i bought another battery yesterday for £8. its only 1000mAh but its tiny and its the only one that will fit in my car receiver box. iv gone off my other design of it hanging off the side as the other day my exhaust got ripped off after clipping a tree and if that had been a battery then the car could of gone wot. works great and i can charge it in 4 mins so i just charge it when it runs out