[Elecraft] KX3/P3 external power source

[Fred Jensen]

Not sure I understand your question Matthew. Lithiumbatteries [all 
chemistries] have exceedingly low internal resistanceand consequently, 
will deliver a huge current if shorted.  Power leads should be fused.  
The flat, automotive blade-type fuses seem to work best... large, low 
resistance contact area.

The voltage vs time function during discharge is probably the primary 
concern for ham QRP use because it determines the total energy you can 
extract from the battery before your radio quits. Good quality LiFePO4's 
have a discharge curve that is very flat after an initial drop from 
full-charge.  Mine [an A123 4S1Ppack] maintains a terminal voltage above 
11.5 V until it is nearly discharged.

Re low-voltage cutoff: Some packs have a cutoff internal.  My K2 shuts 
down [draws negligible current] at about 10.5Vhowever I've only had that 
happen once. Most of the time, other factors [weather, tired butt, bugs] 
will terminate an outdoor session well before the battery depletes.

73,

Fred ("Skip") K6DGW
Sparks NV USA
Washoe County DM09dn

On 6/7/2017 11:34 AM, Matthew MacRoberts wrote:
> Are there any internal resistance or c-ratings that I should be aware of? (Like there are on RC vehicles)
>
> Are Ham’s using any kind of low voltage cutoff with their batteries?
>