Another home solar for charging EV thread...

I didn't want to hijack the other thread, so I started this one.  The requirements should be much easier to meet.  I want to be able to charge an ebike with solar panels.  I'm not sure what specs you all need to help me figure this out?  The ebike I'm looking at is the Aventure Ebike.  These are the motor, battery, and charger specs.

MOTOR
1130W (Peak) 750W (Sustained), 48V Brushless Rear Hub Motor

BATTERY
Removable Internal Lithium-ion 48V, 15Ah (720Wh)

CHARGER
Included is a 48V 3 Amp Fast Charger, 4-5 Hour Charging

I'm trying to figure out what the approximate cost would be to charge this bike on a pretty much daily basis with solar panels.  Acceptable exceptions to me are if it is rainy, overcast weather for 4 or 5 days straight or the like.  I don't want to buy enough batteries for a more extreme situation like that.  I can still rely on my regular vehicle or those times, I would just like to commute as cheaply as possible.  My job is 8 or 9 miles from my house.  With no pedaling at all, the range for this bike is 27 miles, with the highest speed and pedal assist, 19 miles.  Realistically, I may have to charge it every day.  A spare battery to bring along will probably be the first additional purchase.

I appreciate any thoughts anyone has regarding this.

I would look at charging it directly from DC.

If you can't you should be able to get by with a 500-1000W inverter (depends on what else you are powering).

For sizing the battery, for the bike (you need to add for other household usage) 15ah * 5 = 75ah * 48v = 3.6 kWh (I would probably round up to 5kWh)

For solar panels take your battery size divided by the average number of hours of sun at your location.

Those are the numbers but you might want to round up for inefficiency.

I know there are a lot of solar charge controllers in the works that got set back by world chaos. How many, if any, of the things I saw previously will make it to market is up in the air. I have seen a few devices out there that can work, but the prices have gone up on them a bit and they aren't exactly plug and play without testing to see if they are working properly.

Since solar panels are the most robust part of any solar power setup, I'm of the opinion that it makes more sense to just buy more panels when doing small scale solar. Spending $400 or more on a charge controller that's likely to burn out a few times over during the lifetime of the panels to eek out some extra power doesn't add up to me. That money can be spent on a few extra solar panels to provide extra power and they will still be providing power for decades. I've found a few controllers that each have their own caveats.

What I am looking at are Boost Charge Controllers, meaning the input voltage from the solar panel is lower than the output voltage. If you are using a so-called 48V battery or 13S pack, it has a fully charged voltage of 54.6 volts. Pretty much any panel with an open circuit voltage lower than that would work with a Boost Charge Controller. All of the name brand stuff I have found either doesn't do higher voltage Li-Ion, or has more problems than the cheaper offerings.

The 3 options I have looked at recently are as follows:

1 - MPT-7210A - The Amazon links are not endorsements of sellers, just the first ones that come up for me. You can find these things in other places quite possibly for much cheaper even with shipping. This particular option isn't the best, but there are videos on YouTube showing people working with it. The main problems seem to be cheap capacitors, which is relatively easy to fix, and it doesn't have proper Maximum Power Point Tracking (MPPT). Initially this was the first thing I found and at the time it was less than half the current price. It's still not a bad option to try out if you can get it for closer to $30, but with other options available it isn't worth the $50+ most places are selling it at, and I don't think I would bother trying to buy one that hasn't already made it across the Pacific right now.

I think the first video I found from the YouTuber vuaeco was on this device, and he quickly became one of my favorites. I love his DIY videos, and he does a lot with Li-Ion cells, small scale solar, and ebikes. I highly recommend checking his stuff out even if you decide against this charge controller which he goes over here:



2 - CTK300  (CTK EV300, CTK300-II) - There a a few variants of this I have seen around, it seems like one handles more power than the other and the rest are the same with different colors. This one seems a bit better as far as being easier to set up and a bigger case without needing a fan. The other one seems to have a better display. Here is a video which is an update to a previous video, which goes over some important points:



