Jump to content

Vista HCx current consumption


tomc61
Followers 1

Recommended Posts

I read this thread http://forums.Groundspeak.com/GC/index.php?showtopic=175670

and decided to see for myself if WAAS uses more power and how much current

my Vista HCx draws in real life in various operating modes.

I haven't searched this fourm to see if anybody else has already done this.

 

I hooked up my Vista HCx to my Fluke 187 DMM (digital multimeter, which costs more than a Vista HCx)

using two AA alkaline cells, a battery holder and some alligator clip leads.

 

WAAS and the electronic compass were initially turned off.

After I turned on the Vista HCx, the backlight shut off, and it accquired the satellites,

I was getting an average current of 69 mA (milliamps). The reading is not steady,

it pulses several mA about once a second which probably means that some circuitry

is switched on every second or so when needed and then turned off in order to save power,

so I had to use the the Fluke 187's averaging function. It allows you to take maximum,

minimum and average readings. I got 79, 67, and 69 mA respectively.

 

I turned on WAAS and was surprised to see the current nearly the same.

It only increased 1 mA to 70 mA average. Then I turned the compass on

and again was surprised that there was no change. The current was still 70 mA average.

 

The biggest surprise came when I went to the satellite page and selected 'Use With GPS Off'.

The average current went up to 98mA. I have absolutely no idea how turning the receiver off

makes it draw more current.

 

The display backlight uses the most current.

At full brightness the Vista HCx draws 235 mA average current and

the lowest level was 76 mA average, which is only slightly higher than when the backlight is off.

 

My conclusion is that leaving WAAS and the compass turned on should not significantly affect battery life.

 

Tom

Edited by tomc61
Link to comment

...Then I turned the compass on

and again was surprised that there was no change. The current was still 70 mA average.

 

That is excellent info. I always advise getting the Vista HCx over the Legend HCx for a lousy extra $15 (in the real world). I knew the compass has been improved to the point where it used very little battery power as I get the full rated 25 hours of continuous use with my rechargable NiMH batteries and full time compass.

 

But it's nice to have it confirmed.

Link to comment

My prediction was pretty close:

I doubt battery life would be affected. The receivers stay on trying to acquire GPS satellites constantly, and the WAAS signals are just mixed in with the bunch.

 

The backlight would have far greater impact on battery life than receiving a WAAS signal.

 

I haven't had a chance to test my Venture Cx up. It has the older receiver, so the differences with the radio on and off will probably be different.

 

Dan

Link to comment

tomc61, were you using Alkaline AAs or rechargeable? We can't compare device to device without knowing the voltage you were using.

 

Here are the values of a Venture Cx using rechargeable batteries at 2.77V. I provided values in both milliamps and milliwatts. The milliwatts should be used for comparing device to device, because wattage is a measure of power which is independent of voltage. Milliamps can only be compared if the voltage is exactly the same. My batteries are Rayovac Hybrid rechargeable. They are rated 2100 mAh, so I provided the (theoretical) battery life I would get with these batteries.

 

Radio on:

Backlight off:

77.4 mA (214 mW) (27.1 hours)

 

Backlight medium:

144 mA (399 mW) (14.5 hours)

 

Backlight high:

220 mA (609 mW) (9.5 hours)

 

Radio off:

Backlight off:

48.6 mA (134 mW) (43 hours)

 

Backlight medium:

108 mA (299 mW) (19.4 hours)

 

Backlight high:

185 mA (512 mW) (11.4 hours)

 

So, backlight at medium doubles power consumption, which would halve the battery life. Backlight at high more than triples power consumption, cutting battery life to less than 1/3 compared to no backlight.

 

The user manual states a maximum 32 hours battery life. My measurements show 27 hours with these particular batteries, so that is in the ballpark. Garmin would probably have used the highest mAh AA batteries available in order to state the longest possible battery life.

 

Dan

Edited by oisact
Link to comment

The biggest surprise came when I went to the satellite page and selected 'Use With GPS Off'.

The average current went up to 98mA. I have absolutely no idea how turning the receiver off

makes it draw more current.

Interesting! I have always assumed that "Use with GPS off" would drain the battery less, so when I'm using it inside the house I always select that. Guess I won't do that any more :)

 

Did you trying comparing the current consumptions of "Normal" vs "Battery Saver" modes? (From Main Menu -> Setup -> GPS). Just wondering how effective "Battery Saver" mode really is...

Link to comment

I used new AA alkaline cells so the voltage should have been a little over 3V but I did not measure it.

The Vista HCx menu doesn't have Battery Saver. It only has Normal, GPS Off and Demo Mode.

