Modern LED lamps don't use a huge amount of electricity but on a long expedition I believe that a lot of batteries need to be taken. Has anybody explored the idea of a charger for use underground?
A waterwheel driven gadget that could be placed in a waterfall or a fast bit of water?
The energy given off as heat when I descend a large pitch must be huge, any ideas on how to harness that energy and charge a battery? Better yet harness the energy and use it to power a winch to get me back up!

ALEXW said:

on a long expedition I believe that a lot of batteries need to be taken.

Click to expand...

Is this really true, though? The weight of the batteries would most likely equal the weight of any charging device that might be taken along, and the latter would surely cost more than the former.

A geek could undoubtedly make a dynamo which clamps onto rope and generates a storable charge while you drag it down long abseils en route.

http://www.treehugger.com/clean-technology/river-powered-personal-charger-expands-energy-options-for-the-outdoorsy.html

Another option: http://www.gizmag.com/powertrekk-2-in1-battery-hydrogen-portable-charger-unveiled/17870/
Review: http://www.off-grid.net/2011/02/21/water-powered-charger/

Mike

Depends what lamp you're using and what batteries it requires I guess. If it's your normal everyday batteries then a bulk pack of them is probably far cheaper than any charging solution.

Modern LED caving lamps are usually supplied with their own batteries and last a fair while on a modest setting - a few batteries may be costly and probably equal to a charging solution but bear in mind size/weight - even if batteries cost a bit more, I'm pretty sure a few batteries would be less hassle to drag through a cave than a charger.

Guess it utlimately depends how long is a long expedition 

Petzl reckon that with "normal" AA batteries, you can get usable light for over 150 hours from a standard Duo.

I've tried mine by leaving it switched on at home and got over 4 days out of 2000mAh rechargables.

Unless your going for a really long exped, 3 sets of AA's (12 batteries) should be plenty, even if you left the lights on while you were asleep

Been looking into this for years :^) Not for lights really, LEDs are fairly efficient, but to charge drill batteries (carrying lead acid batteries out from the bottom of a cave past epic pitches and waterfalls to charge on a solar panel seems ludicrous).

Our best choice was capturing a stream over a 10-20m drop, channelling it into lay-flat tubing (which can take the header pressure, and is wide enough to not limit the system due to friction) and then driving a permanent-magnet DC centrifugal pump backwards as a generator. Back of the envelope calculations suggested 10-20W was easily achievable with a 'Daren drum' of material, and would be sufficient to charge a drill battery overnight.

Jessop: that's completely in disagreement to my own findings.
With a Duo at a sensible light output, you get about 8 hours before it falls off. This makes sense as you've about 10 Watt-Hours of power in a set of 4AAs, around 100 lumens is a minimum amount of light to (enjoy) caving off, and LEDs are around 100 lumens / Watt in efficiency depending on how old they are + how much is wasted in the optics.

Mikem: Interesting links!
The 'Fuel cell' designs seem a bit of a joke, tiny amount of power + you're basically carrying in a hydrogen battery.
The 'river charger' makes much more sense (proper hydro power - make use of the energy that forms the cave systems!), but these propeller designs are the exact opposite of what you could make use of in a cave (where the flow rate is small but the height change is relatively large).

Here's a quick overview of what we were working on:
Vodna Sled 2010 Hydro Design - Overview

And some pics of a cheap ?20 waterproof pump that we were planning to run backwards.
http://jarvist.posterous.com/pico-hydro-for-deep-alpine-caving

The technology is simple - Victorian engineering with the benefit of modern materials and electronics. However, there's always a project that is slightly higher up the priority list & there's never enough hours in the day nor days in the week.

Bicycle hub dynamo:
http://www.roseversand.com/article/shimano-hub-dynamo-dh-3n20/aid:355676  (?26)
Coupled with the circuitry here:
http://www.forumslader.de/Akkus-fuer-12V-Lader.189.0.html  (in German but I'm doing an English translation at the moment for him)
Circuitry basically a frequency matched bridge rectifier with a CCCV charging circuit plus some protection circuitry for when the battery is full and the dynamo is still pumping power into the circuit.

Most expeditions are in summer, and to brighter places than here, wouldn't solar be the simplest option for batteries of AA size?

Drill batteries are probably going to struggle, 48V batteries in the latest bad boy Hilti drill.

If the expedition is in Spain, you could rig up a twenty or so oranges to charge an AA pack?

Actually, probably need 2000 oranges if the wikipedia number crunching is to be believed.  0.9V per lemon at 0.00003A. :read:

Biffa - how would / do you spin the hub dynamo?

We considered taking a hub dynamo + small bicycle wheel (such as a 16-inch brompton) and building some kind of heath-robinson waterwheel - but it seemed a difficult object to take underground without bending!

The little regulator circuit looks pretty neat - the Red LED lights up when over-charging I guess?

Does anyone have much experience of using solar mats for recharging drill batteries and/or re-chargables for hi-output led divelights.

I'm thinking of more remote areas - maybe lots of sun areas - were mains charging is not an option and batteries are specialised and not taken in great quantities.

What wattage output would be required for a solar mat? Cost? Availability?

Yes - we've used them for 15+ years on Migovec in Slovenia.

Currently the mono crystalline panels from China are the cheapest ones to buy - an 80W (peak) panel should be around ?110 from a UK source. They're heavy but come with a pretty hardy frame. Lighter, semi-flexible, panels are much more expensive + often lower efficiency.

Here's our new (2011) 80W panel having just been carried up, next to an old 30W semi-flexible and a 13W amorphous:
http://union.ic.ac.uk/rcc/caving/photo_archive/slovenia/2011/2011-08-04-12.28.43-Jana%20Carga-Canon%20350D.html

For most of the mountainous limestone regions in Europe, insolation in the summer seems to work out to be around 3-4hrs of 'peak sun' per day, which if you combine with your 'current at maximum power point' will give you some idea of how many Ahrs / day / Wp you get:
http://en.wikipedia.org/wiki/File:SolarGIS-Solar-map-Europe-en.png

The panels are connected to lead acid batteries via standard 12V solar regulators (we have fairly small lead acids that only hold about a full sunny days worth of charge), from this stabilised 12V supply we then run a hobby charger to charge drill batteries, charge the laptop, run USB adapters for phones, charge AA batteries etc.

And if you need more power i can sell 190W and 250W mono crystalline panels for ?0.70/W.
http://www.fusiongsource.com/files/2013/3949/5662/G-Source_Ulica_250W_60-cell.pdf

Be aware the voltage and current are very high so you may need a bigger 12v regulator than the 'normal' ones, however i'm sure someone on here will know of one suitable...

jarvist said:

Biffa - how would / do you spin the hub dynamo?

We considered taking a hub dynamo + small bicycle wheel (such as a 16-inch brompton) and building some kind of heath-robinson waterwheel - but it seemed a difficult object to take underground without bending!

Click to expand...

You need some folding wheels

Those wheel chairs are ace!