[Elecraft] K2 Internal Battery Voltages

[Don]

Carl,

I know little about the K2 battery but assume that it is nickle-cadmium or 
nickle-metal-hydride and probably consists of 10 or so cells in series.

When such a battery is completely discharged the  amount of charge needed by 
each of the individual cells becomes unbalanced.  For this condition it is 
possible that what you think is a normal charge time may in fact charge most 
of the cells completely but not completely charge one or more of the others. 
The " charged" terminal voltage in this case will appear lower than you 
expect.  The cure is to continue charging at a low rate (which overcharges 
those cells already charged but does not hurt them) until *all* of the cells 
come up to their normal fully charged state.

It is possible to damage a battery by letting it run down to nearly nothing 
but it is very unlikely if the rate of discharge is low, as it no doubt was 
if the rig was on receive all of that time.  When the battery is discharged 
like that then the first of the cells to reach zero volts go into "reverse" 
which is a condition where the cells voltage becomes reversed.  Sealed Ni-Cd 
cells (or their metal hydride ni-cd relatives) can tolerate a certain amount 
of this if the currents involved are low.

Don K7FJ

>I just recently replaced the battery in my K2.  I ordered from Elecraft, so 
>this is the "approved" battery.  Last week, after a lengthy QSO, I forgot 
>to turn the rig off, and when I noticed it the next day that battery was 
>completely depeleted.  I charged it up for 24 hours with a 14v supply and 
>it would only charge to about 12.1 volts.  Though I don't remember for 
>sure, I thought this new battery when I charged it originally started out 
>at something like 13.2 volts or so.  Does this sound right?  What should 
>this battery registered when fully charged?  Have I damaged it 
>significantly by letting it rundown to practically nothing?  Obviously, I 
>goofed.  I just hope that I haven't significantly harmed by battery life.
> Thanks and 73,
>
> Carl
> N8VZ