This page is designed to help you get the most from your Rat Zapper. We are keeping our eye on the ever evolving battery technology to help you get the most bang (or more accurately, Zaps) for your buck when buying batteries for your Rat Zapper. We recommend Duracell Ultra with M3 Technology and Energizer MAX alkaline batteries for the Rat Zapper Classic - 4 x AA's To supercharge your Rat Zapper Classic use Energizer e2 Lithium batteries. Tests have proven that the Energizer e2 Lithium Battery works 7 to 10 times longer than the regular alkaline batteries thus increasing the number of kills and stand by time of your Rat Zapper Classic. At a minimum the Classic requires a good quality recognized brand of alkaline batteries. Standard Heavy Duty batteries are not suitable for use in the Rat Zapper. We recommend Duracell Ultra with M3 Technology and Energizer MAX alkaline batteries for the ULTRA Rat Zapper - 4 x D's At a minimum the Ultra requires a good quality recognized brand of alkaline batteries. Standard Heavy Duty batteries are not suitable for use in the Rat Zapper. Rechargeable batteries - we do NOT yet recommend them . In our test with rechargeable batteries we found that they do not have the depth of power to supply the number of kills, or days of stand by power, as the above mentioned batteries. We have had customers report success with rechargeables and it is our feeling that these customers are changing the batteries at least 50% more frequently than is necessary with an alkaline (or better) battery. Rechargeables will not harm the unit and it is not in any way a safety issue either. We are testing some rechargeables as you read this and I am glad to report they are performing well so stay tuned.... Cold weather and battery strength; The cold effects the power output (somehow) of a battery so your batteries could be brand new (test and work just fine in a warm environment) but still not be able to deliver the punch needed for the Rat Zapper to do it's job. Nothing we can do about this sorry, if we find a solution we will post it here. *Alkaline batteries rely upon a chemical reaction occurring. This chemical reaction usually starts to slow down once temperatures go below 8 degrees Celsius. We believe Lithium batteries are not effected by lower temperatures.   Battery life after a Rat Zapper: When your batteries are no longer powerful enough for Rat Zapper, don't throw those batteries away just yet. There is usually plenty of juice to run other devices that require less energy such as flashlights, remote controls, clocks, timers, etc.. And remember, when the batteries are really finished, please check with your local authorities for a safe location to recycle them, it is the right and green thing to do for the planet and all of us that inhabit this earth. Thanks!