+2
BTW I have an an idea for sorting out Insulate Britain protesters the next time they glue their hands to the road.
Leave them alone.
Let them stay there for a week stuck to the tarmac filling their pants full of shit and piss whilst going hungry and thirsty in the cold.
Because they don't have anyone in charge with a mission to cut costs (so increase profits) so nobody ever knows what anything costs and have no interest (or authority) in changing anything.
And an even greater number don't think it is necessary at all.
This is a problem at all levels of the NHS.
Too disruptive - just remove them ... at the worst, it'll leave a layer of skin stuck to the road and they'll be left raw and sore.
It does seem slightly odd, when there is a huge battery, with low self-discharge there. Radio controlled boats, planes, etc. having batteries for the receiver and batteries for the motive power, have long been able to have a Battery Eliminator Circuit added, where the radio gear is powered from the higher voltage motive power battery.
Even if a separate 12V battery is retained, why not have it automatically recharge from the traction battery, whenever it gets low?
Possibly because that would impose a continual parasitic drain on the traction battery. A dead 12V battery is an inconvenience. A totally dead traction battery is bad news for the batteries.
Tim
The traction battery system needs various systems operational - monitoring, cooling, safety. They need power. By powering the basics from a separate battery it means the contactors to the traction supply are only closed when everything checks out. If there's something wrong, the high voltage stays dead.
Another reason is that electronics (ECUs, alarm, etc) expects to run from a low voltage like 12V. To run standby loads from 400-800v would require a DC-DC converter which is another parasitic load. So instead they run from the 12v battery which has a charging DC-DC that can run efficiently when the traction supply is operational. When traction is not operational the contactors are open and the traction battery is isolated.
A reason for using different chemistries is due to temperature range: lead acid goes more sub-zero than lithium. So you can engage basic systems from the lead acid and start to warm up the lithium before you fire it up.
The final reason is recovery: if the 12v goes flat it can be recovered with any jumpstart pack. A dead traction battery would mean a tow, if no AC supply was available.
Theo
After 5 weeks of being unused at the start of the first lock-down, the battery in my four-month-old Fiesta (which has various gizmo electronic doo-dahs) was down to 8V. I could not unlock it with the key fob, and I had to RTFM to find out how to access the covered-up keyhole in the driver's door. When I tried to start the car, it was essentially dead (although when I did turn the key, the alarm went off and wouldn't stop).
I had considerable difficulty getting the battery voltage to rise. I could not get another car close enough to try a jump-start, so I had to use my homemade 'simple' charger. Even with ammeter pinned hard on the
20 amp endstop, and getting very hot, I could not get the battery to more than 9V (which was still not enough to get any response whatsoever to the ignition key). Obviously two cells were at zero volts, or maybe one was reverse-charged.Eventually I got the battery up to about 10.5V, which was just enough to start the car. With the engine running, I immediately checked the battery again, and it measured around 13.5V (so obviously it was charging). I then took the car for a 10 minute run, after which the engine-off voltage was around 13V.
In contrast, my wife's car, which has no modern gizmos, started instantly.
Yes, but when that separate battery is getting low, switch in a contactor specifically for charging the 12V battery. You can add a limiter to how many times this happens to prevent it taking too much from the traction battery.
All the checks need only switch in, temporarily, when the 12V battery is getting low. With a low load, cooling, etc. would not be needed.
So you don't allow the lead acid battery to recharge too many times from the traction battery. Surely a little loss of range is better than coming back from a 3 or 4 week holiday and finding the car unusable, as the 12V battery is flat?
Typically, the reports used for such articles, are ten years out of date.
You have to religiously crank that spreadsheet, each and every year, to make disparaging remarks.
And BEVs are not all the same, as the Chinese ones use Lithium Iron Phosphate, with half the energy density, but an increase in lifetime charge cycles. Each process with its own (different) carbon footprint. Which means each car model that comes off a line, needs its own report, or someone has to sit down and compute an "industry mix" number.
