charges you can do.

[567gh]

But it is far from clear that there ever would be enough of a market of those to make the very expensive swapping stations economically viable.

(there may be

[Paul]

That's likely to be a heat pump. There is an optimal temperature range for charging. The battery may need to be heated or may need to be cooled. If the external temperature is too low for a heat pump to pump heat, a resistive heater will be needed to augment battery heating.

Battery University lists:

Li-ion

Charge 0°C to 45°C Best at 10C to 30C, use lower current when cold Discharge –20°C to 60°C

(

)

There are some recent cars that have switched to Lithium Iron Phosphate batteries (Fairy Light battery), and the characteristics of those could be different. The benefit of that chemistry, is 7000 charge cycles. Other parameters would be slightly worse (energy density for one, the pack needs to be bigger).

Paul

[Paul]

Science is likely to push this solution to the background, given time.

With that technology, you could have a "two-stage" battery. The molten salt battery could be charged in 20 seconds, then the charge from the molten salt battery could replenish your real Lithium Cobalt battery over a period of an hour (while you're driving!).

In this way, the aluminium battery doesn't have to maintain a 110C temperature permanently, but only until the charge transfer into the LiCo has completed. The salt could be re-heated when you're charging at the roadside charger. And then, the time to charge is heating_time plus 20 seconds for a charge, then off you go.

You could also do something similar with ultracaps, but that would be too expensive... and dangerous.

Paul

[alan_m]

And what happens to all this molten salt in a serious car crash?

The equivalent to, say, 50kh in 20 seconds? Remind me to say away from that charging point :)

[Brian Gaff]

YUp, nothing much new there. We need to also make batteries that run using non scarce resources like Lithium. They have to be cheap and efficient, and non toxic. Its gone very quiet on the fuel cell front of late, which of course generates electricity from gasses or fuel and a gas. The efficiency here is a major issue as the catalyst or whatever, needs to be hot and hence wastes energy, unless you can harvest it somehow.

Lets face it we are all ultimately doomed as Humans consistently push their problems down the road with short term patches which are not thought through very well.

Brian

[The Natural Philosopher]

An interesting calculation may be to estimate how much battery depreciation adds to running costs.lets say a battery is junk after

75,000 miles and costs £7,500 to replace

Lets further say that a 75kWh battery does 200 miles ona charge, I feel these are all pretty generous. 75kWh at today's horrendous price of 33p a kWh is £25 for 200 miles. or 12.5p a mile

Add in the 10p a mile for battery depreciation and you get 22.5p a mile.

My diesel Jaguar does about 400 miles on about £100 of diesel That's 25p a mile

In short at today's prices electric cars are not cheaper to run than fuel cars