Illum
Flashaholic
Anyone know of a decent battery charging circuit that does not rely on a thermistor and can be connected to cells indefinitely without overcharging them?:thinking:
A down to earth NiMH charger circuit?
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TheWind777
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How to Charge AA, AAA, 9V and Li-Ion with a bicycle dynamo or generator
OK, this is a VERY IMPORTANT E-Mail. It is an E-Mail from a person who has actually succeeded at creating a charging circuit that runs off a bicycle generator and does something other than charge just 5 volt USB devices... so pay attention. This is the first time I've ever posted about how I succeeded.
I've been across America twice by bicycle. THe first trip was 5000 miles and the second was 3800 miles. I wanted a system that would charge up AAA, AA, 9V and Li-Ion (on different days, of course). So, for about two years I've been experimenting with various ways of charging AA, AAA, 9V and Li-Ion batteries via bicycle.
I use a 12V connector throughout the system that I purchase at Pep Boys. THey have red and white wires. I use white to mean negative and red to mean postitive. The same connector can be used on either end, so be careful that you don't plug an output into an output. I color code each side with shrink tubing. Red is an output (from the bike generator, from the solar panel, from the buck/boost power supply), blue is an input (to the 21 LED light, to the battery box with switches, etc.)
It has one two-conductor connector, heavy-duty, on each end of a red/white wires that are 12 inches long. If I need it to be longer, I cut it in half and splice in with solder two longer wires of the same guage.
I started using that connector because it's what's on my 12 Watt SunLinq folding solar panel, so that way I can plug the same things into my solar panel and into the bike generator.
http://www.batterystuff.com/solar-chargers/PF12w.html
I also use the same charger that I designed with a folding 23W solar panel, as well. Works like a charm.
So, if you have few electronics skills I'd recommend the following. First, get a SON28 hub dynamo to generate the power.
Next, you need to raise the voltage from the dynamo because a hub dynamo puts out only about 7 volts at less than 12 mph. You can get as much as 15 volts out of them (open-circuit) if you go really fast.
They give an almost steady 500 ma output at 6 volts when loaded. So, in order to actually charge four AA or AAA batteries you'll need what is termed a Buck/Boost supply to do that. The one that's designed to be used on a bike is called the E-WERK by Bucsh&Muller. It changes the AC to DC, boosts the voltage to any voltage between
Then just buy a four-battery AA or AAA holder at DigiKey or an electronics place and make sure that your plus and minus are set properly.
Set the voltage on the E-WERK to equal about 1.5 volts for each cell and the current limit at about .1 amp if AAA and .2 amp if AA. Be sure that you don't overcharge the NiMH batteries. Feel the batteries to see if they're hot. Because it will take so long to charge the batteries, you will most-likely be using the power BEFORE they ever overcharge, though. Set the voltage at 1.5 volts for each battery (four batteries, set it at 6 volts. You can try raising that and see if the batteries heat up).
That's if you don't know electronics.
If you do know electronics, use the lowest forward voltage drop Schottky diodes on the market such as the STPS2L40U which has a .3 volt drop in a full-wave bridge rectifier mode (look it up). DigiKey's part number is 497-5574-1-ND. They're a surface-mount device, so they are hard to solder to unless you create a tiny circuit board. Then wet the solder pads with solder and hold the soldering iron on the end a second as it flows.
To raise the voltage to any voltage between 3 volts and 24 volts use the AnyVolt3. It is a little miracle. Set the output to any voltage between those two voltages and from then on the output will stay rock-solid at what you set it at (unless the device needs the voltage to be lower, then you'll see the voltage drop as the current rises). It costs $57 with shipping.
http://www.dimensionengineering.com/anyvolt3.htm
Finally, to charge almost any kind of battery at all, use the Texas Instruments BQ2000EVM.
http://focus.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=SLUU270&track=no
Get it directly from TI. It costs $50
http://www.ti-estore.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BQ2000EVM
It is an evaluation module for the unit that is all pre-assembled with jumpers to set the voltages (regular hard drive jumpers work), screw adjustments for volt in and battery out and it even comes with a thermistor that you can mount near the batteries to have it automatically shut down if the batteries overheat.
