Review: iSDT C4 18650 Battery Charger

by Oscar

I use 18650 batteries daily and the iSDT C4 battery charger has been great. Despite the fact that you can only charge 2 Li-Ion cells at once, the wide variety of battery types it supports and useful features, make up for the limitation.

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Buy the iSDT C4 Battery Charger from: Banggood | Amazon | GetFPV

Basic Spec

  • Input Voltage: 12V – 24V / 2.5A DC
  • Output Voltage: 0.2V – 5V
  • Max Output Current: 3A per slot
  • USB Charger: 5V/2.1A
  • Supported Battery Types: NiMH, NiCd, NiZn, Eneloop, Li-Ion, LiHv, LiFePO4
  • Supported Battery Sizes: AAA, AA, 10440, 10500, 12500, 12650, 13500, 13650, 14500, 14650, 16650, 17650, 18650, 20650, 22650, 26650

iSDT C4 Charger Unboxing

The iSDT C4 18650 Battery Charger comes with the following accessories:

  • AC to DC Power Supply
  • Stickers
  • Screen Protector
  • Manual

A Close Look at the iSDT C4

There is a colour LCD screen on the top of the unit, and three “touch screen” buttons on the right. The battery bay has a clever design, and is able to take 4 different battery sizes:

  • one 26650 battery, or
  • two 18650 batteries, or
  • four AA batteries, or
  • two AAA batteries

You can also charge AAA and AA batteries, or different types of batteries at the same time if space allows.

The cooling fan is located o the top side of the charger.

The DC power supply input is on the left of the fan, the micro and standard USB ports are on the right.

You can update the charger firmware using the micro USB port.

The standard USB port is for charging 5V USB devices such as your smart phone or GoPro camera. However it doesn’t seem to support “quick charge” on smart phones.

Flip the charger over… well, nothing special about it apart from the ventilation. You can find the spec printed on the back.

Note that my charger power supply has a European plug, which doesn’t work in the UK. You might need to get an adapter for it.

The AC to DC adapter has a standard barrel connector of 5.5mm external diameter, with 2.5mm internal diameter.

Operation and Menu

The Menu and operation are fairly straight-forward. Here is the main menu.

One thing I was a little worried about was the “Auto Charge” feature that is enabled by default.

As soon as you insert your battery, the charger will automatically start charging after so many seconds. So far, the charger seems to do a good job of detecting what kind of batteries are plugged in for me.

However, in my opinion this isn’t the safest thing to do in case the charger detected the wrong battery type, or selected charge current that is too high.

I recommend always verifying these settings before charging, and probably a good idea to turn the Auto Charge feature off.

Supported Battery Types

  • Auto (Auto Detect)
  • Li-Ion
  • LiFePO4
  • LiHV
  • NiMH
  • NiCd
  • NiZn
  • Eneloop

Tasks – Charger Modes

  • Charge
  • Discharge
  • Storage
  • Cycle
  • Analysis
  • Activation

Charge Current

0.1A – 3.0A (0.1A increment)

Charging Status

While charging, you get a really nice and intuitive graph showing you the battery voltage going up. Many important data are also available such as voltage, charge current, internal resistance, temperature and charge time.

Notice the little squares and numbers on the left of the screen, they indicate the charging progress. When it reaches 100 (%), the charging is done.

Another nice feature of the C4 charger is the battery analysis.


Good Things about the iSDT C4 Charger

An Excellent quality product.

The colour LCD screen is really bright and readable. It gives you clear information about the batteries, and the menu and buttons are easy to use.

The C4 charger supports a wide variety of batteries and it’s handy if you use many different types of batteries often. I really like the flexibility the charger bay provides you for the various battery sizes.

It has a wide variety of modes to handle your basic and advanced battery needs. Features including reverse polarity protection, battery activation and analysis make the C4 a great option for beginners as well as experienced users.

Did I mention that the C4 charger can be powered by a 4S or 5S LiPo battery so you can use it outdoor too?

Bad Things

The C4 is good, but it’s not perfect.

First of all, I bought this charger primarily to charge 18650 Li-Ion batteries. I normally need to charge 8 to 16 cells every single time, and it’s kind of slow with the C4 because you can only do two at a time. In the end I found myself using my LiPo battery charger more. I can charge all 16 at once as a 4S Li-Ion battery using a DIY battery holder.

Another disappointment is that this charger won’t fit some over-length 18500 Li-Ion batteries with built-in protective circuit.

Lastly, the fan is quite loud which I hope they can fix in future firmware updates.

Instruction Manual

I don’t want to repeat what’s in the manual. If you have questions about the charger, or wonder what each mode does, take a look at the manual first.

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Vašek 12th October 2019 - 8:39 pm

For NiMH AA batteries the capacity limit seems to be always 3500 mAh regardless the charging current.

iLLiac4 8th December 2018 - 2:15 pm

I really like your blog. Very professional articles.
There is one thing I do not understand; how is this possible?
I can charge all 16 at once as a 4S Li-Ion battery using a DIY battery holder.
Can you share a picture and a diagram? TNX

dexterxx 29th October 2018 - 12:31 pm

Did you (or could you) try to charge C/R14 or D/R20 size batteries, with AA adapter?
Is it possible? Does charger handle it properly?

Peter 7th September 2018 - 6:43 am

Hi there.

The setting Capacity Limit On/Off
Have you found any way of setting the specific limit itself?
Or is it simply a 2x multiple of the charge current?