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Update 2016.03.05: the Chinese seller agreed in a part refund and paid me back 4 USD to my PayPal account, however PayPal has billed me 0,5 USD for something. For the money I received? This is ridiculous. The seller offered a change if I send the charger back, but the posting fee would have been more expensive than the product itself. The seller was very helpful.
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I have ordered from Ebay, China, a 18650 battery charger which is also a Power bank. Its "brand" is Soshine, type E3. I have chosen this as it is cheap, cost 17 USD with shipping to Hungary. It can charge up to 4 batteries and it charges them individually. A power bank means that if there are charged batteries in it, it can charge devices through an USB cable. So for instance if we are walking in the forest and there is no mains power to charge our phones, then this can be used after we charged the batteries inside it. The 18650 batteries are not included they have to be bought separately. I will use 18650s from laptop batteries.
It looks great, feels great and it also works, however there is a slight problem with it. One of the slots is overcharging the batteries over 4,2V. 4,2V should be the maximum. Strangely it charges in the next slot till 4,2V next to it till 4,19V next to it till 4,18V. So be careful with it particularly with overcharge protected 18650s. I have complained to the seller because of this, let's see if I will some refund or not. So if I do not use the first slot for charging, this works well.
Oh and one more small thing. This thing consumes 1,4mA all the time, which get raised to 3-8mA in every 3-4 seconds. This means that it drains 62mAh daily from the batteries inside it. I think this drain is shared between the installed batteries. My assumption is that this drain is used by the microcontroller and it fluctuates because it gets out from a power saving state to check the cells in every 3-4 seconds. So be careful with this, if you just leave the batteries in it, they will get drained as the days pass. My solution for this is use a piece of plastic to cut the contact between the batteries and the E3, so it cannot drain them.
How it works. You put in the batteries, it does not matter how many and into which slot. If you connect it to a power source it will charge them, if it is not connected it simply shows the charge levels of the batteries. If you connect a device to be charged to it onto one of the usb slots, then it shows the voltage and mA drained from the batteries. When it charges or it is used, then the LCD backlight is on, this consumes 20mA, but can be turned off if you press the back button for 1 second then releases it.
Is it worth to buy? Unfortunately because of the overcharging I am not so happy, if I get a refund then I may get used to not use that slot. Of course no manual or specification is attached to the power bank. I do not know how this goes in China, but it is funny. If you accept the negative things, it can be used well.
On Ebay they are also selling it under name TOMO V8-4 .
Teardown:
We can see the date and revision of the PCB on the lower right side: 20150615-V2.6. The previous version does not show the voltage and the current when it charge other devices. They have also changed some electric parts as well. Here is the previous version. Some people complain because of the overcharging and the drain from the cells which I mentioned. On the picture above can be seen the 4 charging controller chip and the 4 diodes for the reverse polarity protection. Below you can see the microcontroller which is a PIC16F1933 . This controls everything, including the LCD, it has a temperature sensor inside as well. Of course the cells temperature is not checked on this board.
Have fun!
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