Fellows, in my opinion, it is hard to beat the performance of the black batteries Foxpro is selling. They are a slow discharge battery and therefore have superior shelf life. Foxpro keeps up with what works best in their ecallers, and advise customers accordingly. These are the latest batteries they have tested and stocked to the best of my knowledge. My CS-24 has two ten packs with seperate plug ins on the side of the ecaller. I had not used them in about 90 days, and they needed only a short top off from the smart charger to be ready to go full bore.