FMA Cellpro 10s Charger Review

FMA has engineered an amazing new charger that builds on the phenomenal success of their very popular Cellpro 4S charger. While the Cellpro 10S Charger incorporates many of the same features found in the 4S, the FMA engineers have pulled out all the stops on this exciting new product!



Battery Chemistry Charged:Lithium Polymer, Lithium Ion, Lithium Manganese and A123
Input Voltage:10 to 16VDC, reverse polarity protected
Input Current:Maximum of 25 Amps
Outputs:Two channel, 1S to 5S simultaneously, single channel, 1S to 10S
Nominal Output Voltage:3.60, 4.10 and 4.20 volts per cell
Output Current:Up to 10A when charging through discharge leads and node connector, reverse polarity protected
Battery Pack Capacity:100mAh to 65Ah
Balancing Accuracy:Within 1mV
Charge Rate:Maximum of 3C
Size:168mm x 87mm x 42mm
Weight:597 grams (1.32 lbs)
Warranty:One Year
Available From:FMADirect

A year or so ago, I stumbled upon a product that quickly became my favorite charger. The Cellpro 4S charger amazed me for its simple yet ultra-safe approach to charging the heavily popular lithium polymer batteries. Plug the balance connector of your battery into the 4S, and you are done. Without even hitting a start button, the 4S would recognize not only that a battery was connected, but also the number of cells present. By virtually eliminating the human element of charging these chemically volatile cells, FMA elevated the charging process to an entirely new level of safety. The main shortcoming of the 4S charger was, as it name suggests, that it could only charge a maximum of four cells at a time.

Many radio control enthusiasts like myself find themselves following a natural progression taking them from the smaller park flyer sized aircraft into progressively larger, more powerful planes and helicopters. Larger aircraft mean larger batteries. I have had the great privilege of reviewing several larger planes lately. While my beloved 4S would be capable of charging all of the batteries used in them, it would take it twice as long to get the job done.

Just when I was posturing to purchase another of their 4S Cellpro chargers in order to facilitate charging these larger packs, FMA announced a new charger that would charge either a 10S sized pack or a pair of 5S sized packs. This very timely release of the 10S charger had me knocking on their door asking for one of the first units to be manufactured!

Beta Test of the 10S

As an Author and Reviewer for Ezone and RCGroups, I approached FMA inquiring if they would like their new 10S charger reviewed once it had been released. I was thrilled to receive an email reply from them asking if I would not only review the product but also if I would like to be involved in the Beta testing of it. Would I ever!?

The beta testing was over several months, and the team assembled by FMA included a diverse selection of folks who brought many outstanding abilities and years of experience to the table. My sole qualification to be on the team would have to be that I am a plain Jane (or Jon, as the case may be) super typical user. There is a certain breed of enthusiasts involved in this great hobby who speak "electrons and protons” and I certainly do not claim to be able judge this charger on the higher level of electronics intelligence that those folks possess.

Several of the beta testers were of this noble breed, and FMA even engaged in extensive dialogue with others whom were not included on the beta team. One knowledgeable contributor offered up so much criticism, both positive and negative, that FMA decided to undertake a major rewrite of the code resulting in a jump from revision 1.x to 2.x. The end result was a fast paced parade of programming updates and fresh firmware that often changed several times in a day. And the capability of upgrading the charger via the PC Interface and the Internet meant instant updates. FMA’s engineers are definitely a passionate and hard-working group of enthusiasts. And at the end of it all, FMA brought to market a product with many months of testing behind it, as well as a well-tuned interface and optimized charging algorithms.

Box Contents

Items in the Box:

  • Cellpro 10S Charger
  • Two 5s-to-4s adapters
  • Plug Blocker
  • Banana Plug to Alligator Clip Adapters
  • Adhesive-backed rubber feet
  • Printed version of the Cellpro 10S manual

Items That Are Optional and Recommended:

  • Two way PC USB Interface Module (FUIM2)
  • FREE Cellpro 10s Charge Control Software (CCS)
  • Correct Cellpro Adapters for Batteries You Wish to Charge (Cellpro Adapters)

Notable Features

Up to 10A Max Charge Current

Charges Lithium Polymer or A123 Cells (variable charge rates for both LiPo and A123 cells). Charges 1 Pack of 1s-10s or 2 Packs of 1s-5s Simultaneously

These are the two most popular of battery chemistries used in the hobby today. I have not yet embarked onto the road of the A123 cells, but when I do, the 10S will be ready to charge them for me! If you would like information in connection with using this charger on these batteries, you can find a great deal of discussion by searching the Battery/Charger forum here on RCGroups.

