Jumper Pack Problems

I am having some concerns about these jumper packs there have been several occurrences of weird problems after they are used I myself have one in my garage that I have used several times with no problems so the jury is still out I always thought that the battery cables should have a different connection for the negative and positive to prevent connecting them backwards but the manufacturers still do not listen to me or for that matter ask for my input Any reports of problems would be appreciated perhaps with only one end to connect these are all reverse connection related