The 250Watt Maximum Continuous Power Rating what is it?
The simple answer to this question is it is a CODE an understanding of which enables Motor Builders/ Manufactures to be able to build a motor within the guidelines laid down by European Government(s)( EU) and other individual buyers.It is a means by which to find a PRE Motor build AMPACITY wire rating the definition of which is: - the maximum amount of electric current that a wire (the Conductor) can carry continuously without exceeding its temperature rating -(the safety factor) -it is measured in amperes and depends on the size of the wire and ambient temperature. By looking up on a Wire Gauge Chart a particular wires’ current carrying capacity and then multiplying this by the batteries’ mean average power an idea of a useable power rating in Watts can be achieved. Government has used a wire rating that carries 6.944 amps then multiplied this by 36 volts to get a 250Watt rating. A motor built and operated up to this rating can be used all day without overheating. It is safe.
Unfortunately, because we British have lost out when it comes to Wire Gauge Charts we do the same as everybody else and use the American Wire Gauge (AWG) system but because this system is based on two different temperature ranges neither of which, although good enough for general purposes, is accurate enough when put up against the EU’s assisted bicycle motor testing process, which in testing for the legality of such, has set the ‘ambient’ temperature at a lowly and constant 30˚ Centigrade, Consequently, our Government who is aware of all the confusion it is causing refuses to use the term Ampacity - and has stated instead that ‘an Insulated wire has a voltage rating and a maximum conductor temperature rating it doesn’t need to have an Ampacity rating as that depends on the surrounding ambient temperature’ - consequently, when asked to furnish a simple explanation to the question above they cannot come up with an answer and cop out by pointing the enquirer (me) and anybody else that enquires to all the information to be found in such as that that is in the EN15194 and UN/ECE Regulation N0 85 legislation and that information relates to aspects of POST motor build and testing which are expensive to buy and runs into many thousands of words none of which are relevant to a PRE motor build consumer question the answer to which runs into forty four small simple words:-
It is not a reference to a Peak Power Rating.
It is a reference to a Power point (250watts) from which the (AMPACITY) wire rating used in a PRE motor build can be determined in order to conform to OHM’s Law of safe usage.
The EU governments(s) were quite aware of the power limitations of such a low rating so decided to ditch all that bumph about safety and beggar the consequences legal or otherwise and decided to up the ante and set the bar twice as high setting a maximum useable power limit to an unsafe heat generating 540 Watts. (Reference to this was later rescinded as exceeding the limit would bring failure under the 30min rule).
AND THE CONSEQUENCES ARE
The administration of Law is compromised by the hypocritical nature of the present means of rating an EAPC motor build and a EU advisory committees recommendation that future motor builds were based on the Wattage available under the EAPC Bicycle Classification and not on an Ampacity rating was turned down. It is my opinion in view of the statement above that it will not be long (due to the lack of administration of Law) before bicycles presently looked on as being illegal 350-500 Watts will providing they have been manufactured with the proper wire build to conform to OHM’s Law (like house wiring has to) and cannot exceed 25kmp/15½mph in speed will be classed as legal.
Yours Linfitter.