454 How to Build an Solar Battery Charger for eBike / Electric Bicycle

Today I will show you a project with several aspects. Even if you do not need to charge batteries with voltages of 35 volts and above using a solar panel, you will find learnings for your projects. Or you enjoy that not only you encounter some difficulties in your projects.
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[@AjinkyaMahajan]

9:38 "This is the hard life of an engineer" Hit me straight. Sometime failure gives you practical experience then satisfaction!! Thanks for a great tutorial.

[@AndreasSpiess]

My pleasure!

[@benjaminrich9396]

Brilliant video. Technically interesting and articulate as always. The way you show the process of your setbacks and how you overcame them is really helpful. The way you present the wife/wife's sister problems as if they're engineering requirements to satisfy is hilarious. I especially love the symbols, especially when you added the wife's sister's partner. :)

[@AndreasSpiess]

I thought, the family situation was too complex to understand without a picture ;-)

[@sail4life]

@@AndreasSpiess Ha, just waituntil the wife's sister's husband tells his brothers, wife's daughter what you did!

[@benjaminkieper568]

wie wichtig eine Gute Story hinter einem sonst eher trockenen Projekt ist. Ohne die Story hätte ich das video nicht zuende geschaut. 👍

[@AndreasSpiess]

Da hast du recht: Die Story ist sehr wichtig auf KZbin. Nicht immer einfach bei meinem Stoff ;-)

[@sofronio.]

I love all of your engineer and husband jokes! Better than any comedy.

[@AndreasSpiess]

Thank you!

[@daveys]

I’ve heard you say “Grüezi KZbinrs” so many times but this was the first time I’ve caught it on the subtitles and found out that it meant “Hello”. I hope your customers found out just how much effort that took to solve! Well done!

[@AndreasSpiess]

Indeed, Grüezi means "Hello" in Swiss German... From time-to-time I am also asked about it in the comments.

[@daveys]

@@AndreasSpiess - I thought it was “Gritty KZbinrs” until now! I considered it as a term of endearment. :-)

[@McTroyd]

Things like this have happened to me enough times that I've developed a suspicion of "easy" projects. 😅 If I can't think of a solution off the top of my head, the answer becomes, "Maybe. Let me look into it." Not a fool-proof solution, but it's saved a lot of my hair from being torn out.

[@AndreasSpiess]

A wise answer, I think!

[@Rpol_404]

Nice timing Andreas as I’m just now starting my own DIY pseudo portable solar system. The steps you went through sounds like a typical engineering epic journey, where the problems you had to solve along the way are typical for solar and wind projects. Thanks for the video!

[@AndreasSpiess]

My pleasure! and good luck with your project.

[@gendragongfly]

Nice video, very relatable. I also often start out with a project thinking it's not so hard. So I promise someone that I'll create a solution for them, and then things start to go wrong. And because they don't want to know the technical details, they start to assume I'm not as skilled or smart as I think I am. Usually when I finally manage to finish the project, I set the record straight by explaining in laymen's terms what went wrong. And after a couple of years I usually get happy comments that the solution I designed is still working great ☺️

[@AndreasSpiess]

The result is what counts! If the "customers" are happy in the end, i think, we can forget a lot of pain.

[@DumahBrazorf]

You can really feel the pain...

[@AndreasSpiess]

And hopefully, also the relief when it worked ;-)

[@edvardfranke]

But the problem is that the pressure comes from inside All other people can live with the state that we are failed… Only for us it’s painful…

[@akronyme]

Exactly what I needed... I'm actually in somewhat same position, stuck with the buck-converter. Thank you very much for your help in my problem ;)

[@AndreasSpiess]

I hope it will work in your situation, too!

[@xDR1TeK]

Good engineer Andreas. You figured out the right responsibility for the right roles. Hope your wife's sister's husband is happy about the chance to prove his usefulness. 😂😂😂 Mother in law would be pleased. Not so easy to please her. Good job. However, the mechanic might not be inviting you for beers anytime soon.

[@AndreasSpiess]

We will see if I have to drink my beers alone in the future ;-)

[@gustersongusterson4120]

I suppose one could throw efficiency out the window and charge with AC and oversize the array. Not very portable, but I have seen bikes that pull trailers :) Great work finding a more sensible solution!

[@AndreasSpiess]

The size of the panel is also important because she lives in a rented apartment. Bigger panels need some discussions...

[@Tore_Lund]

Yes not an easy feat. I theory voltage multipliers are simple in design to be efficient, but you both have to incorporate both charging and panel current limit to make it work reliably in all conditions. Thank you for this video. I'm currently trying to get 37V solar into 240V DC charging and my first two approaches turned out to get strange oscillations.

[@AndreasSpiess]

Power supplies and oscillations are partners. They often come together :-( I wish you luck!

[@SkyhawkSteve]

A few decades ago, I got to design a MPPT for satellites. This was an analog design, with a little digital, so it was an interesting project. The basic problem of staying on the right side of the max power point can be tricky, especially when that point is moving around!