Both of those previous options have other videos you can search for more info. A major issue with the off brand stuff is that they may not get design updates and testing that a name brand item would. One thing I heard a number of years ago in regards to computer power supplies is that the #1 cause of failures is shipping and this last option could avoid that problem. I found this DIY charge controller recently:

3 - DIY 1kW Open Source MPPT Solar Charge Controller - I came across the video for this a few months ago and was really impressed by it. There is a YouTube video series about it on that page. I'm a big fan of open source hardware and software, and this seems like a winner. It may not be as great an option for someone who only needs one, as many components are bought in packs of 10 or more. In my case I could build one and then use all the spare parts to build more. With my leg injury taking much longer to heal than I planned, I may not get around to this very quickly. If other people here are interest, maybe we can pool resources and get 10 or more of them built to save both on cost and resources versus buying a bunch of components to sit around and ultimately get thrown in the trash.

It uses an ESP32 for a wireless connection to log data on your phone. With MPPT it will be much more efficient at converting power than most other cheap options, yet cheaper than any name brand models. Given the open source nature, people can make changes and improve on the design and share it with others. I'm hoping to see more people on YouTube put up videos about their experiences building this controller. I have experience with power delivery and interest in electronics, but I don't have the skills to completely reverse engineer something like this by myself. It would be nice to see someone with good test equipment checking out the voltage, switching frequency, and MPPT features to see how they compare to the intended design, to name brand MPPT controllers, and to the numbers shown in the data logging app.

This post is getting mighty long, so I'll leave it here for now. I know there are a lot more options for lower voltage Li-Ion, and I remember Area 13 ebikes (formerly Bolton ebikes) mentioned something about getting a charge controller designed, but the current options have their limitations. If I come across anything new I will post back with more info.

Trace, I assume your work hours have significant overlap with the time the sun is out.
So Ideally a second battery would stay at home and get charged while you are at work.
I suppose you could take the charger that came with the bike and charge the battery at work if needed as well.

Assuming something like 4 sun hours and an empty battery, it needs a bit less than 200W of solar panels to charge it up within a day.
12V solar panels are easy to get, so with two of them you can get 24V, which needs to be stepped up to the 48V of the battery.
A boost converter that allows to set voltage and current limits should work. Since the input power is limited by the solar panel, just a voltage limit should be enough. Just get a multimeter and check the voltage to make sure it outputs what it claims.
And charge the battery in a place where if it catches fire, nothing else burns down....

Sebastian Köln wrote:Trace, I assume your work hours have significant overlap with the time the sun is out.
So Ideally a second battery would stay at home and get charged while you are at work.
I suppose you could take the charger that came with the bike and charge the battery at work if needed as well.

Assuming something like 4 sun hours and an empty battery, it needs a bit less than 200W of solar panels to charge it up within a day.
12V solar panels are easy to get, so with two of them you can get 24V, which needs to be stepped up to the 48V of the battery.
A boost converter that allows to set voltage and current limits should work. Since the input power is limited by the solar panel, just a voltage limit should be enough. Just get a multimeter and check the voltage to make sure it outputs what it claims.
And charge the battery in a place where if it catches fire, nothing else burns down....

That's exactly right, my work hours pretty much take up the daylight hours.

I appreciate everyone's information.  I need to read and watch more Youtube videos, I just haven't reached that point where everything "clicks" for me with solar.

As an aside, I bought the bike, so I will be researching this more intensely now.

Since this bike uses a lithium ion battery, not LiFeP, direct uncontrolled DC charging can potentially be dangerous.  All Li battery charging systems incorporate a Battery Management System, or BMS to control Li charging.  If you look carefully at the plug for your charger, you are likely to see three connections.  The outer cylindrical contact (usually negative), the inner cylindrical contact (usually positive), and then a center pin.  That pin is for the BMS to function.  Without the BMS to carefully regulate charging, Li-ion batteries can potentially rupture, and burst into flames.

This doesn't mean that you can't use solar though.  The safest way to do this is to have the solar panels charging the solar batteries via the solar controller, which feeds an inverter, into which the e-bike charger gets plugged.  There are solar charge controllers that can handle Li-battery charging, but they must be carefully programed for the charging regiment of THAT BATTERY.  If you don't have those exact factory specifications, the safest option is to rely on the factory charger that comes with the bike.

