jlg 40ha

I have a 1997 JLG 40 HA. Battery was dead yesterday. Battery has a red cable bolted to the frame, and a black cable. I hooked red jumper to terminal with red cable, and black jumper to terminal with black cable. Tried to hook jumpers to my pickup(red jumper to red pos, black to black neg) and got huge sparks when I hooked the second jumper. When I reversed them on my pickup battery (black jumper to pos red, and red jumper to neg black) I was able to jump start. Why would this be the case? Also, raised the lift to do a five minute job, and left it idling to continue to charge the battery. When I depressed the foot pedal so I could lower it, engine did not idle up and I could not lower it...I depressed the foot pedal several times before it would idle up, but it eventually did, and I was able to lower the boom and move the machine. When it does ide up, it seems inconsistent in the amount of "idle up". It's not gradual...when I depress the foot pedal, the "idle up" is all or nothing and seems to vary from one time to the next. Why?

jlg 40ha