Doctor Diesel

On a charge

Hi Doc,


Once again, thank you so much for your most informative articles. Martin West’s very interesting letter on batteries etc. was perhaps missing one point. In California, there are a group of Chevrolet Volt owners (a class action) who are presently suing General Motors over the fact that their batteries lost some 27 per cent of capacity in one year. This is why, perhaps, Vauxhall/Opel discontinued the Ampera so quickly in Europe?


My understanding is that most electric cars should only have one ìsuper chargeî every 24 hours. You will no doubt confirm or correct this. I have read what little I could in Norway on their charging points, and the same in Germany. However, it was in Scotland that I finally understood the warning that any people with a ìpacemakerî fitted should not stand between the car and the charging point, nor should they stand behind the charging point. I mentioned this to a very good friend with an elderly Honda who has such a pacemaker fitted. He was thinking about an electric car… but is no more!


You and I have in the past e-mailed each other about the electric current needed to supply the electricity in an underground cable ñ the gigawatts needed for say 100 miles of motorways, all with say six lanes in use. Have you worked out the figures? (I’m afraid I haven’t Bob!) In this monthís Caravan and Motorhome magazine on page 66 and 67, there is a camper van featured with no LPG gas. Just 6 x 100 amp-hours batteries for cooking, barbecue etc. at £1,199 each instead. Is this the future? I think not, for most folk. I realise that the aficionados will go on about Peukarts law, with my 2 x 110 amp-hour lead acid batteries, but they supply all the current needed when wild camping, for the central heating and electric blanket at night in my 5th wheel caravan. 


Kind Regards, Bob Fisher


Hi Bob,


There are apparently around 1,300 Amperas left on UK roads now. I wonder how they are getting on with battery life? But I do have to confess that I recently spent two enjoyable hours behind the wheel of the e-Golf, and the driving experience was really quite enlightening. I really enjoyed driving it, although the ride is a bit choppy, and this is supposed to be one of the better riding EVs ñ supposedly significantly better than the Leaf and Zoe. Without too much effort, I managed to get something around 4.5miles per kWh, which is equivalent to about ten per cent up on their quoted real-life range claim, but that was without any significant high-speed work, and in warm weather without any need for heating or air conditioning. As I say, as an eco-driving challenge, I found it rather fun, but look at the price! The three regeneration settings are interesting, and I think I could soon learn to live with the significant braking effect of the highest setting. The screen graphics offer lots of scope for entertainment, and the acceleration potential was, I found, enough to leave the Audi driver that was tailgating me in a 30mph zone with a rather puzzled expression, when I dropped him easily on passing the 30mph de-restriction sign!


To me, though, the big issue is the lack of sensibly priced EVs for city use ñ which is where the primary pollution benefits are to be gained. Teslas and Jaguars may be impressively engineered and great to drive, but do they offer any real solution to anything but the Benefit-In-Kind company car tax of well-paid executives, most of who probably don’t actually own the car. It’s a one-way bet for the company car people ñ less tax, and no risk!


Ah now. Peukert’s law, presented by the German scientist Wilhelm Peukert in 1897, expresses approximately the change in the capacity (i.e. the loss) of rechargeable leadñacid batteries at increasing rates of discharge. As the rate of discharge increases, the battery’s available capacity decreases, approximately according to Peukert’s law. We won’t go into the detail on this, and it applied then solely to lead-acid batteries. But the effects of fast charging on electric car battery efficiency are known to be significant, and fast and ìsuperfastî charging do create significant heat losses, and therefore overall loss of energy efficiency. 


Best regards, 

The Doc


P.S. I have just being doing some thinking and calculating… on pure plug-in EV numbers, with maybe around 50,000 of them on UK roads today, and maybe at best 60,000 by January 2019. If EV sales were then to double each year, then the UK EV population would be 200,000 by January 2022, and 1.3 million by January 2025… and still under five per cent of the car population! Don’t panic Mr Mainwaring! The only people who might be panicking are the EV owners, when looking for a charging point. Deepest apologies to The Editor for these politically incorrect comments!

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