I didn't check Demo Mode.

 

I took all my measurements with the GPSr indoors sitting on the table.

It would be interesting to see if anything changes while in a moving vehicle or something.

 

Tom

Link to comment

Thanks for the measurements. Confirms what I experienced. Only bout 10 hours with 100% backlight. Though I get near to 20 hours with 50% backlight.

2100Mah Conrad Endurance (Eneloop clone), cycling or walking through the city. Basemap, City Navigator (well modded Metroguide), and Topo transparent active.

 

So allways go easy on the backlight.

Link to comment

It seems like you would be using rechargeable batteries if you were concerned with battery consumption. If you have an endless supply of alkaline batteries, why are you concerned at all?

 

I have a GPSmap 60 CSx and the new Colorado 400t. I use a set of 6 NiMH rechargeable batteries (2 are the newer, pre-charged types as backup) and cycle the other four between the units and the car charger with no problems.

 

I just got a set of new 2650 mAh Duracell Rechargeables for $10.58 at Tom Thumb (the old Safeway grocery stores).

 

Its great that you did all these tests, but the bottom line is that you get great battery performance. - Pat

Link to comment

I read this thread http://forums.Groundspeak.com/GC/index.php?showtopic=175670

and decided to see for myself if WAAS uses more power and how much current

my Vista HCx draws in real life in various operating modes.

Tom

 

Great work Tom! There's been a LOT of speculation on WAAS, compass and power useage and it's nice to have a definitive answer on this subject. Keep up the good work and we'll keep you on another week! :bad:

 

Cache On!

 

JohnTee

Link to comment
tomc61, were you using Alkaline AAs or rechargeable? We can't compare device to device without knowing the voltage you were using.

 

Here are the values of a Venture Cx using rechargeable batteries at 2.77V. I provided values in both milliamps and milliwatts. The milliwatts should be used for comparing device to device, because wattage is a measure of power which is independent of voltage. Milliamps can only be compared if the voltage is exactly the same. My batteries are Rayovac Hybrid rechargeable. They are rated 2100 mAh, so I provided the (theoretical) battery life I would get with these batteries.

 

Radio on:

Backlight off:

77.4 mA (214 mW) (27.1 hours)

 

That is some of the best testing I've seen so far, but I do take issue with how it seems you declared a 1.38 mean voltage for NiMH cells. While a fully charged NiMH will have an initial output around 1.4 - 1.5v depending on load and temperature, it quickly drops in to the 1.15 - 1.2v range. Generally the best way to calculate the actual energy output of a NiMH is thus the amp rating times 1.2v. So a pair of 2.1 amp batteries would be (2 * 2.1 * 1.2) = 5.04 watt/hrs. So 5.04 / 0.214 = 23.5 hours expected runtime. With Alkalines, they have a pretty linear discharge rate, so 1.25v is supposed to be used as their median voltage.

Link to comment

It seems like you would be using rechargeable batteries if you were concerned with battery consumption. If you have an endless supply of alkaline batteries, why are you concerned at all?

 

if you were going on a 7 day hike, and one way used half the batterys, meaning carrying alot less, then it would be of great help.

 

although the test would probably be more usefull done outdoors. when you turned wass on did you actully pick up a wass sat?

 

and with the compass on I would have rotated the unit around, and see if it changes when the compass is trying work.

Edited by Smac999
Link to comment

and with the compass on I would have rotated the unit around, and see if it changes when the compass is trying work.

This would definitely be a good data point. All of the tests I've seen (or done) are with the GPSr motionless, and I've often wondered if rotating it would cause transient current surges in the compass circuitry.

Link to comment

If anyone is interested, this is what I got with my Summit HC:

 

Batteries: Bank of new alkalines - measured at 2.96 V for the test

WAAS: Turned off (no WAAS in Australia)

Compass: Turned on and off, held steady, moved around, turned around, etc - no discernible difference to current demand

 

No back-light: 65 to 70 mA (190 - 205 mW)

50% back-light: 100 to 105 mA (300 - 310 MW)

100% back-light: 150 to 155 mA (440 - 460 mW)

 

I normally use a pair of Varta 2100 mAh "Ready2Use" NiMH batteries. (While they don't have as high power capacity as some NiMHs, I would rather sacrifice a couple of hours potential use for the security of knowing that my spare set will still be effectively charged after a couple of weeks storage.)

