Hi,
What's the reasoning behind the suggestion for upping the car battery voltage to 42V? I would have thought it would make more sense to have started with let's say 42Vwhen you have large loads - starter motor. Then start dropping it as cars have more electronics in them (ie lower voltages and loads).
Cheers,
Michael
To say it in two words: Feature creep.
More and more stuff gets added, some folks want to control valves electrically and so on. Then there are the guys who absolutely have to have a one kilowatt stereo in there. Tchk, tchk, BOOM, tchk, tchk, BOOM ...
If the auro industry would learn to use geared starters that would be a non-issue. But learning doesn't seem to happen too fast there.
-- Regards, Joerg http://www.analogconsultants.com/
But logic says that if you just have to power a whopping big (very technical term I know) starter motor and not much else you'ld have a higher voltage from the off.
Also why's is 42V? One article said they wanted to get this voltage with a
36V battery......?Michael
With a lead-acid battery the cell voltage during discharge is 2 V/cell, and the normal charging voltage is 2.3 to 2.4 V. Using 18 cells you get a 36 V battery and a charging voltage of 42 V nominal when the engine is running.
-- Regards, Carl Ijames carl dott ijames aat verizon dott net (remove nospm or make the obvious changes before replying)
The higher voltages allows for smaller wire. there for, lighter cars (cheaper). and smaller starters and alternators.. actually, with that, what they want to do is make a combination starter and alternator as one unit.. it's all about being cheap..!
-- "I\'m never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Well, cuts down on the cost of copper and cost of batteries.
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The power required for electric valves is the prime reason for increasing the voltage from 12v.
Cheers
It's forecast that electrical power consumption in cars will continue to rise from 1-1.5kW now.. up to perhaps 5-10kW with active suspension systems, electric steering, maybe electric valves, maybe electric A/C, etc.. That would make for uncomfortably fat and heavy wiring at 12V.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Apart from the savings in copper usage, 4*42= roughly p-p voltage for 120VAC rms. Although in another lifetime at Behemoth Oil Co we ended up using a
204 VDC battery pack to make decent 120VAC 0-400Hz (70kW 3-phase AC motor for gas-electric hybrid vehicle). I wonder if any mainstream manufacturer will make the obvious leap to 120 volts.Best regards, Ralph in NH
Triple the present number of cells-- so about 36V with the engine off and about 42V with it on.
It would be nice to go to 200 or 300VDC, but that would raise a lot of safety issues which the car companies apparently don't want to deal with.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
My '07 Prius battery is 201.6 volts, according to their spec brochure. It's rated at 21kW (28hp). But they say "Hybrid System Net Power 110 hp (82 kW)" - this must include the combustion engine, which is rated at 76hp at 5000rpm. They also say: "Electric motor power output 67 hp @ 1200-1540 rpm (50 kW @ 1200-1540 rpm)" which to me implies the battery can deliver at least 50kW, rather than 21kW. Perhaps those two numbers refer to peak power and average power? There's also the matter of momentary pulses of power the motor delivers in its function to replace a flywheel, which is missing.
Anyway, 50kW from a 200-volt battery implies 250A. I'd like to clamp a current meter on the battery cable and take some measurements. It's on my long list of things to do someday.
An additional motivator for the higher voltage (and power) of the 18 cell batteries is so that there is enough power to restart the engine every time the car is restarted from a stop automatically while still in gear, so that the engine can be automatically shut off every time the car is stopped. Many manufacturers have prototyped this fuel-saving arrangement, using an integrated flywheel - alternator - starter motor, which also removes the alternator belt and starter gear losses. Although the parts are well developed now I am not sure if it will ever go into significant production, as higher voltage mild hybrid technology seems to be passing it by, and full hybrid is clearly on the way.
Glen
FYI, in the 60's I had a friend who worked for a dry cell company during the summer while in college. His job was to run load tests on the dry cells for production quality control. He managed to, ahem, free a few for his own use. He claimed that he would wire 4 1.5V A size cells together in series and was able to start his VW bug with them. He did this because his car battery had died and he could not afford a replacement.
Ahh, the good old days before credit cards.
Al
easier to make and cheaper to build the wire harnesses and assoc devices.
powere regeneration usng energy brakes and mass/energy transfer back into the batteries can be done with smaller/less devices & silicon component converters.
its all about the slow migration from hydrocarbon fueled jitneys to (eventually we hope) completely electric jitneys.
why it took so flipping long for the USA manufacturers to make changes?? defies ethical reasoning. except they just are so greedy and lack real ability to impliment change without making some old duffer in some department feel unwanted? it's because we "care"so much about our "people"?? ho ho ho :-))
now they just wait until the whole dang factory is unprofitable, fire everyone and ship the work overseas.its all about greed, profit and truly "UNCARING" about the usaas a coherent local economy. too much spent on advertising and trying to hand the customers what they DONT want or need.
oops,way off the track again, ohhhh well!
Key is that the 'starter', is just one load for a short period. Heating in the wiring is not too much of a problem, and you can use thick wires. Modern cars are gaining a lot more electrically moved kit. Classic relatively 'new' stuff, is electric power assisted steering. There is a strong move towards other kit like this with quite high demands (for instance, I am driving a car, with MHD shock-absorbers). The loads on the electrical system are predicted to rise by as much as 10* over the next few years, with lots of stuff that is perhaps currently belt driven, being given it's own electric motors.
Best Wishes
Win,
The battery supplies about 20kW and an additional 30kW comes from Motor Generator 1 (MG1) that runs from the engine through the PSD sun- planet gearing. This provides the 50kW to Motor Generator 2 (MG2) that drives the wheels directly (via the final drive). By controlling the speed and direction of MG1 it provides variable gearing between the engine and the wheels.
The battery current is limited to 100A by the control system and has a
125A fuse.kevin
Michael,
Have you read "hitchhiker guide to th universe"? that's the path to the reasoning behind the exact number, "42", you can get an idea of the book on wikipedia, too.
Following another line of reasoning, as the creature features inside of cars has increased from a few 100 watts to pushing 1 KW, the current drawn on a 12 volt battery approaches 100 amps. this strain wire size, flexibility, and battery cconnectors. If you had a 1 kw load on a 42 volt supply, the current drops to a more manageable 25 amps. So, an increase in cars batteries is needed, the worlds needs a standard.
Marc
Thanks Kevin, where do you go to learn these things? I'd like to learn more detail about the planetary-gear setup.
Henry Ford (#1) devised the scheme... the pedal "shifts" simply lock the inner or outer ring. Was later used in automatic transmissions.
...Jim Thompson
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Yes, I'm familiar with planetary gears and have used them into some of my designs. But I haven't seen a detailed explanation of the Prius setup, and I think it may well be something unusual. For example, does MG1 somehow control the planetary gear's effective ratio? Toyota's descriptions claim a continuous variable ratio. Not an electrical ratio but a mechanical one, SFAICT. In my looking around I have not found much of the detail Kevin just rattled off.
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