SIMPLE SAFE LI-ION BATTERY (SOLAR) CHARGING

Thread Starter

Hugh Riddle

Joined Jun 12, 2020
23
I am constructing a solar-charged placard carrying 20 LEDs which shine at night and want to power it from an 18650 3.7V 2.8Ah Li-ion cell in the simplest possible way, if possible without using a charging IC even if the charging action is a bit inefficient. I realise Li-ion cells can explode and are easily damaged during overcharge or overdischarge. However, I've examined a couple of solar-recharged garden lighting products powered by Li-ion cells which are charged via a simple diode and lack any obvious protection against over/undercharging.

Does anyone here know how the designers of these products satisfied themselves that the product posed no risk to consumers and that the cell would not be badly damaged by possible over/undercharging? I can only guess that careful choice of PV panel V and I and battery V, I and capacity can eliminate explosion hazard and that cell damage will be too small to be noticed by the consumer. This is very much the stuff of in-house manufacturing know-how but I'd be really glad to hear your ideas on it.
 

dl324

Joined Mar 30, 2015
10,987
Welcome to AAC!
Does anyone here know how the designers of these products satisfied themselves that the product posed no risk to consumers and that the cell would not be badly damaged by possible over/undercharging?
They didn't. They're gambling that no one will sue them if the battery explodes or catches fire.

A responsible designer working for a reputable company would use a battery chemistry that is less likely to do something bad if the battery isn't charged properly. Or use a more appropriate battery chemistry.
 

Thread Starter

Hugh Riddle

Joined Jun 12, 2020
23
Welcome to AAC!

They didn't. They're gambling that no one will sue them if the battery explodes or catches fire.

A responsible designer working for a reputable company would use a battery chemistry that is less likely to do something bad if the battery isn't charged properly. Or use a more appropriate battery chemistry.
 

Thread Starter

Hugh Riddle

Joined Jun 12, 2020
23
Not my experience while working in consumer manufacturing. There's certainly pressure to minimise cost but potential liabilities are taken very seriously.
 

dl324

Joined Mar 30, 2015
10,987
Not my experience while working in consumer manufacturing. There's certainly pressure to minimise cost but potential liabilities are taken very seriously.
It depends on which companies you're familiar with.

Ever hear of a company cutting baby formula with melamine?
https://www.webmd.com/parenting/baby/news/20080912/fda-dont-use-chinese-infant-formula#:~:text=In China, one baby has,Chinese infants, the FDA notes.

Ever hear of companies that contracted with Chinese manufacturers to manufacture counterfeit parts to be sold to the US military?
https://www.computerworld.com/article/2522119/man-pleads-guilty-to-selling-fake-chips-to-us-navy.html

Chinese manufacturers have been known to compete with their customers. Even going so far as to sell counterfeit/reject parts with exactly the same part numbers and logos (I bought a counterfeit BMW ignition switch on Amazon; complete with BMW part number and logo).
 

Papabravo

Joined Feb 24, 2006
13,939
BTW - It seems worth mentioning that there is very little consumer manufacturing that is done here any more. So I'm not sure what your experience in consumer manufacturing even means.
 

dl324

Joined Mar 30, 2015
10,987
And there was I imagining this page might provide something of a refuge from politics.
What I've said has nothing to do with politics.

The company cutting baby formula with poison was doing it to increase their profits. They didn't care that infants could/would die.

The guy specifying the production of counterfeit parts and falsifying certification with the intent to sell them to the US military was just trying to make money. He didn't care that it was a national security issue to have military readiness jeopardized or that people could die because of his criminal activities. He was just trying to make money and didn't care who got hurt in the process.
 

Papabravo

Joined Feb 24, 2006
13,939
The presence of advance fee scammers, IRS scammers, SSA scammers, and tech support scammers using the phone for their activities shows there are people willing to steal an old lady's life savings if they can get away with it. They could care less about the devastation those activities cause.
 

dl324

Joined Mar 30, 2015
10,987
Did I mention all of the counterfeit 18650 batteries (and other sizes) coming from China that could explode and/or catch fire even if they weren't abused?
 

Thread Starter

Hugh Riddle

Joined Jun 12, 2020
23
In DIY of all activities, people are usually on a learning curve as I am on solar charging and the use of Li-ion cells. I'm now thinking it likely that the press may have caused us to over-ingest some of the dangers and susceptabilities to damage of Lithium cells, particularly where energy transfer rates are moderate. One need only study the severity of the tests described in Li-ion cell datasheets to realise how mild are the abuses occurring in the type of solar charged arrangement I have in mind. From my experience a firm which knows it can be held accountable would have tested numerous sample batteries considerably beyond the worst conditions expected in their product - to assess risk and minimise the likelihood of complaints.
 

