Optimal Power Bank Size

[andrew_s]

The best size of power bank will depend on the available input, and whether you need to charge more than one device at the same time.

If you've only one power source (dynamo or single USB wall adapter), a big bank is better.
Having a smaller bank that's full is of no advantage over a larger bank that's part full if both have spent the same amount of time being charged.
You don't get the loss of charging time between bank 1 reaching full and you putting bank 2 on charge, and additionally a bank will normally charge more slowly as it nears full, so the big bank will have been charging at full rate whilst bank 1 is topping up.

If you've multiple inputs available (eg a wall adapter that has 4 x 2.4A ports), you gain with several small banks, as you can charge several banks simultaneously.

For charging devices simultaneously, it will depend on the number of output ports, Larger banks are more likely to have multiple ports, but may not have enough to match several small banks of the same total capacity.


Also, note that if your bank is bigger than about 27 Ah*, you may well not be allowed to carry it on an airplane.

* got to keep Kim happy

[Oaky]

Ok, ta. But the big ones make some people twitch! I'm not sure why. The weight?

Say 25k mAh

*twitches*

I'm guessing it's more about the "k" "m" (== kilo milli == 1000 ¹/₁₀₀₀s == 1)

(25 Ah would probably be less *twitch* inducing  )

[Somnolent]

Not saying it's the best size for you, but on the basis of what you've said, I'd go with my existing two 6700mAh RAVpower units.
A full day's cycling with dynamo & Igaro/e-werk/Plug/Luxos should get close to fully charging one 6700mAh pack, and that gives a daily charge for e-cig and phone. 
Then there is still one pack spare & for emergency top-up of tablet (which you'll generally charge in your occasional hotel nights). 
Being away for a month I'd not rely on a single pack, however highly recommended.

Maybe ditch the Kindle, the functionality can be done not too inconveniently with phone app, albeit with increased battery usage, with but if you keep your phone mostly in flight mode there should be more than enough for a couple of hours reading each evening.

[bobb]

Ok, ta. But the big ones make some people twitch! I'm not sure why. The weight?

Say 25k mAh

*twitches*

I'm guessing it's more about the "k" "m" (== kilo milli == 1000 ¹/₁₀₀₀s == 1)

(25 Ah would probably be less *twitch* inducing  )

Oh, I see. I didn't consider pedantry. How about 9.00 x 10⁴C ?

[frankly frankie]

Having a smaller bank that's full is of no advantage over a larger bank that's part full if both have spent the same amount of time being charged.

The smaller one weighs less.

Maybe ditch the Kindle, the functionality can be done not too inconveniently with phone app,

I would ditch the phone.  Are you on holiday, or what?

[bobb]

I would ditch the phone.  Are you on holiday, or what?

I'm amazed it's taken this long for someone to pipe up with that one 

I'd ditch everything else before the phone...

[Oaky]

Just smoke the phone! 

[Kim]

Ok, ta. But the big ones make some people twitch! I'm not sure why. The weight?

Say 25k mAh

*twitches*

It was your simultaneous use of the kilo and milli prefixes that I was twitching at; they cancel out.  25000 mAh is correctly written as 25Ah.  Obviously marketing trumps common sense, as bigger numbers are more betterer, which is why they don't just use Amp-hours for the bigger packs (and why they don't use Watt-hours, which would likely be a more useful figure for end-users^[1]).

(Yes, I will happily abuse SI prefixes for clarity.  If you're talking about an 800mAh battery, a 950mAh battery and a 1.2Ah battery, I wouldn't object to describing the latter as 1200mAh.)



_{[1] They quote the Amp-hour capacity of the battery inside the powerbank, which is misleading, as some of that capacity will be used up raising the voltage from the nominal 3.7V of the battery to give you your 5V USB output.  So you'll never see the quoted number of Amp-hours at the output.  Sometimes (usually for packs with higher output voltages) they go one further and add up the Amp-hour capacities of series-connected cells, which crosses the line between misleading and is well into outright lies.}

[Phil W]

Yep ditch the phone. If you want one for making calls then get or use an old style Nokia. About 25 days on standby.

[Kim]

Yep ditch the phone. If you want one for making calls then get or use an old style Nokia. About 25 days on standby.

There's a strong argument for tablet + dumbphone in this context, certainly.  Although since the demise of my Nokia E52^[1], in recent years I've just stuck to my normal Android phone which at least means I can hedge my bets with two cellular providers, even if it does need recharging from time to time.


_{[1] The last sensible phone they ever made:  Smart enough to do email, IRC and play MP3s.  Dumb enough for the battery to last a couple of weeks.}

[Valiant]

I absolutely love my Aukey 20000 mah. It's been going over a year and still holds the same charge.

[Kim]

I absolutely love my Aukey 20000 mah. It's been going over a year and still holds the same charge.

I've got a 16Ah one.  That's a bit optimistic as I only get 9Ah or so at the output, which seems a bit low (I'd expect 10-11), but it's otherwise been flawless.

[freeflow]

You'd probably be better off with one of these and a couple of decent sets of protected 18650 batteries.


https://www.ebay.co.uk/itm/Waterproof-4x18650-Battery-Storage-Case-Box-Holder-Pack-For-Bike-LED-Light-Hoc/152101697909?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649.


Which means that at a pinch (if you can source them) you could also use a set of 8 CR17345/CR123A disposable batteries.

[bobb]

Ok, I have decided to ditch the tablet and kindle.

On Saturday I got a new phone It is awesome. As I mentioned previously, last time I did everything I needed on my phone - photos, blogging, googling stuff and posting pictures of my lunch    I only thought about taking my tablet to make life a bit easier, but to be honest, I don't think it will make any difference other than take up valuable pannier space.... The new phone has excellent battery life - of course, it's brand new, but all the reviews I read said it had really good battery life and I've been hammering it and so far battery life does indeed seem good.

