Solar generator to charge e-bike? Is this math correct?

[brainfarmer]

I have a E-bike who's charger says "Input: 100-240V 3A, Output 54V 2A"

If I remember my schooling. P = IV. Which gives Input: 300W Output: 108W

So, am I really only getting 1 Watt out for every 3 I put in via this charger? Also, if I were to try to use a generator/power bank am I correct that I will need one capable of putting out 300W? My hope was to be able to charge my bike via solar, but 30% efficiency isn't going to cut it...

Thank you all

 

[sunshine_eggo]

No.

You will get 54V@2A out.

The voltage supply must be in the 100-240V range, and the maximum it can draw is 3A (technically, the circuit must be rated for 3A - not that it will pull it).

AC-DC conversion is typically 75-90% efficient. If the unit has cooling fans, that will burn additional power.

 

[brainfarmer]

Thank you! I'm good with math and science, but as soon as things get practical I panic . Regarding my second question..

Ok, so given this information , I prob would want a generator that can provide at least 150-200W, yes? I had a cheap Marbero, which I sent back to Bezos after it failed to charge the bike, but that generator was only rated for 100W. And It was cold too (I was living outside in Minnesota, I imagine that contributed). It should have had more than enough charge to fill the bike, but when I woke up the bank was empty and the bike still wasn't charged

 

[sunshine_eggo]

I would assume you'd want to size a power bank for the battery capacity, not just the output. Do you want to partially/fully charge the battery? What battery capacity should the power bank have relative to the e-bike battery?

Something else to consider is that the power bank is actually doing DC-AC-DC conversion, so it's going to be closer to 70-75% efficient compared to the battery of the power bank.

 

[hwy17]

A 200W Victron might do it. But for cheap solar generators you'd want something "rated" for 500W+.

 

[brainfarmer]

Yea, sux being poor . Thanks for all the input guys!

 

[brainfarmer]

I would assume you'd want to size a power bank for the battery capacity, not just the output. Do you want to partially/fully charge the battery? What battery capacity should the power bank have relative to the e-bike battery?

Something else to consider is that the power bank is actually doing DC-AC-DC conversion, so it's going to be closer to 70-75% efficient compared to the battery of the power bank.

Any power bank that can sustain 200W is going to have plenty of charge, it's really more of a glorified scooter, the battery is only 10 Ah.

Regarding DC to AC to DC, that is something I was aware of, but thanks for giving me an estimate on what the efficiency will be.

 

[Ampster]

egarding DC to AC to DC, that is something I was aware of, but thanks for giving me an estimate on what the efficiency will be.

Which is another reason to just charge the ebike with a wall charger than go through a DC to DC conversion with the solar generator.

 

[sunshine_eggo]

Any power bank that can sustain 200W is going to have plenty of charge, it's really more of a glorified scooter, the battery is only 10 Ah.

As a student of the mathses and sciences, you should know... maybe assumptions shouldn't be made?

Regarding DC to AC to DC, that is something I was aware of, but thanks for giving me an estimate on what the efficiency will be.

10Ah * 48V = 480Wh - about 6X larger than the power bank you tried first...

Assuming 75% efficiency, that's a power bank with 640Wh. Given that the power bank itself uses power for its own operation, I'd consider 700Wh a minimum to get ONE full charge to the scooter battery.

If you're trying to charge in temperatures below freezing, you may damage the e-bike battery unless you KNOW it has low temperature charge protection, and if it does, you need to know it WON'T charge if it's below freezing.

 

[brainfarmer]

Which is another reason to just charge the ebike with a wall charger than go through a DC to DC conversion with the solar generator.

Yes, for the average citizen in a liberal democracy that would be the go to solution. Unfortunately I'm looking at some extended time off grid/homeless, take your pick. So AC outlets aren't always nearby.

 

[brainfarmer]

As a student of the mathses and sciences, you should know... maybe assumptions shouldn't be made?



10Ah * 48V = 480Wh - about 6X larger than the power bank you tried first...

Assuming 75% efficiency, that's a power bank with 640Wh. Given that the power bank itself uses power for its own operation, I'd consider 700Wh a minimum to get ONE full charge to the scooter battery.

If you're trying to charge in temperatures below freezing, you may damage the e-bike battery unless you KNOW it has low temperature charge protection, and if it does, you need to know it WON'T charge if it's below freezing.

Wow, Forgot to convert my own battery to Wh . Thanks. That's prob why I didn't graduate .

Thanks a lot!

 

[sunshine_eggo]

Wow, Forgot to convert my own battery to Wh . Thanks. That's prob why I didn't graduate .

Thanks a lot!

You're welcome. Hopefully, it's not too much to manage. That pretty much pushes you out of the sub-$500 range unless you're willing to accept a partial charge from a smaller unit.

 

[brainfarmer]

You're welcome. Hopefully, it's not too much to manage. That pretty much pushes you out of the sub-$500 range unless you're willing to accept a partial charge from a smaller unit.

Yeah, for that price I may as well just buy a second battery for the scooter. I'll save the solar for my phone, tablet, ecig, and arc plasma lighter.