Author Topic: Electrics that I use for bike touring - what works for me.  (Read 15891 times)

mickeg

  • Hero Member
  • *****
  • Posts: 2790
Electrics that I use for bike touring - what works for me.
« on: January 28, 2020, 09:05:33 PM »
Occasionally we have threads on specific electrics or electronic components used for cycling, but I do not recall one thread where anyone explained the big picture of what works for them for bike touring.  This is what works for me, but I am sure that no two people do things the same way, so this is not a how-to, instead this is intended to start a thought process if you are planning for a bike tour and you do not know exactly what you need.

I use a dynohub for power and I try to be self contained without having to draw power from an outlet (or mains) when I am touring, I almost always am camping in campgrounds and most campgrounds do not have outlets in tenting areas.  I try to generate 100 percent of my own power with a dynohub.  Some use solar power panels, I tried that on a kayak trip and no longer try to use solar.  If solar works for you, great, but did not work for me.

Dynohub. I use an SP-PV8.  I think almost all dynohubs put out about same amount of power, it simply is an alternator built into the front hub, alternating current is generated while riding.  The article at the link below is several years old, but it is the best compilation of information I have seen on dynohubs.
https://www.cyclinguk.org/sites/default/files/document/migrated/publication/feature-hub-dynamos.pdf

USB Charger.  For several years I have used the Sinewave Revolution for touring, that takes the alternating current from the hub and converts that to USB power supply.  There are several different chargers out there at different price points and output levels.  Occasionally you see a good article that compares them, and then you suddenly find some new chargers on the market that were not evaluated in the article.  I have not seen a good article for a while now that compares all of the common ones that are available.  The link below with some comparisons is to an older article that was written in German, that link uses Google Translate to English. Figure 13 in this article has good output comparisons in watts for the different units that were available four years ago when that was written.
https://translate.googleusercontent.com/translate_c?depth=1&hl=en&rurl=translate.google.com&sl=de&sp=nmt4&tl=en&u=https://fahrradzukunft.de/21/steckdose-unterwegs-4/&xid=17259,15700021,15700186,15700190,15700256,15700259,15700262,15700265,15700271,15700301&usg=ALkJrhinkvnrcxwGc8xhEoE9-pzKuWjO5A

I am happy enough with my Sinewave Revolution that I am not trying to keep up to date with newer chargers.  Thus, I am ignorant of the many other newer options.

Pass Through Cache or Buffer Batteries.  Several devices did not play well with my Sinewave Revolution without a pass through cache battery.  So I now use one of those too.  The article cited above on USB charger comparisons uses the term "buffer" battery for that type of battery and that article mentioned several small cycling specific ones. 

After having bad luck with small inexpensive pass through cache batteries that failed, I finally decided to just buy one big one that although expensive, should work well for a long time with a large storage capacity.  On a different forum, someone commented that Li Ion power banks that are sold in stores for use with solar power panels usually work well as a pass through cache battery because they are designed to work well with varying amounts of power which is what you get from solar panels on a partly cloudy day. 

And the key line here is "pass through" capability, a pass through cache battery can be charged from the hub while simultaneously being discharged to transfer power to another device.   Most power banks can't do both at the same time.  On that other forum, the writer commented that he had good performance with a Voltaic brand powerbank that are marketed for solar power users.  I bought their V44 power bank about a year ago, at 44 watt hour battery capacity, it is a good sized power bank that should be able to provide a lot of storage.  (The V44 is no longer made, they make bigger and smaller ones, but no longer that specific size.)  I have no idea if Voltaic powerbanks are sold outside USA, but there might be other brands sold in Europe that work just as well as a pass through cache battery.
https://voltaicsystems.com/battery-packs

There are other pass through cache batteries that are made specifically for cycling that have much small capacity.  For touring, I prefer a larger power bank style of battery pack that has days worth of storage capacity.  That way if I have several days in hilly terrain or several short days, I am not finding that I am running low on power.

I always use a handlebar bag when touring, the battery pack stays in the handlebar bag. 

In this forum post I am referring to my pass through cache battery as the battery pack.