I've also installed the Kindle app and have been using that to read for the past few nights and it's absolutely fine - so the Kindle goes.

So.... I have dug out an old 13Ah Anker to do some testing. I'm pretty sure it's a bit knackered - it is a few years old and has been sitting in a draw for over a year doing nothing, so I will still be going for a new battery or two.

One thing I've noticed is that when I charge the phone from the mains it says "Super charging" and it charges in a err...  super kind of way. When I plug it into the Anker, it doesn't say "Super charging" so I guess it's just charging normally.

Can I assume that I'd need a battery that supports some sort of quick charging if I want it to be all super and stuff?

Edit: My phone is a Huawei Mate 10 Pro and apparantly it doesn't use Quick Charge, rather their own fast charging tech... hmmm..

Edit 2: Just found this which pretty much tells me everything I need to know....

Edit 3: So basically, my best bet to get "Super charging" is to get a battery with USB-C to USB-C charging so I get an output of 5V/3.0A.

[tom_e]

Do you need to charge the phone fast?  Generally, you have all night and all day in the pannier to charge the phone from the battery.  The thing you want to be faster is recharging the battery from a power socket, because that's when you may be sat in a cafe or leaving the thing in a random campsite socket or similar.

[bobb]

Good point, no I guess I don't need to use the fast charging on the phone. And indeed a multi port wall charger that can charge the battery (or batteries) fast is what I need...

[Canardly]

I still like my Anker 20,000 mah which is a bit of a lump.

[Ham]

Edit 3: So basically, my best bet to get "Super charging" is to get a battery with USB-C to USB-C charging so I get an output of 5V/3.0A.

Whatever else, you don't need USB C to C, B output to C works fine and if you want to minimise cables and have micro as well, a micro to c adapter is minuscule. all you need is a powerbank capable of delivering fast charge, as the ones I linked to upthread.

[bobb]

Right.... So far I have got a Ravpower 20100 mAh battery. It has a Quick Charge 3.0 input and Quick Charge 3.0, iSmart and USB C outputs. It seems fine and does what it's supposed to do. I'll probably get another one the same and also the wall charger Ham linked upthread that has two Quick Charge outputs and a bunch of regular outputs for charging the things when a socket is available.

I did some tesing today to see how it charged off the Dynamo. I was using it via an Lumotec IQ2 Luxos U rather than an ewerk (which I will try tomorrow) and this is what I found:

I'd ride along and the little red light will be on on the handlebar mount/switch thing and I can watch the blue lights flashing on the battery as it charges. Then the little red light goes out and the battery stops charging.

Even at a constant decent pace the red light would be on for around 25 to 30 seconds and would then go out for about 15 - 20 seconds. So for every minute of riding , I'm only getting just over half actual charging. Even when hammering it down a long hill, this behaviour was still observed. When going up a long hill, it was off for longer, before coming back on (remarkably it came back on just as I crawled to the top of The Mighty North Hill).

I'm assuming that the battery is sucking up all the electrickery faster than it can be generated, hence the continual on/off situation. It's just draining the little cache battery very quickly.

Is this normal? Does it do any harm to the battery?

I had kind of assumed it would just trickle charge constantly rather than doing what it's doing? Charge was defo going in, but I'm going to struggle to get anything more than a little top up from the dynamo when on tour.

I'll try the ewerk tomorrow to see what happens. The same I assume....

[Nick H.]

When you have multiple gadgets, would it be viable to save weight by making them all share the same battery? For each gadget could you remove the internal battery and fit a plug or connector to the battery lead and connect directly to the power pack, perhaps with some sort of rectifier/diode thingummy so that the gadget draws the appropriate current? Maybe the power pack could be comprised of multiple AAA batteries, which would be useful for other things, e.g. head torch and  lights.

[fhills]

[
Agreed.  What you really want for touring is a powerbank that can charge *itself* quickly when you have short-term access to mains.  Ability to charge your phone or whatever quickly is a minor convenience in comparison.

Agree. Stuff can charge more slowly from the powerbank in the tent overnight.

Apologies if i have missed something upthread, but do you know of such a fastcharge powerbank?

None of my devices are quick charge, but as above, not a great problem.

I do have an Anker Powercore 20,100 powerbank - it's good, but not fast charging of course. Takes a long long night.

[bobb]

The one I just bought (RAVPower 20100) has a Quick Charge 3.0 input. Apparantly it will go from empty to full in 4.5 hours. I've not tried that yet, so we'll see....

[fhills]

Thanks bobb, will check it out.

Any others?

Does the fastcharging compromise the powerbank in any way? Shorten its life?

[bobb]

Well, this morning's testing was a disaster. It would seem my ewerk no longer werks. Tried it with various things, swapped leads, cleaned up and sorted the wiring in the brick... and nothing. Nothing at all.

Pain in the arse. It has been sitting in a draw for 5 years, but is that enough for it to stop working?

Now I don't know whether to just go with the intermittent charging via the Luxos, buy a new ewerk (or similar) or try something else I haven't thought of yet.....

EDIT: Ah! I'm a fool. I have the USB werk. After a quick Google it would appear I need a regular ewerk if I want to charge a large battery. I think that's the way to go.

EDIT 2: That doesn't explain why the USB werk wouldn't power the GPS. I would expect it to. I've also successfully charged a smart phone in the past with it. Hmmmm... Maybe it is broken....

[bobb]

I'm much happier now after some more experimentation this afternoon. Rather than trying to charge the battery, I just tried charging various things and it worked just fine. I think I'll save charging the big power banks for when a mains socket is available...