 

These figures suggest a theoretical life of about 9 hours at 100% back-light, 13 hours at 50% back-light, and 20 hours with no back-light. Down here in Oz, we are blessed with plenty of sunlight, so I tend to only use the back-light occasionally. I try to change batteries before they go totally flat (don't like losing data in the middle of my travels), so I can't vouch for actually achieving 20 hours +, but I certainly can go two full days of typical usage (mainly daylight hours use, with limited use of the back-light) without any difficulty, so it's not far off the mark.

 

Interesting that Garmin only claims 14 hours battery life for the Summit HC (although battery type and assumed back-light usage are not noted) - I reckon I get at least that, but my back-light usage may be less than "typical".

Link to comment

If anyone is interested, this is what I got with my Summit HC:

 

Batteries: Bank of new alkalines - measured at 2.96 V for the test

WAAS: Turned off (no WAAS in Australia)

Compass: Turned on and off, held steady, moved around, turned around, etc - no discernible difference to current demand

 

No back-light: 65 to 70 mA (190 - 205 mW)

50% back-light: 100 to 105 mA (300 - 310 MW)

100% back-light: 150 to 155 mA (440 - 460 mW)

 

I normally use a pair of Varta 2100 mAh "Ready2Use" NiMH batteries. (While they don't have as high power capacity as some NiMHs, I would rather sacrifice a couple of hours potential use for the security of knowing that my spare set will still be effectively charged after a couple of weeks storage.)

 

These figures suggest a theoretical life of about 9 hours at 100% back-light, 13 hours at 50% back-light, and 20 hours with no back-light. Down here in Oz, we are blessed with plenty of sunlight, so I tend to only use the back-light occasionally. I try to change batteries before they go totally flat (don't like losing data in the middle of my travels), so I can't vouch for actually achieving 20 hours +, but I certainly can go two full days of typical usage (mainly daylight hours use, with limited use of the back-light) without any difficulty, so it's not far off the mark.

 

Interesting that Garmin only claims 14 hours battery life for the Summit HC (although battery type and assumed back-light usage are not noted) - I reckon I get at least that, but my back-light usage may be less than "typical".

"Endurance Test" results:

 

Just got over 25 hours continuous "general" use out of my Summit HC on a pair of Varta 2,100 mAh "Ready2Use" NiMH AAs. After 25 hours, the battery meter was showing 1 bar remaining, back-light still functioned etc - I didn't want to actually flatten the batteries, so I changed them at that point.

 

Nice to know that it seems the current / battery life theoretical calculations can be applied to make a prediction as to real-world battery life. (Also nice to know that Garmin's claimed 14-hour battery life for the Summit HC seems to be conservative - unusual for a manufacturer's claims to be easy to exceed in the real world, in my experience!)

 

For me, "typical" use over the 25 hour test was as follows:

 

Unit software set at latest version (Software Version 2.50 / GPS SW Version 2.60)

Back-light set to 50% / 30 second delay - probably means back-light was on at 50% level for say 5% of the 25 hour test. Normally, I leave the back-light off during daylight hours (the screen is bright enough to not need it), but I was trying the simulate "typical" usage, rather than going for some sort of endurance record. (Back-light seems to be the biggest user-controllable factor impacting on battery life.)

WAAS off (not applicable in Australia)

Compass on (but as noted above - no discernible impact on current drain)

Track log on "auto"

Ambient temperature varied from about 22 to 28 Celsius (72 to 82 Fahrenheit, say - too warm to need to worry about the low temperature battery endurance issue that seems to concern some of the northern hemisphere correspondents!)

GPSr used to navigate to various locations, paged through the various screens from time to time (meaning that the back-light was periodically activated for 30 to 60 seconds, from time to time).

 

(Your mileage may vary.)

Edited by julianh
Link to comment

Does anyone know if i can use my PDA car power adapter (xv-6700 verizon) that supplies up to 1amp with the Vista HCx?

 

I have this car adapter for the PDA with the Mini USB end and wanted to use that instead of buying the expensive garmin.

 

I dont want to damage the HCx but i dont think it will take more than the rated power (1 amp) of the PDA power cord (cigarette lighter power cord)

 

Thanks

Link to comment

Does anyone know if i can use my PDA car power adapter (xv-6700 verizon) that supplies up to 1amp with the Vista HCx?

As long as it provides the standard USB 5 volts, it should work fine. 1 amp is more than enough. Having a higher than required current rating won't cause any damage.

Link to comment

Does anyone know if i can use my PDA car power adapter (xv-6700 verizon) that supplies up to 1amp with the Vista HCx?

As long as it provides the standard USB 5 volts, it should work fine. 1 amp is more than enough. Having a higher than required current rating won't cause any damage.

 

Thank you!!

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Followers 1
×
×
  • Create New...