Electric Car Repairs/Maintenance ?
Discussion
One thing to watch out for is the "corolla factor" - with less and less maintenance required, as they age will we see more high mileage EV's with knackered wheel bearings, shock absorbers, etc. ?
And I am investing in stick-on windmill production, as well as plug-in battery conditioners (with das blinkenleds too!)
And I am investing in stick-on windmill production, as well as plug-in battery conditioners (with das blinkenleds too!)
AW111 said:
One thing to watch out for is the "corolla factor" - with less and less maintenance required, as they age will we see more high mileage EV's with knackered wheel bearings, shock absorbers, etc. ?
And I am investing in stick-on windmill production, as well as plug-in battery conditioners (with das blinkenleds too!)
I'd invest in printed porn. It's leftfield but what are all the EV owners going to be doing while waiting 8 hours for the battery to charge up at the service station? And I am investing in stick-on windmill production, as well as plug-in battery conditioners (with das blinkenleds too!)
J4CKO said:
as these vehicles get older, subsequent owners may want to tackle stuff themselves or get a non dealer garage to sort something, it may or may not be a problem, I am thinking that EV's will be a lot more reliable and hopefully wont need all the intervention, essentially its a fairly simple system, certainly relative to a modern IC car.
The thing is, from a powertrain point of view an EV is really non-servicable. You don't want to be (or even need to be) poking around in the battery, inverter, or traction motor systems. The only moving part in all that is really the traction motors' rotor, and the systems are intrinsically reliable. If parameters are maintained within the normal operating zones, there is really, with the exception of the battery, no "wear" occuring on a daily basis. Any catastrophic failure will result in a whole chunk of the system needing complete replacement rather than repair. For example, the main power semiconductor switches in something like a Leaf, are only a few 10s of grams of silicon, and yet they pass hundreds of kW of power. Any failure at those power densities leaves very little left afterwards........There will still be all the non-drivetrain stuff that will need repair at some stage.
Suspension loads will be similar to conventional cars of the same size / weight, and there's all the HVAC stuff - aircon, blower fans, etc.
I can't see any of that being beyond a competant garage; even if they have to buy a subassembly from Toyota, it still needs fitting. And diagnosing in the first place.
Suspension loads will be similar to conventional cars of the same size / weight, and there's all the HVAC stuff - aircon, blower fans, etc.
I can't see any of that being beyond a competant garage; even if they have to buy a subassembly from Toyota, it still needs fitting. And diagnosing in the first place.
If brushed motor.. the commutors will need skimming from time to time and the bushes replacing, as well as checking the bearing tollerances.
If brushless the hall sensor may occaionally fail, and also the bearing to be checked from time to time.
Nothing major, but something to enjoy doing
If brushless the hall sensor may occaionally fail, and also the bearing to be checked from time to time.
Nothing major, but something to enjoy doing
None of the current EV's traction motors are Brushed
And a lot of them are moving to "sensorless" control strategies that measure rotor position by the change in field inductance.
Ageing effects are currently topped by degradation of the magnet strength over time (and especially at high temps) and winding "shorts" due to the high dV/dT resulting from fast switching times required for max efficiency. The power silcon can also suffer from some ageing effects, as at really high currents some "material creep" can be experienced with the devices. With purely rotational movement, the rotor bearing systems are extremely reliable.
All those factors are currently massively outweighed (by a factor of at least 100) by battery ageing phenomena!
And a lot of them are moving to "sensorless" control strategies that measure rotor position by the change in field inductance.
Ageing effects are currently topped by degradation of the magnet strength over time (and especially at high temps) and winding "shorts" due to the high dV/dT resulting from fast switching times required for max efficiency. The power silcon can also suffer from some ageing effects, as at really high currents some "material creep" can be experienced with the devices. With purely rotational movement, the rotor bearing systems are extremely reliable.
All those factors are currently massively outweighed (by a factor of at least 100) by battery ageing phenomena!