Amount of Available Power.   I have measured an average of 2.5 watts of USB output from my Sinewave Revolution into the battery pack when doing an exercise ride near home for over an hour, that is mostly flat or nearly flat ground, thus not the slower speeds you have in hilly terrain, and that was on an unladen bike, thus likely a bit faster than I would average on a bike tour.  That measurement was calculated using only rolling time, as time spent at stoplights was not counted by the meter that measured electrical output.  Thus, I think on average while touring I probably get about 2 watts of output, in hilly terrain likely a bit less.  Other USB chargers may get more or less

If I get 2 watts on average from the dynohub and Sinewave Revolution USB charger, and I feed that power into the battery pack, it would take roughly 20 to 25 hours to charge up my 44 watt hour capacity battery pack from empty to full.  Thus, my battery pack is large enough to also serve as a power bank with several days of capacity, that is much larger than the smaller cycling specific pass through (or buffer) batteries that are sold as options or included with some USB chargers. 

For comparison, I also have a B&M Luxos U headlamp that also has a built in pass through cache battery and USB charger.  That battery pack is about 1 watt hour in capacity, thus it only holds about 30 minutes of power out of the hub.  I use that light with that power supply near home, but not for touring.  I only mention it here for comparison.

Some days when bike touring, I might only ride for two or three hours, but I have also had 12 to 14 hour days.  I think on average, I likely am rolling about six hours.  Thus, I am probably putting roughly 12 watt hours of power into the battery pack on days where the terrain is fairly flat.  A guess for days on more hilly terrain I am likely producing no more than 6 or 8 watt hours.  In general terms, if I am using my granny gear on my triple crank or in low range on my Rohloff bike (gears 1-7), I assume I am putting zero power into my battery pack.

It has taken me several years to come up with a solution that works well for me for touring, but my last two tours I think I got it figured out, at all times when i was rolling I was having all hub energy go into the battery pack.  Charging my GPS or phone, I charged them from the pass through battery pack while rolling.  But charging AA or AAA batteries, or charging Li Ion camera batteries, I charged them directly off of the battery pack in the campsite when I was not rolling.

Some on this forum instead charge up their powerbank while riding during the day and then use their powerbank at night to charge up their other devices.  Thus, they use a power bank that does not need to have pass through capability.  I instead prefer to use a battery pack that has pass through capability to charge phone or GPS while rolling.  Then use that battery pack to charge up other things while not rolling in the evening.  It is personal preference how and when you want to charge up your devices.  If charging everything at night in the campground works for you, great.

I do not know how much power is lost when putting a charge into a power bank and drawing it out later, but there are some losses, if you put a watt hour of power in you will not get the full watt hour out.  I have seen some estimates of up to one third of the power is lost.  But I am not making any calculations on how much power I need each day to charge everything, so I am not going to worry about that. 

Cable Quality.  The first few weeks on my five week bike tour last summer I was steadily watching my remaining power in the battery pack decline until nearly empty.  Then I figured out that I was using a high resistance cable between my Sinewave Revolution and my battery pack.  I recharged the battery pack to full in a campsite from the power supply there, after that for my remaining three weeks I used a better cable between my Sinewave Revolution and the battery pack.  I finished my trip with a nearly charged up battery pack three weeks later.

Phone and Efficient Use of Power in Phone.  One other thing that I did after having rapid loss of power in my battery pack during the first couple of weeks was to stop using my phone when it was cold.  I concluded that using my phone in the morning on wifi to check weather forecasts, e-mail, etc., when the temperature was near 40 degrees F (~~5 degrees C.) was causing rapid battery depletion compared to using a warm phone.  Thus, when I was going to use the phone in the morning for weather forecasts, I would warm up the phone in the sleeping bag first.  That greatly helped reduce my electricity consumption in my phone. 

My phone is an 5.5 inch LG Android phone. 

My phone is almost always in airplane mode or off.  Only rarely will I have the phone turned on during the daytime waiting for a call.  My trips outside of the USA, I did not buy a local sim card and my phone plan does not offer a international option, thus when outside of USA my phone becomes a wifi device only.

Some people use a phone as their GPS device.  I prefer a dedicated GPS on my handlebar.  But I have the apps Maps.Me and Komoots on my phone so that when in a campsite looking at plans for the next day, I can compare their recommended routes against my Garmin recommended route.  Komoots requires internet access, Maps.Me can be used off line if you installed the maps to the phone before your trip.  I use the free versions of these apps.  There are many other apps that I do not use, thus if you are looking for suggestions for phone navigation apps, others will have better suggestions than me.

