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AA battery holder to recharge smartphone?

Old 06-08-17, 03:17 AM
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[SOLVED] AA battery holder to recharge smartphone?

Hello,

To tour, I have a 20000mAh Aukey powerbank.

But since I picked up camping, it's possible I might not be able to recharge the powerbank often enough, especially since it takes several hours to fill it when it's empty.

As a backup, I was thinking of simple battery holders so I can just buy 3-4 AA batteries that can be found anywhere.



Problem is, the smartphone expects 5V, so neither 3*1.5 nor 4*1.5 will do.

Are there battery holders that can up/reduce the voltage to match what the phone expects? And how much mAh does each AA battery contain? The battery in my smartphone holds 2,200mAh.

Thank you.

Last edited by Winfried; 06-10-17 at 03:34 PM.
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Old 06-08-17, 04:55 AM
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I think that you are looking for something like this
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Old 06-08-17, 05:45 AM
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https://www.amazon.com/Goal-Zero-Gui.../dp/B00D2SQ6W8
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Old 06-08-17, 07:46 AM
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Thanks. Apparently the Goal Zero Guide 10 Plus Recharger can be used with regular batteries:

"Yes it can. I just tested it with Kirkland AA's and a Motorola Moto X. The phone reported charging. Don't try to charge the Alkaline batteries with the charger though. Alkaline batteries and NiMH battery chargers don't mix. Also keep in mind some phones are picky about their chargers, so while I just tested it with my phone, it may not work for another phone or brand."

Before ordering, I'm interested in any real life feedback.
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Old 06-08-17, 11:53 AM
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Christopher Bennett, an endurance cyclist, uses the goal zero.
https://triduffer.wordpress.com/2016...durance-races/
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Old 06-08-17, 11:59 AM
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There is a small device that can help with charging different voltages...ill see if I can find it.
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Old 06-08-17, 11:59 AM
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I got them at Radio Shack when I had soldering projects..
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Old 06-08-17, 12:31 PM
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Those of us who toy with DIY LED projects and need to achieve a specific voltage to match the LEDs are very familiar with what you want. It is called a DC-DC step down transformer and they are dirt cheap from overseas sources. DC-DC Buck Voltage Converter 4.5-40V 12V to 5V/2A Step-down Volt Transformer*1 | eBay
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Old 06-08-17, 02:35 PM
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I was thinking of the Goal Zero Smart USB Adapter, no longer sold by them for about 5 bucks. Amazon is selling it for 20 bucks.
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Old 06-08-17, 03:07 PM
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Heck I've picked them up off eBay for like $2.

This exact one in fact. I have several. They work fine. 3 weeks shipping from Hong Kong of course.

Portable AA Battery Emergency Travel USB Charger Cell Phone Power Bank Case | eBay
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Old 06-08-17, 04:45 PM
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Typically AA batteries have ~1.5V * 2000mAh = 3 Wh, a typical smart phone has a 3.7V * 2000 mAh = 7.4 Wh.
An even bigger issue is that standard alakaline batteries have a linear voltage drop, so they may only discharge ~30% before cutting off, leaving you with getting maybe 25% charge. Lithium based AA batteries are significantly better but more expensive.

The best solution is using AA sized 18650 cells. Each cell is 3.7V*2500mAH so enough to fully charge a phone. This is what's used in most power banks. The solution is to buy a bigger power bank.

The only advantage that AA cells have is that they're readily available at stores. However, if you're at a place with stores then you can re-charge a phone and power bank.
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Old 06-09-17, 03:24 AM
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Thanks for the infos.

I already have a 20,000mAh powerbank, and it takes over 12hrs to fill it from empty. In case I can't and am stuck with an empty phone when I get to a camp site, I was looking for a solution to simply recharge my phone with off-the-shelf AA batteries that can be found everywhere.

Looks like it's just no feasible. I'll get a lighter, single-charge powerbank: [strike]Are there powerbanks that use a higher voltage than 5V for faster recharging?[/strike] Yes, although they seem to be big, heavy powerbanks.

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Old 06-09-17, 06:52 AM
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Originally Posted by Winfried
Looks like it's just no feasible.
Why not? Works for me. I don't get a full charge out of 2 AAs but I get some. Keeps the phone going.
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Old 06-09-17, 07:48 AM
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Why not a folding solar charger? They work pretty well. Of course, you need to be in daylight, but they even work on cloudy days.
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Old 06-09-17, 08:07 AM
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But then, if the AA batteries stop at 1/3 of a total charge when I wake up the next morning, it's not what I had in mind.

As for solar panels, I was told they're more of a gadget than a real solution. Besides, they're a lot less pratical than an empty charger with AA batteries.
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Old 06-09-17, 01:47 PM
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If?
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Old 06-10-17, 07:02 AM
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Originally Posted by Winfried
But then, if the AA batteries stop at 1/3 of a total charge when I wake up the next morning, it's not what I had in mind.

As for solar panels, I was told they're more of a gadget than a real solution. Besides, they're a lot less pratical than an empty charger with AA batteries.
There are two types. First, there are chargers that are cases for the phone. These don't have enough surface area to catch much sun and aren't good for much more than a minimum charge after a few hours. Then there are folding types that open up that can produce a lot more power as they have a lot more surface area. These can charge a phone in about 2 hours. https://www.amazon.com/Charger-RAVPo...RM04D8Q2VRKK95

There are others like this with even more power. It still isn't practical on a bike as you'd need to have a way to mount it, I guess on the rear rack and open since I'm assuming this would only be used on long touring rides.