Given the changes in battery technology over the last few decades, I would expect the manufacturers to design somewhat "modular" battery systems for the next few generations.
Lead acid -> silver zinc -> nicad -> nimh -> lithium -> ?
Given smart electronics, you have room for a fairly wide range of voltage and charge / discharge management.
Lead acid -> silver zinc -> nicad -> nimh -> lithium -> ?
Given smart electronics, you have room for a fairly wide range of voltage and charge / discharge management.
AW111 said:
Given the changes in battery technology over the last few decades, I would expect the manufacturers to design somewhat "modular" battery systems for the next few generations.
Lead acid -> silver zinc -> nicad -> nimh -> lithium -> ?
Given smart electronics, you have room for a fairly wide range of voltage and charge / discharge management.
It's a bit more complicated than that however due to the low volume nature of EV's currently. For example, power silicon principally comes from the industrial segment (where powerful 'lecy motors have been around for ages) and as such is pretty much available in two flavours, rated at either 600Vdc or 1200Vdc as these encompass the two main grid supply voltages. So, unless you want to design your own power silicon, and not many (rightly so) want to do that, your system voltage really has to fall into one of those two camps. As voltage = power for an electric machine, the higher the better, but that brings a lot more cost (1200vdc silcon much more than twice as expensive per amp, as 600V stuff).Lead acid -> silver zinc -> nicad -> nimh -> lithium -> ?
Given smart electronics, you have room for a fairly wide range of voltage and charge / discharge management.
Then you get to the thorny issue of average and peak system current. Although your car will quite happily drive along at reasonable constant speeds at low currents, hard acceleration, max low speed gradability and of course braking regen capture all push the peak requirement upwards, adding expense to the PE and ESS.
Currently battery ESS are modularised at a level that results in a safe(ish) handling voltage and a usable current capacity. These modules (consisting of multiple cells) are then built up into series and parralel "packs" to provide the necessary system voltage and storage capacity.
Then there is the issue of supply and volumes. The EV/Hybrid segment took quite a shake up with the failure of A123 systems recently, and one thing OEM's hate is there beautifully worked out BOM costs fluctuating wildly as the availability of battery components and raw materials changes due to political, environmental and commercial pressures etc
So, whilst a "global" std for Passenger Car ESS is possible, i think it will be a while coming yet tbh.
I am going to get a Leaf and put a 15 turn double in it, electronic speed controller and ball race it, not sure my EV knowledge still applies though...
Does make me think, I remember when the speed controller lost the plot on my last Tamiya (Dark Impact) and burst into flames very impressively.
The battery packs look like a massive bodge, basically thousands of laptop battery cells, must be pretty labour intensive to produce, can see why they are expensive but I guess the production methods will improve over time, and there was me thinking it was one massive battery.
Does make me think, I remember when the speed controller lost the plot on my last Tamiya (Dark Impact) and burst into flames very impressively.
The battery packs look like a massive bodge, basically thousands of laptop battery cells, must be pretty labour intensive to produce, can see why they are expensive but I guess the production methods will improve over time, and there was me thinking it was one massive battery.
J4CKO said:
... and there was me thinking it was one massive battery.
Try taking any decent sized battery to bits and you'll find a load of separate cells. I think that's just how dry-cell batteries work. Given that you have to have hundreds of separate cells anyway, it would be daft to put them all in one sealed plastic box so you can't replace individual failed units. J4CKO said:
The battery packs look like a massive bodge, basically thousands of laptop battery cells, must be pretty labour intensive to produce, can see why they are expensive but I guess the production methods will improve over time, and there was me thinking it was one massive battery.
They are the real issue in terms of expanding the concept beyond suburban useage, although, when you look at the actual data it is surprising to see that in the UK range isn't actually any form of serious barrier: https://www.gov.uk/government/uploads/system/uploa...
https://www.gov.uk/government/uploads/system/uploa...
It really is down to cost. And obviously a large chunk of that is the battery. At present Li batteries are not recycled for their Li content as it costs too much to collect the millions of small battereis we use in devices. Interestingly, car battery packs contain so many cells that the collection of these does mean that recycling becomes viable.
