How to build a Li-Ion charger myself (windmill, generator, solar cells)??
lucas...@gmail.com
1. On my self suppored bicycle trips around the world I want to use a
digital camera.
2. I have faced reality and accepted that most digital cameras use
Li-Ion batteries, which makes them very small and handy.
3. Currently I'm interested in a Sony DSC-T7 which uses a Li-Ion
battery. The battery specs can be found here:
http://www.calcellular.com/np-fe1.html
4. I don't want to carry a regular charger but I want to use either a
regular bike generator (the ones powering for front and rear light on a
bicycle), solar cells or a home-built mini wind mill which can be
mounted on the bicycle and produce electricity during the night.
So the question is:
Is it possible to build my own Li-ion charger if I have a varying power
source such as a wind mill? I know that Li-ion batteries are difficult
to charge and that they may be damaged if treated wrongly. I have seen
in some other threads that companies such as Texas Instruments are
offering special ICs. What about the small motor/generator for such a
mini wind mill application - does anybody have recommendations? Are
there some published circuits on the internet which I could use?
Regards, Lucas Jensen
Funfly3
0.7C and set a maximum voltage of 4.2 per cell and your done
http://www.shdesigns.org/lionchg.html
<lucas...@gmail.com> wrote in message
news:1130490715.1...@f14g2000cwb.googlegroups.com...
mike
A couple of cautions.
Most people who design simple chargers on the back of an envelope don't
pay attention to the little details. They build one and it works for
their limited application. Then someone else tries to use the design
in a completely different application and has difficulties.
With a bike generator, you're gonna have voltage going all over the
place. That doesn't have to be a problem as long as you design for it.
You're gonna want spike protection on the input so the regulator doesn't
short and apply max current/voltage and blow up your battery.
Worry about transient conditions. The power on transient may not be a
big deal, unless you're sitting on the edge and the transient condition
happens on every pedal stroke. Your average charge condition may not be
what you think. If you use an IC, it may be resetting itself a lot.
Or may get stuck in a condition that it can't recover from.
Ics have safety timers. If it keeps getting reset, that feature
is ineffective.
IF your generator can't supply enough power at the current instant,
the charge current will drop. When the power comes back up, so will the
current and the battery voltage. This will confuse the hell out of the
charge termination algorithm.
Again, not problems unless you don't design for 'em and evaluate under
all possible conditions.
Current limit with voltage limit is probably what you want, but torture
test it under widely varying input conditions with a scope looking at
the outputs.
mike
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with links. Delete this sig when replying.
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Jasen Betts
> So the question is:
> Is it possible to build my own Li-ion charger if I have a varying power
> source such as a wind mill? I know that Li-ion batteries are difficult
> to charge and that they may be damaged if treated wrongly. I have seen
> in some other threads that companies such as Texas Instruments are
> offering special ICs. What about the small motor/generator for such a
> mini wind mill application - does anybody have recommendations? Are
> there some published circuits on the internet which I could use?
if you can get an off-the-shelf charger that uses an external low volltage
DC source that may simplify your task. then all you need is a windmill that
can make 12V (etc...)
--
Bye.
Jasen
Dave D
>
> 1. On my self suppored bicycle trips around the world I want to use a
> digital camera.
> 2. I have faced reality and accepted that most digital cameras use
> Li-Ion batteries, which makes them very small and handy.
But some don't. It would be far easier for you if you find one which can use
AA alkalines and AA rechargeables.
> 3. Currently I'm interested in a Sony DSC-T7 which uses a Li-Ion
> battery. The battery specs can be found here:
> http://www.calcellular.com/np-fe1.html
> 4. I don't want to carry a regular charger but I want to use either a
> regular bike generator (the ones powering for front and rear light on a
> bicycle), solar cells or a home-built mini wind mill which can be
> mounted on the bicycle and produce electricity during the night.
>
> So the question is:
> Is it possible to build my own Li-ion charger if I have a varying power
> source such as a wind mill?
The Li-Ion based cameras I've seen have the charging circuit built into the
camera itself, and the mains adaptor is just a regulated supply. If you are
prepared to charge the battery in the camera, although it may be less
convenient, it would make things a lot simpler.
Here's how I might do it-
You need to find out the voltage of the mains adaptor, let's say it's 6V,
but double check your camera before plugging anything homebrew into it!.
