Battery Life

I had an experience a few weeks ago whereby I couldn’t join the ORCA net on my vx8-dr because of a low battery. From that, I thought I’d run a test to look at how long different types of batteries run in the vx8-dr. The basic protocol is to setup the vx8-dr to transmit APRS location messages on a regular basis and measure the battery voltage over time. The voltage measurement comes from the vx8-dr itself. Yes I’m trusting that it was accurate but with the test running the same way across all the types of batteries, I think it’ll be a valid test. Besides, the reading from the vx8-dr is what I’ll be using in the field.

The vx8-dr can use 4 different types of batteries: 2,000 mAh lithium ion, 1,100 mAh lithium ion, AA alkaline and AA lithium ion. I ran a set of tests over the course of 8 days.

2,000 mAh lithium ion

vx8-dr 2000mAh

relative time voltage
0:00:00 8.2
1:04:28 8.1
2:05:27 8.0
3:14:07 7.8
4:58:20 7.7
6:04:41 7.6
6:46:38 7.6
7:43:17 7.5
8:34:24 7.5
9:30:31 7.4
11:21:29 7.3
12:22:51 7.3

1,100 mAh lithium ion

vx8-dr 1100mAh

relative time voltage
0:00:00 8.2
0:00:00 8.2
2:15:51 7.8
3:06:14 7.7
3:58:57 7.5
6:27:44 7.4
8:01:43 7.1

AA alkaline

vx8-dr aa alkaline

relative time voltage
0:00:00 4.2
0:43:23 3.9
1:26:23 3.8
2:02:19 3.7
2:46:57 3.6
3:43:42 3.6
5:02:25 3.5
8:15:51 3.3

AA lithium ion

vx8-dr aa lithium ion

relative time voltage
0:00:00 4.5
1:23:24 4.3
3:33:47 4.1
5:19:44 4.1
9:04:00 3.9
9:55:36 3.9
20:56:06 3.7

I unintentionally left the vx8-dr running over night and the battery level only dropped 0.2 volts. That was very unexpected.


I came to a few conclusions from this test:

  1. Measuring the voltage will most likely be a good way to keep track of when to change batteries.
  2. Just measuring the voltage doesn’t provide any data on how well the transmitter is working with the available voltage / power.
  3. Judging by the AA lithium ion battery test, I need to re-run the 2,000 mhA and 1,100 mHa test. It looks like the voltage level of the lithium ion batteries may not be linear. That may put a kink in the use of the battery voltage to determine remaining power.

I’ll re-run the 2,000 mHa and 1,100 mHa tests over the next few days to see how long the batteries last. Perhaps lithium ion batteries don’t have a linear voltage level over regular usage.

More importantly, I need to expand the tests to determine the output power level as the batteries are used. I’m not yet sure how to do that. Maybe it’s time to invest in an RF power meter.


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Portable APRS Server

I had a thought yesterday, in the event of an emergency the internet connections will be down. Wouldn’t it be useful to have a localized APRS display to show the location of various people. Set up a radio to listen for APRS transmissions, send them to a small computer, run a webserver on the computer w/ OpenStreetMaps on it, have a wifi connection and power connections. Drop it all into a portable case of some sort and it can be made available to a local group of people who need access to the data.

There’s a bunch of unknowns here but it could be an interesting project. Would it be useful? Reliable? What else is needed?

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Net Troubles

I wasn’t able to get on the ORCA net last Thursday. It’s worked before and I haven’t changed anything on my radio. Very strange.

In talking things through with Peter (KO6R), we realized that the batteries ran low. Without enough power, the VX8-DR wasn’t able to transmit far enough to be heard by anyone. I was running with the AA battery pack instead of the lithium ion battery pack. It looks like AA batteries just don’t have very much power in them and they ran out of power much faster than I expected. I’ll need to experiment a bit to see how the various battery options last w/ the HT.

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First Radio – VX8-DR

I’m now the happy owner of my first radio, a Yaesu VX8-DR. It’s a lovely handheld that I’m looking forward to using and getting on the air.

It’s actually not my first, I have a Micro-Trak RTG tracker that I used on K9 for Burning Man last year. I was able to use it because Phil (K6CQU) was gracious enough to let me run it under his call sign. Now I’ll be able to use it under my own call sign. Simple pleasures!

I chose the VX8-DR because it has a GPS receiver and can receive and transmit on APRS, just like the Micro-Trak RTG. I’m a bit enamored with the idea of tracking locations via ham radio operations.

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Radio Club – ORCA

I’ve joined the local Oakland ham radio club, ORCA. I’m hoping that the other folks in the club will be able to help with any issues and learning about getting on the air.

They also run a local net to help with communications in the event of an emergency. With the classes I’ve been taking through the Oakland Core program, I think it’ll be a nice match.

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