Does high current cause high heat ?

[lowks]

I just wanted to write in and ask a pretty basic concept about chargers. There has been couple of threads on this forum about users trying to break peoples' perception about fast charging being bad and that a high current fast charge vs a slow charge (low current) does not necessarily means it's bad. Is it ? But then when you apply the knowledge that P = I^R and that P ends up being heat ... is it not that heat is also bad for NiMh batteries ? So does that not translate to high current charging being bad for batteries ?

 

[HKJ]

As long as the battery can store the supplied current (i.e. charge), it does not generate heat, except from the resistance in the circuit and battery.
This means that a very high current will generate heat, but a moderate current will first generate heat when the battery is full.
Old or low quality batteries usual has more resistance, this will generate more heat during charge.

 

[lowks]

What do you think of this:

http://www.ephotozine.com/article/uniross-high-speed-battery-charger-10433

From what I see, it does charge up the battery in that time (Verified by Maha) but then the batteries are hot to the touch. Too much current ?

 

[HKJ]

What do you think of this:

http://www.ephotozine.com/article/uniross-high-speed-battery-charger-10433

From what I see, it does charge up the battery in that time (Verified by Maha) but then the batteries are hot to the touch. Too much current ?

With that charge speed you will get heat from the resistance in the battery. Some good quality batteries can be charged on it, but avoid charging old or cheap batteries on it.
The number of charge cycles for a battery will also be considerable lower when charging at these currents.

 

[lowks]

When you say "Charge Cycles" you mean the life of the battery will be lowered charging at these high currents ?

 

[HKJ]

When you say "Charge Cycles" you mean the life of the battery will be lowered charging at these high currents ?

Exactly.