The lithium battery packs typically utilize a PCM to control charge rate, provide a cutoff voltage for the battery pack as dicharging litium cells below a particular voltage in the range of 2.75 to 3 volts kills the batteries, cell balancing and pack temperature monitoring. All of these things are valuable to keep from destroying the batteries. Operation of a lithium pack without the PCM is dangerous to the operator as well as will destroy the pack. The less expensive ones just monitor charge rate and low voltage cutoff, but without the ability to balance the cells during charging the pack cycle life will be shorter( spend the extra $$). Unfortunatly the PCM's are current limited so if the current demand is greater than the PCM can supply it either shuts down or gets toasted or if it is fused the fuse pops. If you get larger than a 250watt motor under high load conditions the current draw can be great enough to cause problems for the PCM. If you want to utilize a motor larger than 250 watts with a 12ahr pack you will probably need to replace the PCM with one of a higher current rating or find one that has a higher discharge current capacity. Over the counter packs should have their max discharge rating and most of the 12ahr packs I am seeing are running in the 10amp range.