Worst Lithium battery charger I have seen. - Page 1
Forum section: electronics / general

author: Buriedcode
author_rank: Super Contributor
timestamp: January 22, 2016, 07:21:19 pm
content: Hi,I've designed a few chargers for lithium polymer batteries before, both from 'scratch' (just a uC controlled CC/CV charger, with safety features and very tight regulation) and using IC's for that purpose, its generally quite straight forward. As with most Chinese manufacturing these days there is a huge range of 'quality', so of course the very cheapest, will most likely be the least effective but this one takes the cake.Its a lower current charger for an Ego T E-cigarette, powered from USB, used to charge batteries 500mAh, 900mAh and 110mAh. Made by a company called 'Vaporon'. I got a couple of ebay for £2 and actually didn't expect much (honestly, I couldn't find one more expensive..). Plugged in the battery and noticed after 10 minutes it didn't get warm like most chargers do (often linear regulators SOIC8, or SOT23-5 dissipating a few hundred mW will of course get warm).So I opened it up, and behold... a PNP transistor, two resistors in parallel for current limiting, and a couple of LED's. No dedicated IC, no voltage regulation, no fuse. Now, its not designed to charge big 8000mAh multicell packs, and the battery itself will (hopefully) have built in protection, but its still far too basic for something designed to charge a lithium cell. It seems the transistor is there to light the LED when the voltage across the current limiting resistors is above 0.6V, and thats it.I'm not saying all Chinese made products/clones are bad, of course not, but at the very low end it starts to become silly.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 23, 2016, 12:57:06 am
content: i believe what you are getting is a china clone from the original china... i have ego e-cig charger that i modded to charge 18650 li-ion 3.7v battery. worked for years without any issue...

author: Muttley Snickers
author_rank: Unknown
timestamp: January 23, 2016, 01:27:38 am
content: You also need to watch out for these types of 18650 chargers as well, the first one we got that came with a Cree torch had virtually no isolation or separation between the mains input and the DC negative output, we sent it back with a nasty letter and I should have taken photos but didn't, the one pictured is very similar and I don't trust them at all.

author: thejoggingmat
author_rank: Regular Contributor
timestamp: January 23, 2016, 01:32:33 am
content: I've seen far worse. There was one charger where the whole circuit is only a zener in parallel. That was all.

author: KL27x
author_rank: Super Contributor
timestamp: January 23, 2016, 09:09:01 am
content: If the zener could handle 400mW and had a breakdown voltage of <4.3V and the battery can handle max charge rate of 500mA, and you only ever plugged it into a USB port that automatically shut down if current draw exceeded 500mA on a port.... I suppose that would be perfectly safe!!!Yeah, that's pretty horrid, but depending on the variables, I might at least prefer that charger to the one OP posted

author: Buriedcode
author_rank: Super Contributor
timestamp: January 24, 2016, 03:24:32 pm
content: With this charger, because the green and red LED's are in parallel when the transistor turns on, the green goes extremely dim, whilst the red is obviously much brighter, but... the green LED flashes (dimly) at about 2Hz. The red remains solid. So this tells me the voltage on the USB side is fluctuating.if the battery is ~3.5V, and USB is at it's max voltage, 5.5V this gives a current of (5.5-3.5)/(10||22) = 2/ 6.9 = 290mA. So the USB should provide enough power without current limiting setting in.Do you think that the circuitry inside the ego battery controls charging in some way or is it all down to that charger? If anyone has a schematic of the tiny circuit inside the ego battery (it has the facility to turn it on and off with multiple presses) I would be grateful. If it just passes through current then I can put my own charging circuit in this thing, but its all based on the assumption that its connected directly to the battery.

author: KL27x
author_rank: Super Contributor
timestamp: January 24, 2016, 07:29:11 pm
content: This is where a voltage meter or a scope might come in handy. That might show something going on in the device. The 2Hz is curious. I would assume it's a PFET and the red LED is connected to its drain. In that case, yeah, it would appear there's perhaps some brief period of an increase in voltage every 2 seconds. Like there's some control in the device that can switch off the supply somewhere between the output and the battery.If the device is doing this purposefully, perhaps it is to test float voltage every 2 seconds? Maybe the micro in the device does that as a fail-safe, and someone decided they could cheap out on the charger.Or maybe the device just draws a lot of power and there's a cyclic period of low draw.Or maybe your USB power rail has something going on.