Individual Cell Internal Resistance to 0.1 m ohm Resolution (Battery Quality Indicator, a feature exclusive to the Cellpro 10s charger)

Early in the beta process, this feature was rolled out. I immediately inquired as to what the significance of the internal resistance of each cell was. The answer I was given was quite indepth and somewhat technical. The 10S charger allows a user to closely monitor the health of each cell of each battery pack by calculating its internal resistance and displaying it in m-ohms. The overall quality of the cells and their C rating is closely linked to their IR. A lower IR means the cell can deliver higher current. Lower IR also means the cell will not generate as much heat. Most of us using this type of battery are well aware that excessive heat can destroy the cell. It is also interesting to note that the IR can also hint at the overall quality of the cells.

Bidirectional P.C. Interface

There are compelling reasons to purchase the PC interface for the 10S charger. Perhaps the main reason is that it will allow firmware updates over the Internet. Another advantage is that the interface enables using the free Charger Control Software on your PC.

It is worth mentioning that the unidirectional PC interface that was available for the 4S charger will not really work with the 10S charger, which requires a full duplex communication link for complete functionality.

Firmware upgrades over the Internet - No need to return the charger to FMA for firmware updates.

FMA made several notable improvements to the 4S charger over its life cycle. One was increasing the maximum charge rate from 3.0 amps to 4.0 amps. Another was adding the capability to charge the A123 battery chemistry. To take advantage of these firmware updates however, the 4S needed to be returned to the mother ship for reprogramming. That is not the case with the new 10S charger. Now you can upgrade the firmware without leaving your shop!

Being able to upgrade the firmware on the fly means you can take advantage of any improvements and new features that FMA could implement in the future. All it takes is the PC interface and an internet connection. And if there is one thing you can count on, it is that the folks at FMA DO listen to their customers!

Adjustable Power Supply Current Availability

A higher power charger like the 10S will make demands on your 12 volt DC supply, whether it be the battery in your car or the bench top supply you use in your shop. Perhaps you have not yet invested in a high dollar, high power bench top 12 volt DC supply yet? No worries, for the current delivering capability of your particular DC supply can be programmed into the 10S charger.

This actually serves to protect your power supply. This particular feature can only be accessed by using the Charge Control Software. The factory default for this value is 25 amps. You can tweak it downward to whatever value your supply can safely deliver.

I used both my old PC power supply and the 13.8 VDC, 28A power supply that FMA carries especially for their charger. Further on in the review, I will illustrate the distinct advantage of having a robust supply.

A Closer Look at the 10S

The Cellpro 10S charger does not come with a confusing array of controls and switches. The only two pushbuttons are labeled "Start/Stop" and "Mode". They are found on the right panel of the charger.

One excellent change made at the suggestion of one of the beta team was to require a maintained closure of the "Start/Stop" pushbutton in order to initiate or terminate a charge cycle. Without this revision, it was all too easy to accidentally terminate the charge cycle by mistakenly pressing the "Start/Stop" pushbutton instead of the "Mode" button (ask me how I know that this was a problem). It is normal to cycle through the various displays while charging your batteries. This is done by repeatedly pressing the "Mode" button. But if you didn't pay attention and you accidentally hit the other button, the cycle would instantly terminate. With the code change, the button must be maintained for a second or so before it is recognized. This is just one small example of the many excellent changes suggested and implemented during the beta test .

Included Accessories

Making the Connections

One of the features of the 4S I really liked was that it safely charged the batteries through the balance connector. This allowed the charger to "read" the battery pack to determine how many cells were there and then charge them automatically. The 10S retains this same functionality and expands upon it as well.

You can still simply plug the battery into the charger via the balance connector, although you will have to initiate the charge cycle on the 10S by manually pressing the "Start" button. Or, you can also connect the main discharge lead of your battery to the 10S for a faster charge rate. The maximum rate of charge when using only the balance node connector is four amps. Connect the main discharge lead, and that rises to ten amps.

Connect one battery and you will need to use the outer two receptacles. Connect two and you will use all four. Should you decide to use only the balance connectors, the plug blocker will need to be installed into the banana receptacles. While FMA batteries will plug directly into the node connectors, other batteries will require the node adapters that most 4S Cellpro owners already own.

According to the manual, there are 26 different ways that you can improperly connect a pair of batteries to the 10S! After pressing the "Start" button, the charger will run a battery checking sequence to ensure that they are correctly connected. If all looks good, the charging will commence.

Decisions to be Made Before Charging

More Accurate Balance or Faster Charge?

