[PStechPaul]

A 240V 15A service can supply only 3.6 kW, which means a 1 hour charge will only take you about 10-15 miles, so you would either need to spend a few hours to get a full charge or at least an hour just to top off to get home or somewhere that offers a faster charge or where you plan to stay awhile. If electricity costs are $0.15/kWh then an hour of charging at a Level 2 station would about $0.54 and hardly worth the hassle and expense of even setting up a coin operated "parking meter".

It would probably be best to offer snacks or entertainment (maybe even a slot machine) where the EV owner can spend the time and a lot more money than what might be made on the electricity. Of course you could charge a lot more than the going rate, but then it might become competitive to a point of zero or negative profit, whereas the food/entertainment can stand on its own merit and compete on the grounds of quality and uniqueness.

 

[PStechPaul]

Without really fast high power charging stations, there is still the drawback of having to wait an hour to charge your vehicle to go maybe another 20 miles, which takes less than 1/2 hour unless you are sightseeing on back roads. So if you will be spending 2/3 of your time at charging stations, it severely limits their practicality except as an emergency measure.

I see a couple of options. One is to have on-site energy storage capable of high burst power, probably in the form of battery banks or pumped water. In this way grid power can be used continuously to keep a reserve energy that can provide at least 50 amps at 240V (10kW) which can give several times the charge in the same time. If you can go 1 hour on a half-hour charge, I think that would be sufficient. For such charging stations, a premium would need be charged, of course. But the capital cost would simply be that of a medium size solar installation, maybe $2/kW, and a 100kW facility would be plenty.

Another option is to equip EVs with an auxiliary battery pack that is easily removable and replaceable, perhaps about 3.5kW per module (240V @ 15A). Charging stations could keep these charged up by drawing grid power at a constant rate and utilizing peak demand optimization. A 3.5kW module is probably the size of a suitcase and may be 50 pounds or less so it can be fairly easily handled by one person, perhaps with a simple lifting crane, and could be switched out in 5 minutes and would give 10 miles range where an equivalent charge at that rate would take an hour. Multiple packs (or larger ones) could be used. Each pack would have its own metering system to monitor usage and SOH of its cells and you would pay a differential based on the relative condition of the packs that are switched.

You can still offer a free low power charging station, but consider that people will need something to do if their charging time is greater than about 15-20 minutes.

 

[PStechPaul]

The charging station just signals the maximum current it can supply, while the charger in the car actually limits the charge current. Just like a simple 6A battery charger can plug into a 20A 120V socket. The charging station could have a current limiter and certainly must have some sort of overcurrent and short circuit protection in case something goes awry once the negotiation has completed and power is supplied to the car's charging connector.

Most EV battery chargers that I am familiar with can accept a DC as well as an AC voltage source. The EMW charger has a PFC front end that regulates the incoming supply to about 350 VDC, and that is ideal for most battery packs of lesser voltage, since a buck switching supply is used. The charger is essentially a switching supply similar to those used almost everywhere, and they first rectify the AC, so plugging into DC is fine, and you don't need PFC.

So, a 350 VDC battery bank at the charging station would be all that is needed, and it can be sized for the expected duty cycle of people using it. A typical charge might be 30A at 360V or 12 kW for 15-20 minutes, for about 3-4 kWh or 10-15 miles of range. If customers come in once every hour, you may need a 5 kW charge from the line, or about 20 amps at 240 VAC, for the 40 minutes between visits, so a 6 kWh pack would be sufficient (just barely). If the proprietor had his own EV with a modest 24 kWh pack, it would be plenty for a single charging station in use continuously during busy times, and then could be fully recharged overnight when there are fewer customers.

You could also have a mobile charging station in a small truck and offer road service calls (for a reasonable fee). People would have much less range anxiety if they know that a charging truck could be a phone call and 15 minutes away, almost anywhere. And the ultimate would be a heavy duty drone that could fly into remote areas to give you a "hot shot".

 

[PStechPaul]

Thanks for the information.

So essentially this is what i understand (Sorry am an electric noob)

Input is a 240 V, 15 Amp socket which is found in all businesses
Current Output could be boosted to 30A at 360V or 12 kW or more
A Battery pack is used to draw in extra current which facilitates high burst power

Let me know if i understand this right so far and please correct me if am wrong. Also here are some Questions.

So power chord that goes into the DC quick charge port of the Electric car is from the battery pack and not the grid, right?

Yes, the battery pack is needed for the high burst power.

This battery pack could be Lead Acid too? Or Does not have to be Li-Ion?

Yes, lead-acid would be perfectly OK, as weight is not an issue, and charging is not as critical. It's also much cheaper as an initial capital expense, and is recyclable, but Li-Ion may be cheaper in the long run.

The grid charges the battery pack overnight or in between customer visits.
Is that right?

Yes, the charger can be connected continuously, and it will draw only what is needed to keep the pack full, but will also supply a good portion of the burst charge.

I like this product - JuiceBox - an Open Source Level 2 EV charging station that can charge your car at up to 15kW / 60A.
Link here - This JuiceBox Level 2 charger

How would u rate this product? No battery needed just fast charging!
The caveat is that, this achieves the high burst power from a NEMA 14-50 outlet, which is a 50 Amp, 240 V socket.

Be aware that this product is designed and built by EMW, and their charger is to a large degree dangerous junk. I am now trying to implement a retrofit to those chargers to make them relatively reliable and safe, and in the case of the two I have from customers, just getting them to work.

I have looked at the schematic and PCBs for the EMW JuiceBox and I found a number of design flaws and questionable safety issues, so I would not recommend it. There seem to be other devices available that are reasonably priced and probably better designed. Read the thread on EVSE for more information and my own suggestions for improvement.

By the way, The idea of using a Heavy duty drone to offer mobile charging is wicked!

It may not even need to be that heavy to supply enough "juice" to get out of a tough spot. If you are off-roading and run out of charge, you are probably no more than 5-10 miles from a main road where a larger truck could supply all your needs or provide a tow to a mains charger. The off-road route might be 5-10 miles, but perhaps only a couple miles "as the crow flies", so the drone might only need to carry a 20-50 pound battery pack a short distance to where you are. It could drop it off for you to connect to your vehicle and bring it back, while the drone could fly back on its own power unloaded, or just ride back with you .

 

[PStechPaul]

It might seem like I am trying to trash EMW and Valery, but I only want to point out problems that I see. It seems that the EMW website no longer lists the charger among its products, and only the EVSE and accessories appear. If you try to find the technical information such as schematics and detailed assembly or BOM, the link is a dead end. I obtained schematics and source code and other documents for the EVSE last year, but they have been either taken down or hidden, even though this is supposed to be an open source project like the charger.

The EVSE is a very simple device, so there is not much that can go wrong if it is properly assembled with good components. IIRC my concerns were about the lack of fuses or a disconnect interlock contactor, and the pilot signaling and sensing circuit seemed suspect. So, it may be OK, but "buyer beware".

I found the following link only via a general on-line search:
http://emotorwerks.com/products/onl...bled-and-tested-emw-smartcharge-12000-charger

Actually. there is a side panel on the products page where you can select charging systems, and some schematics and build info may be available. But not for the EVSE.

Here is the dead link: http://emotorwerks.com/tech/electronics which is on this page:
http://emotorwerks.com/home/latest-news/85-emw/emw-products/133-emw-juicebox