Inside a Nitecore i4 charger

       I have quite a few gadgets, lights and lasers that need different sized batteries so I usually drag around several chargers to accommodate the different battery types that I use.

       I stumbled upon this Nitecore i4 charger that can simultaneously charge 4 same/different cells at the same time so I could just bring one charger during trips. There is also a smaller 2 cell version (Nitecore i2).

       There was a fault on the unit I received but I didn't want to bother sending it back for warranty which gave me another reason to tear it apart.

       I won't be doing a detailed review as there is already one in the internet which includes graphs, plots and measurements so I'm just adding what wasn't there, teardown pics! Enough of that, here's what I took when I had mine apart.

Here's what I received


Removing the four foam feet reveals four small philips screws.
Taking them off removes the bottom cover

Bottom of the PCB. Soldering could have been cleaner but it cost only $20. IPA and a toothbrush should clean it up nicely.
It does have the essential isolating slots separating the live circuitry directly connected to the mains to have enough safety clearance to prevent electrocution.
The big chip in the middle appears to be the main MCU. The PCB is also a nice FR4 substrate rather than the cheap paper phenolic material.

The springs for the battery contacts are soldered on both ends which allows more reliable electrical connection - I haven't seen it done in cheap chargers before

Top of the main PCB. On the top left are the AC to DC converter.
Top right appears to be the two buck converters that steps down the voltage to charge the batteries.
Bottom part controls switching of the two charger channels to four battery slots.

Angled view of the board. The switching controller for the AC-DC converter is a VIPer22A device with voltage feedback using a TL431 and optocoupler
which is loads better than a self oscillating transistor switcher in cheap chargers.

Here's a shot of the offline controller IC. (Datasheet)

Devices that route power from two charger channels to four battery slots are controlled by
what appears to be dual mosfet devices on both the positive and negative battery lines.

Now there's your problem: I found two shorts on the main controller IC which might be causing my problem

Here's how it looks now after resoldering the sloppy joints and cleaning with a bottle of IPA

An interesting bodge. An SMD resistor sitting on top of another.
There was also a big solder blob connecting three points together but I replaced it with a wire link to make it look neater

I greased up the sliding contacts for a smoother feel when inserting/removing batteries

Since the battery contacts are steel, it is possible to use magnetic connectors to connect batteries externally shown here charging the DIY Ophir LPM

       24 Jun 2013:

       An i2 passed through my hands so I had the chance to open it up and take pictures to complete the Intellicharger lineup teardown. If interested, detailed review can be found in the internet.

Here's the brand new i2

Same way of opening as the i4. screws are hidden under the foam rubber feet. Once the bottom cover is out, this is what we get.
You can clearly see the nice clearance gap separating the live circuitry directly connected to the mains and the
DC output which you will come on contact to when inserting batteries

Soldering looks much cleaner than my i4. There's just an odd solder ball on the bottom right of the pic and a piece of tape which were both easily removed with a fingernail

Top of the board. Top half is the main AC-DC power supply which used the same VIPer22A device but with a smaller transformer (yellow/black square part). The buck converters are on the bottom left and right corners using drum core inductors (the i4 used toroids) and the main controller IC is the one in the middle

Another view in an angle

You don't usually get these in cheap chargers. Mains input is fused and an NTC thermistor to limit inrush current
(The i4 has an EMI filter capacitor, this one doesn't)

Page updated and copyright R.Quan © 20 Jun 2013.