Since it can't be adjusted down to 12V, and 15V fans/heater cartridges are rare/expensive, am I right to assume this should be used just for the motors, and a different supply for heaters/fans (or with a buck converter)? Or do the heaters not really care about a bit higher/lower voltage since they're basically a wire resistor? Would the current they draw be a bit too much if used at 15V?