[@ffoska]

That sounds interesting. Can you share some insights, how does the analog circuit work?

[@AndreasSpiess]

I agree. Today, with digital and cheap sensors, maybe it is a bit easier. Particularly if the sunlight fluctuates fast.

[@SkyhawkSteve]

@@ffoska The essense of the MPPT circuit was that the output current command to the buck converter was dithered with a small square wave. This produced a similar ripple on the voltage and current from the solar array. These were multiplied together (with a multiplier circuit) to produce a power signal. As you increased the value of the output current command (by means of an integrator), the power ripple would decrease. In fact, the power ripple was the input to the integrator. As you got closer to the peak power point, the ripple decreased, causing the integrator to gradually approach the peak power point. A small bias was applied to the integrator to keep it from crossing to the other side of the peak power point, which would cause the solar array to collapse. That's the 30 second explanation. 🙂

[@jacobclark89]

Wow that's amazing, what battery chemistry do they use ?

[@SkyhawkSteve]

@@jacobclark89 This was for satellites, and nicads were the only proven chemistry at that time. The battery packs were big and heavy... big enough to be a safety risk when the satellite came back down.

[@mistermagnifico]

I loved the flow of the video, gentle voice over and genuine findings

[@AndreasSpiess]

Thank you for your kind words!

[@zyghom]

at this moment 8:08 I would simply give 5V Zener diode on 42V output to get 5V low current trigger to the battery - let me see the rest of the video to see what you did

[@zyghom]

OK, I saw till the end and I am not sure why you did not think about "my" way ;-)

[@sheggy012]

Smart Idea. Would made the Design a lot simpler.

[@Ruudrad]

Exactly my idea as well, if the current will not be to high, so you can stabilize with a relatively high resistor and Zener diode. However…. It is probably used to feed the charger controller in the bike, so that current must be measured and taken into account.

[@AndreasSpiess]

You are absolutely right. But I started with the buck converter and was focussed too much to step back when I encountered the "insulation" issue.

[@codemakeshare]

My first thought was also "that shouldn't be too hard!" as I have in fact built the same setup for our e-bike batteries, also with a 100W panel, and using a $40 MPPT charger from Ali. It's been working really well for a year now, just missing some monitoring in Homeassistant maybe one day. But your video nicely highlights unexpected pitfalls, and cascading complexities rippling through. I built my own batteries, so I have the easy-to-buy connectors already, and my batteries don't need the 5V enable pin. Easy! But in your case, the need for sourcing 5V sounds easy, and then comes back with more complications even when everything else is solved. I've had exactly the same problems in other projects, where something seemingly simple comes back to haunt you over and over again, and you just can't escape the complexity trap... nice illustration of the life of an engineer, very true.

[@AndreasSpiess]

I assume your battery voltage was lower than the voltage of the panel. Monitoring in HA would be nice. I just built a 7kWh battery with a Daly BMS. It has an UART output and I found a ESP8266 project to connect to this connector. The output are MQTT Messages...

[@pfb3264]

‘This should be easy ..I’m smart ‘ …😂😂 Can so relate . So many little ‘gotchas’ in the video Had so many laughs .. thanks 😊 I charge my ebike via a used solar panel with PWM controller charging a crate of used SLA batts(~24v28ah) to a boost converter set at 42v . Has been working for 5+ years

[@AndreasSpiess]

Also a good idea!

[@simosagimain]

Nice video Andreas, thanks! It's always nice when a technical video explains the whole process, including little setbacks. Couple of questions: 1) How did you find the connector, did you get any hint anywhere about its make? 2) Does the 5V line draw any significant power or is it just a polarization? In the latter case a simple linear voltage regulator fed with the 42V (or even a 5V Zener?) could have been enough?

[@AndreasSpiess]

1. The brand was printed on the charger's plug. The rest was Google 2. I did not measure the current. But you are right, most probably, a Zener diode would be a much simpler solution.

[@simosagimain]

@@AndreasSpiess 1. You were lucky (or the brand is very proud of their connector 😀 )

[@georgedone7997]

@@simosagimain I am asumming the 5V line is not simply a signal line but some sort of power supply to a microcontroller chip built into battery pack which controls and monitors the battery. I still do not think it draws a sigbificant amount of power but might have some situations when it locks itself out when powered from the 42V converter since the converter only works when the battery is prezent and the battery is not detected as prezent unless it receives that 5V supply. I would be interested to know how long it takes to the battery to accept charging after it receives 5V. If it is (almost) instantaneous then is just a signal if it takes 5-10 seconds or more is a microcontroller powered by 5V line which takes a little time to boot and become operational.

