I’m trying to charge a mobile device (cell phone, etc.) from an ergometer (rowing machine). Can I use the LiPo Charger/Booster (PRT-14411) (https://www.sparkfun.com/products/14411) to interface between the generator and the mobile device? I know that I’ll also need a full wave rectifier because the signal out of the ergometer can alternate between positive/negative voltages.
Thanks for reaching out to us on this.
This might be better suited, as it support under-voltage https://www.sparkfun.com/products/10255
Hope this helps, and happy sparking!
Are you charging via the phones charger port or have you cracked open the phone and have wires connected directly to the phones battery? If you have direct access to the battery you could use any of the chargers we carry but it’s recommended to use the charger circuitry that’s built into the phone and charge through the phones charger port. You’d still need to get 5 volts from your device somehow and that would involve changing it’s AC output to 5 volts DC before you can attach that too your charger. You don’t really want a booster, that takes raw 3.7 volt battery voltage and brings it up to 5 volts which is kind of the revers of what you’re trying to accomplish.
What the phone wants to see is a steady 5 volts DC coming in through the charger port and it sounds like your device outputs an unknown AC voltage. What you will need to do is rectify that to change it to DC, then filter it with some capacitors. From there your best option would be to use a DC to DC converter to drop that down to 12 or 5 volts for use in charging your phone.
If you drop it to 12 volts, you can then use any standard car charger to charge your phone via it’s charging cable and port, and that give you the option to plug in other 12 volt devices if you want. if you drop the voltage down to 5 volts, you can apply that directly to the phones charger port via a USB charging cable.
Thanks for your replies above and sorry that I did not fully explain my goals above. To give the most versatility, what I would really like to do is have the generator charge an external battery that has a USB port, and from that USB port, the user can plug in a mobile device or any other USB-powered device.
Ah OK, that makes more sense now!
Your external battery, is that a power bank that also recharges via USB? If that’s the case you just need to rectify the AC voltage from your generator, drop it down to 5 volts and then pass that 5 volts to your external batteries charger input.
Do you have a link to the battery you’re using or can you post some photos of it?
What AC voltage is your generator supplying?
I haven’t chosen the generator or the battery yet. I thought that this might be a good option for the battery: https://www.sparkfun.com/products/13856. I’m assuming that using the LiPo Charger/Booster, I could charge this battery with anything above 3.7V and then it would output 5V out of the +/- pins on the bottom right corner of the board, right?
I was looking at this for the rectifier/low pass filter, but I’m also open to suggestions if you have better ideas. I didn’t see anything similar on Sparkfun. https://www.amazon.com/gp/product/B07PM … UTF8&psc=1.
This hookup guide for the Battery Babysitter https://learn.sparkfun.com/tutorials/ba … y-charging has a section showing the charge cycling, indicating that it should output 4.2v MAX
Hope this helps!
Sadly we don’t have suggestions for a rectifier, you’d need to source or build one that is appropriate for whatever generator you decide to use. You need a steady 5 volts power from your generator before you can do anything, focus on getting that working first.
We still don’t know anything about the generator and a lot depends on its specifications.
If this were my project, I’d stick with a 12 volt sealed lead acid battery (since it seems like weight isn’t a concern) and automotive charging accessories.
In fact, you may be able to repurpose an alternator & rectifier circuit from a motor vehicle.
I like brow’s idea.
Most car alternators have a voltage regulator and rectifier built in and they make more power than you’re likely to ever need. If you recharge a small lead acid battery with the alternator you will even have power available when the machine isn’t running or is running too slow to make power. Plus, you have the option of using other 12 volt devices in addition to a cell phone charger.