ISDT FD-200 Smart Discharger

Written by Terry Dunn
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As seen in the April 2021 issue of Model Aviation.

The FD-200 is a stand-alone discharger than can accommodate a wide range of LiPo batteries. The optional phone app provides real-time data during the discharging process.

TERRY DUNN SHARED the following review of the ISDT FD-200 Smart Discharger, available from Buddy RC for $79.99. LiPo batteries can degrade if they remain fully charged for more than a few days. That’s not a problem if you always fly every battery that you bring to the field, but there are many reasons why you might reach the end of a flying session and still have topped-off LiPos. It is helpful to have a tool in your workshop that can discharge those unused batteries to an appropriate storage level. Most LiPo chargers have discharge functions that will safely drain a battery. The only problem is that the maximum discharge power is often as low as 10 or 20 watts—a mere trickle. As a result, discharging on a charger can take a few hours for packs with high voltage and/or high capacity. Although it is extremely wise to monitor the process, nobody wants to babysit discharging batteries for that long. The FD-200 from ISDT is specifically designed for discharging. It can dump up to 200 watts of power, allowing batteries to be drained in a reasonable amount of time. It handles LiPo batteries ranging from two cells (7.4 volts) to eight cells (29.6 volts) of any capacity. This stand-alone discharger unit is approximately the size of a paperback novel (142 × 100 × 63mm). The battery being discharged provides power for the electronics within. An XT-60 battery connector is integrated into the discharger’s aluminum housing. I made several adapters to accommodate the varied connectors on my fleet of batteries. A small, printed user’s guide is included with the FD-200. It provides all of the basic information needed to operate the discharger. There is also an informative video on the FD-200 product page on the company’s website. This helpful video takes a deep dive into the features of this unit. There are two ways to operate the FD-200: manually or via a phone app. The manual option is simple and easy. Two buttons are used to select the number of cells in the pack and the desired discharge current (5, 10, 15, 20, or 25 amps). A row of multicolored lights indicates your selections. The unit automatically stops discharging and emits a loud beep when the battery pack reaches 3.8 volts per cell. Using the phone app to control the FD-200 requires you to connect with Bluetooth. The app can be slightly quirky, but the basic functions are intuitive and work well. There are two primary advantages to using the app. One is the fact that there are many more options for discharge current. This is especially helpful when discharging low-capacity batteries (less than 500mAh). The other benefit of using the app is that it provides a wide array of data. It shows battery voltage, discharge current, discharge power, elapsed time, and even the discharger’s operating temperature. If you like to engross yourself in the details of your RC equipment, the app offers plenty of information to digest. The FD-200 only considers the total voltage of a battery pack. It does not monitor individual cells. You can attach a dedicated voltage meter to the battery’s balance plug if you want to observe the voltage of each cell during discharge, but it is generally unnecessary. A built-in fan prevents the discharger from overheating. As you would expect, the fan gets loud when it revs up. You always know when the discharger is working! Although it is noisy, the ISDT FD-200 is a versatile and time-saving tool that helps electric fliers care for their LiPo batteries. SOURCES: Buddy RC (614) 808-4488 www.buddyrc.com

By Terry Dunn | [email protected]

Comments

smaller version

Ahhh, I just got the smaller one FD-100 80w one.. Didn't even see this one! I made mine "smart" by piping the lipo through, you guessed it, a watt meter! I use two daisy chained xt60 parallel plugs to do three packs at a time.

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"Smart" LiPo discharger

This is an interesting article for anyone who desires to evaluate their LiPo batteries using actual discharge values. However, I would add a caveat to this article regarding the lack of individual battery cell voltage measurement by the FD-200 dis-charger product.

Proper and safe charging of multi-cell lithium batteries require individual cell voltage measurement and matching chargers, and the same monitoring requirements apply during the discharge cycle. We don't apply these discharge safeguards to our batteries under actual flight operations: the on-board ESC units only measure total battery voltage and removes or reduces the flight electrical loads when this total battery voltage reaches some predetermined voltage.

The "excuse" for not measuring and using individual battery-cell voltage as an end-point value for the battery capacity in the aircraft is the weight penalty, wiring complexity, and additional cost of the ESC to achieve this "more-technically correct" method of battery discharge under flight conditions.

However, the FD-200 dis-charge product could be brought up to a much safer and more valuable instrument by simply plugging in one of the many-available five-dollar LiPo cell voltage alarm modules to the balance leads of the battery pack before beginning the discharge operation of the FD-200.

These cheap cell-voltage alarms usually have a programmable cell-voltage alert level, and a very loud alert buzzer. I am surprised the company that makes the FD-200 did not throw in one of these simple five-dollar monitors along with their system as a customer perk.

With a little additional circuitry, the FD-200 could have been designed and offered with one of these alert modules built in, and an active disconnect circuit in series with the load and battery main leads to remove the battery from the discharge load automatically at a user-determined individual cell-voltage level.

Frank Horine, Experimentalist

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