[@avibank]

Interesting. TeachingTech just did a video explaining how he created his own custom connector for an obscure terminal with pins and 3D printing ("Making an unavailable, proprietary USB cable with 3D printing"). I suppose if it's used on a daily basis, it would have to be really well designed which means lots of iterations. So maybe it would have taken the same time and cost(?) as buying it. But you may have to do it one day when the supplier goes out of business or no longer makes the connector :P Let me know what you think of that video if you get a chance to watch it. As for your video - brilliant as always and thank you for sharing!

[@AndreasSpiess]

I agree, 3D printers are marvellous devices to print spare parts. But here, I also needed very special contacts. That made the thing more complex, I think.

[@lua-nya]

Also it's difficult to get it as sturdy and smooth with 3D printing.

[@GoatZilla]

@@AndreasSpiess Depends on if you needed to make the male side or the female side of the pins. If you only need to make the male side of the connector, you'd be surprised what you can actually get away with. I've retrofitted some connectors using things like old 2mm RC plugs and machined pins glued into a 3d printed plug replacement. Actually I had one sitting right here and realized... I actually made the female side of the plug using 2mm RC female contacts heh.

[@georgedone7997]

Very nice, interesting video. You could say "I accepted the challenge not because it was easy but because I tought it would be easy"

[@AndreasSpiess]

I agree.

[@katiekumcgil]

thats one of the best boost converters ,was originally designed in colaboration with ebikes CA,Grintech

[@lukehome]

As always a very informative video, thanks. Your storytelling about „the way to a happy sister in law“ put a smile on my face 😊

[@AndreasSpiess]

My pleasure!

[@yonaguska2050]

Nothing like a project for a family member to spark the creative juices and determination to get it right.

[@AndreasSpiess]

Indeed, a good goal is important for projects!

[@qzorn4440]

Wow, this sounds like some of the stuff that I get into. The old saying "All you have to do." 🤣 Then run for the hills. 😎 Thank you for the very interesting project. LTspice is nice.

[@AndreasSpiess]

You are welcome!

[@PatrickFelstead]

Andreas is branching out into comedy - thanks for the entertainment! And I'm glad you solved your technical issues too :)

[@AndreasSpiess]

Glad you liked the video!

[@PATRIK67KALLBACK]

I loved the comment about your wife's sister's housband of his usability as a mechanic. Now you can tell him that there's a whole youtube community that can remind him 😊

[@AndreasSpiess]

:-))

[@inlywang8157]

Hello Andreas, I am really touched by you, I found that you answer every commnent, you are so nice, really beat majority of KZbinrs. 😃

[@AndreasSpiess]

Yes, I try to answer all comments because people take their time to write them...

[@inlywang8157]

@@AndreasSpiess 💯👍👍

[@AerialWaviator]

Stories and projects with happy endings are the best ones.

[@AndreasSpiess]

I agree!

[@superdau]

The double DC-DC converters are a bit of an overkill, aren't they? ;) Since it's really just an on/off signal, it's very likely that anything from 3-5V would trigger charging on the battery. A simple 10:1 resistor divider on the battery voltage should be enough. That divider should even easily fit into the connector that goes to the battery.

[@AndreasSpiess]

Others suggested a Zener diode instead of the second resistor. I agree, these would be simpler solutions!

[@coolchop]

This video is very helpful. I walked the exact same way. But give up after testing the cheap PWM Solar Converter. I think I will give it another try now.

[@AndreasSpiess]

Good luck! I hope it will work.

[@stepheneyles2198]

Thank you for this! Having just purchased an E-bike 'conversion kit' for my ride I'm thinking about a portable solar charger so my battery can be refilled while I have a rest/picnic mid-ride! (Edit: removed bit about lower voltage - my charger is 42 Volts as well!) The family problems brought home the things us 'tinkerers' have to face - "why is it taking so long?" "Why don't you just buy one instead of making it yourself?" etc.!

[@AndreasSpiess]

We all have two batteries for long trips. Solar is not a solution for that problem in my opinion. To big for what you get in a short time.

[@johankotze42]

Very informative and told in a very humorous way!

[@AndreasSpiess]

Thank you!

[@JDSchuitemaker]

Love the way of how you picturized the concept of a sister in law

[@AndreasSpiess]

:-) Thank you!

[@dennyfox3139]

Quite a story Andreas, persistence pays off!

[@AndreasSpiess]

Indeed. But here I had no other possibility ;-)

[@rollandmaro8958]

I like this kind of teaching. I am going through something similar by the way.

[@AndreasSpiess]

Thank you!

[@bahaajobs]

loved the story behind the video 🥰

[@AndreasSpiess]

Thank you!!

[@tasmedic]

If I'd taken a year to achieve this, I think I would have found my belongings outside on the lawn after the first couple of weeks! You have a very patient wife, Andreas. And, she must love you very much to make all those excuses to her sister!

