Depends where you are putting it. If it's in a place where people are expected to park for several hours, "fast" (ie. actually slow) chargepoints are the right answer. For locations where people only stop a short time, rapids are the only thing that makes sense. In general, slow charging is to provide a service to people who are already coming to that location for other reasons, while rapids should expect to attract traffic to the location for people intending to charge (hence no good if it's a hard location to get at due to traffic, and needs to have something for them to do for the 30 mins they are waiting).
In both cases, the parking regulations need to match the charging speed - it must be prohibited to park for long periods at a rapid, and equally putting a slow chargpoint in a carpark with a 2-hour max stay (has been done!) would not allow anything like a full charge.
The three key criteria are:
- Reliable. Many existing schemes rely on getting mobile signal, on lots of wonky back-office software working perfectly, on mobile phone apps apparently written by inexperienced amateurs etc. etc. rendering what on paper might have been reasonable schemes extremely undesirable.
- Easy to use, with minimum pre-requisites. Needing to apply in advance for smartcards, needing to own a particular brand of mobile phone, accepting only UK-issue bank cards are all significant impediments.
- Not adding undue extra cost. Since the actual value of the electricity is small, the cost of collecting the fee often ends up greater than the value of the electricity. This is to an extent unavoidable, but if it works out too expensive then the whole project becomes a waste of time because nobody will want to use them. This consideration often forces compromise.
If it's at a carpark with parking charges, integrating the cost with the parking cost scores well on all these fronts.
Introducing your own local scheme with your own smartcard is probably the worst thing you could do, as the admin will be disproportionately expensive and you make it available only to those people who thought in advance to get the card. Bear in mind that unless you are offering it for free or you live in a very dense urban area, most of your local drivers won't want to use the facility anyhow - they will be better off charging at home - so your facility is aimed at visitors or long-distance commuters.
Payment with cash or contactless bank cards is great on the easy-to-use front, but may fall down on the cost to operate (both expensive capital and ongoing fees).
Providing reliability is tricky, since most of the established chargpoint designs have turned out to be junk, while the newer ones are hopefully better but have not yet got much of a track record. In the multi-story situation, relying on mobile phone signal either for customers or the chargepoint itself is high risk; you may need to budget for wired network connection. Whichever way you go, budgeting for adequate maintenance is critical - there's far too many schemes out there where the initial project only considered the capital cost and once they broke there was no money to maintain them.
Fixing the per-transaction cost issue generally means joining one of the established chargepoint networks, which vary both in the deal offered to the end user and the deal offered to the site owner.
As a user, I rather like PodPoint's new model where the reliability issue is addressed by giving 15 minutes free charge (which after all only costs the site owner about 20p), which offers a get-out-of-jail if the comms is completely broken, and give the user time to wander around and find working mobile signal. They also have a combination of apps on popular phone platforms plus website that should give access from other smartphones etc.
Franklin Energy have proposed to solve the mobile signal issue by using wired comms for the point and making it into a wifi hotspot to serve the customers wanting to initiate charge from their smartphones; however I don't think they actually have this in operation yet.
CYC have their voice response system as the ultimate answer to people who don't like smartphones, though this largely relies on mobile comms to the chargepoints and so has reliability issues.
Yes if the town centre is the sort of place that attracts people from out of town to spend time there (major shopping destination that attracts people from a wide area? Theatres etc? Hotels?). But not if it's the sort of place that mainly attracts locals who are able to charge at home for less money. Probably not a good place for rapids.
You want multiple chargepoints at one location: to be actually useful, there has to be a good probability that when you turn up the facility will be available, and the maths works out that 2 points can serve vastly more than twice the traffic for a given level of availability. This also keys in to reliability. So if you were thinking about rapids and installing half a dozen across the borough, it might be better to find three really good sites and put two rapids on each rather than 6 sites with one.
For slow charging, the same applies but even more so as there's no prospect of waiting for the car in front of you to leave - they are likely to be there for hours (and forcing/encouraging them to come back early greatly reduces the desirability of the facility).
Also, you need to have in mind what you will do to expand if the facility becomes popular.
For slow charging, it would be desirable to find equipment that lets you install a large number of points that share out the available power (on the basis that not all will be in use all the time - some will have finished charging, some will be charging more slowly, some will be ICEd etc.).
