In this post I’ll be reviewing the iSDT SC-608 charger. iSDT is a relatively new company that makes a few different LiPo chargers and accessories, which are very different from most of the others on the market (that generally follow the same ‘4 button’ or iCharger inspired templates).  After looking at their unique designs, I really wanted to try them and I’d like to thank Gearbest for providing this charge for free to review (though with the customs duties + DHL’s ridiculous ‘storage and handling fees’ I ended up paying the same as the cost of the charger). If you are interested in reviewing products from Gearbest, take a look at this post on IntoFPV and get in touch with them.

Here is a quick disclaimer (inspired by SoloProFan on RCGroups) before we get to the review itself.

Disclaimer: This product was provided for free to review by Gearbest. I will do my best to keep this review fair and unbiased. Product specifications and quality may vary at the manufacturer’s discretion, and are beyond my influence. I cannot guarantee you will get a product that performs exactly the same as seen and described in this review.

Product Specifications

Here are some important specifications as provided by Gearbest:

  • Input voltage: DC 9 – 32V
  • Maximum charge power: 150W
  • Maximum discharge power: 5W
  • Charge current range: 0.1 – 8.0A (this is not a very useful figure as max charge current depends on the charger power and voltage of the battery you are charging).
  • Discharge current range: 0.1 – 3.0A
  • LiPo / LiFe / Lilon / LiHV cells ( 1 – 6S )
  • NiMH / NiCd cells: 1 – 18S
  • Pb battery voltage: 1 – 12S
  • Net weight: 110g
  • Dimensions: 88 x 58 x 21mm

You can find the instruction manual of this charger here.

Unboxing/ First Impressions

Sometimes it is hard to get a sense of how small something is just by looking at the dimensions. What struck me first as I opened the box was just how TINY it really is. All you get in the box is the charger, and a sheet with some basic information about the charger (a ‘getting started’ guide). You don’t get any cables or adapters, which may be a disadvantage for some. In fact, this charger definitely does give off a minimalist vibe, with a single scroll wheel/ push button for all the controls. It is aesthetically pleasing, sleek and no visible seams or hardware. It has a single male XT60 plug for input, another male XT60 for the output, and a single row of pins that fits a standard 2-6S JST-XH balance plug. I would say to make full use of this charger, you should use a parallel charging board. Overall, it seems optimised for field charging, allowing you to plug a larger LiPo pack for input and use it to charge your smaller packs. I will share my field charging setup later on in this article.

For charging at home, you will need a DC power supply. I would recommend something around 24V and 8-10A. Even though this charger can run at lower voltages, higher voltage PSUs will run cooler and some chargers cannot deliver the full rated power when the input voltage is at the lower end of the range. ISDT makes a compact power supply that seems specifically designed for this charger, though it is a little expensive compared to regular power supplies. It is available at Banggood.

Usage

I really do not have much to say here. The controls are very intuitive and easy to grasp. Short press the scroll wheel to access the menu where you can select whether you want to charge/ discharge/ set the battery to storage voltage. You can also select the battery chemistry, cell count, charge current etc. and start the process. Long press the scroll wheel to access the charger settings which lets you switch off the annoying beeps, check firmware version etc. While the charge process is on, you can access a few different screens using the scroll wheel. This includes

Firmware Updates

Another nice thing about this charger is that the firmware is under active development by the manufacturer, allowing you to update it to fix bugs/ add new features. Unfortunately, this charger does not use a standard USB port, or even have male pins broken out for a USB-to-serial adapter. Instead, it uses a 3.5mm 4 pole jack. You can either buy the ‘official’ firmware update tool here, or make your own. I will keep this post updated once I try making the cable myself.

My Field Charging Setup (and a little useful math)

So this is how I plan to use this charger at the field. A parallel board is connected to the input, allowing me to connect multiple batteries to power the charger. There is also a parallel board at the output, which allows me to charge more batteries at once. Thanks to the respectable 150W power of this charger, I can charge 4 1300mAh 4S packs at 150/16.8 = 8.9A, which is a bit less than 2C (read this article for a little more info on parallel charging).

Caution – Normal LiPo batteries are made with matched cells (cells with very similar internal resistance) so they discharge equally. When you connect packs in parallel, the cells are no longer matched. Combining different brands/ capacities as I am doing creates the risk that the batteries will become unbalanced, possibly posing a fire hazard. This system appears to be working for me so far but it will require further testing. If you try this, it is at your own risk.

Now let us look at the maths that lets you calculate how many times you can charge a battery from another battery.

Scenario 1: Powering the charger with 2x 4000mAh 3S packs in parallel.

These are packs I bought close to 2 years ago from HobbyKing to power my 450 size quad. Since I no longer have that quad, I now use them for powering a charger. When wired in parallel, they behave as a single 8000mAh 3S battery. Therefore:

(average) energy stored in the battery = voltage x capacity = 11.1 (nominal) x 8 (in Ah) = 88.8 Wh

(average) energy stored in a single 1300mAh 4S pack = 16.8 x 1.3 = 21.84

88.8/21.84 = 4.

Therefore I should be able to charge 4 1300mAh 4S packs from these 2 4000mAh 3S packs. The mAh values cannot be compared directly as they are at different voltages. A couple of things to watch out for I have taken the fully charged voltage of the packs I am charging but the nominal voltage of the input batteries just to be safe. Also, the charger will not be 100% efficient so the full 88.8Wh may not be usable. However, since the 1300 mAh packs will not be fully drained, I think it is safe to say we can charge 4 of them. Always, always use a LiPo alarm on the batteries you are using for input so they are not overdischarged.

Scenario 2: Powering the charger with 3x different 4S packs.

I also have a Tattu 1800mAh, Dinogy 1500mAh and puffed Bonka 1300mAh I no longer fly with. Since the voltage of these packs is the same as the ones we are charging, we can compare the mAh values directly. Therefore:

total capacity = 1.8 + 1.5 + 1.3 = 4.6 Ah

number of 1.3 Ah packs that can be charged = 4.6/1.3 = 3 (rounded down for safety).

Again, make sure to use a LiPo alarm.

Conclusion.

WIP