[@AndreasSpiess]

I know I am lucky with her ;-)

[@phester28]

Cn3722 boards or similar range on aliexpress are closer to mppt than the pwm controllers you tried early in the video, I have one working in my shed for a few years and modified them with potentiometers to have control of finish voltage. Also an aside if anyone tries to copy for a different applications. You can not float charge lithium batteries. So when the current draw of the batteries drops to a low level the charger should stop. A BMS may provide a disconnect but that is usually a over charge condition 4.25V/cell and is already doing damage to the cells.

[@AndreasSpiess]

I am not sure if you would not encounter the issues I encountered with the PWM charge controller because of my special situation.

[@sandrosachser]

The real name of this channel is "GREAT ANDREAS"!!! Regards from Brazil

[@AndreasSpiess]

:-) Thank you!

[@LarryKapp1]

I think most of the bike chargers go from constant current to constant voltage ( at a low current) at the end so the bms can top balance the cells in the battery by shunting current around the high cells to let the low cells come up. At least that is how my bike battery charger worked, but it was a LiFePo4 battery - maybe your sisters is a lion type - if so better not to charge it too close to a building because those kind of batteries are more prone to catch on fire if something goes wrong with charger.

[@solwidotnl]

These bike batteries contain Li-ion cells (18650 or 21700). All major bike brands have a decent battery protection circuit. The charger in the video is CV and current will decrease when the battery voltage gets near the setpoint. Still I would recommend to charge up till 41V and then switch off the charger until the voltage drops below 40 V or so. This way you can skip the last part of the charging which is slow and causes wear on the cells. Balancing occurs very rarely, as the cells are so well matched nowadays. It would be enough to fully charge the bike a few times per year using the factory charger.

[@AndreasSpiess]

During charging, the voltage is given by the battery pack because the current of the solar panel is smaller than the current of the original charger. And because I set the maximum voltage of the charger to 42 volts, the current drops the closer it comes to 42V. So I assume the battery is ok with what it gets from solar.

[@jescojakob6534]

Deine Videos sind einfach nur großartig. Technisch sowieso, aber auch der Unterhaltungswert ist extrem hoch- ganz großes Kino quasi ;-) Danke dafür!

[@AndreasSpiess]

Danke für deine netten Worte!

[@mcconkeyb]

Yup, battery charging with solar panels is no joke. I've been thinking of a battery maintainer for my automobile but haven't found the time to do it yet. I'm sure it will be even more complex than your story here, as I'm also thinking of adding a temperature controller (winter days in Canada can get as cold as -40C and that really changes how batteries charge and discharge). 😃

[@AndreasSpiess]

So you have a project for the dark days next winter!

[@wherami]

good video to show all of the complications in this work. its excellent knowledge

[@AndreasSpiess]

Thank you!

[@DarrenDignam]

Happy wife, happy Life! Gruezi from Basel!

[@AndreasSpiess]

I agree!

[@JensHeuschkel]

My inital thought would be to take a current limiter boost converter and replace the trim resistor with a digital resistor. Then, adding a arduino to measure the open loop solar voltage, adjust the the digital resistor to match limit the current to a good point and close the loop to start charging. Opening and closing the loop can be done by a cheap relais and should be done every now and then. Think that schould work with the stuff you have in your lab from the journey ;)

[@ivekuukkeli2156]

Yes, the right solution. Current mode stepup converters have been aviable for more then 40 years. Output current limited by Arduino program. Switching current is quite high so a parallel pair of fets is needed.

[@JensHeuschkel]

@@ivekuukkeli2156 parallel to the already existing fets? Can't he just pick a higher rated converter to be safe?

[@AndreasSpiess]

I agree. I also thought about it. But the "digital resistors" I used so far were for 5V. And these power supplies usually use much higher voltages. This is why I also considered to use a servo and a potentiometer... In the end, I was happy I did not have to go this way.

[@JensHeuschkel]

@@AndreasSpiess maybe you could come away with a voltage devider and a transistor as "high voltage digital resistor". Woth a try (or a video?) ;)

[@superdau]

Trying to "control" the trim resistor may seem like the "logical" way, but IMHO way more complicated than it needs to be (you need the right digital pot and an µC to set it depending on ADC measurements). The much simpler way is to "mess" with the feedback voltage, which pretty much all buck/boost converters expect on their pins for voltage and/or current control. You will have a voltage divider feeding that pin with one of the resistors being a pot in adjustable converters. I've used various methods on different converters to make them self "adjusting". Like: Pulling the pin just a bit higher (through a transistor and resistor), makes the converter think the output voltage is too high and essentially switch off. This can be use as a simple on/off for example. Shaping the feedback voltage with an opamp for whatever you need (I've turned a few voltage control only converters into current control converters that way). Even using smoothed PWM works well on some converters.

[@gustavoenriquejimenez8098]

You know you are an authentic maker when you buy parts just in case.

[@AndreasSpiess]

:-))

[@klassichd10]

Thank you! For my model year 2010 26V Panasonic drive I use third pary batteries with XLR charging connector. So, a small Victron MPPT and a popular RD DC DC converter did the trick. Was not the cheapest solution but worked straight forward. An the RD DC-DC converter is also usable in my lab. I charge my Ebike to 96% only. This doubles the lifetime.