All that said, I've never tried one myself as overnight touring/camping isn't my thing. I prefer a hotel, bed and shower.
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Old 06-10-17, 07:15 AM
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Thanks. A solar panel is too big/heavy for my folding bike. A second external battery would be lighter and simpler.

I'm new to camping. I also used to only consider hotels, but camping makes it possible to plan tours that would otherwise not be possible, or require detours/longer days. Besides, campsites do provide showers, and sometimes power as well.

Conclusion: I'll have to either add more stops at hotels so I can charge the Aukey overnight (about 10hrs @ 2A), or pack a second, smaller external battery as backup. Or consider adding a Shimano dynohub.

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Old 06-10-17, 11:17 AM
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Originally Posted by gsa103
Typically AA batteries have ~1.5V * 2000mAh = 3 Wh, a typical smart phone has a 3.7V * 2000 mAh = 7.4 Wh.
An even bigger issue is that standard alakaline batteries have a linear voltage drop, so they may only discharge ~30% before cutting off, leaving you with getting maybe 25% charge. Lithium based AA batteries are significantly better but more expensive.

The best solution is using AA sized 18650 cells. Each cell is 3.7V*2500mAH so enough to fully charge a phone. This is what's used in most power banks. The solution is to buy a bigger power bank.

The only advantage that AA cells have is that they're readily available at stores. However, if you're at a place with stores then you can re-charge a phone and power bank.
I'm going to agree. I had a two AA cell power bank and in most cases it wouldn't even give me a quarter charge ( my phone has a larger battery ). A 4-cell might be better but I'd go with a 6 or 8 cell AA bank just to make sure I get a full charge. One of the ads for one of the 4-cell claims to be able to charge a phone 3 times. That's just plain BS. Standard AA cells just don't have the available watt hrs. that the 18650's Li-ions have.

You also want to pay attention to the ( output ) charge rate of the power bank. Keep in mind that you are probably only going to get maybe 500ma ( output ) out of anything using AA cells. Compared to a standard 18650 power bank ( 1000-2000ma ) that is a very slow charge rate. If you find one using 6-8 AA cells and it charges at 1000ma. I'd go with that. Sadly, after doing a quick search, I'm not seeing any AA power banks using more than 4-cells.

Now as for replacement AA's...you can buy standard Lithium ( non-rechargeables ) AA cells but generally I don't see these being sold in typical stores like CVS, 7-11, etc. The lithiums would give you more watt-hours but cost a whole lot more.

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Old 06-10-17, 01:12 PM
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External battery things made for extending run time and recharging phones have gotten pretty cheap of late.

look around. they're USB powered, a mains to usb plug is cheap too..

top up your phone during lunch .
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Old 06-10-17, 03:31 PM
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Indeed, lithium batteries are harder to find, and more expensive (Ç = euro).



So, for the time being, I'll just stick to my 20,000mAh Aukey powerbank, and plan stops accordingly.

Thanks everyone for the input.
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Old 06-11-17, 12:40 PM
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Originally Posted by Winfried
Indeed, lithium batteries are harder to find, and more expensive (Ç = euro).



So, for the time being, I'll just stick to my 20,000mAh Aukey powerbank, and plan stops accordingly.

Thanks everyone for the input.
Yeah but that's like comparing a single grape to an orange. Here in the US the price of a lithium cell is a little more than twice that of a typical brand Alkaline cell ( when bought in bulk ). Sadly it looks as though the price difference in Europe is not the same. Regardless, if I were you I'd still buy a 4-cell AA bank-charger and bring it along with the intent to only use it in an emergency. If it were me I'd go with the lithium cells if I could find them while on the road. The lithium cells should provide at least 3X the available power of a typical brand name Alkaline cell. If it were me I wouldn't touch an off brand "discount" cell. Not for something that might be used in an emergency. If you can't find lithium cells than get something like Duracell copper tops or the best brand Alkaline cells you can find.

Like you said, best to try to use the good Li-ion power bank you have as much as possible. If you get in a situation where your phone is down to say 20% power and you don't know when you might get access to line voltage and your Li-ion bank is almost dead, that would be the time to use the AA bank. Turn the phone off and plug in the AA charger. Keep in mind it will take a very long time to charge a phone with only a 500ma input current. During that time try not to use the phone if you can. Once you get access to line voltage hopefully you can charge both the phone and Li-ion bank at the same time.
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Old 06-11-17, 01:39 PM
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Having more precautionary mindset, perhaps the safe Haz-Mat disposal costs are built into the sales price..
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Old 06-11-17, 02:01 PM
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One option is using a small solar panel to re-charge a USB pack. They have limited charging capability, but it's very easy if you have a fixed camp site.
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Old 06-11-17, 02:14 PM
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Originally Posted by gsa103
One option is using a small solar panel to re-charge a USB pack. They have limited charging capability, but it's very easy if you have a fixed camp site.
I have never found anything that put out enough juice to do the job in a reasonable amount of time.

I recently bought an external battery from Amazon:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

With this thing I can fully recharge a smartphone 4 times. The battery itself can take as much as 12 hours to recharge.
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