Bike Headlamp.  When I use my S&S coupled bike for touring, it takes a long time to assemble and dis-assemble the bike for packing and unpacking.  After several tours where I installed a headlight on the bike for tunnels or night riding and then never used that light, I decided to stop installing a headlight on my S&S bike.  My last tour, I brought a small light that did not have an internal battery that I carried inside my handlebar bag that I could strap to the the handlebar with an elastic if I needed it, that light had a USB cable I could plug into  the battery pack for power.  On my last tour I never used the light, but I think you should always carry a light just in case you need it. 

ADDENDUM ADDED LATER:  I wrote this post specifically about touring on my S&S coupled bike.  But I have two other touring bikes that are not S&S coupled.  When touring on those bikes, since I do not have to disassemble and reassemble the bikes I leave a dyno powered headlamp on those bikes.  And one one of those non-coupled bikes also has a dyno powered taillight.  But those lights are typically off during a tour so I can charge batteries, I might not use my dyno powered lights at all during a tour, instead focusing on battery charging.

Other Electrical Devices Used When Touring.  This list is based on a tour where I am doing loaded touring, staying in campgrounds for a tour that lasts for several weeks, etc. If I was going for only part of a week or if I was credit card touring, the list would be much shorter.

Regarding use of AA/AAA batteries versus internal Li Ion batteries for devices like taillights, GPS, headlamp (for my head in the campsite), you can buy similar devices that have an internal Li Ion battery and can be charged with USB power.  Thus, you do not need AA or AAA batteries for a bike tour.  But I find it more convenient to be able to swap out the batteries when the batteries are low instead.  For that reason I use AA or AAA batteries for these devices.  I use NiMH batteries and recharge them as I go instead of buying disposables.  The exception is my GPS, according to Garmin, that GPS can't directly be used to charge NiMH rechargeable batteries, but there is a work around that I use to charge the AA batteries in it from USB power directly to the GPS.  Thus, I do not need to swap batteries in it.  The reason that I use a GPS that uses AA batteries is that I want one that works well for general recreation purposes, such as backpacking, canoeing, kayaking, etc., thus I do not use a cycling specific GPS.

Other devices include the following:

  -  I use a Garmin 64 GPS, that operates on AA batteries. 
  -  Headlamp (for my head in campsite), depending on which one I brought with me, one AA or four AAA batteries.
  -  Two Taillights, each powered by a pair of AAA batteries.  Planet Bike Superflash and Planet Bike Superflash 65.  I change the batteries weekly even though they still look bright, that way I always have bright taillights.  I usually have one turned on in flash mode during the day, if foggy might have both on.  If I am in Germany where flashing taillights are illegal, these lights have a constant on mode too.
  -  Phone, charged with a USB cable.
  -  Camera, Pentax WG-3.  Can be charged with a proprietary cable but instead I use a separate Li Ion battery charger, carry several spare camera batteries and change batteries as needed.  It is a small five year old point and shoot waterproof camera that I have found to work great for bike touring, especially on rainy days.
  -  Power Chimp AA and AAA NiMH charger, powered by USB cable.
  -  Lenmar Li Ion battery charger, powered by USB, use this for camera batteries.
  -  I also use a wrist watch, heart rate monitor and bicycle computer, these are powered by coin type batteries.
  -  On one tour I wanted to be able to treat water, just in case I needed to wild camp.  I did not want to carry a large filter.  I carried a Steripen that has an internal Li Ion battery that is charged by USB.  Never used it.

Closing.  I hope from describing what I use, how I use it, and why I picked what I use for electrics is helpful to others that are trying to figure out what they want to use for bike touring.

I recognize that some of my equipment choices may be a bit eccentric.  Some ultra light cyclists might choose lighter equipment, I am aware of one cyclist that only carries a tiny little light that uses a few coin batteries, the entire light is smaller than a single AAA battery.  Some prefer to use a GPS navigation app on a phone instead of a bike computer or GPS.  Some consider AA and AAA batteries to be from the bricks and mortar era, ok, I am from the bricks and mortar era too.  And some will want to use laptops for updating their blog every day.  And some will want a GoPro camera so they can show how brave they were on the downhills.  I am not saying what I use is better than what everybody else uses, I am only describing what works for me for a multi-week bike tour in case it may be of assistance to others planning such a trip.

