Just check if the axpert, like mecer has the floating bug issue. Mine does so the floating voltage needs to be set high which isn't great , else it never charges under over the floating voltage it seems and also the mecer axpert (not sure about others) doesn't seem to be able to take a battery past 50 percent whereas lithium battery can go to 30 percent discharge - meaning if you go lithium later you are giving away 20 percent usage for nothing.