I have just purchased a 6V, 4.5Ah sealed lead-acid to power my arduino-controlled bicycle LED lighting system.
The battery is to be charged by the variable power provided by a hub generator, which has a rectifier/stabilizer (diode bridge + capacitor + zener).
Currently the hub-generator/stabilizer setup is being successfully used to power the LEDS directly (arduino is not in the circuit yet). At full load I have a consumption of around 0.45A @ 6V.
My goal, after incorporating the battery and the arduino, is that the system (arduino + LEDs) works "by itself" once turned on, in the sense that:
- The system gets its power from the battery or the hub generator, whichever is "more active" at a given moment;
- All the excess power provided by the generator and not consumed by the system will end up recharging the battery. The battery thus would be used in "floating" mode;
I believe this is a fairly standard configuration for this type of application.
My doubt is: The battery manufacturer recommends around 6.8 Volts for a constant-voltage (floating recharging regime between 10°C and 30°C), but my system is designed to work at 6V.
So it appears that, if I used a 6.8V zener diode (1N5342) to regulate hub voltage, I would successfully float-charge the battery, but could also be "over-volting" the system.
On the other hand, if I use a 6V zener (1N5340), as I am using now, I would not have enough voltage to charge the battery.
As a last confusing point, the open-circuit voltage of a fully charged battery of this model is around 6.5V, so even without being recharged, it is expected to "present" these 6.5V to the system, isn't it?
So, my questions are:
- Should I be worried about this extra 0.8V if my system is expected to run on 6V? Considering that it's made up mostly of LEDs, I suspect this is not a big problem, but I'm unsure;
- Suppose I absolutely needed to have strict 6V at all times, how would I float-charge the battery while the system is running without exposing the system to 6.8V? Is there something I could do, such as an extra circuit? Is there a standard way to do that?