scwhiteley
New Member
Hello,
I've found a number of posts regarding this (or related) topics, but I still have a few questions. This project is part a bigger project that involves a bicycle stereo powered by a 12V 1.2Ah battery. The current setup requires a wall charger to recharge the battery, but I'm looking into using pedal-power as well.
The dynamo I picked up is a common, super cheap "bottle" style dynamo. After mounting it to my bike, I found it produces about 8 to 10VAC (not attached to any load) when I pedal at a moderate pace. I can get it to max out at around 12VAC, just as I start to break a sweat.
If I understand everything correctly, to charge the 12V SLA, I need to apply slightly more than 12VDC to the battery.(In fact, according to the charging instructions on the battery casing, I need to supply 13.5 - 13.8 V for stand-by use, or 14.4 - 14.7 V for cycling use, although I'm not entirely sure what the difference is.)
Here's what I've done with the dynamo so far:
I hooked up the dynamo to a 1A max bridge rectifier and put a 33 ohm resister across the DC end. At a moderate pedal (I'm guessing around 10-15 mph), it generated about 6V @ 200mA
I also tried using a simple full-wave voltage doubler (using 2 diodes and 2 220uF caps), also with the 33 ohm load, this generated 7V @ 220mA (please keep in mind, these are all fairly rough measurements made with a multimeter strapped to my handlebars)
I upped the load to 1000 ohm and tested the dynamo again with the bridge rectifier and the voltage doubler, yielding 8V @ 7mA and 24V @ 25mA respectively
So I guess the main question here is, is the dynamo generating enough juice in the first place? And if it is, how should I use it to charge the battery? I've researched a number of charge control ICs available on the internet, and it seems the main issue to worry about when charging a SLA battery is over-charging (although that doesn't even seem to be that big of an issue when compared to other battery chemistries). I'm not sure that my little dynamo can generated enough power to damage (or even charge for that matter) the battery. Some of the other posts and websites I've gone over suggest simply applying the DC power right to the battery leads and calling it good... Perhaps I can use the voltage doubler and attach it right to the battery? I'm a little wary of using a voltage regulator or a charge control IC simply because it may rob me of some of the precious few volts and amps I'm producing.
Okay, sorry for being so long winded, but I'm definately reaching the point where my own knowledge is running dry and I need to depend on you guys and gals. (I've never taken a class on electronics, but I think I might soon... literature suggestions?)
Finally, a word on the actual intended use for the battery. I'm nearly done with a small stereo that will go on the rear rack of my bike. (Not that I don't love my current bike stereo, but there's always room for improvement.) It appears that the stereo draws between .7 and .8 A at full volume, so in theory, it should last over an hour before it needs to be recharged (no problem, I rarely ride for more than a consecutive hour in a day, and I can plug it in at night). It seems clear(ish) to me that the dynamo could never actually power the stereo totally by itself. In other words, I would still eventually have to charge the battery from the wall (unless perhaps I rode around for hours with the stereo off and the battery charging). But perhaps the dynamo can augment the life of the stereo on a single charge? Maybe this is the most I can hope for, or maybe I can get a better dynamo...
Thanks,
SCW
I've found a number of posts regarding this (or related) topics, but I still have a few questions. This project is part a bigger project that involves a bicycle stereo powered by a 12V 1.2Ah battery. The current setup requires a wall charger to recharge the battery, but I'm looking into using pedal-power as well.
The dynamo I picked up is a common, super cheap "bottle" style dynamo. After mounting it to my bike, I found it produces about 8 to 10VAC (not attached to any load) when I pedal at a moderate pace. I can get it to max out at around 12VAC, just as I start to break a sweat.
If I understand everything correctly, to charge the 12V SLA, I need to apply slightly more than 12VDC to the battery.(In fact, according to the charging instructions on the battery casing, I need to supply 13.5 - 13.8 V for stand-by use, or 14.4 - 14.7 V for cycling use, although I'm not entirely sure what the difference is.)
Here's what I've done with the dynamo so far:
I hooked up the dynamo to a 1A max bridge rectifier and put a 33 ohm resister across the DC end. At a moderate pedal (I'm guessing around 10-15 mph), it generated about 6V @ 200mA
I also tried using a simple full-wave voltage doubler (using 2 diodes and 2 220uF caps), also with the 33 ohm load, this generated 7V @ 220mA (please keep in mind, these are all fairly rough measurements made with a multimeter strapped to my handlebars)
I upped the load to 1000 ohm and tested the dynamo again with the bridge rectifier and the voltage doubler, yielding 8V @ 7mA and 24V @ 25mA respectively
So I guess the main question here is, is the dynamo generating enough juice in the first place? And if it is, how should I use it to charge the battery? I've researched a number of charge control ICs available on the internet, and it seems the main issue to worry about when charging a SLA battery is over-charging (although that doesn't even seem to be that big of an issue when compared to other battery chemistries). I'm not sure that my little dynamo can generated enough power to damage (or even charge for that matter) the battery. Some of the other posts and websites I've gone over suggest simply applying the DC power right to the battery leads and calling it good... Perhaps I can use the voltage doubler and attach it right to the battery? I'm a little wary of using a voltage regulator or a charge control IC simply because it may rob me of some of the precious few volts and amps I'm producing.
Okay, sorry for being so long winded, but I'm definately reaching the point where my own knowledge is running dry and I need to depend on you guys and gals. (I've never taken a class on electronics, but I think I might soon... literature suggestions?)
Finally, a word on the actual intended use for the battery. I'm nearly done with a small stereo that will go on the rear rack of my bike. (Not that I don't love my current bike stereo, but there's always room for improvement.) It appears that the stereo draws between .7 and .8 A at full volume, so in theory, it should last over an hour before it needs to be recharged (no problem, I rarely ride for more than a consecutive hour in a day, and I can plug it in at night). It seems clear(ish) to me that the dynamo could never actually power the stereo totally by itself. In other words, I would still eventually have to charge the battery from the wall (unless perhaps I rode around for hours with the stereo off and the battery charging). But perhaps the dynamo can augment the life of the stereo on a single charge? Maybe this is the most I can hope for, or maybe I can get a better dynamo...
Thanks,
SCW