first of all you need tick data for renko chart
renko charts are independant of time so if you interpolate it with any time frame other than tick, then you are cheating yourself like the cat who drinks milk with shut eyes thinking no body is watching it, meaning the tick data on which renko is dependant, will be compressed with the introduction of timeframe, thus will not plot the true price movements as and when it happens and therefore you will not know the actual price movements which happened within every preiod of timeframe set value.
if you have been making profit trading your method, then you have been just plain lucky.
