Emergency Backup Battery for Cell Phones

[Kevin Rooney]

I few months ago I entered the ranks of smart phone users and bought one in the 'droid family. I'd been resisting it for a long time, but ... now I don't know how I lived without one. It's really a small computer with a phone app.

In any case, about the only downside was the amount of battery life between charges, especially on days when I'd stream NPR. Sometimes it wouldn't last the entire day without recharging. So, for about $20 I got a 4,000mAh battery from Amazon, and after conditioning it according to their recommendation it will now go sometimes 48 or even more hours between charges. I put the original battery and case in a safe place where I could find them in a couple of years when I upgraded the smart phone.

A couple of days ago it dawned on me - why not put the spare battery and cover in the emergency sack in my pack? It weighs almost nothing. And Phil's story on the fellow stranded on Marcy overnight, and the key role his cell phone played in locating him seemed to illustrate how important a working cell phone can be in a jam.

So, what do people think about the suggestion of a spare battery for the cell phone? We carry spare batteries for our headlamps and GPS's - perhaps it's time to add cell phones to the list of backup devices?

 

[DougPaul]

So, what do people think about the suggestion of a spare battery for the cell phone? We carry spare batteries for our headlamps and GPS's - perhaps it's time to add cell phones to the list of backup devices?

Makes sense. Make sure that both the cellphone and the spare are fully charged before leaving. Also leaving the cellphone off between the last charge and during the hike will ensure the maximum battery life if needed. (BTW, if the spare battery is lithium-ion, it will last longer if you store it in the refrigerator in between hikes.)

There are also AA battery powered emergency cellphone chargers. You could probably use one of these with an AA lithium battery. That way you don't have to worry about charging the spare and the spares can be shared with your GPS and/or headlamp.

I have an "old-fashioned" non-smart cellphone--the standby battery lifetime rating is 8 days (and it is normally turned off...). Not much need to carry a spare battery...

Doug

 

[DMOutdoors]

I sometimes carry an extra rechargeable battery for my Iphone. My Iphone's battery has pretty good life and I have a good sense of it. The one I got was from Brookstone for $40. I haven't needed to use it, but I have carried it on some hikes. My car charger isn't working right now, so it sometimes charges my phone up full on the ride home. That means its not a bad idea to at least have it in the car, but on you would be better for longer hikes or in winter.

 

[chinooktrail]

my X-husband just made me one of these;

http://www.ladyada.net/make/mintyboost/index.html

I have not used it yet, but it charges anything with a USB port.

Hum, maybe I should have an explosives expert take a look at it first...

 

[Jeff List]

I sometimes carry an extra rechargeable battery for my Iphone.

How hard is it to replace an iphone battery in the field? Thnxs for the info.

 

[MichaelJ]

There's no replacing an iPhone battery, they're sealed; however, something like what Chinooktrail has is an excellent tool. I have the iGoGreen http://www.igo.com/mobile-devices/charge-anywhere/invt/ps002730001/ it is basically a wall charger *and* battery. Has two USB ports, and comes with a cable for which you can buy various different plug ends, though if you just need USB (mini or micro) you can use any cable. You can charge your devices with it plugged into the wall just like any other charger. The difference is that you then charge *it* plugged into the wall. Then, in the field, you plug your phone/ipod/device into it, and its battery charges your device. I've had much success with it.

Note that to get the best results out of any extra battery, be it a real spare (like for a 'Droid phone) or one of these "battery" chargers, in winter you need to have it warm. Keep it in an inner pocket near your body heat. The same principle applies to the original batter - warm it up against your body and it may well come back to life.

If I was using the Minty, I'd put lithium AA batteries in it. They last so much longer, especially in the cold. I struggle with my NiMh rechargeables (as shown in the photo). The iGoGreen is lithium rechargeable internally.

Side note for geeks: the cable that comes with the iGoGreen is a high-power USB crossover cable. It shorts the two data lines, which prevents using the cable for data, but is a signal to the device that it is connected to a strong power source (i.e., a charger, not your laptop) and can draw more current and recharge faster.

 

[Kevin Rooney]

MichaelJ - Does the iPhone use a 9V charger? I followed Chinooktrail's link, and that was the spec.

My 'droid (a Samsung Stratosphere) uses a 5V DC input, as do many other devices I own. This level of "interchangeability" means I don't need unique AC & DC chargers for each device. Rather, I only need a USB cable, although in some instances the USB cable is device-specific. Still, that's progress.

