I travel off-grid in my vehicle with my bicycle and want to convert a brushless DC motor into a generator, in a style similar to the link above, so that I can charge my battery with my pedal power.
Anyone see any reason in principle why this wouldn’t work? Following this guy’s instructions, I think I could skip the inverter and just run straight from the bridge rectifier to some sort of plug that would plug straight into my EB150. Since it has a built-in charge controller, I wouldn’t have to worry about modulating the voltage coming from the bike.
FWIW an “easy” training ride for me is ~2 hours at 250w (I’m elite). I wouldn’t be pushing the motor by doing over 500w very often, but there could be times when I do 450w for 5 minutes. Steady state though, i’d say it would be between 150 and 300w of force on the pedals, with a little loss between the pedals and the motor, so maybe 130-270w at the motor consistently.
Could get a pretty good 400wh charge (like 30%) in a workout. Especially good if the sun’s not out.
What do you all think?
Sounds like an interesting idea!
Over 40 years ago I got my hands on an old front loader and rigged up a used bicycle to wash and spin it. It was a direct drive so things kind of thunked along in a non-smooth manner. Spin cycle worked nicely.
It wasn’t a success in that it was more trouble than it was worth but it did work!
Your idea of a nice smooth electric drive sounds promising. Some of the units, like the EP500, have standby losses of 30 watts so you would need to provide enough wattage to make headway to actually charge it.
Let us know how it goes!
Before connecting that generator to the EB150, measure its DC voltage output to prevent damaging the EB150 input by exceeding its voltage limit. If it does exceed the limit, get a voltage regulator between both.
I think it sounds like a lot of work, but fun to play around with.
It’ll definitely be some work. The promise is supposed to be that if I have low battery in inclement weather where solar charging is unrealistic, and if I need to train that day, I can set my trainer up under a tarp or awning, do my 2-3hrs at 200-250w average, and charge my battery while I’m at it. Might as well capture and store some of that mechanical energy if it’s going to be expended anyway.
I can also charge my battery through the AC outlets in my vehicle while it’s running, but unless I’m already driving somewhere, I prefer not to just burn gas for the sake of putting electrons in my battery.
Thanks for the tip. Remind me of the voltage limit on the EB150 input? Is it 60?
Very interesting and I think it should work. If you have a variable voltage supply, connect it to EB150’s input and play with the voltage up and down to see what happens. I think it would work at steady paddling speed. The question I have is how quickly the EB150 MPPT would adjust as you speed up and slow down, kind of like a day when clouds are passing over head with the sun peeking in and out.
What is the characteristics of this AC->DC generator setup? How does the output voltage vary with the current at various paddling speeds? I suppose at a steady peddling speed, there is a certain VI curve and the EB150’s MPPT charger would sweep and find the max power point if the curve is similar to a solar panel. As you paddle harder or softer, then the curve would shift just like a solar panel is getting more or less sun.
I haven’t successfully found any regulators that can handle my output voltages. If I’m doing steady 250-300w but can sometimes spike into 500w territory, what kind of top-end voltage would I need on the input side?
You may not need a regulator. In fact, having a DC DC converter would hurt efficiency. I won’t want to use one unless it is absolutely necessary.
I would check the open circuit voltage of the system. Paddle as hard as you can and see what the max voltage without any load is. If that is under the voltage limit of your MPPT, then everything is good on the top end. Next, paddle at a leisurely pace and see what is the voltage, if that is above the minimum voltage for the MPPT then you are set.
That would be a manually operated charge controller.
Yep, just to close the loop, this is the one I found that I think will work. And an additional instructable from Gene for the higher watt loads I’d be generating.
I’ll update on progress, but in the meantime, does anyone know what kind of cable will work to wire the charge controller to the Bluetti charge input?
You do not need this. This takes input 0-60V and steps down to 0-50v. The EB150 can accept 16-68V input. If this unit can take it in, then so can the EB150. Just measure open circuit voltage when you bike hard to ensure it is below 68V and if it is, just connect directly. This converter won’t do anything for you.
Thanks, I needed to hear that. And frankly, I have the powermeter live data on my garmin head unit, so if I know my voltage exceeds 68v at e.g. 750w, then I can keep it in my pants enough to avoid blowing this thing up.
Side note: is there a way to calculate the wattage that would generate 68v, assuming perfect efficiency? E.g. w / 68 = …?
Super stoked to get this thing wired up! I think I just need to hook an 8mm input cable to the bridge rectifier and start peddling.
And cable-wise for the input from the bridge rectifier, would something like this work? Assuming I cut off the solar input sides and hook on something else that would connect to the rectifier?
Power is the product of voltage and current. So at 68V and 10A it would be about 680W.
You don’t have to worry about the current. As long as the voltage doesn’t exceed 68V when you paddle as hard as you can, you will never damage the EB150. The EB150 can accept up to 68V at 10A, so about 680W. Any more current won’t damage the unit, it just won’t be used. You cannot exceed the voltage though.
Each device has a particular voltage and current relationship at various level of power. Most likely, the open circuit voltage, voltage when you are not drawing any power to charge the battery will rise pretty quickly as you speed up paddling. But would stabilize at a certain level, then current capability will increase as you speed up.
You will just need to measure what is the max V when you paddle hard. If it is <68V, then you can never break the EB150.
@ProPower can I just tell you how freaking excited I am to see you get this rockin’?!?! Hahaha you better show us some videos man!!
Imagine if the spinning class at a local gym does this. PV on roof by day, human power at night. Can be worth something.