It's essential that the camera sees a constant and well regulated 6V
throughout the charge cycle, don't power it from the dynamo on your bike or
a windmill, at least not directly. You'll at best find the battery never
charges properly and at worst you'll destroy your camera.
What I suggest is a car type arrangement. Use your bike's dynamo (these are
usually around 6V AC IIRC so you'll need to rectify to DC ) to charge either
a 6V lead-acid gel battery or 5 NiMH cells, using appropriate charging
techniques.
Build a voltage limiter to keep the battery output voltage below, say, 6.1V.
A crowbar circuit to prevent catastrophies is recommended. Feed the DC from
the battery into the adaptor input on your camera. An inline fuse would be a
wise move.
The battery should ensure that the voltage stays fairly constant, and if you
choose large enough capacity cells, it should keep charging the Li-Ion
battery when you aren't pedalling, and may even be able to completely charge
the camera overnight while you sleep. IOW, the bike battery charges during
the day, then it charges your camera overnight.
You could even wire your lights into it so they stay on when you stop
pedalling! You'd need to increase the capacity for this.
So basically I'd aim to charge the camera with a battery, which in turn
would be topped up by the bike's dynamo. This is exactly what happens when a
mobile phone is charged via a cigar lighter socket on a car.
This is just a very rough idea, it would need to be well thought out before
implementing. I believe that if it's done properly, it would work out rather
well.
Dave
Kryten
> news:1130490715.1...@f14g2000cwb.googlegroups.com...
>>I have a crazy idea:
>>
>> digital camera.
>> 2. I have faced reality and accepted that most digital cameras use
>> Li-Ion batteries, which makes them very small and handy.
Charging Li-Ion cells is non-trivial - they can overcharge and die
catastrophically.
>> So the question is:
>> Is it possible to build my own Li-ion charger if I have a varying power
>> source such as a wind mill?
Possible - yes, simple - no.
You'd need a gadget to get a decent steady supply from the dynamo/windmill,
and then you need a charger smart enough to manage Li-Ion cells.
lucas...@gmail.com
I've been searching the internet for suitable AA battery cameras, but
they are all too bulky. I understand that you want to stabilize the
voltage my means of a battery pack in between. But this is not a
working solution, because the entire system has to be really
lightweight. I know of some chips called something like 7805. They are
designed to give a constant output voltage as long as the input voltage
stays above a certain value. The 7805 would give a 5 V output. Frankly,
I hate the bike generator solution the most because it gives more
friction which I personally hate. I would rather stay with the mini
wind mill or the solar cell. As for the solar cells, they readily
produce DC current at a defined voltage. As I remember a solar cell
will always produce the same voltage if exposed to the same light
soruce (for instance the sun) and only the intensity will determine the
current. This means that you should have a fairly stable voltage but
alternating current (due to clouds etc).
Lucas
Jim Thompson
LiIon cells are "managed" both in charging AND discharging. It's not
a trivial task to build your own. I would suggest purchasing a
commercial unit.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
James Sweet
Sure it can be done, have a look at www.maximic.com, they make a whole
range of Li-Ion charger IC's, and you can even get free samples to play
with. As for the generator, you could regulate the output with a small
high efficiency switchmode regulator, National Semiconductor makes a
line of those which are very easy to work with, and again samples are
available.
sandra....@zonnet.nl
Jim Thompson schreef:
> >Charging Li-Ion cells is non-trivial - they can overcharge and die
> >catastrophically.
>
>
> LiIon cells are "managed" both in charging AND discharging. It's not
> a trivial task to build your own. I would suggest purchasing a
> commercial unit.
>
Don't worry. Your Li-Ion battery is NOT managed.
Adhere to Funfly3.
Charging your battery is like charging a lead-acid battery: Constant
voltage with current limiting. Correction for temeprature might be
required. That is where the third connection is for. As far as I know
there is no standard for a temperature sensing element in Li-Ion
battery packs, so you have to find out!
Take care, but don't be afraid for explosions etc. Li-Ion battery packs
are internally protected by means of
(1) discharge valve. prevents pressure build-up inside the cell
(2) thermal fuse
(3) semiconductor fuse
So, if you do something wrong, the battery pack will be defective, but
will not explode.
Reason for "managing" Li-Ion battery packs (the ones with 4 or 5
connections) is
a) For "fuel gauging". As the discharge characteristic of a Li-Ion
battery is almost flat, it is almost impossible to determine the
state-of-charge from the battery voltage
b) For faster charging. Using appropriate algorithm can charge
batteries faster
c) Universal battery chargers. The battery charger can obtain battery
pack data from the battery pack.