I need to peruse the Minty Boost's FAQ's to determine whether it will recharge devices other than the iPhone/Apple devices.

 

[DMOutdoors]

How hard is it to replace an iphone battery in the field? Thnxs for the info.

No problem, to clarify, the product I linked to is an external rechargeable battery for the Iphone, so it simply plugs into the bottom where the charger would be plugged into. It extends from the bottom, so in terms of using it in the field, it is not ideal if you were still on the move on the trail, unless you were carefully holding it. It has to be set down, really.

 

[MichaelJ]

MichaelJ - Does the iPhone use a 9V charger?

The iPhone charges off USB, which means 5V. It draws 1A to do so and is claimed to take an hour. That makes 5Wh from the charger, which is thusly rated for 5W. A standard USB port is 2.5W (5V / 0.5A). This is where that cable trick comes into play about drawing more power or not depending on whether the USB data connection is shorted.

Following the "process" link from Chinooktrail's link, there is a discussion that explains that most build-your-own-USB-charger designs use a 9V battery and a linear 5V regulator. It additionally goes into detail about how this arrangement can only provide 300mAH. This woman's design uses "two AA's have 3000mAh each for a total of 2 * 1.5V * 3000mAh = 9Wh, about twice as much power." It also uses a step-up converter to get from 3V to 5V.

Read through what this woman did, including doing her own PCB (printed circuit board) etching. She's pretty hardcore. It was probably a lot of fun for her, too. [note: if you read what she's done at and since MIT, you will see that is likely very true]

The iGoGreen provides USB power (5V) and specifies 5W with a 1800mAH battery.

I hope I did that math right, it's been a long time since I had to think about the watt-amp-voltage relationship.

 

[Peakbagr]

MJ,

I have the IGoGreen charger. Any idea how long it holds its charge. And how long if it's out in a cold car or winter pack?

Thanks

 

[erugs]

I have the iGoGreen http://www.igo.com/mobile-devices/charge-anywhere/invt/ps002730001/ it is basically a wall charger *and* battery. Has two USB ports, and comes with a cable for which you can buy various different plug ends, though if you just need USB (mini or micro) you can use any cable. You can charge your devices with it plugged into the wall just like any other charger. The difference is that you then charge *it* plugged into the wall. Then, in the field, you plug your phone/ipod/device into it, and its battery charges your device. I've had much success with it.

Thanks for the idea, MichaelJ. I did a little shopping and found one on Amazon, added a tip I need to charge my old Ipod Shuffle to the order and used some of my Amazon points. I have used the Igo system for quite a few years and have tips I no longer need but couldn't find the one I do need for my Shuffle. My original investment when phones had all kinds of different charges continues to be a good deal for me. I was wondering how I'd have a back up for my longer sailing trips, or traveling when away from regular electricity sources.

 

[MichaelJ]

I've never done a solid test of how long it lasts. I know that when I had the 'Droid I would get back to the car with a near-dead battery and I could get it back to half-charged, while still turned on and bluetooth-connected to my car, before the iGoGreen pooped out. But that was not necessarily a frozen iGoGreen.

It does work to plug a standard iPod/iPhone cable plugged directly into the unit, though certainly having one cord and couple of tips is a lot more convenient.

 

[Kevin Rooney]

The iPhone charges off USB, which means 5V. It draws 1A to do so and is claimed to take an hour. That makes 5Wh from the charger, which is thusly rated for 5W. A standard USB port is 2.5W (5V / 0.5A). This is where that cable trick comes into play about drawing more power or not depending on whether the USB data connection is shorted.

Following the "process" link from Chinooktrail's link, there is a discussion that explains that most build-your-own-USB-charger designs use a 9V battery and a linear 5V regulator. It additionally goes into detail about how this arrangement can only provide 300mAH. This guy's design uses "two AA's have 3000mAh each for a total of 2 * 1.5V * 3000mAh = 9Wh, about twice as much power." It also uses a step-up converter to get from 3V to 5V.

Read through what this guy did, including doing his own PCB (printed circuit board) etching. He's pretty hardcore. It was probably a lot of fun for him, too.

The iGoGreen provides USB power (5V) and specifies 5W with a 1800mAH battery.

I hope I did that math right, it's been a long time since I had to think about the watt-amp-voltage relationship.

