Power Pack Advice

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Power Pack Advice

Postby adventuremum » Thu 05 Nov, 2020 8:08 pm

Hi
Any power pack advice? (for charging x2 old iphones - iphone 6 & iphone SE, which don't have great battery life!)
For hiking, bikepacking, cycle touring etc
Lightest for most power? and reliable?
Have had Goal Zero Flip 10 (70g) but only gives 1 iphone charge (so my 14 year has had flat phone for part of his 7 day 327km school adventure (cycling/paddling/hiking)
What do people recommend? And where's cheapest to buy?

[list=]Klarus CH1X (30g) + battery/batteries 18650 3600 mA (52g)
Klarus K1X Smart Charger (46g) + battery/batteries 18650 3600 mA (52g) 21700 5000mA (72g)
Anker Astro 6,700 (122g)
Anker Astro 10,000 (181g)
Anker Astro 13,000 (255g)
???
[/list]

And if I go with Klarus CH1X or K1X (or equivalent) what brand of rechargeable LI batteries do people recommend?

For longer hikes in southeastern Australia, is mini solar panel worth extra weight?
Or does weight & long charge time (& lack of sun in some seasons) make it lighter to carry x2 power packs? (Or with Klarus spare batteries?)
What solar brands/models do people recommend?
Thanks
Ruth
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Re: Power Pack Advice

Postby keithy » Fri 06 Nov, 2020 10:03 pm

With both your older iphones, you have batteries inside of around 1800mAh.

I use a rule of thumb to roughly guess how much power I'll need for a particular trip. For example, I use an estimate of efficiency of 80% of the powerbank capacity (in mAh) to allow for losses thru conversion/heat/transfer/etc). So for your example, the smaller (lighter charger and separate cell battery) options might only charge 1.5 times per iphone - 3600mAh x 0.8 / 1800 = 1.6. For a 10000mAh powerbank (10000 x 0.8 / 1800) you might get around 4.5 charges from a flat iphone.

This will give you a rough idea of how many charges you can get with your powerbank. So depending on how you use your phone and how many times you expect it to be flat, you can work out a rough guide as to how big (in capacity) a powerbank you'd need.

I nerd out a bit more and test how much my powerbanks output via some inline ammeters, and have found different brands have higher efficiencies up to 90%, but if you don't have access to that sort of thing, the rule of thumb works out as a general guide.

For powerbanks I have had experience with Anker and quite a few other brands. For best bang for buck, the Xiaomi powerbanks offered good alternatives to the Anker powerbanks.

For lighter powerbanks, go with the ones that have a flat lithium ion internal cell, like the Anker PowerCore Slim 10000 for example, or the Xiaomi 10000mAh Mi Power Bank 3. If you compare these "slim" versions side by side with the older fatter 10000mAh versions, the fatter versions are inevitably heavier, as they contain a series of cylindrical 18650 lithium batteries inside.

There's some previous discussion on the Xiaomi powerbanks here viewtopic.php?f=21&t=19706&start=60 with photos of the "slim" versions vs the "fat" versions.

For small solar panels, have a look at this thread - viewtopic.php?f=21&t=24317&start=60

Avoid tiny solar panels (eg the ones the size of a phone or a paperback book). They are too small to charge up a powerbank adequately in a day. Avoid powerbanks with "built-in" solar panels for the same reason, and the fact that the powerbank will get hot sitting in the sun, and lithum batteries don't charge well over 45°C. Get a panel that can restart, or if failing that, a powerbank that can accept charging restarts (when the panel is obscured by clouds or shade).

I've not used the Klarus chargers you mentioned, as I have too many chargers already at the moment, but note that some chargers do not work well with solar panels. In fact, if I was going this route, I usually avoid using chargers with a built-in LED display with my solar panels. The main reason is that the display takes some of the power from the solar panel to power the LCD screen. I would prefer using a charger with just a small LED light to indicate charge state when using with a solar panel.

If you are bike packing/ cycle touring, you can probably carry a larger/heavier panel. I have had success in using larger 21W folding panels, like the Anker, Goal Zero or Blitzwolf trifold panels which can weigh between 500g to 1kg. Larger panels usually = higher charge current = quicker charging.

With the small lightweight panels mentioned in this thread, viewtopic.php?f=21&t=24317&start=60 I would get a charging current of between 0.6A to 1A in optimum sunlight in real life use.

So with that information, assuming a perfectly sunny day, where you are able to angle the panel at optimally the sun, you can roughly calculate how much power you can generate from the panel. Eg. Assuming you can achieve 0.75A (750mA) on average, with minimum losses, a 10000mAh powerbank would take at least (10000 / 750 = 13.33) 13.33 hours to fully charge. This is a very rough estimate, but should give you an idea of what would suit your needs.
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Re: Power Pack Advice

Postby ChrisJHC » Sat 07 Nov, 2020 6:18 am

Hi, Keithy, you clearly are all over this subject :)

What is the best way to charge up your devices from a power bank?
Let them drop to nearly flat then charge them fully?
Let them drop to nearly flat then charge them to somewhere between 50 and 100%?
Keep topping them up once they drop below 50%.
Or some other approach?
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Re: Power Pack Advice

Postby adventuremum » Sat 07 Nov, 2020 8:10 am

Hi Keithy
Thanks so much for all that info & links
Much appreciated.
Have ordered one of small & lightweight $10 solar panels via fasttech.
And will order Anker PowerCore Slim 10000 or Xiaomi 10000mAh Mi Power Bank 3
Thanks again
Ruth
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Re: Power Pack Advice

Postby Mark F » Sat 07 Nov, 2020 9:42 am

The final 10-20% of charge of LI batteries is done using a different charging algorithm which is less efficient than the bulk charge to 80-90% full. I find it best to top up the phone charge when it get to about 40% and fill it to about 80%. Best not to run things flat as it means they are not available if there is an urgent need. Eg you get bushwacked and need to walk into the night. Your headlamp and phone (if being used for navigation) need to have some juice in them. If I am using my solar setup and have time and sunlight I will top up to 100% once all devices are at the 80% level.
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Re: Power Pack Advice

Postby ChrisJHC » Sat 07 Nov, 2020 8:55 pm

Mark F wrote:The final 10-20% of charge of LI batteries is done using a different charging algorithm which is less efficient than the bulk charge to 80-90% full. I find it best to top up the phone charge when it get to about 40% and fill it to about 80%. Best not to run things flat as it means they are not available if there is an urgent need. Eg you get bushwacked and need to walk into the night. Your headlamp and phone (if being used for navigation) need to have some juice in them. If I am using my solar setup and have time and sunlight I will top up to 100% once all devices are at the 80% level.
I assumed it was something like that but good to have confirmation.
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