Hello ! :)

I've been riding on my bike on and off for almost a year now and it's come across a problem after some a bit intensive driving for four days (two 20minute trips going around 20-25mph each day)

It's come to a point where I've charged my battery to max (¬48v) and after turning everything on the lcd3 display tells me sometimes the battery's empty or full depending on how it feels ... I used the voltmeter and the battery's still got plenty of juice in it.
What would happen is - I'd push down the throttle almost till the end while I'm static and the display would show me the wattage jumping all the way up to 600w 700w in like a second and then cut out. (Unsure if it used to jump this high normally or not)
Another way of going about this is - pushing the throttle down just slightly and going at about 5mph but even then the lcd display starts to show that the battery level is rapidly decreasing and eventually after couple seconds it would cut out all power.

I'm running a 48v battery to 48v controller to 500w hub motor.
Personally I'm thinking it might be the controller's fault as it's a simple chinese one and I've read that they tend to die after some time but still figured I'd ask here before running off to get a new one.
I've got two exactly the same batteries and for both of them the outcome is the same... I've even checked all the cable connections and everything seems ok, unplugged and pins look fine - reconnected all and still nothing.

Let me know what yall think ! :)