[@AndreasSpiess]

I had such RD converters in my hands! But unfortunately, all ended at around 36V. Otherwise, they would have been a perfect solution with the displays and the current limiter built-in. I assume the Victron is a good solution. But they start at around 100 dollars if I remember right...

[@klassichd10]

@@AndreasSpiess yes, you are right. As I wrote: Not the cheapest solution but straight forward. At that time I budgeted it to emergency provisions. Ebike charging was just a nice "bycatch".

[@AndreasSpiess]

@@klassichd10 Bycatch in this respect is always welcome ;-)

[@clixium]

Great mptt charger, I'll look it up but why not just use $5 step up converter? Ebike battery has overcharge protection so there should be no issues. I'm charging my 52V ebike from 12V battery that gets its power from solar ocasionally, it served me well for past 2 years.

[@AndreasSpiess]

I thought I mentioned why a standard booster did not work in my case...

[@clixium]

@@AndreasSpiess sorry, I always follow your videos from start to finish, I somehow missed that

[@Milkybar3320011]

DIY = don’t involve yourself! Love this video

[@AndreasSpiess]

Thank you!

[@obsoquasi]

We live in Zurich and wanted to charge our two Flyers as well with solar energy. Since neither of us has an electrical engineering degree, we went the easy route. 2 x 100W Panel (on garden shed) -> Ecoflow River Pro Battery (720Wh) -> A/C output port -> Flyer battery charger -> Flyer(s). It's very easy to build and except for the battery quite cheap. Next part of the project: Protecting the battery from cold weather. We are moving the battery inside the house (near the circuit box) and connect it to that part of the house grid that feeds the power outlet in the garden shed where we charge the bikes - with a switch in the circuit box that lets us choose between grid power and battery power. In this phase we'll also add a third panel since they are so cheap. Now, sure I would have LOVED a direct charge solution like yours, but 18 months ago, nobody was able to provide a solution. I even wrote to Flyer, that this would be an awesome opportunity for them to create a eco-friendly solar charge system exclusive to their bikes. I really wonder why nobody jumped on that train yet...

[@AndreasSpiess]

Indeed, your solution is easier to build. And can be used for many other situations, too. But, as you mention: The price is very high because of the built-in battery. Here we invested this money into a second bike battery which is used during longer trips. So we can charge one and use the second one in normal situations. 18 months ago, I also did not know how to build it. Maybe a startup uses the idea ;-)

[@wjn777]

Great video, lots of laughs at your jokes and happy to know you also sometimes struggle with promises. Thanks for sharing

[@AndreasSpiess]

My pleasure!

[@lua-nya]

That's a nifty MPPT! Thanks for the video and the link.

[@AndreasSpiess]

You are welcome!

[@electrobob]

This sounds so easy if you had direct access to the battery. A solar panel of the right voltage is already a current limited source, so all you would need is a voltage regulator (MPP, LDO or DC/DC) to regulate the output to the full battery level. The BMS will take care of the balancing of the cells.

[@AndreasSpiess]

The battery has a built-in BMS. The problem is to get a relatively small panel with 42 V MPP...

[@joeltimajo7979]

I love your story here. 😍

[@AndreasSpiess]

Thank you! 😊

[@meandyousharinglife1137]

Good Job, Mr Swiss!

[@AndreasSpiess]

Thank you!

[@jyunnheikusada7003]

I had a project last year to harvest the sun light from my apartment windows. I also used a MPPT controller. My battery is reused from my scooter which can nolonger starts the engine well but fine for the solar controller. Any power exceed the tiny scooter battery I charge it to battery banks through the USB ports on the controller. Since my panels can only get indirect sunlight and stay vertical behind the windows. I get about 20Wh a day each window with 120W panel. But there are some benefits other than the power generated. The room get a bit cooler. I think the energy that the solar panels converted were used to heat up the room.

[@AndreasSpiess]

I think you are right that the power converted to electricity cannot heat your room. But maybe also some energy is reflected by your panel.

[@tanishqbhaiji103]

An easy solution would be to buy 2*24v 50W panels in series and using a common MPPT buck regulator.

[@AndreasSpiess]

I agree. This would also be a solution if you do not have an MPPT boost converter.

[@MyKharli]

Your brave , i went for fairly inefficient but off the shelf panel with battery and inverter and use the recommended or equivalent battery charger .

[@AndreasSpiess]

Another good idea (with probably a slightly higher price tag). But very versatile.

[@leonleon1809]

Awesome project. Especially nowadays when you have to save energy. This could be also a project to be rebuild by the community in several different variations (smaller/larger solar panel). One could describe the project more in detail and others can then rebuild it. 😊

[@AndreasSpiess]

Good idea. Go for it!

