A few days ago i had to jump a neighbors car. Tried it from the post in the engine bay. Her car would barely turn over even with letting it sit for a few minutes. After about 10 - 15min of trying it that way i said screw it backed my car up hooked the cable up to the battery. Went to start her car and it started right up. So if your jumping anything bigger then a lawn mower don't use the posts.....i was jumping a 91'ish Blazer with the 4.3 V6.