Folks,
Good morning/afternoon/evening wherever you are.
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This is my 1st post, and may seem a little rambling, so apologies in advance.
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For the family, I recently ordered some CREE cycle lamps from HKG, and some ultrafire 3000 mah 18650s, and a cheap "universal" mains charger to assess.
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I have many programmable chargers that I use for R/C Aircraft use, which are obviously capable of charging Li-ion cells accurately/safely to 4.1, or 4.2V, but I wanted some cheap chargers the kids can just shove the 18650's in without needing to select all sorts of parameters.
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Anyhow..... I have just tested the recently-delivered cheap charger, and the LED will change from red to green at 4.45V (ouch!!), measured with decent mastech DVM.
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That's not the end of it....if I leave it further, it seems to continue to trickle charge, as voltage will continue to increase, if not removed.
So.... in the interest of safety, this charger's going in the bin (probably that cell also!).
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But..... please can someone answer the following query:-
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The above 18650's have inbuilt protection PCBs, with over-voltage protection threshold of 4.25V.
Regardless of the voltage I can measure across the cell while charging, is the actual cell also seeing the same, or is the PCB actually performing some kind of internal regulation to clamp things at 4.25V??
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In other words, what exactly is the over-voltage mode of these integral pcbs?
(I thought I read somewhere that the PCB would actually irreversibly trip under an overvoltage condition....obviously not the case, as cell still useable etc)
-
Please comment if you can.
-
Many Thanks,
Steve
Good morning/afternoon/evening wherever you are.
-
This is my 1st post, and may seem a little rambling, so apologies in advance.
-
For the family, I recently ordered some CREE cycle lamps from HKG, and some ultrafire 3000 mah 18650s, and a cheap "universal" mains charger to assess.
-
I have many programmable chargers that I use for R/C Aircraft use, which are obviously capable of charging Li-ion cells accurately/safely to 4.1, or 4.2V, but I wanted some cheap chargers the kids can just shove the 18650's in without needing to select all sorts of parameters.
-
Anyhow..... I have just tested the recently-delivered cheap charger, and the LED will change from red to green at 4.45V (ouch!!), measured with decent mastech DVM.
-
That's not the end of it....if I leave it further, it seems to continue to trickle charge, as voltage will continue to increase, if not removed.
So.... in the interest of safety, this charger's going in the bin (probably that cell also!).
-
But..... please can someone answer the following query:-
-
The above 18650's have inbuilt protection PCBs, with over-voltage protection threshold of 4.25V.
Regardless of the voltage I can measure across the cell while charging, is the actual cell also seeing the same, or is the PCB actually performing some kind of internal regulation to clamp things at 4.25V??
-
In other words, what exactly is the over-voltage mode of these integral pcbs?
(I thought I read somewhere that the PCB would actually irreversibly trip under an overvoltage condition....obviously not the case, as cell still useable etc)
-
Please comment if you can.
-
Many Thanks,
Steve