Some of the large car companies, are now in the process of making their own battery factories. Which means they'll have a bit of catching up to do, or they'll be paying licensing fees for processes to use. And competition in the battery business, is a good thing, because the history of batteries, is the formation of monopolies. And we can't afford that for bulk storage applications, to let one supplier control everything.
Paul
Each battery chemistry has its own self-discharge rate.
You will have to look up the value.
And yes, the value, whatever it is, is significant, because it is "money down the drain". Of course the operator of the BEV, needs to know this value, for planning purposes.
Some cars use Lithium cobalt, some use Lithium nickel, the Proterra bus uses Lithium and titanium. The Chinese BEVs use Lithium Iron Phosphate (it seems to be a country specific policy of theirs).
That's why there is no glib answer to this.
The BatteryUniversity site usually has the info you need on the topic.
At a guess, Lithium will be better than Lead Acid. But I'm not going to make a table for you, with all the values. Lead Acid would be pretty bad, at a guess. The effect could be temperature dependent as well.
*******As a BEV owner, it's up to you to study your usage pattern. While the car is damn clever, it cannot guess that you've gone of vacation for a month. So it cannot offer suggestions on the LCD panel, as to "what a clever fill level would be".
When I refer to speculation, I refer to informed speculation. You might use a certain filling technique, when working five days a week and going to cottage on Saturday. There will probably be a pattern that makes best use of the big big battery.
Nobody is served by parking a BEV at 100% fill and letting it sit for three months. That wears on the battery, the 100% fill. If you don't drive a lot, simply fill to 100% just before leaving for cottage. For weekly driving pattern, fill to
80% makes best usage of charge cycles and lifespan.If you lived in India, and you knew there would be blackouts all the time, you would adjust the average fill level on your car, to suit the situation. Maybe you would fill to 100% level, and say to hell with battery life. if the lekky supply is 100% reliable, then you can tend your battery, as if the charge cycles mattered.
Since an expensive car has some room for adjusting fill pattern, you can perform more tricks with it, than one of the cars that has a tiny pack. Roadside chargers charge by the minute, instead of charging by the kilowatt, so "supercharging" between 0% and 60% full, gives best economy, even though the tariff to do so, is at least 2x higher than home charging. If you have to use a supercharger, use it when the needle is at 5-10%. Don't drive in at 70% and sit there for two hours filling to 100%. Horrible idea. On the highway road surface, you use the bottom portion of the battery curve, for lowest trip cost. Which means your trip plan, you cannot afford to run into a roadside charger, where all the cabling is ruined or defective! And guess what... That's what happens.
There is at least one car that used molten salt. Um, what a horrible idea. That doesn't sound particularly good as a long term storage concept :-) The reference I found to that vehicle, the owner claimed to have "not driven it a lot". I don't know why...
Paul
No. Adam is right. Put up detour signs and ensure nothing gets through to the protestors. They will then understand that actions have consequences. I wouldn't mind the inconvenience, knowing that they were being inconvenienced too.
Can I ask how often you use your car for this?
After all, you don't take your car on holiday to the US. So you've already accepted that an alternative means of long distance travel is OK.
Not beyond the bounds of possibility to provide a charging point near everywhere a car can be parked. After all they managed to put in individual parking meters at one time. Installing a charging point in the street outside your house or in the car space you use would be a tiny percentage of the costs of a new EV, for most.
That cannot last as EVs become more common. The lost duty from petrol etc sales will have to be made up somehow.
The first thing I was told on my EV charging course is that there simply is not enough electrical power produced and even if there was the distribution system in the UK is crap and is not up to the job to go all EV.
There are no effective detours for the M25 though which is why they are constantly stopping it.
If I let my cordless drill or Karcher window vac go totally flat it will never charge for safety reasons. There must be some additional circuitry to allow for this possibility in an EV car ?.
That may be true at the moment but DNO's have received funding from the regulator OFGEM to reinforce their networks and this has actually started to happen on the ground.
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