GoHub Overheating

Hello,

Can somebody please help me? I have been running a GoHub 48V set up on SLA for about 1 year. Everything was great, until recently. Now, every ride, I blow a fuse. For those who don't know, the pre-wired pack comes with a 20 Amp blade fuse wired in series.

The fuse keeps blowing, anytime I run up a big hill, or full throttle on a long straight away. If I touch the fuse holder, it is really hot, almost too hot to touch.

So, it seems somehow the batteries are overheating. I'm not sure why. Can anybody offer any advice? The only thing I can think of that may have a caused problems is I left the pack on for about 4 days, resulting in pretty much draining all 4 batteries. They still take a charge, at least wired together. I have no idea if each battery is charging to capacity however.

Thanks in advance for your help