The "managed"battery packs have a serial interface (normally the Smart
Battery Bus) for communication between battery and camera or charger.
Funfly3
"mike" <spa...@netscape.net> wrote in message
news:4361FB43...@netscape.net...
charged and the current will have dropped to zero, there are plenty of 12v
chargers for the model industry and all these just limit the current and
voltage even a school boy could design one, ask on one of the radio control
groups as we are big users of Li-Ion and Li-Po batteries from 3.6 volts to
40+ volts and current ratings from MAh to tens of amp hours I have a $10
charger that will charge 1 to 3 cells at various current
Rich Grise
I'd try to arrange it so that the windmill turns the same bike generator -
just gear it suitably. I'm also thinking some kind of vertical windmill,
maybe even with a telescoping shaft, but then you'd need guy wires
or something...
Have Fun!
Rich
PeteS
<<Charging your battery is like charging a lead-acid battery: Constant
voltage with current limiting.>>
Bzzt. You missed an important point.
A Li+ battery *can* be constant voltage charged (if you can live with
the loss of life - figure 60% vs. constant current / constant voltage),
but what you forgot is the voltage limiting. Never charge a Li+ to more
than 4.2V per cell unless you want to see interesting light and nasal
effects (I know this to be a fact - I have a charger where the voltage
management failed).
Cheers
PeteS
Funfly3
"PeteS" <p...@fleetwoodmobile.com> wrote in message
news:1130532448....@g44g2000cwa.googlegroups.com...
current limiting ,at the beginning of the charge the current is the limiting
factor at the end voltage is the limiting factor?
Kryten
http://www.batteryuniversity.com/
for all you need to know about batteries.
How often do you expect to use your camera, and will you need a flash. Once
you fill a card, you will have to store or send it somewhere: will you be
carrying a PC or PDA around too? If so, that is going to need power as well.
Theft is a risk, if you are travelling outside the first world - carrying
something worth say $600 is the same sort of temptation to a desperately
poor person as ten to a hundred times that amount is to someone in an
affluent country.
It is a bit strange that in 1990, I simply mailed my films home.
In 2005, the memory cards are too expensive to mail home and buy new ones.
So you need an expensive gadget to do this for you.
Maybe one day cameras will be able to send photos somewhere safe via the
cellphone network. I know some phones can do this but they are generally
rather low resolution compared with proper cameras, but I was thinking more
about a simple phone tacked onto a camera than a simple camera tacked on a
mobile phone.
However I can see the appeal of what you are doing.
There must be a market for a power supply for the technovagrant :-)
budgie
>chargers do not need any algorithms as when each cell gets to 4.2 volts its
>charged and the current will have dropped to zero
BZZZZZTT! Wrong. As anyone who has worked on the design of CC/CV chargers
would know, when transition from CC to CV occurs, the cell is about 60% charged.
Also, the current does not "drop to zero" at transition - rather it starts an
almost exponential decay from the CC value. Typically this will take 2 hours or
more to drop to 10% of the CC value.
Chris Jones
The above idea about using a second battery to power the camera seems likely
to work. If you want to charge the battery outside the camera then the
following information might be of use:
It looks like your battery is a single cell.
Some information on charging lithium batteries is here:
http://www.energyplus.com/articles/Panasonic_LiIon_Charging.pdf
Most lithium packs have built-in MOSFETs and protection circuitry to
disconnect the battery from the terminals if any cell is charged over some
very accurate threshold which (according to Panasonic) is 4.30V +/- 0.05V.
The safety circuit will probably also disconnect if you try to discharge
the cell to too low a voltage, i.e. it disconnects at 2.3V +/-0.1V, but you
shouldn't discharge it below 3V. Don't rely on the safety circuit to
control your charging, it is meant as a backup, and I wouldn't be surprised
if once it disconnects, it's time to buy a new battery pack.
If you are charging single cells, then the important things are:
Never exceed 4.2 Volts/cell, regardless of current or anything else. For
some cells this should even be 4.1 Volts, depending on the cell chemistry.
This needs to be an accurate regulator (1% accuracy will do).
Never exceed the current limit specified for the cell (which is usually
about 0.7C, i.e. the current you would have to draw to flatten the cell in
one hour). For your battery it would be about 0.45 Amps
Never flatten the battery below about 3V or so, nor allow it to
self-discharge below about 2.5V, the battery will undergo permanent damage
and some people say it becomes dangerous. Basically don't store them
completely flat for long periods. I have seen it suggested that optimum
life results from storing with 40% charge in the battery.