Here is a budget system that will work for you.  Get two 6V golf-cart batteries at Costco for ~99$ each that you wire in series for 12V.  Shop for solar panels on Craigslist instead of the internet.  I just got 260W panels three months ago for 65$ each.  One or two 250-260W panels will be enough to fully charge that size battery.  Then get a MPPT charge controller with at least 40A capacity.  The MPPT controller will let you wire the panels in series to get 60+VDC to feed the controller.  The higher DC voltage will cut down on wiring voltage loss.  The Epever 4220AN is an economical choice. Finally, a 12VDC to 120VAC inverter, in the 400-600W range.  This will power your bike charger, and allow for some extras like AC lighting, or even a TV.

I was digging around and found some more interesting stuff. Grin Technologies has a PDF for the second charge controller I mentioned above. I really like Their YouTube Channel. The guy behind it has been passionate about ebikes for years. The PDF is rather short and to the point:

CTK300 Boost Charge Controller Manual

One important note here - unlike buck charge controllers (ones that drop panel voltage for charging) which power the controller from the battery, boost charge controllers source power from the solar panel. Solar panels come with blocking diodes, and running these off of a bench power supply can destroy that power supply. You might be able to get away with adding your own diodes to a power supply, or using a lead-acid battery that can take the abuse of a short power backfeed, but I would stick with using a solar panel within the specifications and no battery attached until it is programmed properly.

I looked around on their shop and didn't see the CTK300 available anymore, but I did find a new model. The case says it is an Elejoy Model: EL-MU400SP. It seems to be an upgraded 400W version of a previous model. I'd imagine since the CTK300 is still available that they changed to selling this Elejoy charger for a reason, whatever that may be. Either way, they have a PDF manual for it and they have it for sale, which might cost a bit of shipping from Canada. The only other place I see it for sale is AliExpress for around the same price.

Elejoy 400W Boost Charge Controller Manual

Elejoy EL-MU400SP at Grin Technologies

I'm still hoping the DIY 1kW controller gets put up for sale on some place like Tindie. I would rather pay twice the price for hand selected components and support the creator for his awesome open source endeavor. Surface mount soldering is beyond what I can currently do with my current level of skills and tools.

Daniel Schmidt wrote:I was digging around and found some more interesting stuff. Grin Technologies has a PDF for the second charge controller I mentioned above. I really like Their YouTube Channel. The guy behind it has been passionate about ebikes for years. The PDF is rather short and to the point:

CTK300 Boost Charge Controller Manual

One important note here - unlike buck charge controllers (ones that drop panel voltage for charging) which power the controller from the battery, boost charge controllers source power from the solar panel. Solar panels come with blocking diodes, and running these off of a bench power supply can destroy that power supply. You might be able to get away with adding your own diodes to a power supply, or using a lead-acid battery that can take the abuse of a short power backfeed, but I would stick with using a solar panel within the specifications and no battery attached until it is programmed properly.

I looked around on their shop and didn't see the CTK300 available anymore, but I did find a new model. The case says it is an Elejoy Model: EL-MU400SP. It seems to be an upgraded 400W version of a previous model. I'd imagine since the CTK300 is still available that they changed to selling this Elejoy charger for a reason, whatever that may be. Either way, they have a PDF manual for it and they have it for sale, which might cost a bit of shipping from Canada. The only other place I see it for sale is AliExpress for around the same price.

Elejoy 400W Boost Charge Controller Manual

Elejoy EL-MU400SP at Grin Technologies

I'm still hoping the DIY 1kW controller gets put up for sale on some place like Tindie. I would rather pay twice the price for hand selected components and support the creator for his awesome open source endeavor. Surface mount soldering is beyond what I can currently do with my current level of skills and tools.

Daniel, it's clear you know your stuff about this, but I have to admit, I don't even know enough to understand some of what you are talking about :)  I'll watch the videos you recommended and go from there.

