Kenwood TS-590 Current Draw Measurements

After last weekend’s adventure taking the TS-590 out in the field, I started thinking about operating ‘picnic portable’.  The TS-590 is a really nice little compact radio and lends itself well to setting up at a remote location that does not require schlepping my gear for long distances. But how much current does it draw? What battery capacity will I need?  I decided to find out.

I have a Fluke 23 DMM that supposedly will measure DC current up to 10 Amps.  Probably not enough. What I needed was a shunt.  I love it that all the big electronic component supply houses are now on the internet. It took just a few minutes to discover that Newark has just what I needed, so I ordered one.

It arrived and I rigged up a quick wiring harness that would attach to the TS-590’s power cable (I love Anderson Powerpoles) and a 7.5Ah gel-cell battery.  This is what I found:

Some assumptions:
1. Using the discharge curves for the average gel-cell, I can really only use about 60% of the batteries capacity (in Amp-Hours) without damaging the battery.

2. I’m assuming 50% transmit and 50% receive.

If I operate ‘picnic portable’ at the 20 Watt power level then I need about 9.5Ah of battery capacity for each hour of operation.

BatterySpace.com has a 12V 20Ah SLA battery for $37.85 that would give me 2 hours of operation, which seems like a reasonable number.