Power banks for tramping
Lately I've been updating electrical devices (torch, gps, camera are my main three). More and more they're trending towards charging and/or running straight of USB, whether or not they have replaceable batteries. I used to try and always get stuff that ran off AA batteries to make it simpler to manage spare power between them, but now it's making more sense to have lighter devices and carry a power bank instead. I presume many people here are already doing something like this. I haven't bought one for a while, though. With a tentative look there seem to be lots of power banks out there, but much of which also looks very consumer grade and aimed at people are are just hanging around town and worried about their phone battery running out. Are there any favourites out there for tramping purposes, or thoughts on what might be good value for money? In my mind I'd like something reliable and reasonably durable, like if I knock it or if it got a little wet then I'd want it to keep working. Weight's always of interest, as is having a decent charge and some kind of indicator of remaining charge. I'm not expecting to get it perfect first time, but I might as well try. Any thoughts?
Ok @bernard. Having read up on it the theoretical charging efficiency of Lithium ion can approach 100%. But every power bank I've used charges to approx 30-40% of its nominal capacity when charging real world items. I've quizzed peolle on this before e.g. on the garmin inreach forum the universal experience of those that responded to my query was it took a power bank 2-3 times the capacity of the inreach battery to fully charge it. Likewise those I've spoken to about charging cellphones, like me, get about 30% charge from their portable packs - mine is a goal zero switch (2600mAh). So whats going on? A) Well the battery bank vendors could be overstating their capacity. B) Whatever they use to step the voltage up from 3.6v to 5v (probably a voltage doubler followed by a voltage regulator) at the usb output and then what your device uses to drop that 5v to 4.2v to charge the battery will both add some inefficiency C) or the theoretical 100% charging efficiency of lithion ion is only not delivered in practice Any tech minded people out there with ideas?
Xiaomi battery packs are the best in an affordable price range. https://www.mi-store.co.nz/products/mi-powerbank Review: https://www.pcworld.com/article/3260638/xiaomi-10000mah-mi-power-bank-pro-review.html I have one for the last couple years and it's been much better than any of the others I have had/used.
One other option rather than a suingle heavy high capacity unit is a power bank that takes removable batteries. Like: https://www.jaycar.co.nz/2600mah-power-bank-with-removable-18650-li-ion-battery/p/MB3717 Then you can take one lightweight powerpack and as many charged lithium ion batteries as you need for the trip. Might get one ... Edit: the jaycar one is discontinued so bought one of trademe. Will report back
Thanks, everyone. This is exactly the type of discussion I was hoping to provoke and it's giving me some useful ideas to chase up.
My Asian friend bought me back a charger from a trip to China. Its a no name thing. Its small. It charged everything I have, cellphone, garmin watch, batteries for GPS etc. For a five day hunt in the Bush.
" Having read up on it the theoretical charging efficiency of Lithium ion can approach 100%. But every power bank I've used charges to approx 30-40% of its nominal capacity when charging real world items." Part of the reason for this is the current limit in the battery pack. To run the device and charge its battery can run the battery pack at capacity. Batterys do not give full capacity at full load. You can bet the rating is done at a much lower current. There is a way round that although it might not work in a tramping situation. I use my power pac for work with an ipad. Plugged in all day I normally have about 30% ipad battery left at the end. Dont plug it in till lunch time and the ipad is flat by 2pm. Good if you want to go home early. This was a battery pack the same size as the ipad battery. If you can run the device continuously off the battery pack it uses the pack before its internal battery overcoming the charging loss. Of course this means cables everywhere while walking.
Just tested my goalZero (2600mAh) charging a flat galaxy A5 (3000mAh). The goalzero battery went from full to flat in 2hr55 outputting a steady current of 0.42A. This charged the phone to 49% according to the phone. The phone was (and always has been) turned off durung charging (@geeves point if I understand right) That gives 1225mAh total output from the goalzero - well below the nominal 2600mAh - 47% of the nominal output current capacity. Combined with losses in the phone it explains the 30-40% figure I've been seeing. EDIT: I've rerun the test with a brand new 3000mAh samsung 18650 INR lithium ion battery as the power source to charge from charging the galaxy A5's 3000mAh battery from flat. That also charged at 0.42A down the wire but I didn't see how long it took to calculate exact mAh. However it was under 4 hrs and charged phone to 52%. So it seems its not just a dud battery in the goal zero - but that around 50% of source battery capacity ends up in the battery being charged when charging lithium ion from another lithium ion battery via USB.
fast charging might make the efficiency worse for phones and powerpacks that support it. it generates a lot more heat and lost energy
Bought this last year, found it to be excellent. Charges my iPhone at least twice. https://www.mightyape.co.nz/product/xiaomi-mi-10000mah-power-bank-2-black/29127312
@madpom whatever you're doing, it's wrong. You should see 85% efficiency in your case. But get a professional powerbank as listed in this thread, and a decent USB cable. Powerbanks can crank out a lot more than a measly 0.42A.
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