Have 2 of them. only use them when i know the cars will not be driven for more than 4 or 5 days - so far no problem with them or the batteries they are connected to. They are cheap and simple (convenient size too), and that is the good and bad of them: can buy as many as you need and keep at diff locations, etc. Bad b/c the indicator light is almost useless, would be nice to have better connection status or a meter. As stated in the link above, the technology is simple so too many bells an whistles not necessary for function. I'd buy more if the need ever arises. Hope this helps.