| Author |
Message |
Guest
|
 Posted:
Fri Oct 28, 2005 2:11 pm Post subject:
How to build a Li-Ion charger myself (windmill, generator, s |
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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
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Funfly3
Guest
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| Posted:
Fri Oct 28, 2005 2:56 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
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These cells are one of the easiest types to charge just limit the current to
0.7C and set a maximum voltage of 4.2 per cell and your done
http://www.shdesigns.org/lionchg.html
<lucasjensen@gmail.com> wrote in message
news:1130490715.159698.124860@f14g2000cwb.googlegroups.com...
| Quote: | 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
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mike
Guest
|
| Posted:
Fri Oct 28, 2005 3:19 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
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|
Funfly3 wrote:
| Quote: | These cells are one of the easiest types to charge just limit the current to
0.7C and set a maximum voltage of 4.2 per cell and your done
http://www.shdesigns.org/lionchg.html
lucasjensen@gmail.com> wrote in message
news:1130490715.159698.124860@f14g2000cwb.googlegroups.com...
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
|
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
--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
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Jasen Betts
Guest
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| Posted:
Fri Oct 28, 2005 4:35 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
["Followup-To:" header set to sci.electronics.basics.]
On 2005-10-28, lucasjensen@gmail.com <lucasjensen@gmail.com> wrote:
| Quote: | 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 |
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Jim Thompson
Guest
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| Posted:
Fri Oct 28, 2005 4:35 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
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On Fri, 28 Oct 2005 15:27:32 GMT, "Kryten"
<kryten_droid_obfusticator@ntlworld.com> wrote:
| Quote: | lucasjensen@gmail.com> wrote in message
news:1130490715.159698.124860@f14g2000cwb.googlegroups.com...
I have a crazy idea:
1. On my self supported 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.
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.
|
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. |
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Guest
|
| Posted:
Fri Oct 28, 2005 4:35 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
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Hi Dave,
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 |
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Dave D
Guest
|
| Posted:
Fri Oct 28, 2005 4:35 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
<lucasjensen@gmail.com> wrote in message
news:1130490715.159698.124860@f14g2000cwb.googlegroups.com...
| Quote: | 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.
|
But some don't. It would be far easier for you if you find one which can use
AA alkalines and AA rechargeables.
| Quote: | 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 |
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Kryten
Guest
|
| Posted:
Fri Oct 28, 2005 4:35 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
| Quote: | lucasjensen@gmail.com> wrote in message
news:1130490715.159698.124860@f14g2000cwb.googlegroups.com...
I have a crazy idea:
1. On my self supported 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.
|
Charging Li-Ion cells is non-trivial - they can overcharge and die
catastrophically.
| Quote: | 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. |
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James Sweet
Guest
|
| Posted:
Fri Oct 28, 2005 9:53 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
lucasjensen@gmail.com wrote:
| Quote: | 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
|
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. |
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Guest
|
| Posted:
Fri Oct 28, 2005 10:00 pm Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
Jim Thompson schreef:
| Quote: | 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. |
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PeteS
Guest
|
| Posted:
Sat Oct 29, 2005 12:35 am Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
Sandra wrote:
<<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 |
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Kryten
Guest
|
| Posted:
Sat Oct 29, 2005 12:35 am Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
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|
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.
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 :-) |
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Rich Grise
Guest
|
| Posted:
Sat Oct 29, 2005 12:35 am Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
On Fri, 28 Oct 2005 02:11:55 -0700, lucasjensen wrote:
| Quote: | 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?
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 |
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Funfly3
Guest
|
| Posted:
Sat Oct 29, 2005 12:35 am Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
"mike" <spamme0@netscape.net> wrote in message
news:4361FB43.4040106@netscape.net...
| Quote: | Funfly3 wrote:
These cells are one of the easiest types to charge just limit the current
to 0.7C and set a maximum voltage of 4.2 per cell and your done
http://www.shdesigns.org/lionchg.html
lucasjensen@gmail.com> wrote in message
news:1130490715.159698.124860@f14g2000cwb.googlegroups.com...
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
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.
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, 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
| Quote: | 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
--
Wanted, Serial cable for Dell Axim X5 PDA.
Return address is VALID but some sites block emails
with links. Delete this sig when replying.
FS 500MHz Tek DSOscilloscope TDS540 Make Offer
Bunch of stuff For Sale and Wanted at the link below.
MAKE THE OBVIOUS CHANGES TO THE LINK
ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
|
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Funfly3
Guest
|
| Posted:
Sat Oct 29, 2005 12:35 am Post subject:
Re: How to build a Li-Ion charger myself (windmill, generato |
|
|
"PeteS" <ps@fleetwoodmobile.com> wrote in message
news:1130532448.631162.18160@g44g2000cwa.googlegroups.com...
| Quote: | Sandra wrote:
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
I think you missed the point A Li-Ion is constant voltage charged but "with" |
current limiting ,at the beginning of the charge the current is the limiting
factor at the end voltage is the limiting factor? |
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