9V Heavy Duty Standard Battery Review

Aside from the TENS AA digital unit, the majority of TENS/EMS devices utilize a 9 volt battery. One of these 9v batteries is included with each product that requires it to function. The only problem is that long lasting as they may be, these batteries aren’t eternal. And they aren’t rechargeable either Therefore, if you want your TENS/EMS machine to be up and running at a moment’s notice, you need to be fully stocked on 9v heavy duty standard batteries. After all, you wouldn’t want to be one battery away from much needed pain relief. 
This product is also known as a transistor battery, since it was originally developed for transistor radios. Manufactured since the mid 50’s, 9v batteries came to be when a low voltage battery was needed to powered transistorized radios, as opposed to the 22.5v batteries used for vacuum tube/thermionic valve hearing aids and photo flash gun. Other names it has received throughout its existence include PP3, radio battery, and Japan 006P, but perhaps more famously, square battery. Other than TENS/EMS units, 9v batteries can also be found in pocket radios, smoke detectors, electro-acoustic guitars, and radio controlled vehicle controllers. 

You can easily tell why they are called square batteries just by looking at one. They are famously shaped like a rectangular prism. Its recognizable look is completed by round edges and a polarized snap connector on the top. Its specific dimensions are height 48.5 mm, length 26.5 mm, width 17.5 mm. As for its inward contents, a square battery contains a connected series of six cylindrical or flat cells. Its chemical make-up consists of primary carbon-zinc and alkaline chemistry, or primary lithium iron disulfide. 
The snap connector mentioned above houses both terminals, male and female. The former is circular and positive, and the latter is octagonal and negative. Nine volt heavy duty batteries provide a very reliable and long-term performance. It wouldn’t be strange that you actually took them for granted, and became surprised when one finally started to fail. However, that is a likely scenario, and all the more reason to keep at the very least one extra battery at all times. That way you will be able to replace it presently and continue to be able to use your TENS/EMS device for as long as you need to. And at this price, you won’t have any trouble buying as many as you want to.