The BQ2000 can charge NiMH, Ni-Cad and LI-ION, ***AND*** it can figure out automatically what kind of battery you're charging. The board is set to charge at 1 amp rate as the highest current, so it is greatly more than you'll need from a bicycle.
You can choose to top off the battery (you should) with a jumper. Then you choose C, C/2, C/3 or C/4 (1 amp, .5 amp, .33 amp or .25 amp), you choose the number of cells (NiMH 4, 5, 6, 8 or 10) or Li-Ion 1,2,3 or 4 (you know because one Li-Ion is 4.2 volts, so if it is 8.4 volts, it's 2).
Set the AnyVolt3 to 12 volts (set it without any load) while monitoring with a volt meter.
That's it. The batteries should charge at about a 300 milliamp rate. Each time you stop your bike and start it up again the computer in the BQ2000 will re-evaluate the kind of battery and automatically start charging again. There's a little surface-mount LED on the board that you can't see, so I removed it and soldered in an external LED so I can see the charging cycle. It blinks when it can't figure it out (has only happened twice). If that happens, just stop the bike and start again. It will start charging again.
The BQ2000 is incredibly smart, so it will first figure out what battery it is, then it will start fast charging it at full current that it can without destroying the battery or even heating up the battery (the big danger with NiHM batteries. If they heat up they won't explode, but it will greatly affect their lifespan).
I built a box to put it all in that velcros to my front rack. It can charge four AAA, four AA, 1 9V and 1 7.2 volt Nikon EN-EL1. I use a cheap 3 pole four-position rotary switch Alpha rated .3 amps at 125 vac (which works out to 1 amp at 30 vdc).
This swiches the voltage to the corresponding battery, the charge rate for each corresponding battery (solder the common to one of the top line of pins on the charge rate header), and the number of cells (solder the common of that one to the top row of pins on either the NiHM or Li-Ion header).
Then, when you select each battery, it will automatically set the charge rate and number of cells. Make sure you stop your bike, move the switch, and start your bike back up or the charger might get confused and start charging the AAAs at a 9V charge.
For overkill I built my own buck/boost power supply that has a voltage and current reading so I can keep track of how it's charging.
I can't afford a SON, so I just use one of those cheap $16 Tang-Lin generators. It works fine.
......
Settings that I use... I use DuraCell Pre-charged batteries (they hold their charge a long time). 2000mAh AA, 850 mAh AAA. I set the charge rate at C, set Top-off to yes, choose the Y side of the C charge rate. Then I set the jumper for 4 cells.
To charge 9V batteries, I use a Tenergy 250 mAh 9V battery. I set the BQ2000EVM at C/4 with Top-off. I set the cell count at 8 NiMh cells (charges at about 10.5 volts).
Although I haven't yet experimented with Li-Ion, I'm planning on charging the Nikon's Li-Ion battery for my Nikon e4300 camera, which is 7.2 volts by setting the jumper on the Li-Ion side to 2 cells and setting the jumper to full C (1 amp) charge with Top-off. I'll also be trying it without top-off as well.
I'm going to use this cheap charger, yank out the guts and use it as a battery holder.
http://www.amazon.com/dp/B000AO8NHI/?tag=cpf0b6-20
...
The Buck/Boost supply that I designed is a 3 amp unit that can put out anywhere from 5.4 volts to 28 volts DC. Although I bought the low-voltage drop Schottky diodes, I'm currently just using a bridge rectifier I pulled from an old computer's power supply and it seems to be working fine. I'll have to create a circuit board to try out the four low-drop diodes. I don't expect to get much improvement over what I'm already getting, though.
I've also tried using it without the buck-boost power supply. In my case, because the cheap generator I used
http://www.amazon.com/dp/B000OBWMGK/?tag=cpf0b6-20
(it's $24 with shipping)
... can easily push out greater than the 10 -24 volts that are needed by the BQ2000EVM... it works fine without the buck-boost supply at the front end. You'll probably need one with a SON though, as it would drop to 7 volts and that's not enough to power the BQ2000.
