Battery Life, Part II

I previously posted about monitoring how long my vx8-dr would last on different types of batteries. One of the things that I noticed was that there is a relationship between battery voltage level and the output power but I had no way of watching what was happening. So I invested in a Diamond SX-600 SWR & power meter along with an MFJ-261 dummy load and re-ran parts of the battery test.

2,000 mAh lithium ion w/ power

vx8-dr 2000mAh power

relative time voltage wattage
0:00:00 8.2 4.2
1:35:31 8.0 4.2
3:59:07 7.7 4.1
5:50:41 7.6 4.1
7:16:26 7.5 4.1
8:21:35 7.5 4.1
9:19:13 7.4 4.0
11:04:18 7.4 4.1
12:33:02 7.3 4.0
13:56:41 7.2 3.9
14:37:08 7.0 3.8
15:10:24 6.9 3.0

This is pretty much what I would expect. As the power available from the battery goes down, the output power on the radio goes down.

AA alkaline w/ power

vx8-dr aa alkaline power

relative time voltage wattage
0:00:00 4.2 0.90
1:48:19 3.7 0.15
2:40:05 3.7 0.10

This, ladies and gentlemen, is utterly ridiculous! Starting with fresh AA alkaline batteries, the output is less than 1 watt and it quickly deteriorates from there.

I swapped out the AA alkaline for AA lithium ion and found a similar output power level. Since it started with less than 1 watt output power, I didn’t bother running through the whole test. This was not at all what I expected, The input power voltage level is critical for the vx8-dr to perform well.

My original intention was to use AA lithium ion and / or AA alkaline batteries as a backup power source for the vx8-dr in the event of an emergency. This now looks like a bad plan. Running on anything less than the lithium ion battery packs has a detrimental effect on output power. It might do as a backup to the backup power but I don’t think it’s a good idea to count on it.

Right now, I’m thinking multiple 2,000 mAh lithium ion battery packs, a charging dock and perhaps a solar panel to charge it all. Plus an automotive plug adapter. And a plug w/ anderson powerpole connectors.

This was an interesting experiment!


 

Update:

I was asked about the discrepancy between the maximum measured power out of 4.2 watts with the battery voltage of 8.2 and the published maximum of 5.0 watts. I have a couple thoughts on that though they’re not based in much more that aether.

  1. The published specs may be coming from theoretical maximums.
  2. The published specs may be coming from values measured in a lab under ideal conditions.
  3. Maybe the battery’s just not quite fully charged.
  4. The SX-600 power meter may be off calibration.

I did plug the radio into the wall wart that comes w/ the charger. The voltage showed at 10.8v and the output power at 4.3 watts. Using the automotive cigarette plug, the voltage shows at 12.8v and the output power was measured at 4.5 watts.

BTW, the manual for the vx8-dr has specs for the supply voltage maxing out at 12v.

From all this, I take the maximum output wattage as being 4.5 with a more typical of 4.0 to 4.2.

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4 thoughts on “Battery Life, Part II”

  1. Wow. That is something they -really- should have mentioned in the manual or some such! “While your radio comes with a AA battery holder, using alkaline batteries in the radio will cause your radio to completely suck.”

    Do they offer a 3S lithium battery? wouldn’t that offer 11.1 volts for the 12 volt max transmitter? Though I don’t know how important that extra transmit wattage is, or if that might affect the life of the radio.

    1. The standard battery that comes w/ the radio is a 1,100 mAh li-ion that pushes 8.2 when fully charged. I was hoping to use AA alkaline batteries as a backup source in the event of an emergency since they’re likely to be more readily available than power to recharge a li-ion pack. With this little experiment, I’m going with multiple li-ion packs and will ensure a mechanism to charge is available.

      I haven’t see anything about 3S lithium batteries being available. Plus the difference between 4.2 and 4.5 watts won’t have nearly as much of an impact as between 0.9 and 4.2. I think the li-ion packs will work fine for my purposes…

  2. Peter,

    Wow, you opened my eyes! I too have a VX-8DR. I “thought” having an ample supply of Costco AA alkaline batteries (and just getting ready to purchase some AA lithium batteries) was enough to keep me well supplied. Boy, was I wrong. Guess it is time for a couple more 2000 mah Lion packs if I want anywhere close to the advertised 5 watt output. Thank you very much…Peter

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