Later I might add some photos to this thread if people are interested.  And later I might also edit this a bit and post it on another forum.  And I probably will read some statements here that make no sense later, so expect a few edits later.


ADDENDUM - Aug 9, 2022.  I recently bought a Cycle2Charge USB charger which I plan to use on future tours instead of the Sinewave Revolution that I have used.  The Sinewave still works, but the Cycle2Charge puts out more power than the Sinewave.  I wrote up a post on my initiall thoughts on the Cycle2Charge and my initial testing of it at this post:
http://thorncyclesforum.co.uk/index.php?topic=12890.msg110295#msg110295
« Last Edit: August 09, 2022, 08:05:14 PM by mickeg »

Andre Jute

  • Hero Member
  • *****
  • Posts: 4125
Re: Electrics that I use for bike touring - what works for me.
« Reply #1 on: January 29, 2020, 04:12:39 AM »
Thanks for that very useful overview, George.

You probably won't need this, because you already know your current consumption and have devices chosen accordingly. But others trying to work out how many Amp-hours (Ah) they must provide might be grateful for a device that measures consumption, with a totaliser to accumulate current draw over time:



At the left end in the photo above, you plug it into the USB outlet of the power supply and at the other end it has a socket for plugging in the device whose consumption (or recharging rate) you want to measure. The dial shows, top left of the readout window, instantaneous voltage reading which is just a check because some devices, like those from Apple, are extremely finicky about the voltage supply (this item doesn't interfere with that -- I use it with iPhones and iPads on my treadmill all the time). Top right it shows elapsed time since the recessed button on top of the meter was pressed (you can see it at the right hand side of the dial through the clear plastic); you press the button every time you want to measure a new device and it zeroes all counters. In the second line on the left you have instantaneous current draw, and to its right, a current accumulator, which is the important one.

The thing is tiny, and self-powered from the current flowing through it for measurement, and weighs only a few grammes, so you could take it on tour but it might serve better to determine how much generating power you will need before you go on tour. It's relatively sturdy. My first one lasted a handful of years or so before constant use and spills about my treadmill pulled the male USB connector out of its board. It wasn't worth resoldering it for a couple of quid, so I just bought a new one.

My latest one came from
https://www.aliexpress.com/item/32856164012.html
for a few pennies over GBP2 delivered to my door. The right version is second from the left in the first row of the purchase selector beside the first photo you see at the top of the page. This is a source for the little meter branded by its maker, but you can buy it with other brandnames on it with confidence, probably for less, because it is all the same thing made in the same place, a testament to the overproduction and waste of resources inherent in Communist central planning.
« Last Edit: January 29, 2020, 04:17:50 AM by Andre Jute »

mickeg

  • Hero Member
  • *****
  • Posts: 2790
Re: Electrics that I use for bike touring - what works for me.
« Reply #2 on: January 29, 2020, 05:56:15 PM »
Thanks for that very useful overview, George.

You probably won't need this, because you already know your current consumption and have devices chosen accordingly. But others trying to work out how many Amp-hours (Ah) they must provide might be grateful for a device that measures consumption, with a totaliser to accumulate current draw over time:
...

That is what I used to measure the output from my Sinewave Revolution into by battery pack on an exercise ride.  It gave me total milliamp hours and time that current was flowing, I assumed 5 v as USB voltage to convert to average watts. 

USB battery packs are often labeled for milliamp hour rating for the internal Li Ion battery, but that battery has a different voltage than the USB port, thus the battery pack will not have the capacity in milliamp hours at the USB port that the battery pack is rated at.  And when I also use NiMH batteries with yet a different voltage, I find it simplest to always think in terms of watts and watt hours as that takes the different voltages into account.  Thus, in my write up I only cited watts and watt hours.  And when i am making any calculations, i always convert to watts to make sure I am not getting things calculated wrong.

I also cited in my writeup that I had a high resistance cable.  Sitting in a laundry room at a campground where I decided to charge up my battery pack while doing laundry on a rainy day, I plugged my battery pack into an outlet (or mains), and using a meter like that I was surprised how slow my current flow was.  Tried a different cable, current flow nearly doubled.  That is how I discovered that I needed to change cables.  Fortunately, I had brought a meter like that on my bike tour.