If you have any questions, contact me at [email protected]
OK, this is a VERY IMPORTANT E-Mail. It is an E-Mail from a person who has actually succeeded at creating a charging circuit that runs off a bicycle generator and does something other than charge just 5 volt USB devices... so pay attention. This is the first time I've ever posted about how I succeeded.
I've been across America twice by bicycle. THe first trip was 5000 miles and the second was 3800 miles. I wanted a system that would charge up AAA, AA, 9V and Li-Ion (on different days, of course). So, for about two years I've been experimenting with various ways of charging AA, AAA, 9V and Li-Ion batteries via bicycle.
I use a 12V connector throughout the system that I purchase at Pep Boys. THey have red and white wires. I use white to mean negative and red to mean postitive. The same connector can be used on either end, so be careful that you don't plug an output into an output. I color code each side with shrink tubing. Red is an output (from the bike generator, from the solar panel, from the buck/boost power supply), blue is an input (to the 21 LED light, to the battery box with switches, etc.)
It has one two-conductor connector, heavy-duty, on each end of a red/white wires that are 12 inches long. If I need it to be longer, I cut it in half and splice in with solder two longer wires of the same guage.
I started using that connector because it's what's on my 12 Watt SunLinq folding solar panel, so that way I can plug the same things into my solar panel and into the bike generator.
http://www.batterystuff.com/solar-chargers/PF12w.html
I also use the same charger that I designed with a folding 23W solar panel, as well. Works like a charm.
So, if you have few electronics skills I'd recommend the following. First, get a SON28 hub dynamo to generate the power.
Next, you need to raise the voltage from the dynamo because a hub dynamo puts out only about 7 volts at less than 12 mph. You can get as much as 15 volts out of them (open-circuit) if you go really fast.
They give an almost steady 500 ma output at 6 volts when loaded. So, in order to actually charge four AA or AAA batteries you'll need what is termed a Buck/Boost supply to do that. The one that's designed to be used on a bike is called the E-WERK by Bucsh&Muller. It changes the AC to DC, boosts the voltage to any voltage between
Then just buy a four-battery AA or AAA holder at DigiKey or an electronics place and make sure that your plus and minus are set properly.
Set the voltage on the E-WERK to equal about 1.5 volts for each cell and the current limit at about .1 amp if AAA and .2 amp if AA. Be sure that you don't overcharge the NiMH batteries. Feel the batteries to see if they're hot. Because it will take so long to charge the batteries, you will most-likely be using the power BEFORE they ever overcharge, though. Set the voltage at 1.5 volts for each battery (four batteries, set it at 6 volts. You can try raising that and see if the batteries heat up).
That's if you don't know electronics.
If you do know electronics, use the lowest forward voltage drop Schottky diodes on the market such as the STPS2L40U which has a .3 volt drop in a full-wave bridge rectifier mode (look it up). DigiKey's part number is 497-5574-1-ND. They're a surface-mount device, so they are hard to solder to unless you create a tiny circuit board. Then wet the solder pads with solder and hold the soldering iron on the end a second as it flows.
To raise the voltage to any voltage between 3 volts and 24 volts use the AnyVolt3. It is a little miracle. Set the output to any voltage between those two voltages and from then on the output will stay rock-solid at what you set it at (unless the device needs the voltage to be lower, then you'll see the voltage drop as the current rises). It costs $57 with shipping.
http://www.dimensionengineering.com/anyvolt3.htm
Finally, to charge almost any kind of battery at all, use the Texas Instruments BQ2000EVM.
http://focus.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=SLUU270&track=no
Get it directly from TI. It costs $50
http://www.ti-estore.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=BQ2000EVM
It is an evaluation module for the unit that is all pre-assembled with jumpers to set the voltages (regular hard drive jumpers work), screw adjustments for volt in and battery out and it even comes with a thermistor that you can mount near the batteries to have it automatically shut down if the batteries overheat.
