DIY solar-powered electric bicycle charging setup

[FlatSix911]

Check out this guy's simple, DIY solar-powered electric bicycle charging setup

As far as electric vehicles go, electric bicycles are famously energy-efficient. Most can easily travel 100 miles (160 km) on...

electrek.co

Interesting reading from Electrek. "As far as electric vehicles go, electric bicycles are famously energy-efficient. Most can easily travel 100 miles (160 km) on around $1 of electricity. But what if instead of paying for that electricity, you could capture it from the sun instead? That’s exactly what Richard Drumm did when he built a simple DIY electric bicycle solar-charging setup."

 

[Handlebars]

I'm trying to order my solar setup today. I know how to pick panels but not how to pick the voltage boost controller. I know that heavier wire and connector are desirable but I also want everything to match for fit and I don't need excessive for the intended use of a 3 Amp charger for 48V. Now to watch the video you posted a couple of times to see if there is help on that.
Grin has a MPPT boost controller for $100 plus shipping but I think that's a bit of a price rip for what it is, so I'm looking for a less costly 48V boost.

 

[tomjasz]

Yikes Yeti 1400, an $1800 investment!!

 

[FlatSix911]

Yup, more than the $1,500 price tag of the bike.

 

[fooferdoggie]

plus will you ever recoup the cost in savings? nope.

 

[GypsyTreker]

I certainly would not spend 1500 on a Goal Zero for just charging my eBike, however, we have a 400 Yeti that we can use as an inverter plugged into our Subaru while driving to charge our batteries while keeping our Domestic 65cx cooled. So when you get multiple out of the investment it's cheaper. We can use a Solar panel to run our reefer via the Yeti and while camping in Yellowstone, Moab relied on it for refer and LED lights in our Aliner. Never came close to running out of juice.

 

[Browneye]

I would be curious how much of an inverter it would take to charge a ebike batt with a deepcycle battery or two. I don't know how to do the math for consumption.

For the RV house bats I run two GC batts in series for 220ah of 12v, half usable. And a 160w folding solar panel that will put out about 8a with good sun. Usually we can get 10 hours of solar gain, so about 80ah max. Our daily consumption onboard is generally about half that, so no problem keeping the batts up. All lighting has been converted to led, led tv, the power-hog now is the furnace.

This setup costs about $500 or so, depending on what kind of inverter would be needed to power a the ebike charger. And for a bike charger you might get away with a single 12v deepcycle, further reducing costs. A couple hundred watts of panel and a controller is a couple of hundred if you build it yourself. I think I gave $150 for this setup, so add a storage battery and a 12v to 110 inverter.

Anyone care to do the math? I'm good with 12v stuff, but have trouble with the voltage and amperage conversion calcs, consumption and duration of charge, etc. I thought I read where a bike charger was about 150w at 110. I think that's about 1.5a, but not sure now much 12v it takes to push that through an inverter to 110v. I'm thinking it's about 10amps, so a 5 hour charge would draw 50amps. Does that make sense? That would take about 6 hours with the solar panels to recharge a 12v battery, and a regular 120ah batt would be plenty of juice to do it. Especially if you could charge it while solar charging the 12volt storage battery. And I think a four or five hundred watt inverter would power the charger.

The is our setup dry camping...we sat for four days near Zion Park in UT, no issues. The two batts do provide up to 100 amp hours though at 50% discharge. They're like little energizer bunnies.
Boy would I like to take the eMTB'S up there, it's gorgeous.

 

[Browneye]

I just looked at my giant charger and it's 3a in at 110 and 3a out at 41.7. I just don't know what kind of 12volt amps it takes to power that for a ebike charge cycle.

Okay, this calculator says it takes 30.6 amps at 12v to make 3amps at 110: https://www.batterystuff.com/kb/tools/dc-to-ac-amperage-conversion-run-through-an-inverter.html

That's quite a bit of juice for 12v. A 5 hour ebike charge would take 150 ah of 12v battery. Really fuzzy math for me.

 

[WinterKill]

It can’t be 3 amps at both 110 & 41.7 volts.

amps x volts = watts.

Watts will remain constant. Voltage of the charger should be constant. So amps will change

42 volts x 3 amps = 126 watts. So at 110volt. 126 watt / 110 volts = 1.15 amps. So at 12 volts. 126watts / 12volts = 10.5 amps. (this assumes the charger output voltage is 42 volts)

Keep in mind that the inverter takes so power as well. If we assume that is 90% efficient 10.5 amps/90% = 11.7 amps at 12 volts. 5 hours x 11.7 amps = 58.5 amp hours out of your 12volt RV batteries.

Your inverter in this case has to be bigger than 126 watts to run the charger.

(The 42 volts in the calculations above need to be the output voltage of the charger not the bike battery voltage. The charger will run at a higher voltage than the battery, A car charging system works at 13.5 volts for a 12 volt battery)

 

[Browneye]

Yes, 3a @ 110 in certainly isn't the same as 3a @ 42v out, but that's what's printed on the charger label. Then Giant comes along and calls this one a '4a charger'. LOL
Their 'smart charger' is 6a, I'll have to look at the label on that one.

So I wasn't that far off, but not sure why the calculator I found said 30ah. Anyway, a solar setup would surely be nicer to live with than a generator - was discussed on another thread, and there are certainly some detractors for anything that runs on gas. I get it, and a good one is expensive as well, I think the little honda one is a grand.

I do have interest in sorting this out since we would like to take ebikes in the RV and there aren't always plug-ins, or at least it would be nice to be able to park in a casino lot or something on the road and still be able to charge them. IMO $1500 is too much for a remote charging setup. If the numbers above are realistic then it could be done for about a third of that.

The company that was selling the 'suitcase' solar panels seems to have closed. At least I can't find them anymore. But they are easy to make, and a basic pwm controller is really cheap and okay for this application, when using 18v max-output panels. My two 80's folded are 2x4 feet, about 2" thick, and slide into a storage compartment in the RV. Initially I had looked at roof mount systems, but there were so many advantages for the portable that I went that way instead. We don't use them very often, but when needed are really slick. We used to have to run the genny every day to stay charged, but this obviates the need to do that, unless you need air conditioning - then all bets are off. The built-in Onan is 4kw, drives a 15Kbtu ducted roof AC. Even then those are only good for about a 25deg drop in interior temp, which is fine when it's a hundred or less, but gets warm for really high ambient temps, like the dez, or AZ over summer. We'll even run it motoring down the hiway as the dash-air can't keep up.

 

[WinterKill]

https://www.amazon.com/dp/B000RGF29Q?tag=duckduckgo-ipad-20&linkCode=osi&th=1

This power monitoring device will show you how much power you are using a 120volts. If your charger label is somewhat vague you can confirm your numbers. It showers volts, amps and watt hours used.

You can confirm the Chargers input amps as well as track how much electricity is need to charge your batteries.

 

[WinterKill]

One thing I did not take into account, does the charger put out a constant 3 amps or does it tapper off as the battery charges. If it does that and 3 amps was the peak amps the total amp hours would be less.

If the 3 amps is the average then the inverter would need to be larger.

You could confirm this with the watt meter listed above. With the battery discharged see how many amps it is drawing at 110 volts. Then calculate wattage for minimum size inverter. Volts x amps = watts.