In some countries I have heard that even a small item that is only worth a small amount of money can trigger a sizeable customs bill when you receive it in the mail.  I am not sure the exact customs duty rules to USA (where I live), but I think there is an exemption for anything less than $800 USD.  I bought my meter on Ebay, shipped from Asia, shipping can take a month, less than $800 so no duty when it arrived.  (When my Rohloff arrived in the mail, I was really surprised there was no duty on that either.)  Have bought several of those meters, one died and I gave one away. 

Anyone looking for one on Ebay should do a search for charger doctor and you will find several styles of such meters, some do not include time and totalizers, some do.  Change the search from most relevant to lowest cost, screen out the sellers with low ratings buy one (or a few) and be patient for shipping.

Aushiker

  • Jr. Member
  • **
  • Posts: 72
    • Aushiker: Bicycling and Bushwalking in Western Australia
Re: Electrics that I use for bike touring - what works for me.
« Reply #3 on: January 30, 2020, 10:03:23 AM »
Thanks to you both for your informative posts.

My setup is pretty similar, just that I use different tools and have different electronics.

Dynamo: SON 28 15 150 on my bikepacking  bike (Salsa Mukluk Fatbike) and a Son 28 on my Surly Long Haul Trucker
Charger: Prototype charger from Kerry at Klite.com.au - Now nicely packaged and can be found at https://www.klite.com.au/product-page/klite-usb-charger



Battery: I am going over to a Nitecore F2 with two batteries (minimum). I prefer this approach as it is very small (important on the fatbike) and light, plus it gives me flexibility in terms of the number of batteries carried.



My approach is to charge the battery during the day (and if possible phone etc) and then use the battery to top up my GPS etc as needed during the night.

My electronics are USB charged. They are:

Garmin Edge 1030 GPS
Garmin inReach MINI (only used to transmit my overnight location/ok message/SMS messages as I am often out of range)
Headlamp: Black Diamond Iota
Phone: Google Pixel 3 (left off and only turned on to send SMS and/or calls)
Tablet: Samsung Tab A 8"

I have ordered one of the suggested voltage testers from AliExpress for a whole AU $4.00 delivered to get a better idea of what is happening and to help me make a decision about the number of batteries to take.

Regards
Andrew



Matt2matt2002

  • Hero Member
  • *****
  • Posts: 1940
Re: Electrics that I use for bike touring - what works for me.
« Reply #4 on: January 30, 2020, 08:36:01 PM »
Thanks Mick.
The Voltiac products are sold in the UK by Funky leisure co UK.
The V15 is £34.99
V50 is £74.99
Never drink and drive. You may hit a bump  and spill your drink

Aushiker

  • Jr. Member
  • **
  • Posts: 72
    • Aushiker: Bicycling and Bushwalking in Western Australia
Re: Electrics that I use for bike touring - what works for me.
« Reply #5 on: June 09, 2020, 01:25:34 PM »
I purchased one of the Keweisi KWS-20 testers as recommended here and plugged into my pre-production KLite USB Charger. I went bikepacking on Monday and today. This was low-speed riding averaging just under 12 km/h over two and a half hours riding (around 30 km) each day. According to the KWS-20 the accumulated mah was only nine mAh from today's riding. The voltage was 5 volts but I didn't capture the amps (not sure if that is important or not).'

My Garmin consumes approximately 1,188 mah over days riding (around 7.5 hours). What concerns me is if these numbers are correct I am lucky if I will get 27 mAh of charging a day.  Does this sound right? Kerry's gear is normally well respected so i am a bit surprised by this. 

The cable might have part of the problem ... it is still on the bike so I cannot check right now which one I used but even still would that make a such a difference?

mickeg

  • Hero Member
  • *****
  • Posts: 2790
Re: Electrics that I use for bike touring - what works for me.
« Reply #6 on: June 19, 2020, 04:34:25 PM »
I purchased one of the Keweisi KWS-20 testers as recommended here and plugged into my pre-production KLite USB Charger. I went bikepacking on Monday and today. This was low-speed riding averaging just under 12 km/h over two and a half hours riding (around 30 km) each day. According to the KWS-20 the accumulated mah was only nine mAh from today's riding. The voltage was 5 volts but I didn't capture the amps (not sure if that is important or not).'

My Garmin consumes approximately 1,188 mah over days riding (around 7.5 hours). What concerns me is if these numbers are correct I am lucky if I will get 27 mAh of charging a day.  Does this sound right? Kerry's gear is normally well respected so i am a bit surprised by this. 

