The KA7OEI FT-817 pages
Current consumption of the FT-817


Front panel view of my FT-817
A Front-panel view of the FT-817.
Where does all of the current go?

One of the "complaints" that I've heard about the '817 is its battery consumption.  Its average power consumption is certainly much more than that of a typical HT - and some believe that the fact that it can run off batteries must mean that it can do so efficiently. (For more information on operating the '817 from various types of batteries, look at the Lithium-Ion page as well as the NiCd/NiMH/Alkaline page.  Also, take a look at K6XX's FT-817 pages for power consumption information.

Well, the fact is that the '817 does pull a fair amount of current in comparison with your typical battery-powered radio.  There are a number of mitigating factors that can help one understand why the current consumption is what it is.  (Disclaimer:  I'm sure exceptions may be found to most of the points below, but that's why this is just an article and not a novel...)

There are also a number of mode/band/option selections that can significantly affect current consumption.  Below is a list of various parameters that can affect current consumption.  These measurements were taken at 9.0 volts:
 
How much current does the radio consume from its internal batteries when it is shut off?

Like most modern TVs, VCR, and radios, the FT-817 consumes a bit of current even when the radio is turned off!

Why?  Well, you may have noticed that the power switch is a pushbutton.  Pushing the switch does not connect/disconnect the radio's power supply, but rather it applies power to the computer in the radio, which then turns the rest of the radio on.  It may come as no surprise that this circuit consumes a small amount of current to perform this function. 

How much current? 

At 8 volts, this is between 100 and 200 microamps, going up to as high as 300 microamps at 16 volts, with the exact amount depending on temperature (lower temperature = lower current.) 

What does this mean?  At a continuous current consumption of 200 microamps it will deplete the useful life out of a set of AA alkaline batteries within a year - more or less. 

In other words:  Don't leave batteries in your '817 for a year and expect them to work! 

When powering the radio from the rear panel, things are different:

If rechargable batteries are installed, the '817 trickle charges the pack at 10-15 milliamps - even when the radio is off.  This small amount of current is unlikely to damage any cells (due to overcharging) that are left in the radio - even for long periods of time - but you should keep this in mind if the voltage to the rear panel is supplied by a battery. 

One "gotcha" to be aware of:  If you are using the CAT interface, power to the adapter is applied at all times - and 10 milliamps of current is consumed whether the radio is on, off, internally, or rear-panel powered.

Supply
Voltage
Current
(mA)
Power
(watts)
7.5 290 2.18
8.0 291 2.33
8.5 293 2.49
9.0 293 2.64
10.0 296 2.96
11.0 298 3.28
12.0 301 3.61
13.0 304 3.98
14.0 308 4.31
15.0 311 4.66
16.0 314 5.02
Table relating current and power consumption versus power supply voltage.









While the current consumption is only slightly affected by the supply voltage, power consumption is much higher at the increased voltages.  Since power is determined by current multiplied by voltage, even if current consumption were to not increase, power consumption would still increase.  The table shows current and power consumption under the following conditions:  10 meters, receiver unsquelched, minimum volume, USB mode, noise blanker turned off, front antenna selected, and backlight turned off.

As can be seen from the table, while the current consumption increases only by 8% or so from 7.5 volts (the lowest voltage at which the '817 will operate without much degradation) to 16.0 volts (the highest rated voltage) the power consumption more than doubles!

What does all of this really mean?

From this information, there are several things to do to minimize power consumption when trying to conserve battery power.  The most important of these are as follows:

In short, just turning off the backlight, using the front antenna connector, and turning off the noise blanker will reduce the current consumption by 20%.  Using headphones and minimum transmit power will also go a long way toward battery longevity as well.

Other FT-817 pages at this site:

Go to The KA7OEI FT-817 "Front Page" - This is, well, the "front" page of the '817 pages here...

Any comments or questions?  Send an email!

This page maintained by Clint Turner, KA7OEI and was last updated on 20060511.  (Copyright 2001-2006 by Clint Turner)

Since 12/2010: