BFL13 wrote:
No idea where you are getting that idea from.
A bit off on a tangent......
A friend of mine has a charger similar to those pictured.
We checked the charging voltage and saw it go up as high as 17.5 volts. That seems a bit high to me.
On topic: My guess is that having identical chargers might increase your chances of success......might.
The idea comes from the fact that "smart" chargers adjust their output based on the "back voltage" or internal resistance it sees from the battery. If part of what it sees is NOT the battery but another device, the odds of things not working right are high.