I got a new battery for it, and the led blinks very slowly now. so I tried the steps here:
What to do next if Jl Cmder will not connect and wipe - BlackBerryFAQ
and now apploader will connect and start to erase and reinstall, but on the second step, waiting for device initialization, it disconnects and reconnects a couple times, and then gives the error code "unable to reconnect the device during a multi-stage load operation."