Added to this, the Japanese and Chinese now control the Li mines in South America, so production/supply reliability is no longer in the hands of flakey, bankrupt ex military dictatorships. This historically has allways added an enormous premium to the cost of the ore as it needed to be stockpiled and prices were eratic with no real exchange trade ability to hedge risk.
The fundamental voltage of a battery cell is set by the chemistry being utilised. However, that voltage, for all current (and practicable) chemistries is less than approx 4v per cell. If you make the individual cells bigger (larger volume, more surface area) then you do get more energy storage capacity, and more current carrying capacity but you don't get any more voltage. So a battery that just had a single massive cell would be practically useless, unless you just wanted to run an LED or similar low voltage device for a long time ;-)
For an electric motor, the supply voltage is the main limiting factor in the maximum power it can produce, so ganging up multiple strings of cells in series (to increase the voltage) is a good idea. if that doens't result in enough energy storage or current capacity, you then have to add extra parallel strings to meet those targets. it all gets quite complicated, and requires a suitable battery management system to handle the charge and discharge of all those series cells, and then you have to consider the voltage "swing" with charge state. ie, when fully charged your battery might output a nominal 400vdc, but when max discharged (a long way from "flat" to ensure suitable life, typically >50% SOC remaining) it might only output 340vdc for example. Again, all that is a result of the chemistry and physical architecture of the ESS chosen! This can have an effect on the vehicles performance, unlike a conventional ICE vehicle, which makes the same power with a quarter filled fuel tank as a full one.........
By the time you add in the requirements for maintaining certain ambient limits (temps, humidity, pressure etc) you can start to see why a commercial electric traction battery is so damm expensive currently
For an electric motor, the supply voltage is the main limiting factor in the maximum power it can produce, so ganging up multiple strings of cells in series (to increase the voltage) is a good idea. if that doens't result in enough energy storage or current capacity, you then have to add extra parallel strings to meet those targets. it all gets quite complicated, and requires a suitable battery management system to handle the charge and discharge of all those series cells, and then you have to consider the voltage "swing" with charge state. ie, when fully charged your battery might output a nominal 400vdc, but when max discharged (a long way from "flat" to ensure suitable life, typically >50% SOC remaining) it might only output 340vdc for example. Again, all that is a result of the chemistry and physical architecture of the ESS chosen! This can have an effect on the vehicles performance, unlike a conventional ICE vehicle, which makes the same power with a quarter filled fuel tank as a full one.........
By the time you add in the requirements for maintaining certain ambient limits (temps, humidity, pressure etc) you can start to see why a commercial electric traction battery is so damm expensive currently
Gentlemen, we have our first proper, geeky tech discussion on EV's, a watershed moment I think you will agree.
Loving all the info, to go with my half baked knowledge of Combustion engines.
The Electric Motor really appeals to me nowadays, it is such a beautifully simple device compared to even a small piston engine, the lack of an iffy rubber band synchronizing many expensive metal parts in close proximity at high speed is a big plus point. Obviously we all love the IC engine but look at the internals of even a small one and they are so much more complex.
A Tesla Model S does an equivalent of 90 odd Mpg, three to four times more than you could expect from a comparable petrol car which I find amazing.
http://en.wikipedia.org/wiki/Miles_per_gallon_gaso...
Loving all the info, to go with my half baked knowledge of Combustion engines.
The Electric Motor really appeals to me nowadays, it is such a beautifully simple device compared to even a small piston engine, the lack of an iffy rubber band synchronizing many expensive metal parts in close proximity at high speed is a big plus point. Obviously we all love the IC engine but look at the internals of even a small one and they are so much more complex.
A Tesla Model S does an equivalent of 90 odd Mpg, three to four times more than you could expect from a comparable petrol car which I find amazing.
http://en.wikipedia.org/wiki/Miles_per_gallon_gaso...
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