On the phone so can't do a big copy/paste but @molgrips that's a fair question. Quite a lot of the failures I'm more concerned with were on pumps that generally ran in earnest for a few days a few times a year or else tested every few weeks so comparatively low use. I'm not sure how you could compare the duty cycle but it was certainly a lot more stop than start.
@whatgoesup fair point I see what you mean now. There are things you can do with an electric motor that can tune it for reliability/efficiency or performance, its just going to take time to see where the red lines are in this particular application. I hope you're both right about vibration and especially heat issues , yes there is a lack of high frequency vibration but certainly more shock loading.
In response to the link to National Grid Mythbusters about EVs.
They seem to base it all on an annual average for power production and consumption by EV users. Everyone will be fair and use a smart device and charge their EVs when they're told to...which is obviously nonsense as many in the UK are selfish.
The head of Decarbonisation at National Grid was on Top Gear and came out with the 10% extra statement. He wasn't that close if you look at number of cars and average mileage and convert that to EV and energy use. (32 million cars, an average of c7000 miles per annum and use an optimistic 1kw per 4 miles you end up adding 56 billion Kwh to the c 300 billion kwh the UK uses. Domestic use is cited as being c 27% or c80 billion kwh)
56 billion is over 18%. They've not even added the push for ASHP into the EV equation nor have they mentioned the loss of most of our nuclear in the coming years. (We lost Hinkley B on the day National Grid did the mythbusters page)
They obviously have time to sort stuff out by 2035/40 but the overall plan for energy seems somewhat foolhardy. That buffoon Johnson obviously believed that wind could power the entire country by 2030, if only he'd thought of those cold, grey winter days when it is still and energy demand is high.
The road I live on has about 50 properties. The cables supplying electric are decades old. I have my doubts that they would stand up to a doubling of power thru them if we are pushed down the ASHP route, coupled with EVs (and perhaps electric hobs/ovens etc)
certainly more shock loading
That is a good point, when you hit a pothole in a hard corner there must be a fair old shock to the motor since it's directly connected. But that's so true of a manual transmission I'd imagine.
1kw per 4 miles
Don't you mean 4 miles per kWh?
Don’t you mean 4 miles per kWh?
Yes.
the motor since it’s directly connected
The motor is typically in the middle of the car and connected to the wheels with cv jointed driveshafts, rather like a conventional transmission is. I used to think they were best directly mounted at the hubs but that increases unsprung mass which is a bad thing.
I don’t know if the motors are soft mounted to the chassis or not - can’t see why they couldn’t be though if it helps with life (giving the motor bearings an easier time).
@squirrelking - yes, more shock loading in this application than in a stationary one such as pumps. There is good accumulated experience of electric motors in environments with high shock loadings though so hopefully that helps to get it right first time.
Let’s hope it’s better than the E-bike motor manufacturers have as there seems to be a world of pain going on there re motor reliability.
Quick check - Teslas at least seem to soft mount the motors to the chassis (probably more to stop motor vibration making its way to the cabin) so that gives the motors some shock protection.
It is pretty clear that for widespread EV purchase/use two major things need to happen;
1. Price is lowered to at least get close to equivalent petrol version
2. Charging speeds need to increase
Point 1 will no doubt happen over time but point two has a physics element to it although the more expensive EVs tend to charge faster but then back to point 1.
Charging speeds need to increase
Yes. The 800v architecture cars are already pretty good for this - 10-80% charge in 18 mins. If that’s not quick enough then imagine we can hopefully halve this to 9 mins, allow for payment whilst charging rather than before or after and the total charge time would be pretty much on a par with buying petrol and paying in the kiosk.
The other factor here is that for “most” journeys the car starts off fully charged* so charging away from home becomes a fairy uncommon thing, and in the majority of cases is part way through a long journey when you’d want a break anyway, so the the car can do it’s 20 min 10-80% charge while the driver is grabbing a drink / toilet etc.
The bit thats more of a concern to me re charging right now is the number of chargers and their reliability. I’ve heard too many stories of people queuing for quite a long time to use the single functioning charger at a service station. That has to change pretty quickly.
* this assumes that people have a means to charge overnight which not everyone does. This also needs to change and is probably the hardest bit to solve.
The motor is typically in the middle of the car and connected to the wheels with cv jointed driveshafts, rather like a conventional transmission is. I used to think they were best directly mounted at the hubs but that increases unsprung mass which is a bad thing.
I guess at end of day, if it is cheaper to have one motor bolted directly to a conventional diff and then driveshafts to the wheels, that's what will be done. Having two motors directly connected to two wheels likely complicates the electrical system (on top of the unsprung mass issue) more than a diff complicates the mechanical system.
