help with low cost current detector

I need a simple/cheap method of detecting current ( battery charging). Max 
current is 500mA. All it has to do is turn on an led if battery is
charging. 
I did try just a simple resistor + transistor, but it gets too hot. Looked

at maxim high side current detectors but uses expensive lo ohm resistors
and 
maxim stuff is expensive and hard to get.