If you do not want your batteries look like in the picture above, here's my personal humble piece of advice that works with any charger. Just to be on the safe side after one morning I've found my battery almost "red hot" (but luckily not melted, swollen and fused together) I've got the idea to use a regular cheap mechanical cyclic timer along with the chargers I plug in the timer. I set the timer to turn OFF and ON every 15 minutes, so the batteries and chargers have time to cool down and chargers detect the charging state of the battery better when just turned ON as I've noticed after dealing with about a dozen of different chargers for the last 5 years of e-biking.
This way chargers do not have a chance to get stuck in the ON state charging indefinitely until the battery melts. Besides, since the timer is 24 hours while only approximately 6 to 8 hours is needed for a complete charging of the battery, you can set up additional 3 or 4 zones or charging modes for your battery like extended charging periods or extend the cooling time. If that sounds too complicated or too "techie" to you, you can always order the right timer already setup for all these modes just by letting me know that you need one, pay by PayPal or e-mail and get it soon by a regular mail or UPS or you can purchase it thru E-bay if it is more convenient or preferable way for you.
You can find timers anywhere, even in dollar store these days, but make sure they are mechanical, cyclic and are able to switch as often as every 15 minutes to make sure your charger doesn't get too much rest during the night shift :-). Usually cheap timers are able to switch ON and OFF only every 30 minutes, so those with better 15 min timing resolution are a bit harder to find, but not too hard. I picked one from Walmart for 20 bucks or so which comes with the power bar, so you should find one like those easy as well. So, that's just my two cents in preventing battery melting - the cheap and easiest way (at least until you're rich enough to afford a better charger that does not melt any batteries at all :-) Obviously aforementioned method is just a preventive measure, it is not a panacea to prevent overcharging. After all there are also just plain faulty batteries with shorted cells and so on, so keep an eye even with timer on your charger and battery as often as possible. But panacea or universal and foolproof method of preventing battery melting actually does exist. That would be a thermal shutdown protection, which turns off the charger as soon as the battery temperature reaches the certain temperature threshold like let's say 40C. I'm going to look for this sort of solution, so stay tuned and visit my blog or sign up for updates.
And if you find a better solution or even cheaper 15 minutes timers here in Toronto, let all the readers here know posting down bellow your findings in the comments. That would be your two cents :-) Thank you in advance!