[setmenu]

Over discharged my poor nims, blubber blubber, I am trying to nurse my patients back to life at this very moment.....
Will they ever forgive me?

The amp pack went to 5v and the dac pack went to...2.5v

I doubt they will ever be willing to work such long hours for me again.

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[tangent]

That's nothin'. I've drained a NiMH pack to zero, less a diode drop or two. The cells still work.

Not that I'm recommending a repeat performance...

 

[MD1032]

You mean fully discharging NiMH's is bad?

 

[flecom]

IIRC fully discharging rechargables is bad except for refreshing NiCd..

although cant you refresh NiMH batteries also? my canon batteries are NiMH and the charger lets you refresh (completely discharge/recharge) them?

 

[setmenu]

Well after a couple of charge/discharge cycles the patients seem nice and perky again

Repeatedly deep/over-discharging would definitely be a bad habit to get into
as the life span and the capacity of the cell can be severely reduced by such
abuse.
Best practice for nims is to top up rather than deep discharge,making sure individual cells don't go down to 1v too often and avoiding dropping below
at all.
Every couple of months a full discharge down to 1-1.2 v helps keep them in good shape.

I learned the above from here:

http://www.batteryuniversity.com/index.htm

It obviously pays to maintain ones cells with a decent charger/discharger.

Radio control electric model vehicle enthusiasts have been keenly nurse maiding their batteries for years so they can reliably thrash them during discharge many times before replacement.


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[tangent]

Quote:

You mean fully discharging NiMH's is bad?

As far as I have been able to tell, the main danger here comes from "reversing" one of the cells in a series battery pack. This happens when one of the cells discharges faster than the others and reaches zero while the others still have voltage. After that point, apparently, the poles reverse on the low cell and damage occurs.

In the PPA battery board, where this has happened to me, there is a diode or two in the way which can prevent damage: the low cell would have to be a diode drop or two lower than the others in order for reversal to happen. Once the whole pack's voltage equals the diode drops, no current flows, so damage can no longer occur.