You can use a NIMH 6 volt pack but you are operating on the Cream of the battery charge. Once that is gone the ignition shuts off. They told me on the phone that they recommend at least a 6 cell pack(7.2 volts). You could do that also, but if you are the least concerned about weight you end up with a lithium battery. They also told me that the ignition came default to the short silencer, but I ended up having to program it to the short silencer mode. Not hard, but necessary.