Bushwalk Australia

In the event of saving some weight, I was on the hunt for a lightweight USB battery pack. I thought I would share what I came across, unfortunately I can't find the original link, but here is one similar on BPL: https://backpackinglight.com/forums/top ... /#comments

The idea is to use 3400mAh 18650 rechargeable lithium batteries (the highest legitimate capacity available) and a USB Miller charger.

18650 Li battery = 46g
Miller charger = 34g
10cm USB to lightning cable = 4g

84g set up for 3400mAh to charge my phone whilst hiking. If you need more juice, you can just bring more batteries along to meet your energy requirements which will depend on what you are charging, how long your hike is and your time away from a power socket.

6800 mAh: 130g
10200 mAh: 176g
13600 mAh: 222g
17000 mAh: 268g

And so forth...

Only unprotected batteries fit in the Miller charger, but you can do a quick DIY to the charger to accomodate protected cells (see above link).

Miller charger: https://www.fasttech.com/products/1421/10001919/1137904
18650 batteries: https://www.fasttech.com/products/0/100 ... 00mah-3-7v

Wish I'd known about those chargers sooner, I couldn't find anything like it so I bought a xiaomi. 330gm for 16000 mAh is not terrible but could have been a lot cheaper and more useful this way !

CasualNerd wrote:Wish I'd known about those chargers sooner, I couldn't find anything like it so I bought a xiaomi. 330gm for 16000 mAh is not terrible but could have been a lot cheaper and more useful this way !

I was using some cheap Chinese power pack off eBay which claimed 50,000 mAh, but in reality probably closer to 15-20,000mAh. Weighed in around 370g.

The good thing is this option is not only lightweight but also quite cheap.

Miller Charger = $6.08 AUD
2 x 18650 batteries = $11.38 AUD
10cm USB cable = $1.00 AUD

Less than $18.50 for a battery pack that weighs 130g and provides 6800mAh of power.

Better than that, I already have the 18650's lying around. If I could find a compact 18650 headtorch then I would use nothing else !

CasualNerd wrote:Better than that, I already have the 18650's lying around. If I could find a compact 18650 headtorch then I would use nothing else !

Have you considered lightweight headlamps or micro torches?

Petzl eLite is 28g or so.

eGear picolight torch is 11g.

Good suggestion, especially if you already have unprotected 18650s.

There were issues with the Miller charger with version 7.1 http://lygte-info.dk/review/Review%20Ch ... %20UK.html

I have one from Version 6. I see that Hendryk has reviewed the version 8.1 which seemed to have resolved the overcharging issue - version 9 is being sold now by Fasttech and has the led battery indicators.

I have a few Xtar chargers and have the SP1 that has USB output. http://lygte-info.dk/review/Review%20Ch ... %20UK.html The SP1 is heavier than the Miller charger at about 58g, and can handle multi chemistry lithium batteries with an adjustable slot. The USB charging capability is good, and it can handle various sizes without needing spacers. For me the annoying thing was it's 12V barrel input, which meant I can't use it to recharge with my portable solar panels in my travel kit. I wish Xtar would make something like the SP1 that would handle USB input as well as keeping the USB output.

So these I take an xtar MC1 plus charger to USB charge 18650 or 14500s via solar panels and use them in my torches rather than using them as a USB battery power source.

Have you tested the fasttech 18650s you linked? They seem to be a really good price for a pair of 3400mAh cells. I think I paid almost the same for a single Panasonic cell that FT have listed for the pair.

keithy wrote:Good suggestion, especially if you already have unprotected 18650s.

There were issues with the Miller charger with version 7.1 http://lygte-info.dk/review/Review%20Ch ... %20UK.html

I have one from Version 6. I see that Hendryk has reviewed the version 8.1 which seemed to have resolved the overcharging issue - version 9 is being sold now by Fasttech and has the led battery indicators.

I have a few Xtar chargers and have the SP1 that has USB output. http://lygte-info.dk/review/Review%20Ch ... %20UK.html The SP1 is heavier than the Miller charger at about 58g, and can handle multi chemistry lithium batteries with an adjustable slot. The USB charging capability is good, and it can handle various sizes without needing spacers. For me the annoying thing was it's 12V barrel input, which meant I can't use it to recharge with my portable solar panels in my travel kit. I wish Xtar would make something like the SP1 that would handle USB input as well as keeping the USB output.

So these I take an xtar MC1 plus charger to USB charge 18650 or 14500s via solar panels and use them in my torches rather than using them as a USB battery power source.

Have you tested the fasttech 18650s you linked? They seem to be a really good price for a pair of 3400mAh cells. I think I paid almost the same for a single Panasonic cell that FT have listed for the pair.

I bought the same exact ones off eBay for twice as much unfortunately.

This is the set up I will be rocking on my next trip:

Which model of charger do you guys recommend for 18650 batteries?


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The Miller chargers have a good reputation and I have just purchased a ML-102. The main purpose of buying this charger is to see if I can charge 18650 batteries in the field with solar and to charge devices from those 18650 batteries. There are more sophisticated chargers for use at home - more weight, dollars etc. I have a Nitecore D2 which seems to be quite reasonable for battery charging from 240v, 12v.

