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Smart Phones and battery life
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eric chan
(bearbreeder) - F
Smart Phones and battery life on 09/23/2011 15:11:50 MDT Print View

im guilty of posting the original article ... and im guilty of posting this as well ... oh well its raining in squamish and i wont be able to climb till tmr, so might as well have more fun and games till then ... at least its not about guns and fires ;)

on a more serious note ive encountered climbers using topos on their iPhones which i think is not the best idea ... not only do you risk dropping said phone and expose it to the elements ... when you may need it for a rescue the bat life may be poofay by then

ill always have a printed out copy ... and a pdf on my phone should i require it as a backup ...

hmmmmm ....

Smart Phones and battery life
I’ve written previously about how you shouldn’t use smart phones for backcountry navigation. In that article I made some claims about battery life. My article was reposted (not my me) in a forum, and some of the replies to that post seems to indicate that people think that the battery life issue is solved by turning off the wireless (Wi-Fi), Bluetooth and cellular radios in the smart phone.

This turns out not to be entirely true.

Turing off the radios does help, anything that reduces the power draw on the batteries is bound to. However, if you’re not making a phone call it turns out that main power draw on a modern smart phone is the screen, and not the radios. the GPS receiver and Bluetooth tend to draw very little power in comparison.

The Research
In a paper published in 2010, two researchers at the University of New South Wales instrumented several smart phone devices and did some experiments on its power consumption in a number of scenarios. The conclusion of their research was that the major power draws of the device were the cellular radio, followed closely by the display.

Making a phone call is by far the biggest draw of power. In the experiment, the researchers made a 57 second call. They found that the GSM radio used the most power, followed by the backlight.

However, in tests sending an SMS message, sending an email, or browsing the web, the power draw was dominated by the screen’s power requirements.

The display is broken into three separate power draws: the LCD screen, the graphics chip, and the backlight. The light draws the most power.

Their conclusion:

In all except the GSM-intensive benchmarks, the brightness of the backlight is the most critical factor in determining the power consumption.

It can only be surmised that using a smart phone for backcountry navigation would make extensive use of the screen and backlight, since the phone would most likely be used in daylight conditions. Each time the device is taken out to view the map would take about 1/3rd of the power of a single 60 second call.

The Crutch
It has been pointed out to me by some of my SAR friends that you can buy a number of devices to recharge your mobile phone in the field. One of the guys on my team demonstrated a device that contains a hand crank and a several different connectors that can recharge a phone. There are also solar panels, and external battery packs as well. These are all great.

However, my primary argument is that you shouldn’t be using the phone as a navigation device, and that using it as such drains the batteries so that the phone is not available for its primary use, to make a phone call. The phone is also fragile, and not waterproof.

If you’re going to go to the trouble of buying external battery packs or hand cranks, then go out an buy a purpose built wilderness GPS unit.

Weight and weight savings
In the same forum where my original article was reposted there was a lot of talk about saving weight and going light. The smart phone as navigation device is attractive to people who obsess about grams and making their pack as small as possible. Aside from the possibility that you are already cutting it close, to really be prepared you should waterproof the phone and carry an extra battery.

At some point in this equation, the addition of the phone’s case, extra battery or external charger is going to be more than a GPS unit would weigh. For those that are interested, the Garmin GPS 60csx weighs 213 grams with batteries. An iPhone weighs 137 grams.

I’m pretty sure most of us can handle the weight of a GPS unit.

Final Note
A few years a go I wrote about SMS and rescue, in that article I wondered if an SMS message used less power than a phone call. The paper by Carrol and Heiser sheds some light on this issue: an SMS does use less power as long as the SMS message doesn’t take too long to send. You should be able to send two or three SMS messages in the same amount of power as it cakes to make one 60 second phone call.

The advantage of SMS: the phone will keep trying to send it until it gets a signal. The disadvantage is that you still can’t send text messages to 911. However, sometimes the text is the only thing SAR has to go on, as the recent search near Tingle Peak attests.

Nathan Watts
(7sport) - MLife
Re: Smart Phones and battery life on 09/23/2011 21:05:47 MDT Print View

Don't you also risk dropping a paper topo map? At least the phone won't blow away on you either.

I'm just playing devils advocate a little here. I can't say I totally disagree with you.

and i also wanted to note that my phone gets many hours of battery life when I take it with me in the wilderness. And I can store a whole guidebook in it without any weight penalty

Stephen P
(spavlock) - F

Locale: Mid-Atlantic
Re: Smart Phones and battery life on 09/23/2011 21:56:10 MDT Print View

The biggest drain on the battery is when the phone is looking for a cell signal when there just isn't one present for miles and miles. I'm hoping the new iOS update will allow verizon customers to disable the cellular antenna (similar to removing the SIM card in AT&T phones.

I can't justify carrying my phone AND a GPS unless I was doing some major bushwhacking, or out for more than 3-4 days. My iphone with case already weighs 7ounces. It's a heavy phone!! Wish I could use one of my old phones, but us verizon users don't have the luxury of a SIM card!!

Ty Ty

Locale: SE US
Android on 09/28/2011 11:53:59 MDT Print View

With my android phone I can just put it on airplane mode and it turns off all signals. I can then turn the screen no the lowest brightness setting, end all programs and get a lot of battery life.

I see mine as a camera replacement that does other things too. I also like to download a book onto it and read that before I go to sleep at night. I have thought about running Runkeeper on there while hiking to record distance and pace but that would require leaving the GPS running which eats battery life.

Stephen M
(stephenm) - MLife

Locale: Mind your own business
View Ranger and Andriod on 09/29/2011 07:02:09 MDT Print View


I have a Waterproof Motorola Defy Android Phone running View Ranger GPs software,
The battery lasts one full day and I carry two spares in my pack.

A lot of UK Mountain Rescue Team uses the View Ranger System with Nokia 5800 phones.



Andrew McAlister
(mcalista) - F
Hunting for signal on 09/29/2011 07:22:17 MDT Print View

I agree with spavlock - hunting for a non-existent signal in the backcountry is a major power draw.

my understanding is that when a phone can't find a signal, the radio starts putting out maximum power trying to find a signal. The summary of the paper suggests they didn't try this scenario - only testing the power draw in standby mode when there was a detectable signal. Airplane mode can be a major power saver in such situations.

joseph peterson
(sparky) - F

Locale: Southern California
Smart Phones and battery life" on 09/29/2011 14:52:19 MDT Print View

In airplane mode my phone lasts five days when used as a camera. Hundreds of pictures and HD video. I bought a second battery for ten bucks for extended trips.