Luck-based lithium charging
bigclivedotcom 9:08
373 views · 363 likes Watch on YouTube ↗
I'm really not sure why stuff like this is made. Lithium cells are energy storage devices that need to be treated with respect, but in this case they've literally broken every single rule.
At first I thought that the chip may have been a dedicated solar garden light chip with integrated charge control, but it appears to be a very standard cheap microcontroller where they have abused the internal protection diodes to charge the lithium cell, while doubling up as dusk sensing. I hoped they might have done something clever like detecting a high voltage on the microcontroller power rails and then toggling the load on and off to shunt excess charge, but they haven't.
I made a test setup where I emulated the solar panel putting out 50mA and used a battery of three NiMH cells to emulate the lithium cell with less risk when overcharged. I terminated the test at 4.4V with no sign of charge regulation. When the battery is disconnected the charge voltage floats up to the full solar panel output (6.5V) minus the diode voltage drop.
A classic all in one lithium protection chip could have helped here, but does also pose a risk of allowing the supply across the chip to float quite high when it breaks the circuit.
In some climates these units would be usable by relying on the amount of solar energy during the day not being able to fully charge the lithium cell, and then general usage at night making sure it was fully discharged again overnight. But in sunny climates or where the unit was left in its off-state or not triggered much at night, the cell could soon be overcharged.
When you add the high temperatures these solar cells are exposed to on hot days, and the very taboo way they attempt to charge the cells at sub-zero temperatures then it's amazing that there aren't more fires caused by these lights.
The final test capacity of the 14500 lithium cell was 264mAh.
There is no proper current limiting for the LEDs. They seem to rely on the cell, wire and transistor gain/resistance to limit the current.
If you buy one of these as a novelty to explore, then I do not recommend mounting it anywhere it can cause a fire.
If you REALLY want a link to this dodgy product then here's an (affiliate) link to it:-
https://s.click.aliexpress.com/e/_c3QC3Y69
But seriously - there are better versions. This should be treated as an exotic piece of bad tech.
If you enjoy my videos, supporting the channel on Patreon helps keep it independent of YouTube's quirks, avoids intrusive mid-video adverts, gives early access, bonus footage and regular quiet Patreon live streams.
https://www.patreon.com/bigclive
Alternatively, for a single coffee contribution you can use PayPal:-
https://www.paypal.com/paypalme/bigclive
#ElectronicsCreators
At first I thought that the chip may have been a dedicated solar garden light chip with integrated charge control, but it appears to be a very standard cheap microcontroller where they have abused the internal protection diodes to charge the lithium cell, while doubling up as dusk sensing. I hoped they might have done something clever like detecting a high voltage on the microcontroller power rails and then toggling the load on and off to shunt excess charge, but they haven't.
I made a test setup where I emulated the solar panel putting out 50mA and used a battery of three NiMH cells to emulate the lithium cell with less risk when overcharged. I terminated the test at 4.4V with no sign of charge regulation. When the battery is disconnected the charge voltage floats up to the full solar panel output (6.5V) minus the diode voltage drop.
A classic all in one lithium protection chip could have helped here, but does also pose a risk of allowing the supply across the chip to float quite high when it breaks the circuit.
In some climates these units would be usable by relying on the amount of solar energy during the day not being able to fully charge the lithium cell, and then general usage at night making sure it was fully discharged again overnight. But in sunny climates or where the unit was left in its off-state or not triggered much at night, the cell could soon be overcharged.
When you add the high temperatures these solar cells are exposed to on hot days, and the very taboo way they attempt to charge the cells at sub-zero temperatures then it's amazing that there aren't more fires caused by these lights.
The final test capacity of the 14500 lithium cell was 264mAh.
There is no proper current limiting for the LEDs. They seem to rely on the cell, wire and transistor gain/resistance to limit the current.
If you buy one of these as a novelty to explore, then I do not recommend mounting it anywhere it can cause a fire.
If you REALLY want a link to this dodgy product then here's an (affiliate) link to it:-
https://s.click.aliexpress.com/e/_c3QC3Y69
But seriously - there are better versions. This should be treated as an exotic piece of bad tech.
If you enjoy my videos, supporting the channel on Patreon helps keep it independent of YouTube's quirks, avoids intrusive mid-video adverts, gives early access, bonus footage and regular quiet Patreon live streams.
https://www.patreon.com/bigclive
Alternatively, for a single coffee contribution you can use PayPal:-
https://www.paypal.com/paypalme/bigclive
#ElectronicsCreators
Category (YouTube): Science & Technology
Playback is via YouTube's official embedded player. Data from YouTube; Exumo is not affiliated with YouTube.