Bad Product Comparisons and EVs

When companies design products a major concern seems to be what the reviewers will have to say about it. For any product of significant value the users are unable to perform any reasonable test before buying, for a casual user some problems may only be apparent after weeks of use so professional reviews are important to many people. The market apparently doesn’t want reviews of the form “here’s a list of products that are quite similar and all do the job well, you can buy any of them, it’s no big deal” which would be the most technically accurate way of doing it.

So the reviewers compare the products on the criteria that are easiest to measure, this lead to phones being compared by how light and thin they are. I think it’s often the case that users would be better served by thicker heavier phones that have larger batteries but instead they are being sold phones that have good battery life in a fresh installation but which don’t last a day with a full load of apps installed.

The latest issue with bad reviews driving poor product design is electric cars. For a while the advocates of old fashioned cars have touted the range of petrol cars which has become an issue for comparing EVs. I have been driving cars for 35 years and so far I have never driven anywhere that’s out of range of the current electric charging network, even with the range of the LEAF (which is smaller than many other EVs). If I ever felt the need to drive across the Nullarbor Plain then I could rent a car to do that and the costs of such car rental would be small compared to the money I’m saving by driving an EV and also small when compared to the premium I would have to pay for an EV with a larger range.

Some of the recent articles I’ve seen about EVs have covered vehicles with a battery range over 700Km which is greater than the legal distance a commercial driver can drive without a break. I’ve also seen articles about plans to have a small petrol or Diesel motor in an EV to recharge the battery without directly driving the wheels. A 9KW Diesel motor could provide enough electricity on average to keep the charge maintained in a LEAF battery and according to the specs of Diesel generators would take about 55Kg of fuel to provide the charge a LEAF needs to drive 1000Km. The idea of a mostly electric hybrid car that can do 1000Km on one tank of fuel is interesting as a thought experiment but doesn’t seem to have much actual use. Apparently a Chinese company is planning to release a car that can do 1400Km one one tank of fuel using such technology which is impressive but not particularly useful.

The next issue of unreasonable competition is in charge speed. Charging a car at 2KW from a regular power socket is a real limit to what you can do with a car. It’s a limit that hasn’t bothered me so far because the most driving I typically do in a week is less than one full charge, so at most I have to charge overnight twice in a week. But if I was going to drive to another city without hiring a car that has better range I’d need a fast charger. Most current models of the Nissan LEAF support charging speeds up to 50KW which means fully charging the battery in under an hour (or slightly over an hour for the long range version). If I was to drive from Melbourne to Canberra in my LEAF I’d have to charge twice which would be an annoyance at those speeds. There are a variety of EVs that can charge at 100KW and some as high as 350KW. 350KW is enough to fully charge the largest EV batteries in half an hour which seems to be as much as anyone would need. But there are apparently plans for 1MW car chargers which would theoretically be able to charge a Hummer (the EV with the largest battery) in 12 minutes. One obvious part of the solution to EV charging times is to not drive a Hummer! Another thing to note is that batteries can’t be charged at a high rate for all charge levels, this is why advertising for fast chargers makes claims like “80% charge in half an hour” which definitely doesn’t mean “100% charge in 37.5 minutes”!

There are significant engineering issues with high power applications. A 1MW cable is not just a bigger version of a regular power cable, there are additional safety issues, user training is required and cooling of the connector is probably required. That’s a lot to just get a better number in the table at the end of a review. There is research in progress on the Megawatt Charging System which is designed to charge heavy vehicles (presumably trucks and buses) at up to 3.75MW. Charging a truck at that rate is reasonable as the process of obtaining and maintaining a heavy vehicle license requires a significant amount of effort and some extra training in 3.75MW charging probably doesn’t make much difference.

A final issue with fast charging is the capacity of the grid. A few years ago I attended a lecture by an electrical engineer who works for the Victorian railway system which was very interesting. The Vic rail power setup involved about 100MW of grid connectivity with special contracts with the grid operators due to the fact that 1MW trains suddenly starting and stopping causes engineering problems that aren’t trivial to solve. They were also working on battery packs and super capacitors to deal with regenerative braking and to avoid brownouts in long sections of track. For a medium size petrol station 14 bays for fuelling cars is common. If 6 such petrol stations were replaced with fast charging stations that can charge cars at 1MW each that would draw the same power as the train network for the entire state! There is a need for significant engineering work to allow most cars to be electric no matter how it’s done, but we don’t need to make that worse just for benchmarks.