Papabravo

Joined Feb 24, 2006
13,939
In DIY of all activities, people are usually on a learning curve as I am on solar charging and the use of Li-ion cells. I'm now thinking it likely that the press may have caused us to over-ingest some of the dangers and susceptabilities to damage of Lithium cells, particularly where energy transfer rates are moderate. One need only study the severity of the tests described in Li-ion cell datasheets to realise how mild are the abuses occurring in the type of solar charged arrangement I have in mind. From my experience a firm which knows it can be held accountable would have tested numerous sample batteries considerably beyond the worst conditions expected in their product - to assess risk and minimise the likelihood of complaints.
How is it that you would be able to sue a Chinese company in a US Court?
 

dl324

Joined Mar 30, 2015
10,987
From my experience a firm which knows it can be held accountable would have tested numerous sample batteries considerably beyond the worst conditions expected in their product - to assess risk and minimise the likelihood of complaints.
Have you dealt with any companies that have sold counterfeit parts, including lithium ion batteries, who knew they were selling counterfeit parts or cared? They just claim ignorance. When it starts interfering with their criminal enterprise, they go out of business and start selling under a new name.

Here's an example where Nikon was taken:
https://www.dpreview.com/news/4819009922/nikon-confirms-some-counterfeit-en-el15b-batteries-were-sold-by-authorized-retailers

You can stick your head in the sand all you want. Counterfeit lithium ion batteries can short circuit and cause fires and/or explode with no abuse.
 

Audioguru again

Joined Oct 21, 2019
1,595
I have many solar garden lights, none use a dangerous and expensive Lithium-ion battery. Old ones used a cheap AA Ni-Cad cell and newer ones use a cheap AAA Ni-MH cell. The solar panel is selected to limit the charging current and an IC steps up the voltage and limits the LED current.
 

Thread Starter

Hugh Riddle

Joined Jun 12, 2020
23
I've managed to explore my reading lamp further and find its single (unidentifiable 8pin SOIC) IC disconnects the lamp when Vbat sinks to 3VDC then re-enables its constant current drive (2.5kHz 100mA pulses, 1/3 duty cycle) at 3.6VDC, presumably to avoid providing low rate recovery from very low Vbat. Overcharge seems avoided by PV panel selection (Voc 5.9V, Isc 180mA) so that Vbat never exceeds about 3.9V. Not claiming that covers every conceivable condition (eg left unused for years). Can you think of any others?

The lamp is interesting, appearing to have two parralleled LED filaments wired directly to E27 base of retro envelope and exhibiting single white LED V-I and is driven by 2.5kHz 100mA constant-current pulses at 1/3 duty cycle. Must be the easiest ever lamp to blow up by accident! Could each filament comprise an array of parralleled (rather than the usual seriesed) LEDs? So parralleling the filaments compounds the outrage and fundamentalists (incl some here) may seethe.

I don't doubt there are bad Li-ions are around (also heard most 18650s don't deliver claimed capacity). But engineers have to handle many areas of uncertainty while Li-ion's potential is very great and technologies often improve over the years (e.g. dendrite elimination). That's why, on my learning curve, I take an interest in, rather than damn, a product which appears to venture outside received wisdoms.
 

Thread Starter

Hugh Riddle

Joined Jun 12, 2020
23
I have many solar garden lights, none use a dangerous and expensive Lithium-ion battery. Old ones used a cheap AA Ni-Cad cell and newer ones use a cheap AAA Ni-MH cell. The solar panel is selected to limit the charging current and an IC steps up the voltage and limits the LED current.
Yes, that's what I have generally found - up until now. That step-up IC (XY8019?) used with single NiMH is fascinating but I can only find Chinese or minimal info. Please, have you found fuller data for it in English anywhere? I'm wondering whether constant-current/constant-energy and max Vs and Is, turn on V etc) and reluctant to risk blowing up the only one I've got by experimenting!
 

Audioguru again

Joined Oct 21, 2019
1,595
Most of my Li-Ion and Li-PO batteries work perfectly because they are Name Brand. Many 18650 and hobby batteries bought on ebay are counterfeit fakes and even ebay and its seller do not know who made them.

My solar garden lights light only one LED all night long not very brightly. Most of then use a QX5252 and here is its datasheet:
 

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