Today, non-rechargeable lithium-based batteries are common. Used in many cardiological and neurological implants, they provide between seven and ten years of life.

如今，不可充电的锂电池较为普遍。应用在心脏病和神经源性疾病的移植设备中，一般能够提供7年到10年的使用时间。

And because of that, there weren't many helmets available and they didn't modify them to small enough and comfortable enough to be common use.

正因为如此，可用的头盔不多，他们也没有把它们改装得足够小和足够舒适来普通使用。