[Elecraft] KX3/P3 external power source

[Terje Elde]

> On 8 Jun 2017, at 20:06, Jim Brown <jim at audiosystemsgroup.com> wrote:
> 
> The other limit is the minimum voltage to which the battery can be discharged without damage to the battery. Li batteries of all variations are damaged if discharged below a certain voltage. That voltage depends on the chemistry used -- LiPO, LiFePO3, etc. For LiFePO3 chemistry, the individual cells that make up the battery should not be discharged below about 3V per cell. Once the cell has fallen to that voltage, it is nearly discharged, and continuing to draw current from it will cause the voltage to fall very quickly, and damage can occur.

Backing this, and just adding:

LiFePo4 should be fine down to about 2.5V pr. cell, but you want some margins. Also keep in mind that one cell is the weakest, and you don't want the battery of that cell dropping below, even if the average is above.

Oh, and also good to keep an eye on the difference between voltage under load, and voltage during idle/receive. 

Also, some of this damage can be dangerous. I wouldn't panic about it, but for normal LiIon and LiPo, if they've spent some time below 2V, I'd think twice before using it again.

Just like you need to dry out a tent before packing it away to avoid mold, best have a habit of charging LiIons before putting them away.

Terje / LB8KH