If the battery happens to have a voltage below 2.9V, the charger is supposed
to reduce the charging current to 0.1C (the amount of current that would
flatten a charged battery in 10 hours). This would be 68mA for your
battery. If you can manually verify that you haven't flattened it this far
then that ought to suffice.
So you need to limit the current to 0.45Amps and you need to limit the
voltage very accurately to 4.1 or 4.2V. If the voltage has reached 4.2V
and the current dies down to 0.1C (68mA for you) then the battery is full
and you should disconnect it for best life, though I don't think it is
dangerous to continue charging it at 4.2 Volts.
There are 'intelligent' charging chips available from several manufacturers
that will manage the whole charging cycle, but these chips would probably
expect a steady and constant supply voltage from start to finish which you
will not have unless you use the second battery route when you might as
well use the camera's internal charging circuit.
Since you require opportunistic charging, I would suggest rectifying the
generator output and filtering it with a big electrolytic capacitor, and
limiting the peak voltage with a zener diode of perhaps 8.2V, 5 Watt or
whatever power rating you find necessary. This can then be applied to a
non-intelligent charging IC such as the ADP3820.
http://www.analog.com/UploadedFiles/Data_Sheets/490002128ADP3820_a.pdf
Chris
stor...@gmail.com
Bob Monsen
You should use a set of solar cells. A windmill would be pretty annoying,
and probably powered by your legs rather than the sun.
If you only want to charge a single cell (4.2V) you can use a 6V solar
cell pad. Limiting the current to 0.5C won't be an issue with solar cells,
assuming you don't go nuts and buy too many. The cells are generally
speced for a particular current. The voltage limit will be the main issue.
Use a regulator, like an LM317 (see the datasheet at www.national.com for
an appropriate circuit). You can get these at radio shack, where the
packages have schematics on the back. A small 1 hour timer would be a good
thing.
Look here and elsewhere for information on solar cells:
http://www.siliconsolar.com/portable_power_system.htm
---
Regards,
Bob Monsen
It is mathematics that offers the exact mathematical sciences a certain
measure of security which, without mathematics, they could not obtain.
- Albert Einstein
mike
OK, sanity check.
You are not gonna pack a windmill on your bicycle. File that under,
"sounded like a good idea at the time."
You are not gonna build fixtures to hold all your batteries for external
charging poking out all over your bike rugged enough to hang onto the
batteries when you ride down that mountain trail. File that the same place.
Get yourself 10 high capacity AA NiMH cells and pack them into a thing
that snaps on like a tire pump. Hook them up to your bike generator and
charge the crap out of them. Use a thermal cutout in series that opens
when they start to get warm. Do some experiments using your typical
riding speed to see if you are applying way too much charge current and
add a resistor as required.
Don't worry too much about properly charging the NiMH. Just let the
overtemp switch take care of it. Might want an indicator so you can
manually switch 'em off. Plan on throwing them out when your trip is done.
At night, snap off the cell pack and use adapters with fixed voltage
outpts to connect to your devices for charging. Let the device manage
its own charge/discharge. You can charge multiple devices
simultaneously until you run out of energy.
Not the most efficient way, but at least it's practical.
przemek klosowski
> LiIon cells are "managed" both in charging AND discharging. It's not a
> trivial task to build your own. I would suggest purchasing a commercial
> unit.
http://www.stensat.org/Docs/battery_test_results.pdf describes an
actual test showing that they are surprisingly robust. I was surprised to
learn that discharging dead short didn't kill the pack. On the other hand,
long-term short (over a day) and overcharging tend to do Li-ions in.
Jasen Betts
On 2005-10-29, Kryten <kryten_droid...@ntlworld.com> wrote:
> To save long on-line discussions, got to:
> http://www.batteryuniversity.com/
> for all you need to know about batteries.
>
> How often do you expect to use your camera, and will you need a flash. Once
> you fill a card, you will have to store or send it somewhere: will you be
> carrying a PC or PDA around too? If so, that is going to need power as well.
> Theft is a risk, if you are travelling outside the first world - carrying
> something worth say $600 is the same sort of temptation to a desperately
> poor person as ten to a hundred times that amount is to someone in an
> affluent country.