[@hssnov]

I almost cried, thankfully it was a happy ending. By the way this project is not easy you need a microcontroller and a control system to design it. I have a couple of my friends working PhD on this, while i am working on control systems design 🙂.

[@AndreasSpiess]

So good luck with your project!

[@deibitrubi]

Awesome project. I enjoyed watching how you finally succeeded.

[@AndreasSpiess]

:-)

[@RicardoCerveraBlanco]

I did something like that a few years ago but my way to solve it, I use the reverse approach, looked for a solar charger controller that works with 36v/42v batteries, I also looked into a 36v inverter "very difficult to find", manage to get a Epever solar charger controller, then I added 2 solar panels "I think 3" and it works fine, I think it has an usb port too which are normally 5v but I didnt need it for my setup...

[@AndreasSpiess]

Good approach. Much better than mine!

[@deangreenhough3479]

Great project Andreas and with some interesting hurdles to get over. I had ever faith in you 🙂

[@AndreasSpiess]

Thank you, Dean!

[@wktodd]

You inspired me to look at my kalkhoff bike charger and battery - Nothing as simple as a 5v pin - The two have a simple conversation before the charger is enabled !

[@AndreasSpiess]

Bad luck! So you need a logic analyzer and some hacking. I assume, the conversation always is the same and can be created by an ATTiny.

[@wktodd]

@@AndreasSpiess actually not that bad , I should have stressed the simple: 3v pulses from charger on to sense line , trigger battery to enable a 2.5s battery level on V+ (so charger can determine battery state) , then charger responds with 6v on sense for 2.5 seconds and then starts the controlled current charging . I was hoping to make a 12/24v charger but now I think an inverter might be the easiest option.

[@JasonDurrett]

Wow, I felt your pain Andreas! My smaller project recently involved a small multi-purpose auxiliary battery that had to be rugged and functional for charging not only in the vehicle 12 volt system from the alternator, but also direct plug when I can use a solar panel. It was an interesting adventure but far easier than yours, I'm impressed. Great job friend!

[@JasonDurrett]

It consisted of 4 Headway 38120 LiFePo4's and a cheap BMS from Heltec. It's perfect for my job as a SCADA technician.

[@AndreasSpiess]

I am glad you found your solution. Always a good thing!

[@katiekumcgil]

you are right though ,i tried a pwm controller i already had and it continuosly had up and voltages which would drop out the boost converter unless allways had direct sun,the mttp starts up as soon as i gets decent daylight

[@carloscolson3652]

I hope everything is OK, when the youtube of a Swiss doesn't appear at 9:00😂thanks for the work👌

[@AndreasSpiess]

My mistake. All ok. I just was too late ;-)

[@Doping1234]

Great timing, I had a similar project idea in mind - now I will wait a bit to tell my wife about it ;)

[@AndreasSpiess]

So you will be better prepared than me ;-)

[@LouiesLog]

Thanks for no mid roll ads gwasa

[@AndreasSpiess]

You are welcome. I do not like them. This is why I do not want you have to suffer ;-)

[@whereserik]

You have so many good videos, but this is my favorite

[@AndreasSpiess]

Thank you!

[@johnmccormick2883]

Interesting… but the biggest takeaway is twofold: a) your persistence & b) your ability to find a part that you bought long time ago in your workshop. Two things that I struggle with … 73’s

[@AndreasSpiess]

Not only you! Also here, motivation is needed for persistence ;-)

[@emilalmberg1096]

A nice story, in more ways than one! The basic problems are several. Charging batteries takes time, and you cannot use the solar panel's power in a meaningful way. It is best not to think that a panel should have a task, such as charging a bicycle battery, but instead supplies the house's electrical system, which is better able to charge small batteries. People also have such high thoughts about technology, we must dare to be clear that we must think and calculate the problem first...

[@AndreasSpiess]

I agree, I could have built a "balcony power plant" and connect it to the home grid. But this was not the wish of my wife's sister. In this project, efficiency or cost were not important, I can assure you ;-)

[@Badg0r]

What a good video! Thank you for a new type of learning video.

[@AndreasSpiess]

Glad you liked it!

[@PhG1961]

Really awesome and something I'll reproduce myself asap. Btw, in the beginning of the video... of course you say yes without thinking... we all do! Especially if the wife asks something...

[@AndreasSpiess]

:-)) Glad you liked the video. The project contained such a lot of work I had to create a video ;-)

[@AL6S00740]

amazing :D So rule never promise before evaluating the deal properly :D and the difficulties of the project at hand :D

[@AndreasSpiess]

I agree!

[@tinker7722]

Very usefull, thank you for sharing your Know-how!😊

[@AndreasSpiess]

Glad you liked it!

[@Captain_Char]

I would have just started with a 48v solar panel and worked down, but the fact this worked well is interesting

[@AndreasSpiess]

48V panels probably would have worked without a controller. But the ones I know are quite big and heavy.