The cable might have part of the problem ... it is still on the bike so I cannot check right now which one I used but even still would that make a such a difference?

If you were putting the USB power into the NiteCore F2 that you referenced in a prior post, this Youtube video near the end of the video said that when power input to the F2 fell below 0.5 amps, it would stop charging the batteries in the F2.
https://www.youtube.com/watch?v=7p4oMn1S8HI

Thus, if your riding was mostly slow speed, perhaps the F2 did not take any power when at lower speeds and you did not get much power for the day.

I am not sure what the minimum speed would be on my Sinewave Revolution before it stops generating power, but it is a pretty low speed and at that low speed the power generated is minimal.  My Voltaic powerbank will accept power at pretty low amperage, much lower than the 0.5 amps that the video cited for the F2.  But still, low speed is not going to produce much power even if your system keeps generating.

Aushiker

  • Jr. Member
  • **
  • Posts: 72
    • Aushiker: Bicycling and Bushwalking in Western Australia
Re: Electrics that I use for bike touring - what works for me.
« Reply #7 on: June 20, 2020, 04:22:20 AM »
Thanks @mickeg. Yes, it was the Nitcore F2. I am planning to do the same ride again in a week or so but using my Surly Long Haul Trucker as a comparison test (for the charging and my overall speed) as I have three weeks ~2,000 km outback ride coming up and I cannot decide which bike to take.

I will take a closer look the amps this time to see what is coming through.

Also planning to switch out the tyres on the fatbike to Schwalbe Big Jims which according to https://www.bicyclerollingresistance.com/ have much better rolling resistance compared to the tyres I currently have on the bike and the rolling resistance is apparently on par with the Schwalbe's I have on the Surly.

Thanks for the video link. Off to take a look.

mickeg

  • Hero Member
  • *****
  • Posts: 2790
Re: Electrics that I use for bike touring - what works for me.
« Reply #8 on: June 20, 2020, 01:11:03 PM »
Thanks @mickeg. Yes, it was the Nitcore F2. ...
I will take a closer look the amps this time to see what is coming through.
...

See manual at:
https://nitecore.com/Uploads/FLASHLIGHTS/download/1515327986.pdf

Under section Product Attributes, 1. Charging batteries:
(2)  ... In the case that the power supply cannot provide enough power input to charge all batteries and the connected external device, the F2 will divert 0.5A of the total power input to charge batteries and all remaining input to charge the external device.
(3)  When input wattage is less than 2.5W, the F2 will charge with all available power input, however, the power indicator may not work properly.


So, where the youtube video says that it quits charging at below 0.5, the manual says it will keep charging but it will not send power to any device you are trying to charge.

So, I have no clue what will happen when you are going slow enough that you produce less than 0.5A, which may be much of the time.  It appears that youtube video and the manual are not in agreement.

***

I was curious if this would work for me, so I was looking into this further.  I am happy with my Voltaic powerbank that I described above, but it is big and heavy.  I was thinking that there may be applications where a smaller lighter unit might work for me, that is why I was checking out the F2.

But it is clear to me that the F2 is not what I am looking for.  I want a battery pack that I can plug my Garmin (or phone or other device) into and simultaneously also charge that battery pack with my USB charger that is powered by my dynohub.  And - here is the key point, when I am riding slowly or stop rolling, I want the battery pack to keep supplying the Garmin at an adequate rate.  It sounds to me like the F2 will cut out the power to the Garmin when my dynohub is rolling slowly.

Or more simply, I want my Garmin (or some other device) to have the priority on where the power goes, and the F2 prioritizes charging the attached Li Ion batteries instead of my Garmin.

In my case, I am not sure what the lowest speed that my Sinewave will still produce USB power when I am rolling up a hill, but at those slow speeds even if it is producing power, it is minimal.  And when I go fast down the other side of the hill, that is for such a brief period of time, not much power is generated.

After trying lots of different small pass through cache batteries (some did not work and some worked for a few years before dying), that was why I finally decided (over a year ago) to buy that Voltaic at 44 watt hour capacity.  That is big enough that if I am using power faster than I am generating it with my dynohub, at least I have several extra days of surplus power so I do not have to worry day by day on my power status.

I like the concept of the F2, you can carry spare batteries for it so if you want more storage capacity you simply swap batteries.  That is why I had interest in it.