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Flashing LED Lights for Bicycle

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WooferHound:

--- Quote from: rossw on October 02, 2018, 05:18:19 pm ---Woof, I don't wish to pick on you ... but cripes, can you check your work??

Firstly. you can't have a current flow into an open circuit.
Next, 0.125mA seems waaaay too low. Certainly too low to be any practical use.
If your LEDs are drawing 240mA, it would take you 80 WEEKS of uninterrupted full sun to charge your battery up enough for 1 HOUR of operation, at 0.125mA. And over that timeframe, the self-discharge would eat most of it up anyway.

1N4007 or even schottky diodes at those voltages are hideously inefficient. A tiny P-channel mosfet off ebay will cost you less than a 1N4007 diode, and when wired as an "ideal diode" will have virtually no voltage drop in this application.

--- End quote ---

Yes, a significant typo there. That solar panel produces 125ma (short circuit) at 4.75 volts. But after today, charging through the Schottky diode the battery only gets up to 3.6 volts, which is fine for my uses. In my discharge tests, these 18650 batteries have great power between 3.7 and 3.2 volts. The 240ma bike lights could run more than a couple of hours after beeing charged up to 3.6 volts, plus safety when charging and using these lithium batteries up to 3.6 at .125 amp is almost guaranteed.

And yes you are also correct talking about how difficult it is to work with voltages between 2.6 and 4.2.

WooferHound:

--- Quote from: kurt on October 02, 2018, 06:08:19 pm ---those batteries from the laptop pack are lithium cobalt batteries they really do not like being charged by anything other than chargers specifically designed for them and they have a tendency to get angry and explode and spit fire that will not go out when abused google lipo fire there are allot of videos of it. i would suggest spending a couple bucks and buying a few batteries of a safer chemistry to play with

might i suggest a couple of those aa size lifepo4 cells with built in over voltage and over discharge protection  be much safer

--- End quote ---

Yes Kurt, you are very correct that charging Lithium batteries incorrectly can be Fire and Death ! !

However I have spent some hours reading about Lithium 18650 charging, plus I have become a "YouTube Expert" on the subject.

The Key Points are . . .
Do Not Exceed 4.2 Volts or there will be Fire
Do Not Discharge Below 2.5  Volts or you will damage the Cell
Do Not Charge or Discharge the battery faster than Half of it's capacity
Do Not Short-Curcuit or there Will be Fire
Use Balanced Charging. Lithium Batteries in Series do not remain Equally Charged and must be Maintained Individually to keep the Charge Equalized
It is also good to keep them Cool as possible and Protect them from Physical Damage

So if you are only using a single 18650 battery, with low charge/discharge currents, and stay between 2.6 volts to 4.1 volts (hard limits), you will have a lovely experience.
It acts much like a large capacitor and as long as you watch the voltage limits it is a happy playground to play in.
I built a Dual 18650 charger using a 6 volt centertapped transformer, very few parts and charges the batteries up between 4.0 & 4.1 volts over a 6 hour period.

WooferHound:
Did a Discharge test yesterday. Started with an almost full 18650 battery. Connected a 15 ohm resister making a 250ma load which is the same load as my lights would make. Checked the voltage every hour and noted it down

4.04
3.94
3.84
3.74
3.65
3.60
3.57
Sleeping
3.45
3.40
voltage rapidly declines at this point and it does not take long to get down to the 2.5 volt limit

So most of the power appears between 3.7 and 3.4 volts. My Bicycle Lights would work well for 5 hours with a charge of 3.6 volts.
At home the bike is parked outside, in some bushes around the house and the solar panel would get Full Sun a couple of hours a day which should be plenty. I would use the lights for about an hour a week riding at night, usually about 20 minutes on late rides home from work.

Was also thinking about adding a connector for attaching accessories, like Christmas Lights or a small LED Spotlight, maybe an MP3 player or something. Would also use the connector for checking the battery voltage. Wondering how to do that and stay weatherproof?

Made a Order to Parts Express for the LED resisters using 3.6 volts as the source voltage, 82 ohms for Red and 33 ohms for White. Also ordered some 56 ohm resisters for White LEDs on a 4 volt full charged battery.  Also have some 18650 Battery holders coming for some future projects.

WooferHound:
Getting almost done on this Bicycle Lighting project


Took the Front Reflector off of the bike and epoxy glued 6 white LEDs to the back of it. The dropping resisters were included to make the wiring work out better. This is all of the LEDs for the Front of the bicycle. Top two will be aimed Far Field, middle LEDs aimed Near Field. The Bottom LEDs have had the lens on the front ground flat so they throw a wide beam, and they will be aimed straight down at the road. I have tested this a few times with a stand-alone precharged battery and it works wonderfully.


This is the front & back of the Solar Panel. I glued some aluminum foil to the back of the front panel to help reflect the heat away from the battery. There will be 8 LEDs placed all over the back of the bike, 4 white pointed down at the road, and 4 red pointed to the rear of the bike. All the LED Dropping Resisters are inside the inside this box so they won't be exposed to weather outside. A phone wire goes to the front for a negative connection and a power switch on the handle bars. All 8 LEDs will have a pair of wires going to each one.


Here is the Solar Panel assembled and ready to install on the bike. There is a 1/8 inch connector that supplies unswitched power direct from the battery. Thinking about epoxy gluing the LEDs into their final position. Total of 14 LEDs: 4 white forward, 6 white wide angle pointed down at the road, and 4 red wide angle pointed to the rear, making a total of .280 amp.

Working for a few days so may be awhile before this is finished.

hiker1:
Your all lit up..now for sound...here's my little solar powered radio..old Sony ..bike radio...used one of my solar lawn lite..for power..it has one fat 3.5-4v batt built in..perfect for my 2 cell radio...

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