Last September, I bought the new iPhone 6s. Battery life was poor to begin with, so I added the Apple "piggyback / saddleback" battery case, custom-made to fit the iPhone. I find it extends battery life so I can use the phone with constant Wi-Fi "pinging" for nearly three full days. On a recent trip to Belgium, I used the case in the constant Wi-Fi ping mode for three full days before I had to stop and charge the phone/battery.
Apple programmed the iPhone, and this case, so the phone charges first to 100%, then the battery case charges. On use, the reverse is true. The battery first drains completely, then the phone depletes itself. So, you will see that the phone is at 100% charge for something like a day and a half, or longer, before the phone battery level starts to drop below a displayed 100%. So, once you see less than 100% displayed, you know you are on your last day and need to recharge the battery and phone.
While this iPhone, case combination is great for general use, I am thinking it is too heavy, at a combined 289 grams, 10.2 ounces for Camino use. Read on...
I have experimented with alternative battery packs and find that it takes a 1000 mah battery pack to fill my iPhone once, from about 8-10% charge to 100% charge. Hence, you will need about 2000 - 2200 to fill your iPhone twice. Others have commented on this same relationship. but, these larger capacity exterior batteries are heavier.
Though I am leaving for Madrid this Monday, I am still experimenting with field charging alternatives. I have a Zippo lighter sized 220 VAC wall charger made by Apple, with a retractable cable that can be used to charge or synch both Lightning and micr0-USB devices. I also have a flat prong USA type plug adaptor so I can use this rig in the US on my way out to Spain or coming back. My airline (UA) has power outlets at most all seats now. When walking, the charging setup rides in a cargo pocket where it is always with me. I carry a low-profile "cube-tap" to share an outlet with others in my rucksack toiletry kit.
I am comparing the weight of the Apple "Piggyback" or "Saddleback" case to the weight of portable charging battery "sticks." So far, the lightest option I found is a 1000 mah stick sold at Staples, and elsewhere, under the PNY brand. I think Best Buy also sells this generic product.
The Apple Battery Case weighs 1o1 grams, or 3.6 ounces by itself. The PNY battery stick weighs only 65 grams or 2.3 ounces. I can use the single retractable charging cable mentioned above to charge and feed from this stick. I have weighed other 1000 mah sticks. The PNY is the lightest I have found for this capacity.
The weight of the PNY, single full charger and the naked iPhone is 213 grams or 7.5 ounces. Conversely, the weight of the iPhone in the Apple "piggyback / Saddleback case is 250 grams or about 8.8 ounces.
So, the overall difference between having a separate battery, good for a single charge, and a Apple-specific battery, good for probably two full charges of the iPhone is about 37 extra grams or 1.3 extra ounces. On a cost-benefit basis the Apple "piggyback / saddle back" case is the winner. However, this is the Camino. Extra grams and ounces quickly add up to pounds and kilos. Do I need the third charging cycle capacity in the integral Apple case? Am I prepared for the weight-tradeoff?
The other serious consideration is that I usually carry the iPhone, as I did my old iPod Touch before it, in a LokSak ziplock-style plastic bag, certified waterproof to 200 feet. It rides in a cargo pocket of my zip-off trousers. The LokSak keeps the electronics from getting fried in a heavy rainfall. I can use the touchscreen through the Loksak material. However, the Apple pigyback case is a VERY grippy silicone material that will not easily fit in this superb plastic bag. So, that is the dilemma, far superior battery life at the risk of the iPhone getting wet...TBD
STOP THE PRESSES!!! I just located a 4" x 7" Loksak bag. The iPhone 6s in the Apple "Piggyback / Saddleback" Silicone Case fits snuggly into the bag. Problem-solved!
It is not easy to get the iPhone in and out, but I think I am "good-to-go." I can position the iPhone in the bag so the open end of the bag is on the same edge as the Lightning port. Then I will not even have to remove the "outer wrapper" to recharge either the iPhone or the battery." Decision made. I will suck-up the extra ounce and a half overall weight in return for the much longer and predictable battery life. I was hoping to use fseom GPS capabilities on this Camino. This solution helps in that regard.
I hope this rambling dialog helps someone out there.