[@Whereswally606]

Got two of theses elejoys a few years back after a review by justin le elmoire of the grin cyclery in canada. Going to use them in my env200 van conversion to add a tertiary battery voltage of 40v (i already have lots of mower batteries that power my ebikes) and this hopefully with allow me to cheaply implement a leisure battery that can be topped up by the solar where as it is technically much more difficult to charge the 400v bev battery directly from the solar.

[@AndreasSpiess]

At least here, it works. So it should work also for you...

[@Whereswally606]

@@AndreasSpiess yep already did a yt vid on it a while ago. Works but the batteries i have are not designed to be charger on anything but their charger so i wonder whether like your wifes sister's if there is a simple 5 volt enable signal.

[@morpheusde]

Toller Beitrag Andreas aber ganz toll und typisch, auch für mich ist der Satz "No plan, but: yes i can :-)" so mache ich das auch immer hihi

[@AndreasSpiess]

Das sind die Optimisten... Bringt aber über alles eine gute Lebensqualität!

[@peter.stimpel]

Nice one, Andreas. How did you came to the idea of feeding 5V to start charging?

[@jochen_schueller]

Maybe the original charger does so?

[@AndreasSpiess]

As Jochen wrote: When my charger did not work, I searched for the problem and found the 5V. All other pins had no voltage.

[@Plutoid-mz1ty]

Grüezi. Great video. I plan do build something similar for my Bosch and Shimano batteries. I already bought the boost MPPT controller and have 18V and 41V panels to play with. Li-ion batteries need a special charger that uses CC and then CV when they reach 42V in the case of a 10s battery. 1. Where is this happening in your setup? 2. Is there a termination charge when the current reaches 1/10C? Do you have to use a relay on a timer to stop the charge? Or just relay on the battery to stop the charge? 3. Assuming that the panel would be 500W or more instead of 100W, how would the current be limited such as not to trip the battery's BMS? The controller does not seem to have a current limiter. 4. You wrote several times in the comments that if the panel has a sufficiently high voltage you can charge the battery without a controller. I have a 400W Vmp=41V Imp=9.8A but I think that connecting it to the battery without some form of current limiter would destroy the battery or trip de BMS. What do you think?

[@AndreasSpiess]

I just emulated my charger that supplies a constant voltage. The rest is done by the BMS inside the battery. This might be different in your case. You have to do your measurements. Constant current is no problem with small panels as they never reach any currents the batteries support. If you have a big panel, again check the currents to see if it is limited by the BMS.

[@Alan_UK]

Perseverance pays off! Congratulations on getting it working. I bought one of those PWM blue controllers to charge a 12V lead acid car battery from a 20w Mono Solar Panel but in the winter with low temperatures it is not enough to start the car if it has not been used for a week. The alarm system is taking energy. On another topic. Have you found a way to control an electric hot water heater from excess solar? I have built a energy monitor. When there is > 1kW of spare energy it switches on the heater (1kW element). It measure the excess solar every 4 mins but I'm "chasing the sun". I would like to heat the element when there is less than 1kW of spare energy. So presumably the voltage need to be varied. But I have yet to find such a controller. Maybe I do not know the right words to search with.

[@AndreasSpiess]

AFAIK they use standard "dimmers" to reduce the power of the resistive heaters if connected to your home grid (AC side). For regulation, you can use the smart meter (or a shelly at the same position if you cannot access the smart meter). Always when it starts to "sell" energy, you switch the heater on till it stops "selling".

[@TheEmbeddedHobbyist]

what is the current taken by the 5V input, does it power the internal cct or just a signal. it must power the cct as if it was just a signal i expect you would have just used a Zenner to provide the 5V from the 40V charger power out side side.

[@AndreasSpiess]

I did not measure the current. But I am pretty sure your solution would be much easier!

[@Nebulorum]

Eletronics and life advise. Loved it.

[@AndreasSpiess]

Thank you!

[@erikladefoged6108]

Great video. Now, I wonder would the lady be able to put the solar panel on a trailer and charge the battery while riding the bike? I.e. charging the battery while at the same time consume energy from the battery for riding the bike?

[@AndreasSpiess]

This was tried by a few KZbinrs. Unfortunately, without success because it takes a long time to charge the batteries. Much longer than you drive your bike.

[@simonlinser8286]

When I have an idea it seems easy, I know it is possible, but then when I try to do it I realize it's a bit a more complex. Example, i was trying to build a solar panel by connecting a bunch of little panels. I didn't know they all have to be identical or else they will all have the output of the lowest amp panel, lol, that was a lesson though. Sometimes it's better to buy things, sometimes it's not. Ive been thinking of a way to have a battery that can charge at 12v, by making a charging circuit that splits the battery pack in to 12v segments, they get charged in parallel, but for use the whole pack is 52v... which seems like a really cool idea to me.

