18650 Under voltage protection

There are 18650 cells available with a protection board built in ....approx $5.00 each delivered through Ebay.

https://www.ebay.com.au/itm/TrustFire-High-quality-PCB-Protected-18650-3-7V-battery-2-pairs-3000mAh-T2E0/253287982984?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Individual cell USB charger boards are also cheap at around $0.33 each.

https://www.ebay.com.au/itm/10pcs-T...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

 

You can get "battery protection board" shipped world-wide on eBay (usually coming from China). Will they not ship to you?

A few other thoughts about this project...

Some major brand 10W LEDs are fairly good quality, but many of the generics that look like the following picture, have very poor quality manufacturing and a large % of them are defective in having excessive leakage, essentially being very inefficient and creating excessive waste heat, to the point where they cannot be run at ratings or else that will cause cascade failure from one die at a time.

I simply would not use that type of LED for any battery powered project, especially in this case which leads up to my next suggestion which is that whether it is a cell phone battery or an 18650, this seems quite undersized for something meant to withstand the duration of a power outage.

Consider that you're starting with 3.6V (nominal) and boosting to around 12V, and suppose it's about 90% efficient. The result would be that even from a 3000mAh 18650 cell, it won't even run for an hour.

Then there is the other problem. Although the LED is spec'd as 900mA at 12V, this is just a generalization. It should still have current regulation rather than the voltage regulation. It should be limited to 900mA, then whatever voltage it takes to achieve that, not 12V then whatever the current is to achieve that.

Really not even that if it is as mentioned above, that it's a generic Chinese LED. In that case I would only drive it at half power for both LED lifespan and increased efficiency BUT as I also mentioned, I just wouldn't use a generic Chinese LED at all. You might literally get the same amount of light with less than 2/3rds the current using a major brand LED.

With experimentation you could get the XL6009 to work for this single prototype by monitoring the current then once the LED heats up to max temperature, adjust the voltage down to where it needs to be to have 900mA, but if you do not have the XL6009 yet, then I would just abandon the idea of using it and get a 10W (or as already mentioned a 5W might be more suitable with the other parameters) current regulated driver. These too should be available on eBay with worldwide shipping for $2-3 USD.

If I were building something like this for the described purpose, I would more likely pick 2 x 18650 cells in series as the battery, powering 2 x 3W LEDs in series, after a buck current regulating driver. Many such drivers will continue to power the LED at progressively lower current until you get most of the rated capacity out the cells while a single 18650 boosted to 12V, not so much.

Edit: Almost forgot the pic of the generic 10W LEDs I'd avoid, which use a 3x3 array of dies in them:

 

These protection boards are available to you in Thailand for about 2 Baht postage.
Cost around 95 Baht for 10 pieces.
They are for individual 18650 cell (1S).

https://www.ebay.com.au/itm/10pcs-1...5ccd0d1:g:HBgAAOSw9X9a-lCC:rk:4:pf:0#shpCntId

 

What I do with undervoltage Lithium cells (usually salvaged) that the charger refuses to accept because their voltage is under the minimum acceptable to enable the charging process, is apply 3 to 4 Volts to raise the minimum.
Then, the charger accepts them for a normal charging process.
Cheap single 18650 cells chargers are about $1. This will work in a place with difficulty in obtaining parts.
The cheap chargers look like
----> https://www.aliexpress.com/wholesale?SearchText=18650+charger&opensearch=true

Another way I recharge lithium cells is by applying regulated 4.100 Volts directly. It recharges them just fine and never presented safety problems nor heating. Perhaps this helps.

 

Many videos on YouTube show fake 18650 lithium cells with FIRE in their name sold on Chinese websites.

 

I love the teardown video where the guy opens one up and pours out a bunch of rice and a tiny battery.

(Oh, we meant 2000uA hours, it’s a typo)

Bob

 

FYI this is a report on the ones I linked to.... enjoy.

https://lygte-info.dk/review/batteries2012/TrustFire TF18650 3000mAh (Flame) UK.html


Also another useful site for 18650 cell recognition.
https://secondlifestorage.com/celldatabase.php?fkeys=&fbrand=&fform=18650&fmincap=&fsort=1

 

Umm...

I wonder if the reviewer meant batteries or fingers?