Thanks Mark. I did a separate search and is primarily looking at a home charger at this point, one that can handle NiMH and 18650 as I'm now dipping my toes into these Li batteries. The pricing on the Nitecore i4/D4 seemed to be quite reasonable for a main powered charger and can be used in the car when needed. I seemed to be trigger happy today for some reason.

Mark F wrote:The Miller chargers have a good reputation and I have just purchased a ML-102. The main purpose of buying this charger is to see if I can charge 18650 batteries in the field with solar and to charge devices from those 18650 batteries. There are more sophisticated chargers for use at home - more weight, dollars etc. I have a Nitecore D2 which seems to be quite reasonable for battery charging from 240v, 12v.

The micro-USB on the Miller is used to charge the batteries, where as the USB port on the Miller is for your device you want charged. So providing your solar panel can be plugged in via micro-USB, or you get an adapter, you should be good. Unless you're questioning the strength of the current produced by the solar panel?

GPSGuided wrote: I did a separate search and is primarily looking at a home charger at this point, one that can handle NiMH and 18650 as I'm now dipping my toes into these Li batteries. The pricing on the Nitecore i4/D4 seemed to be quite reasonable for a main powered charger and can be used in the car when needed.

The Nitecore i4/D4 is an ok multi chemistry charger. I have the i2 and i4. But you should be careful - there are fakes out there now.

Someone on CPF received one from eBay, and took it apart. It failed the validation code (the one time verify code had previously been verified) – so it could be a recycled code, and didn't have all the things that Nitecore suggest make it an original product, but from his pictures, it looked like a good quality build. I suggested earlier that he contact Nitecore directly, and he did. They replied that it is not a genuine Nitecore product.

http://www.candlepowerforums.com/vb/sho ... -from-eBay

So be careful. There are fakes out there. http://charger.nitecore.com/counterfeit ... ger-buyers

And if you are charging Lithium batteries in it as well, it's better to be on the safe side.

For not much more money when it's on sale, you could also consider the Xtar VC4 for a home charger.

When it was on special, it was as around AUD $30 delivered from China (around about November last year from Gearbest). I'll hunt around to see if there's a discount code currently active.

As I posted, I have the Nitecore i4 and i2, and was looking at the D4 or the Xtar VP4 before I saw the Xtar VC4. Some of the differences I saw before getting the VC4:

• The D4 shows progress bars, charge current and cell voltage, while the VC4 shows the cumulative mAh charge that is input into each slot (you see 1&4, and 2&3 at a time), as well as the charge current and the cell voltage. The better information is provided by the Xtar VC4
• The D4 operates almost the same way as the VC4, but splits 0.75A when using 4 slots, instead of 1A. So when charging 2 cells in slots 1&4 in the VC4, it charges at 1A, while on the D4, it charges at a max of .75A when using one slot, .375A when using 2 slots. The Xtar VC4 has a slightly higher charging rate (but you need to make sure you use a good quality 2A 5V USB power supply).
• I also noticed that the D4 operated at higher temperatures compared with the VC4 (most likely dues to the DC vs USB inputs).
• The VC4 has a reconditioning feature, which I don't think the D4 has.
• Again, the D4 shows the voltage and charge that is going in to each charging channel, but not the cumulative charge that has gone into each cell. The VC4 gives the mAh charged into each cell, as well as the voltage of each cell.
• The D4 can accept up to C size batteries, while the VC4 can take up to a D.

To confuse you a bit more, there is another multi chemistry charger I would recommend having a look at as well the Opus BT-C3100. This one is an analysing charger, so will report the charge capacity of each cell, as well as being able to do a controlled discharge of your batteries.

While the Xtar VC4 shows the charge mAh that has gone into each cell, it is not an analysing charger as it cannot do a discharge and recharge to report on the actual battery capacity.

This might sound confusing, but as an example, if you have a half full AA 2100mAh eneloop battery and put it in the Xtar VC4. When it finishes charging, it might show that only 1000mAh went into the battery - this is not the battery's entire capacity, but the amount of charge that went into it. Since you know it was a half full cell, that probably makes sense. The Opus BT-3100 or other analysing chargers will do a discharge of the cell first, and then recharge it, and report the total capacity that has gone into the cell, therefore giving a more accurate report of the battery's capacity.

An in depth review of the Xtar VC4 is here: http://lygte-info.dk/review/Review%20Ch ... %20UK.html

And a review of the Opus BT-C3100 is here http://lygte-info.dk/review/Review%20Ch ... %20UK.html Note that the latest version has revised software and is up to 2.2 or 2.3.

Sorry to take this off topic.

GPSGuided - I had a quick look and Gearbest currently have the VC4 on a Flash Sale for around AUD$28. I got mine around $38.

http://www.gearbest.com/chargers/pp_160440.html

To bring it back on topic, I have also just ordered a Liitokala LII-100 http://lygte-info.dk/review/Review%20Ch ... %20UK.html to try out with my portable solar panels. It does both NiMH and Lithium batteries but also has a USB output to act as a battery bank with Lithium batteries. I'll report back on how it goes when I get it.

