Charging time

WarpedOne · 10-02-2006, 11:19 AM

Has anyone caught any info about how much is 3,5 hours full charging time mandated by battery tech and how much by tipical electrical outlet power?
If a power outlet capable of delivering say 200A at 220V was availabe would charging time decrease (and how much) or not (because of battery limitations)?

My GSM takes about an hour for a complete refill. Why would 6800 GSM took any longer? If required power was available of course.

electrified · 10-02-2006, 06:02 PM

You are probably right. However, larger currents would require 3 phase power, which in turn would require an industrial power installation. You could not do that at home. However, a commercial recharging station might. If electric cars take off, I would expect to see charging stations in parking lots, particularly near interstates and simular highways. Some of these could be 3 phase. Tesla could adapt the car for 3 phase because the motor runs 3 phase. I suppose some reading this don't understand 3 phase electricity, but it alows better use of wires. The comercial grid is 3 phase.

WarpedOne · 10-03-2006, 04:06 AM

I was thinking in line of CCS (Commercial Charge Stations) with powerful connections, yes.
50kW CCS could fill you up in about an hour. That would give you just enough time for lunch. :)
If batteries would allow that, of course.

WarpedOne · 10-05-2006, 12:28 AM

Tesla is using 17kW charger unit, that is capable of recharging it in 3,5 hours.

This paper: http://www.acpropulsion.com/PDF%20fi...201772%20AC%22 makes me believe charging time is limited by charger unit and not batteries alone. With higher power charger (and connection) a charging time could be reduced, but you couldn't do that at home. Not many homes have such powerful electric connections.

What is needed is higher power charging standard, so charging stations could be established offering fast charge service. Of course, some premium would be paid for luxury of fast charging and you could still afterall charge at home at night at low costs.

iisjsmith · 10-25-2006, 11:58 AM

If I remember correctly most batteries have a maximum level they can be charged at.

For instance, the Kokam SLB 452128 lithium rechargeable battery has a maximum charge current of 1C. Since the capacity of this battery is 145mAh they spec 1C as being 130mA. For reference the max discharge current of these batteries is 260mA, or 2C.

So most batteries are limited to what current can be supplied during recharge, but I have seen Li-Po batteries with high charge currents. For instance, the A123Systems new nanoparticle Li-Po batteries are rated at 2300mAh and can endure a 10A charge current. They can also discharge at 120A for a 10 second discharge!!

WarpedOne · 10-25-2006, 02:06 PM

You are correct, batteries have their internal limitations that in effect constrain minimum posible charging time.

What I am suggesting here is that minimum charging time for current Tesla's batteries is NOT 3,5 hours but considerably less, same as your standard cellphone with LiIon battery - about 1 hour. A quick calculation tells us that putting 50kWh of energy into any battery in one hour requires at least 50kW of electrical power. Charging gear would have to channel 500Amps at 110V or 250Amps at 220V. This is some SERIOUSLY STRONG electric current and quite hazardous to fiddle with at your home. So, Tesla took a safe path and used most powerful home charging standard in existance. It is spec'ed at 17kW and provides for full charge in 3,5 hours.

With this same 17kW charger and same home electrical installations no new miraclous battery technology can considerably shorten charching time. More powerfull charging standards and more powerful home electrical installations that are required for that are both very unlikely to come into existance anytime soon.

I expect when batteries that are capable of storing more energy come into usage, charging time will even LENGTHEN. Putting 100kWh of energy into the batteries will require about 7 hours of charging. But they will also give you at least 500 miles of range. The best solution is to simply accept this charing time as an inherent feature of electric car and adopt to it. If you charge your electric car every night it suddenly becomes a no-issue. Every morning the batteries are fully charged and you have waited for exactly ZERO MINUTES.

iisjsmith · 10-25-2006, 02:28 PM

>> What I am suggesting here is that minimum charging time for current Tesla's batteries is NOT 3,5 hours but considerably less, same as your standard cellphone with LiIon battery - about 1 hour.

We can't know this without knowing the maximum charge current for the cells that make up the Roadster ESS. For all we know that 3.5 hour number could be the absolute maximum. We need some more info on what type of cell they used.

Hopefully as cell capacity increases there will be a matching increase in both discharge and charge current maximums. So that as capacity increases we will not see a increase in charging time, like you suggest. But it is possible that cell designers could put more research into expanding capacity, thinking that is what consumers want, rather than charging times.

WarpedOne · 10-25-2006, 03:00 PM

>> We can't know this without knowing the maximum charge current for the cells that make up the Roadster ESS.

Ok, I agree. We can't be 100% sure into 1hour charing capability of current Tesla batteries. I am pointg out that there are already mass-produced LiIon batteris that are capable of 1hour charging time. Almost everybody has them in their cellphones. Tesla probably could use them if they choose so. So no new battery technology is needed to reach that 1h charging time, only more powerful charging standard and installation.

TM could probably use (cheaper?) batteries, that take longer to charge, because of its 17kW charger limiation. Fast charging would go unused.

iisjsmith · 10-25-2006, 07:58 PM

Yea, that 1 hour time is pretty easy to hit with current batteries. I have seen plenty of li-ion cells with 1C charging current limits.

I think what you are likely to see in regards to a charging station is large flywheel or capacitor arrays stored underground...just like the large fuel tanks are stored now. These would be kept charged from the grid. You could pull up, plug into a line, and get a fast blast of charge into your pack.

Active Power (http://www.activepower.com) have a CleanSourceDC flywheel product (CSDC-500) that stores 500kW and has a maximum rated output power of up to 550VDC. They can be linked in parallel into 2000kW arrays!! That's enough to charge 40 Roadsters.

Like you said, the battery tech is already there. We just need the stations! ;)

iisjsmith · 10-25-2006, 08:28 PM

For some more information on the Active Power flywheel systems, I was also looking at their CS2 product:

CS2-500 is a dual flywheel system that delivers 500 kW to the DC bus at 480 VDC
- system footprint = 42”w x 34”d x 78”h
- output = CS2-500 delivers 500 kW to the DC bus.
- voltage range =360 VDC to 550 VDC. The voltage level remains constant during discharge at a preset level.
- maximum current output = 1042 Amps for approximately 15 seconds. The Voltage level remains constant.
- minimum current draw during recharge = as little as 15 amps per flywheel.
- optimum current draw during recharge = 105 Amps per flywheel.
- full recharge time = fully recharged after at full discharge in less than 2.5 minutes.
- short recharge time = little RPM is lost during short discharge and recharge is complete in a few seconds.
- input voltages = 120, 230, and 480VAC at 50 or 60HZ. 480VAC 60HZ is standard.
- life expectancy = 20 years.
- link options = up to 4 units can be daisy chained in parallel for up to 2000 kW.

Combine this with li-ion or li-poly cells with 2C to 5C charge currents, and you are down into minutes for full pack recharge.