[@AndreasSpiess]

Indeed, it is good to use very similar panels if you connect them in series ;-)

[@steveanimatrix3887]

I wonder if getting 2 panels in series for ~40v output would have been easier, and as a bonus charge 2x as fast?

[@AndreasSpiess]

This would work if their MPP would be around 42 volts

[@xDR1TeK]

"yes, I can" is every engineer's bane. Been there, done that.

[@AndreasSpiess]

:-)) That is why I thought I would share the story.

[@keithw32123]

Very interesting and funny. Thank you for making this.

[@AndreasSpiess]

My pleasure!

[@magikben]

For the 5v signal: simple voltage divider to bring the 42v down to the input level of a 7805 or MIC2940-5?

[@AndreasSpiess]

I agree. Others even proposed to add a Zener diode...

[@Prostatafocal]

Excelent video! Not only informative but also funny

[@AndreasSpiess]

Thank you!

[@eugenegoldenau485]

Usefull, interesting and ... funny! Thank you!!!!!

[@AndreasSpiess]

You are welcome!

[@ralphj4012]

Well done for surmounting all those challenges. Could you have also used a portable power station (connected the panel to the power station to charge the internal battery and used the mains output to power the original bike charger)? Not a cheap option, I know.

[@AndreasSpiess]

Yes, this would have been the most expensive solution. In-between would have been to use a microinverter and feed the power into the home grid.

[@tonyh6309]

'Danger Will Robinson!!!' Those cheap isolated DC-DC converters are typically unregulated and require a minimum load of 10 to 20%, otherwise the output voltage could be *double*, or more, the rated voltage. A RECOM part I tested had the output voltage go beserk when the input voltage dropped significantly below (around 20%) the minimum input voltage (coupled with a less than minimum specified load) - so be careful if the load is voltage sensitive. Especially check out startup/shutdown conditions when normal input voltage doesn't apply.

[@AndreasSpiess]

Good information. Thank you! I saw that they do not provide a stable voltage and moved with the input. But my input was stable. So was the output. Anyway, others suggested to use a simple Zener diode instead and connect it to the 42V. Maybe I will go this direction...

[@scoutjonas]

I have a similar setup, but after some thinking I realised a simple buck or boost would no solve it. I wanted to charge 12V lifepo4 with 20W solar. So a MPPT would be to pricy... So I used a fuse, a LED and a diode instead. You would need a solar panel with higher voltage or 2 in series. And you would not get the maximum efficiency. But you would be done in a day and it would be cheaper...

[@AndreasSpiess]

I agree, if you find panels with an MPP of 42 volts you can save the controller.

[@pepethefrog7193]

There is a $8 40A boost converter with "input low voltage protection" on ali which does the same job. Set "low volt prot" to solar MPP volt. $12 shipping.

[@AndreasSpiess]

I am a bit skeptical with boost converters. Unfortunately, the MPP voltage is not constant (as I showed in the video).

[@pepethefrog7193]

@@AndreasSpiess MPP is mainly influenced by temperature, not so much by intensity. If you aim at MPP minus 5% you on the safe side.

[@sail4life]

Oh the joys of working your butt off for people who will never understand how hard it can be! "Why is is so difficult, you just plug it in and it works, see!"

[@AndreasSpiess]

If it is family, it is ok for me. But I once refused to work for such a boss. There, this behavior is dangerous ;-)

[@iliazark1]

I've had to solve a similar problem... The cheapest solution I found is to reverse engineer the DC-DC converter, add an op-amp as a comparator between the input voltage and an analog out of a microcontroller and feed the output to the feedback of the controler on the converter... Add some kind of current sensing (the hall effect ones are the easyest to use) and some lines of code later you are ready to go... The microcontroller can dictate the minimum input voltage (through wich it can find the MPP) and you still have max output voltage and output current control from the potentiometers wich usually come with the converter... This solution has been working perfectly for me for about 7 years now..

[@AndreasSpiess]

That is a good solution and for sure, I would have gone a similar way without the latest catch. I assume that my MPPT boost converter works in a very similar way.

[@YoutubeHandlesSuckBalls]

Personally, I would have put a decently sized car battery (100 AH) between the panel and the bike. There are plenty of cheap controllers you can put between the panel and the car battery, then you just need to interface between a 12V car battery and the bike which should make the problem an easy one. You can run your 5V from the battery and then boost the output from the battery to charge the bike, which is a smaller capacity than the car battery so should not discharge it. As long as the charge into the car battery is lower than the discharge into the bike it will be fine (and you can even charge the bike at midnight). You get all the amps you need from such a battery at any time of the day.

[@AndreasSpiess]

Also a good solution. The bike battery has 625Wh and AFAIK you can discharge the car battery to around 50%. So a 100Ah battery would be big enough. But also heavy to carry around if you need.

[@YoutubeHandlesSuckBalls]

@@AndreasSpiess Ah, I didn't realise the charging system needed to be portable. Yes, they are quite heavy but could be put on a sack truck