>
> It is a bit strange that in 1990, I simply mailed my films home.
so email the photos home, or to an account on gmail.com etc...
public email terminals are a little harder to find that postoffices, but
only a little harder.
Bye.
Jasen
Jasen Betts
Will charging them at a lower voltage or current damage them ?
ISTM that if the poster correctly implements a current and voltage
limited charger using his portable windmill, then the worst that
can happen is that his batteries don't get charged when there's no
wind.
during periods of low wind the charge current may be less than optimum
(or the voltage may be below the limit) but is that goinmg to be a
problem?
Bye.
Jasen
stic...@gmail.com
you have an important advantage: this newsgroup. There is nothing
magical about Li-Ion batteries. Of course, if you are launching them
into space and you need them to work reliably for fifty years, you
could spend the next few years researching the topic, but if you need
them to work reliably for one bicycle tour at a time without exploding,
I'm sure you can come up with a suitable design.
Besides, there really can't be much of a commercial market for a
human-powered battery charger. Most people are too lazy to plug
rechargeable batteries in and just use the disposable ones. Imagine
having to pedal!
Are there currently any, or have you considered building,
bicycle-powered 110V generators? You could bring your wall-wart along
for the ride and charge other gadgets as well.
Funfly3
"Jasen Betts" <jas...@free.net.nospam.nz> wrote in message
news:mh2c33-...@news.compass.net.nz...
charge and if you go below 2,8v a cell most will just give up and die
clifto
> http://www.stensat.org/Docs/battery_test_results.pdf describes an
> actual test showing that they are surprisingly robust. I was surprised to
> learn that discharging dead short didn't kill the pack. On the other hand,
> long-term short (over a day) and overcharging tend to do Li-ions in.
I have a pair of packs (old cell phones) that aren't worth their weight
in potato chips after being stored mostly charged for a couple of years.
They were rather good when in regular use.
--
If John McCain gets the 2008 Republican Presidential nomination,
my vote for President will be a write-in for Jiang Zemin.
Rich Grise
> budgie wrote:
>> On Fri, 28 Oct 2005 19:41:22 GMT, "Funfly3" <donte...@ntlworld.com> wrote:
>>
>>>chargers do not need any algorithms as when each cell gets to 4.2 volts its
>>>charged and the current will have dropped to zero
>>
>> BZZZZZTT! Wrong. As anyone who has worked on the design of CC/CV chargers
>> would know, when transition from CC to CV occurs, the cell is about 60% charged.
>> Also, the current does not "drop to zero" at transition - rather it starts an
>> almost exponential decay from the CC value. Typically this will take 2 hours or
>> more to drop to 10% of the CC value.
>
> OK, sanity check.
> You are not gonna pack a windmill on your bicycle. File that under,
> "sounded like a good idea at the time."
> At night, snap off the cell pack and use adapters with fixed voltage
> outpts to connect to your devices for charging. Let the device manage
> its own charge/discharge. You can charge multiple devices
> simultaneously until you run out of energy.
>
> Not the most efficient way, but at least it's practical.
Or, he could even get one of those stands that lifts the back tire off
the ground, and pedal while he watches TV at camp. :-)
Cheers!
Rich
Rich Grise
Just rectify and filter the 12V from the generator and use a 110V
inverter. You could probably build a 25-watt inverter in about the
space of a couple of packs of cigarettes.
Cheers!
Rich
Chris Jones
Better to use a low-dropout regulator rather than the LM317, otherwise
you'll waste a good fraction of your hard-won solar power in the regulator.
Chris
Chris Jones
>[...]
> Just rectify and filter the 12V from the generator and use a 110V
> inverter. You could probably build a 25-watt inverter in about the
> space of a couple of packs of cigarettes.
>
> Cheers!
> Rich
energy is wasted in a wall-wart or cheap inverter when one must generate
that power through one's own muscles.
Chris
jay_be...@hotmail.com
from 10 AA NimH rechargable batteries. I'll charge them at anyplace I
can..ie restaurant, hostel, local's willing to trade a few cents worth
of power for some stories of the road. I'll get a universal smart
charger that is good for 110-240 volt..good for the whole world.
Charge the pack up and power your camera for hours or use the pack to
recharge your cameras batteries several times. You'll pedel by power
sources daily..even in africa, bolivia, mongolia. It gives you a
chance to meet more people. Cycling is a lonely hobby. Does anyone
out there forsee any problems with this project...besides a little more
weight? I plan to hook the battery pack up to a female car cigarrett
lighter adapter so I can plug my cameras male adapter or mp3's male
adapter into it easily...this will cut the 12 volts down to the 4 or
the 5 needed for my different devices. Will this be inefficient? any
help would be great.
