If you have a digital multimeter you can use it to find the polarity of a power supply. For recharging I too used wall warts that were the right voltage and wattage, but I got tired of monitoring the recharge process so I wouldn't fry the battery. I got a nice plug and forget recharger at Zbattery for $13.45. The best money I ever spent on a recharger. They also have good prices on SLA batteries.