Review last updated: January 19th, 2011
The Cellpro 4S Gold is one of the four chargers FMA, a US based company, offers. It is the 3rd generation of the Cellpro 4 line, following the 4 and 4S, adding an ABS case and PC connectivity to the 4S but otherwise retains the same basic functionality of the 4S.

The idea behind the Cellpro 4 series has always been simple, make a simple and safe charger for the masses. That these charger do well. Most users will buy one, adjust the settings to one of the auto modes and then never touch the single button again. Because of this simplicity, the line has been a big hit with both new pilots and nitro pilots looking for a no-fuss lipo charger.

In today's market the 4S Gold is a baby among titans in terms of features and output, but it still has it uses and is still appreciated in the market. I specifically bought this unit for use in a university lab environment because it is effectively foolproof, just plug and charge.

First impressions
The first balance charger I owned was a Cellpro 4S. As such I am very familiar with the line but I have not had the opportunity to use a Gold version until now. As with the 4S, the box it comes in is smaller than you expect. Opening it I couldn't help but smile at the small, innocent looking little charger staring back at me.

The original 4 and 4S models were a raw circuit board and panel wrapped in a clear plastic shrink wrap. I liked the open and simple design but many complained that it looked unfinished and wanted a proper case. FMA obliged and the Gold version now comes in a black ABS case. I have to admit, now that I have one to hold, I like new case.

My only complaint with the physical design is the use of a proportionally large, stiff input lead. This is the same as my older 4S and like it, the cord has the ability to push and pull the charger around as you move it. A smaller, softer input lead would have been much appreciated.

There are a total of 5 notable items on the whole outside of the charger, the LCD on the front, the output port and single button on the right side, and the input cable and PC port on the left side. Here are some side and back shots.

How the Cellpro 4S charges
The Cellpro 4S Gold charges and balances through the pack's balance lead, leaving the main leads of the pack are unconnected. Some believe that the 4S Gold charges each cell individually but that is not true. Like almost all smart chargers, the 4S Gold charges the series pack as a whole and discharges individual cells in order to balance the pack. But instead of connecting to the main pack (+) and pack (-) separately like other chargers, the 4S Gold uses the 1st and last balance wire to charge, as these are connected to the pack (+) and pack (-) as well.

Cellpro balance wiring layout
(image from FMA manual)

Due to the fact that the 4S Gold charges through the balance lead, a unique balance port wiring layout was used. This means that unless you are using FMA lipos, you will be required to buy one balance boards made for this charger. Because this charger has such a limited intended user group, I see no problem with this.

The GP/KO adapter board I received

Power requirements
The Cellpro 4S Gold allows for an input voltage range of 10-16V DC. In order to get the full output, a minimum of 12V is needed. The charger is capable of drawing up to 6A. With such light needs, a car battery, or a deep cycle, will power the 4S Gold well. For a power supply, a 12V 5A unit will suffice for 90% of users but a 12-15V 10A unit
would work well.

Using the Cellpro 4S Gold
This should be a short section because the Cellpro 4S Gold is probably the simplest smart charger on the market.

When you first power on a Cellpro 4S Gold, it defaults to the last used settings. In the case of my 4S Gold, that was the A123 setting. To change the charge mode or rate, press and hold the "Mode" button. The charger will begin cycling through the available options including .25-4A LiPo charge, 1C-3C auto charge, LiPo storage (charge only) and A123. When you see the option you want, let go. That's it.

Ready to begin A123 charge

When you connect a pack to the charger, it will say "Checking V." and if all is well, it will begin to charge. Again, that's it. Below are the screens you can/will see when charging.

A few notes on the above screens
  • The initial charging screen includes a "Fuel" gauge %. This should only be used as an indicator of the charge and is inherently inaccurate, especially when the pack is depleted. Do not rely on this number for the 80% rule.
  • The 4th screen shows "x.xxx Ah added". This is where the charger tells you how many mAh has been returned. It is simply denoted in Ah instead of mAh. (0.123 Ah = 123mAh)
  • At some point during the charge cycle, the charger will beep once and change the screen from reading "FAST CHARGE" to "BALANCING". This is FMA speak for changing between the CC and CV charging phases. The 4S Gold balances the entire charge cycle.
Once the pack is charged, the charger will beep a number of times and then fall silent and wait for you to disconnect the pack. Once you disconnect the pack, the charger resets and is ready to charge another pack.

Note: If you would like to view the mAh returned after a charge cycle has completed, do not disconnect the pack. Once the pack is disconnected, the charger resets and all info is lost. Instead press the Mode button twice and note the mAh. Then you can disconnect the pack.

The Cellpro 4S Gold is the simplest smart charger I know of. It offers near foolproof automatic charging of most lithium battery types equipped with balance lead, and it's priced well. I see this charger as a great match for both the small heli/plane flier and the new-to-electrics older pilots needing a simple charger.
Specs - Features - Photos


Battery types supported
LiPo, LiIon, LiMn, LiFe
Pack capacity
250mAh - 20Ah (8 hour max charge time)
Input voltage range10 - 16VDC
Input current
6A max @ 10V
Power conversion
DC/DC converter, 62.5kHz, 90% efficiency
Nominal output voltage
3.60V, 4.20V per cell; max 16.8V
Max continuous output power
58W @ +12VDC input
Voltage calibration
+/- 10mV
Current calibration
+/- 6mA
Accuracy: Voltage resolution
Accuracy: Voltage tolerance
+/- 10mV
Accuracy: Charge current
+/- 1%
Accuracy: "Fuel Gauge"
+/- 20%
Serial data output
19.2kbps, 8 bits, 1 start bit, 1 stop bit, no parity (checksum, CRC checking)
Output battery connection
JST-PA, 5-position
 LCD2-line, 16 character, non-backlit

  • Auto charge mode (AUTO 1C, 2C, 3C charge rates available utilizing advanced fuel gauging technology)
  • High Impact ABS Plastic protective enclosure
  • Supports all Lithium Chemistry batteries including LiPoly, LiIon, LiFePO4, A123, LiMn
  • Supports 2-way P.C. Interface (FUIM3) which allows the charger to operate with the free Charger Viewer Software
  • Enhanced Internet Upgradable (IU) Charger Viewer Software (free download)
  • IU Firmware support (free for the life of the product)
  • Accessing the various charging modes is as easy as pressing a button. Press and hold the MODE button to cycle through fixed charge rates, followed by 1.0C, 2.0C, 3.0C, STORE, and A123 modes.
  • Supports native Cellpro brand batteries automatically, adapters available for all popular R/C battery brand
  • Supports LiPo STORAGE charging.
  • The charger will handle continuous 4 amp charge current indefinitely up to 100 degrees F ambient temperature. When the temperature is above 100 degrees F, the high temperature mode drops the charge current down to a lower current setting. This feature is useful when charging in the hot sun as the charger won't be damaged from overheating.
  • Cellpro 4s GOLD can seamlessly and safely handle packs whose cells are at or near 0 volts. Automatic Safety Charge and Pack Restore modes will kick in in certain situations.
  • Cold weather mode automatically reduces end-charge voltage to 4.1v below 55 deg F to prevent battery damage
  • The active integrated power balancing is microprocessor controlled so the balancing is done continuously as the cells charge.
The FMA Cellpro 4S Gold comes in a small box with the charger, alligator clips for charge leads and a 1s charging adapter.

Here is a link to the user's manual.

Stock photos

(image linked to from FMA site)

Available charging adapters.
(image linked to from FMA site)

Additional photos
Cellpro 4S Gold compared
to an iCharger 206B

Charging an 2s A123 pack