Good luck on your trip. May tail winds be with you.
Jay
jay_be...@hotmail.com
http://www.hotmp3gear.com/powerrunner.htm
I'd buy it, but I'm cheap..and yes the sad truth is that theft is a
great possiblity on long distance cycle trips. Back up those picks at
every cyber cafe you come to (there are thousands in Central South
America and South East Asia...people in those countries cant afford a
home pc so they go to cafes that charge 20 cents an hour) Cafes are
harder to find in the first world. Send the cds home via airmail.
This device is heavy. Lighter if you dont need the charger and can use
the generator to charge the Nimh battery pack. Just pack well. People
pack way too much junk they dont need on trips like this. Cut weight
in other places. You only need a few changes of clothes...you WILL
stink no matter how many undies you have.
Sorry if this has turned into a backpacker/Cycler forum.
Jay
Zak
> Better to use a low-dropout regulator rather than the LM317, otherwise
> you'll waste a good fraction of your hard-won solar power in the regulator.
Even better to use a shunt regulator: no voltage loss.
Thomas
Rich, Under the Affluence
I'm going to have to get to work on my recliner bike design - it has
a novel feature: a gearless gear shift. :-) But the point would be that
you could kind of kick back and pedal, which just kinda intuitively seems
like it'd be less work than sitting on top of a conventional bicycle.
There might even be a way to couple hand movements into the drive mech,
since you'll be sitting still, watching TV. :-)
Cheers!
Rich
Eric R Snow
>I have a crazy idea:
>
>1. On my self suppored bicycle trips around the world I want to use a
>digital camera.
>2. I have faced reality and accepted that most digital cameras use
>Li-Ion batteries, which makes them very small and handy.
>3. Currently I'm interested in a Sony DSC-T7 which uses a Li-Ion
>battery. The battery specs can be found here:
>http://www.calcellular.com/np-fe1.html
>4. I don't want to carry a regular charger but I want to use either a
>regular bike generator (the ones powering for front and rear light on a
>bicycle), solar cells or a home-built mini wind mill which can be
>mounted on the bicycle and produce electricity during the night.
>
>So the question is:
>Is it possible to build my own Li-ion charger if I have a varying power
>source such as a wind mill? I know that Li-ion batteries are difficult
>to charge and that they may be damaged if treated wrongly. I have seen
>in some other threads that companies such as Texas Instruments are
>offering special ICs. What about the small motor/generator for such a
>mini wind mill application - does anybody have recommendations? Are
>there some published circuits on the internet which I could use?
>
>Regards, Lucas Jensen
Lucas,
I have been reading some of the posts here and have a suggestion.
First, I'm not very knowledgeable in electronics so take what I say
with a grain of salt. Anyway, here's what I found when researching
battery chargers and batteries for use in digital cameras. Buy a
camera that can use AA size batteries. Many cameras that do will
accept alakiline batteries, NiMh batteries, and lithium ion batteries.
Buy a charger that will charge NiMH batteries and power this charger
from the bicycle charger. Keep a lithium battery or two in you
backpack as backup. These batteries are light and have a very long
shelf life. If you get in a situation where the Nimh batteries are
dead and the LI ion batteries are dead, then you should be able to buy
batteries to tide you over until the charging situation is fixed.
Since you will have up to 4 choices of batteries to choose from your
power needs are quite flexible. Finally, NiMH batteries are much more
tolerant of bad charging situations. Li polymer and Li ion batteries
can explode or catch fire. Because of this some (maybe all) Li
batteries have a device built in to prevent overheating the battery.
I buy batteries and chargers from Thomas Distributing. This company
was well recommended by more than one person and web site. I have no
interest in this company, just a satisfied customer.
Cheers,
Eric
peter
input for in-car use. Of course these could be powered from any 12v
source, so you could charge a bullet proof pack of nicads from your
cycle generator, I suggest a simple full wave rectifier charging 2 or 3
cells in series at a time and then power the Li-ion charger from 9 or 10
cells in series. I suggest nicads because they have the best tolerance
to abuse. I know it's a 2 step process, but it's simple and the tricky
bit can be handled by a professionally manufactured gizmo.