Thanks for all the detail, and I think the guy is actually a gal.

I know that when I had the 'Droid I would get back to the car with a near-dead battery and I could get it back to half-charged, while still turned on and bluetooth-connected to my car, before the iGoGreen pooped out.

The other day my 'droid was dead flat, and I plugged it into my vehicle's DC USB charger, the recharging process was extremely slow. When I plugged it into the 120v, 150W inverter, it recharged at a rate similar to the wall outlet - much faster. The vehicle DC method is fine, in my experience, if you are spending a few hours driving, but if you're in a hurry - use AC as the source.

 

[MichaelJ]

Thanks for all the detail, and I think the guy is actually a gal.

Indeed you are correct. I should fix my post.

The other day my 'droid was dead flat, and I plugged it into my vehicle's DC USB charger, the recharging process was extremely slow. When I plugged it into the 120v, 150W inverter, it recharged at a rate similar to the wall outlet - much faster. The vehicle DC method is fine, in my experience, if you are spending a few hours driving, but if you're in a hurry - use AC as the source.

I wonder if the USB cable trick was in effect here at all, either in the cable or the plug? If it thinks it has a higher-wattage source available, it will draw it and charge a lot faster.

 

[Kevin Rooney]

I wonder if the USB cable trick was in effect here at all, either in the cable or the plug? If it thinks it has a higher-wattage source available, it will draw it and charge a lot faster.

Am not sure. FWIW, I was using the same USB cable, just switching the source of the charge.

 

[DougPaul]

The other day my 'droid was dead flat, and I plugged it into my vehicle's DC USB charger, the recharging process was extremely slow. When I plugged it into the 120v, 150W inverter, it recharged at a rate similar to the wall outlet - much faster. The vehicle DC method is fine, in my experience, if you are spending a few hours driving, but if you're in a hurry - use AC as the source.

The car electrical system is capable of supplying far more current than the 'droid needs. (After all, the inverter is powered by the car electrical system...) The difference is in your chargers (and/or the cables)--not whether the charger is 12VDC powered or 120VAC powered.

Note that there are several types of USB port with differing current ratings: some allow a maximim of 500mA (at 5V) and some up as high as 1.5A or 5A. (See http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power for more info.) Perhaps the current ratings on the USB ports on your chargers are different.

Doug

 

[JacobH]

I have noticed the same thing. My car charger takes 30-40 minutes from dead to full. The wall charger, I'd guess, would take about half the time? There's definitely a noticeable difference. Great thread!

 

[Nessmuk]

The car electrical system is capable of supplying far more current than the 'droid needs. (After all, the inverter is powered by the car electrical system...) The difference is in your chargers (and/or the cables)--not whether the charger is 12VDC powered or 120VAC powered.

Note that there are several types of USB port with differing current ratings: some allow a maximim of 500mA (at 5V) and some up as high as 1.5A or 5A. (See http://en.wikipedia.org/wiki/Universal_Serial_Bus#Power for more info.) Perhaps the current ratings on the USB ports on your chargers are different.

Doug

People have complained that the USB charger they use for their iPod does not work for the iPad, even though the connectors are the same in iPod and iPad. This is generally true, for the exact reason Doug has noted. If you buy an inexpensive third party (non-Apple) charger, chances are it is rated only for the lower power devices, it will not charge an iPad in any reasonable amount of time, and not at all if the iPad is switched on. You have to spend a little more to get the correct charger rated for the higher power output.

 

[MichaelJ]

Ayup. The iPad requires a 10W charger. That's (relatively) a lot of juice. Not the easiest thing to recharge, but fortunately it recharges wicked quick. The iPhone or an iPod draws a lot less power to recharge, and are more amenable to the battery-based, or solar, chargers.

 

[pks4000]

Hey Kev,
I always carry a spare battery for my cell phone.
No responsible montaineer would climb or hike without one.

Ive always felt those who have cells and dont carry them are simply selfish or trying to prove something they were born to late to maker happen.
Why?

Because if they are overdue need assistance or rescue they can save the rescue party time or even their lives in the search by giving a "last known location".
By the way if you are CAUGHT OUT WITH A MARGINAL SIGNAL TEXT AND IT WILL GET OUT WHEN THE SIGNAL IS MINIMAL.. Voice takes more signal
. SORRY FOR THE CAPS..... ooops