[Elecraft] Good Battery for K3 Portable Ops

[Dominic Baines]

On 12/08/13 22:36, PGrig wrote:
> I would appreciate knowing the experiences of folks who have run their K3 on battery power for several (4-8?) hrs., with perhaps a 20% TX duty cycle.  What types and sizes of batteries seem to be the best balance of staying power and portability?
>
>     -Paul Grigorieff, N1HEL
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Largest charge 12V (13.8V normally) lead acid battery you can carry :-)

If you are running 100W then anything less than a 75-80 AH will run flat 
very fast and even they will only last about 2-3 hours if fully charged 
and when you drain them to <50% the power will out will not be stable 
towards the end and the battery voltage might drop and you might damage 
the battery so do not work expecting to get the whole charge from a battery.

I run KX3 off a 7AH at 5W out for about 3.5 hours without any issue. K3 
current draw will be a bit more than that whilst qrp. This is SSB mostly 
and about 40% TX duty. If I can get a car battery 75AH it will last all 
day and well into the night.

Best option really is figure out what YOU need, everyone going to try /P 
should really do this anyway ... monitor your current draw into the rig 
(your K3) and anything else 12V you use when you want to operate and 
then calculate what the charge needed for the operating session was, as 
opposed to what you thought it might be (surprise differences are 
interesting) will be and you'll be able to calculate what battery charge 
you need. Then work out what battery/batteries will provide it.

You can expensive Li batteries but you need expensive chargers and you 
will NOT be able to fly anywhere with them (legally anyway).

If you are trying to do this with a rucksack and lightweight then get a 
smaller radio :-) If you have a vehicle, and no limits then get as large 
a battery as you can recharge (jump leads between the vehicle and the 
battery will recharge it cheaply and that is why I would not suggest 
expensive Li batteries. If you want you can 'float the battery' between 
the vehicle (or a generator) and the rig as well.

72

Dom
M1KTA