The BQ2000 can charge NiMH, Ni-Cad and LI-ION, ***AND*** it can figure out automatically what kind of battery you're charging. The board is set to charge at 1 amp rate as the highest current, so it is greatly more than you'll need from a bicycle.
You can choose to top off the battery (you should) with a jumper. Then you choose C, C/2, C/3 or C/4 (1 amp, .5 amp, .33 amp or .25 amp), you choose the number of cells (NiMH 4, 5, 6, 8 or 10) or Li-Ion 1,2,3 or 4 (you know because one Li-Ion is 4.2 volts, so if it is 8.4 volts, it's 2).
Set the AnyVolt3 to 12 volts (set it without any load) while monitoring with a volt meter.
That's it. The batteries should charge at about a 300 milliamp rate. Each time you stop your bike and start it up again the computer in the BQ2000 will re-evaluate the kind of battery and automatically start charging again. There's a little surface-mount LED on the board that you can't see, so I removed it and soldered in an external LED so I can see the charging cycle. It blinks when it can't figure it out (has only happened twice). If that happens, just stop the bike and start again. It will start charging again.
The BQ2000 is incredibly smart, so it will first figure out what battery it is, then it will start fast charging it at full current that it can without destroying the battery or even heating up the battery (the big danger with NiHM batteries. If they heat up they won't explode, but it will greatly affect their lifespan).
I built a box to put it all in that velcros to my front rack. It can charge four AAA, four AA, 1 9V and 1 7.2 volt Nikon EN-EL1. I use a cheap 3 pole four-position rotary switch Alpha rated .3 amps at 125 vac (which works out to 1 amp at 30 vdc).
This swiches the voltage to the corresponding battery, the charge rate for each corresponding battery (solder the common to one of the top line of pins on the charge rate header), and the number of cells (solder the common of that one to the top row of pins on either the NiHM or Li-Ion header).
Then, when you select each battery, it will automatically set the charge rate and number of cells. Make sure you stop your bike, move the switch, and start your bike back up or the charger might get confused and start charging the AAAs at a 9V charge.
For overkill I built my own buck/boost power supply that has a voltage and current reading so I can keep track of how it's charging.
I can't afford a SON, so I just use one of those cheap $16 Tang-Lin generators. It works fine.
......
Settings that I use... I use DuraCell Pre-charged batteries (they hold their charge a long time). 2000mAh AA, 850 mAh AAA. I set the charge rate at C, set Top-off to yes, choose the Y side of the C charge rate. Then I set the jumper for 4 cells.
To charge 9V batteries, I use a Tenergy 250 mAh 9V battery. I set the BQ2000EVM at C/4 with Top-off. I set the cell count at 8 NiMh cells (charges at about 10.5 volts).
Although I haven't yet experimented with Li-Ion, I'm planning on charging the Nikon's Li-Ion battery for my Nikon e4300 camera, which is 7.2 volts by setting the jumper on the Li-Ion side to 2 cells and setting the jumper to full C (1 amp) charge with Top-off. I'll also be trying it without top-off as well.
I'm going to use this cheap charger, yank out the guts and use it as a battery holder.
http://www.amazon.com/dp/B000AO8NHI/?tag=cpf0b6-20
...
The Buck/Boost supply that I designed is a 3 amp unit that can put out anywhere from 5.4 volts to 28 volts DC. Although I bought the low-voltage drop Schottky diodes, I'm currently just using a bridge rectifier I pulled from an old computer's power supply and it seems to be working fine. I'll have to create a circuit board to try out the four low-drop diodes. I don't expect to get much improvement over what I'm already getting, though.
I've also tried using it without the buck-boost power supply. In my case, because the cheap generator I used
http://www.amazon.com/dp/B000OBWMGK/?tag=cpf0b6-20
(it's $24 with shipping)
... can easily push out greater than the 10 -24 volts that are needed by the BQ2000EVM... it works fine without the buck-boost supply at the front end. You'll probably need one with a SON though, as it would drop to 7 volts and that's not enough to power the BQ2000.
If you have any questions, contact me at [email protected]
