Easily charge an 18650 Li-ion battery directly with a 5V Solar panel

Fast and easy way to charge a single (1S) Li-ion battery pack with a 5V Solar panel. The living proof is at 7:55 showing this light I made over 2 years ago and it's still on it's original 18650 I put in back then. That also means this LG 18650 cell has been through almost 1,000 cycles (365 days x 2.3) and still going strong. See how dusty it is now with spider webs and dead bugs on it! Here's the link to the video I made in March-2016: • How to charge a 18650 ...

[@andytipping70]

resistive dropping is NOT good enough regulation - as current drops as the voltage of the battery rises, then the voltage will continue to rise until the full voltage of the solar cel, less 0.6v drop of the diode, will be seen across the battery. you need a constant voltage source set precisely to 4.2volts. In fact - you should use a constant current constant voltage source - but the solar cell will never supply enough current to do any ham so thats why nothing has blown up -yet! if you have a big enough solar array connected, you WILL destroy your battery using your method of voltage reduction.

[@CANTON76A]

You only need the solar panel and a protected lithium cell. The panel will not push enough amps to damage the battery, and the protection circuit will stop it overcharge,. There are plenty of videos about that on YT.

[@kd5txo]

Yes, this is true. As a practical matter, I would suggest only using the diode to prevent nighttime discharge of the battery into the solar panel cells. This would preserve the battery stored energy for use by the light only. Also, if the light fixture is opened and examined closely....You will find a diode is already there in some form to protect the original NMH rechargeable batteries from nighttime discharge into the solar cells. So, really no need to add another diode yourself.

[@arrich4605]

Thanks for sharing this wonderful idea.

[@BAKKER2727]

this wonderful idea.

[@beelan9165]

very good explanation, very educative

[@youyoo3408]

Nice vid, very useful soon many 18650s around..charge them up through 5v usb.

[@southwestelectronics4902]

GREAT JOB !!!

[@chicagotruckerlifeforlife5570]

Thank You My Friend...👍

[@dieterleuchtenmueller8642]

Interesting concept; I experimented similar idea with reasonable success. As a suggestion in your Ohm's Law calculation, you need to consider the voltage drop across the diode (which is usually around 0.7 volts, depending on diode type and current flowing thru it). My prototype consisted of 10 cells hooked up in series with a common ground connection, and positive leads tapping off of cells 7-8-9-and-10. Connnecting to cell #8 would offer an approximate 4-ish volts; I didn't have to worry about overcharge. My prototype is strictly for experimentation purposes; I'm measuring charging efficiencies (compared to MPPT) and to satisfy my own curiosities. Be careful with your design as solar panels behave in very dynamic fashion depending on temperature, sun irradience, 18650 internal impedance, load, and so forth. They don't output power linearly based on these factors. ....enjoy.

[@williamc1]

Thank you very informative

[@ttibor]

Can I use a variable step down converter circuit, set to 4.15V? (Plus a diode of course.) In theory the end result should be the same, the circuit even stabilises the voltage if the solar panels output spikes up for some reason.

[@milvolts1]

Great stuff as always V. I have a panel that produces 5 watt and 9volts. Would this work for a 2s 7.4v. I need over 5 volts output for my light project. Thanks

[@octaviovillasenor6638]

You can use tp4056 Lithium ion charger

[@vuaeco]

Yes, you can. But you can't get a TP4506 from a local Walmart. You have to order it online and it usually takes weeks or even months from China. But with this, you can just pull out some old electronics, salvage some resistors and diodes, and you're good to go.

[@caseymuni4097]

The voltage drop is calculated at maximum charging current. When the battery is fully charged the voltage drop will decrease and the lithium battery will be over charged. In addition- internal resistance of the solar cell and reverse diode leakage would discharge the lithium battery in the winter months and long night hours.

[@vuaeco]

Yet, 3 years later, this is still working!

[@benzpinto]

is this some sort of voltage divider?

[@pooorman-diy1104]

the resistor will not stop the charging current once its full .. the voltage drop of diode will ..

[@youyoo3408]

Since the max current from the small solar panel is already limited to less than the max charging current rating of that battery, no current limiting is needed, maybe two, 1 amp diodes in series would drop about 0.6v +0.6v =1.2v and have about 3.8v for the batery, if that is enough for some devices.

[@jordanramage9355]

Hi, I have a sunforce led solar light with ni mh battery’s. It had 3 aa at 1.20 v and fully charged at around 4.20v am I alright to put a 18650 without modifying the Circuit board because im thinking it would have a built in protection for the ni mh batterys ?

[@miguelsantos6969]

I got a Christmas lights that had 3 batteries of 1.2v 400mA and i replace it with a 18650 battery of 1600mA and so far is working perfectly, just notice that the solar panel is not powerful enough to charge the battery, so next is to change the solar panel for something stronger.

[@flyrobin2544]

This is what people need to use instead of the gravity led lights, which cost $80. Thank you for your videos I'm enjoying them :)

[@johnbozi]

would love to see if this works in series cells. video please :)

[@David-bc4rh]

you'll need another solar cell for each new battery cell

[@DJMcMahon6740]

What a genius. I'm creating my own battery pack and this just inspires me to learn much more about batteries

[@PolakeXD]

It looks very interesting but I would prefer one of those (new version) tp4056 charging units which I can get as bulk order (38 boards) for around 7,22$ With this Boards I can just solder a 5,2v solar panel and charge my 18650 cells with it. In the evening I can just plug in a microUSB charger and use it to continue charging. There is also a possibility to add one of those ESP8266 boards to monitor everything with your devices which have WiFi ;) I actually tried to do this but I failed with the arduino programming language : P If it would work with c++ or python then I would be able to successfully Programm this fake arduino

[@adityaprabhu6]

Where did you get the solar panel from? The ones I find are more rectangular - the one you're using looks just right. Was curious if they can be found somewhere in stores. Appreciate any thoughts.

[@TDH75]

Is it me or does this guy have a southern US accent? Lol.

[@vuaeco]

It's you.

[@BeNtOoOoOo]

Only works without clouds... 1 little bit of shade and out of the window that hack goes. TP4056 costs 0.5, no point on doing that.

[@TomTom-rd3iy]

nonsense started at 2:45. also forgot the diode with 0,7V in ohm calculation ;)

[@jamesnash2900]

First

[@octaviovillasenor6638]

You used tp4056 chargers