It's definitely an expanding space. We would certainly have a lot of better options available if things like shipping and economy hadn't been so chaotic in recent years. It's one of the few aspects about solar powered transportation that I can't brute force my way through or find simple used alternatives to repurpose, so I've been keeping my eyes out. I'll be certain to update on any better offerings I come across.

I guess I must have missed the video that Grin Technologies posted last year. It's pretty heavy on the technical side (which I personally love) and not only do they sell the one name brand charge controller that I wasn't able to find elsewhere, but he also doesn't recommend it. Before I go any deeper into this let me show the video here:



I'm going to go deep into the technobabble here. I'll put a divider and make some final comments on other solutions that may be more straightforward.

It's a bit long and covers his Cycle Analyst device which isn't necessary for solar charging, but he brings up a lot of good points. I was just commenting elsewhere how complicated people try to make solar, coming up with solar trackers, solar concentrators, and other stuff that greatly increases cost and complexity often for barely double digit performance gain. He explains you don't need his extra stuff or any of this extra complexity to just point a panel at the sun and get decent results.

The reason I didn't bring up the Genasun device earlier is because I only saw the lead-acid versions for sale and it's non-adjustable. I like that you can program things like the Elejoy controller so you aren't pushing cells to 100% if you don't need it to extend battery life. There are caveats to that. Most important would be that some (most?) Battery Management Systems (BMS) don't have constantly active cell balancing. They do what is called a top balance. If one cell, or parallel set of cells, hits 4.2V first, it bleeds off energy to adjacent cells until they all reach 4.2V. This helps keep them balanced. If you never fully charge then it never balances and reduces the minimum battery capacity because the BMS will shut down once any set of cells hits the minimum threshold. My experience has been that the brushless motor controller will cut out at a higher voltage, and voltage drop under load means the motor will never drain the battery to 0%, but it's still a good idea to keep cells balanced. I don't know if the average person fielding customer service calls for ebikes would know the topology of the battery BMS unless they build batteries in-house.

I realize this is outside of most people's wheelhouses, but I figured I would give some of the nuts and bolts about it in case anyone else comes along and wants to learn. The video demonstrates what is needed to power the controller with a solar panel, set the charging voltage, and then plug in the battery and start charging. He mentions they have some adapters for sale to attach to a few different types of battery connectors. The charger has some limitations noted in the PDF, such as 400W maximum output. That means around 7.3A @ 54.6V charging voltage for a 13S "48V" system. I would probably go with an 8A 125V fuse on the output of the controller. The BMS should handle the battery fine, and the wires should be more than adequate for the amperage, but I'd rather lose a fuse or have a slightly overheated component in the charge controller than to leave it unprotected and go up in smoke. The battery should already have its' own fuse.

I'm definitely going to order that Elejoy controller when I can. Even though I don't need it, I might get the Cycle Analyst. Not only would I be supporting someone innovative in this space, but he even has a native Linux version of his software to interface with the device. I was dumbfounded when I saw that! I usually just mash numbers in my head with reasonable accuracy, but it might be helpful for others if I quantify things with numbers that aren't estimations.

/Technobabble Rant

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Before I went down this rabbit hole today, the question, "What exactly is the goal here?" came to mind. If you purely want to offset the power usage of the ebike (you mention wanting to commute as cheaply as possible), then it would probably be way cheaper and easier to hook panels up to a grid-tie inverter and call it done. If you are super minimalist where your house uses almost no energy while you are at work and your electric meter doesn't support power coming in from the house then that may not be a viable option.

Michael Qulek mentioned above to use a standard solar setup with batteries and an inverter. It's a very well documented method, and having the batteries on hand would mean you can potentially charge other things such as laptops, phones, USB boost packs, tool batteries etc. Plus you can use it for all of those things as well as running lights and more when the power is out. You would likely need a pure sine wave power inverter to run the battery charger. To me, it really stinks that we don't already have a lot of great options for direct DC-DC charging. Much like the ~$40 Million Dollar Man ($6 Million Dollar Man in today's money), we have the technology! It just hasn't matured yet. I have iron focus towards making some of this work which is why I've gone on at length about it. If you can stack functions and find other use cases for the lead-acid batteries and inverter then it's a great option.