It seems with solar charging that real world performance is often at odds with the theoretical. It will be interesting to see how it pans out.

Thanks for the quick summary and the VC4 link Keithy. I've also been scanning a bit on candlepower forum and have pulled a few triggers. Now the wait... Should I upgrade my Zebralight too to a 18650 model? This transition to Li is getting expensive.

GPSGuided wrote: Should I upgrade my Zebralight too to a 18650 model?

If you're happy with the AA Zebralight, I'd stick with it. The benefit of the 18650 is that the battery is slightly lighter and provides a greater output from the torch, and you'll get longer out of it on the medium settings when compared to the AA versions. But at the highest output while you get a brighter output, you'll get about the same lifespan as the AA versions.

Anyway, just back on topic, as an update - I got my Liitokala LII-100 charger.

Tintin - it is slightly larger and at 45g it is heavier than the Miller ML-102.





For me the ability of charging both NiMH and Lithium cells as well as protected 18650s is an advantage over the Miller. It also has selectable charging current and can charge LiFePo 3.2V and 3.85V cells. The output 5V is a little lower than the Miller at 1A though.

It automatically detects NiMH, but for Lithium you can select the voltage. The selection leds also act as battery charge indicators.

I have yet to try it out with my USB solar panels, but the build quality appears quite good.

It's endless gadgets! My head is about to explode just as I settled in with the Miller... Keep them coming Keithy.

If going bigger, you could of course build (probably buy?) a charger based on honking great headway cell or two?

Just a follow up on the performance of the Miller ML-102 charger and Panasonic NCR18650B batteries. I have been using them to charge my Samsung S4 which uses a 2600mAh battery. All four Panasonic batteries have now been through four charge cycles and fully discharged into the phone. Each 18650 battery almost manages a full recharge of the phone battery - about 10% to 95%. This is enough to keep me connected for about 6 days not on aeroplane mode as I got a great deal on data here in Denmark. In aeroplane mode This system would stretch to about 14 days.

Mark F wrote:Just a follow up on the performance of the Miller ML-102 charger and Panasonic NCR18650B batteries. I have been using them to charge my Samsung S4 which uses a 2600mAh battery. All four Panasonic batteries have now been through four charge cycles and fully discharged into the phone. Each 18650 battery almost manages a full recharge of the phone battery - about 10% to 95%. This is enough to keep me connected for about 6 days not on aeroplane mode as I got a great deal on data here in Denmark. In aeroplane mode This system would stretch to about 14 days.

Are those the 3400mAh Panasonic batteries ? I have exactly the same batteries I think, but I use the xiaomi 16000mAh charger and have been up to 5 day trip without running out of juice.

As a comparison 5x 3400mAh 18650's and a v9 miller 102 is about 280grams for 17000mAh, and the xiaomi is 330grams for 16000mAh.

I wasn't commenting on my phone's power usage which is very high as I am using 4g data continuously. I was commenting on the performance of the charger and batteries so people have an indication how they might perform for them.

Mark F wrote:I wasn't commenting on my phone's power usage which is very high as I am using 4g data continuously. I was commenting on the performance of the charger and batteries so people have an indication how they might perform for them.

I think CasualNerd was commenting on your Panasonic NCR18650B batteries - are they the 3400mAh ones?

Xiaomi have also released a 20000mAh battery bank which is 340grams (10grams heavier than the 16000mAh one, and uses a lighter weight casing).

I was thinking of picking up some Panasonic 3400mAh protected 18650s and trying them out on my Liitokala Lii100 as a powerbank. The Lii100 is heavier than the Miller charger at 45g, but because it can take batteries up to 70mm long will fit most protected cells as well.

• Lii100 - 45grams
• Protected 3400mAh 18650 - 49grams each

So with my Lii100 and 5x3400mAh protected cells it will be around 290grams to get a total of 17000mAh.

The only thing I haven't weighed is the cases for the 18650.

• A waterproof 2 x 18650 case (with o-ring) - 20grams
• A 2 x 18650 case without o-ring - 15grams
• A single 18650 silicone sleeve - 7 grams

So adding the battery protection will for the 5 cells to get the 17000mAh total will still add up to around 318g-330g (configured as either 2 x double cases or 4 x silicone sleeves with the 5th battery sitting in the charger itself). So not much weight saving compared with the new Xiaomi 20000mAh battery bank (340g).

Of course, if you didn't need that much power and took fewer cells, it could still work out to be a lighter weight solution.

With my Liitokala Lii-100 I have tested it with a few of my portable solar panels but so far only with 14500 and NiMH batteries. It works fine, and depending on the solar panel used, with my testing gear, the input draws up to 1A current and has a charging current of 1A with AAs, and 0.5A with my 14500s. I will get another so I can test with two different panels at the same time and give some 18650s a try as well. I will probably have to wait for the weather to improve though.