Version 2.x of the firmware contains completely rewritten charging algorithms, as well as the unique feature of allowing the user to decide what is the most important aspect of the charge cycle. Would you like the 10S Cellpro to spend a little extra time getting the best balance possible? Select the "Accurate Charge" mode. Or if you want the charge cycle to achieve completion a little faster but at the expense of a little coarser balance, select the "Faster Charge" mode.

To toggle between the two, it is only necessary to tap the "Start/Stop" pushbutton before beginning the charge cycle..

Using the 10S Charger

When the charge cycle is complete and you begin to disconnect all of your cables and connections, it is very important to make sure you NEVER unplug the main charge cables from the 10S before first disconnecting the battery!

Respect the power of the lipoly batteries or you could get very seriously hurt!!

Charger Control Software

If you purchase the USB PC interface for the 10S, you will undoubtedly want to download the free Charger Control Software that is available from FMAs web site. What extra value does it provide?

There is a lot of information available to the user when using the 10S to charge their batteries. To access it, you must page through several screens. When charging a pair of four or five cell batteries, it is much easier to view the data using the CCS due to the constraints of the two line LCD display. The "Cells" tab contains the individual voltage of each cell, carried out to the third decimal, as well as a host of other information. The total time of the charge cycle increments on a counter, as does the total mAh put into the cells. All of this is viewable at a quick glance using the CCS. In addition, there is a hyper link to the USB drivers on the bottom left corner that is accessible from any of the CCS tabs.

One of the most interesting and freshly engineered features of the 10S Cellpro is its use of the internal resistance of each cell. This information is also available on the 10S LCD display, by paging through multiple screens, or on one tab in the CCS. FMA is on the frontiers of LiPo charging technology with the use of this data. The CCS tab reminds the user of the importance of this data by including a three part definition of what it really means and what variation one should typically expect in this data. The IR of the cells will only be calculated and displayed if the batteries were discharged below the 75% fuel level and after at least 12 minutes of the charge cycle has elapsed.

If there is a preferred charging configuration that you find yourself using over and over, the best way to handle it is to use one of the six slots provided for Presets. The "Supply" tab is the place to go if your 12 VDC supply cannot provide all of the current that the 10S is asking for. You may get a fault code if your supply is not up to the task of feeding this potentially hungry charger. Though you may wish to purchase a more robust supply, this tab will allow you to "derate" the input power that the 10S is expecting from your supply. The current can be adjusted to more accurately reflect what your DC supply can provide current-wise. The tab also contains a reminder on how you can temporarily return this value to the full 25 amp default value. Perhaps you are not using your normal 12 VDC supply but your vehicles 12 volt battery? By holding down the Mode button as you power the charger up, any derating entered in the "Supply" tab will be temporarily overridden. I think I had better put this on a sticker and affix it to the bottom of the charger so I do not forget how to do it in the field!

The CCS will automatically check for not only a new version of itself, but also any recent firmware revisions that have become available. A pop-up will notify you if the revision you have is not the latest and greatest for either. Brief release notes are also provided, as well as a Log to see what firmware revisions you have toyed with.

This is, in my opinion, one of the best features of the 10S Cellpro charger. There is absolutely no need to ever be faced with not having your charger to use because you had to return it to the factory for a new revision of firmware. No down time is a very, very good thing indeed!

Though there is always a risk of rendering a device inoperable should the flashing of its firmware not execute properly, or if it is interrupted before it is complete, FMA has included a special check box labeled "My Charger is Dead". This permits you to resurrect the charger should the firmware update go south. However, during the course of the beta test, I updated mine over two dozen times with absolutely no errors or problems. Updating the firmware is a very easy process on this piece of hardware.

The final tab of the CCS will let you customize various parts of your 10S. Would you like the screens to automatically cycle while charging? Is the contrast of the LCD not to your liking? Tweak it. Is the 10S charger waking the baby with its charge complete alarm? Turn it down or completely off! You can also set the default charge optimization mode here. (More accurate or quicker charge)

Another major feature of the CCS package is that it will let you graph the charge cycles of your packs. You can theoretically graph and log each and every charge of each and every battery you own. Initiate a "Start" cycle and a pop-up will prompt you for a filename under which to save the charge cycle data. The format of the data file is semi-colon delimited, which means you can import it into Excel or other applications for custom analysis.

And the graphs are somewhat configurable. You can view the amps, volts, internal resistance or Fuel % in the battery. The graph is actually real time and will continuously update while the charge cycle is ongoing.

Additional Features and Modes

The 10S charger utilizes some of the same proven features and modes as found on their 4S charger:

  • Low voltage restore mode - Have you ever over-discharged a battery? The 10S will recognize your mistake and attempt to repair the cell(s).
  • Storage Charge Mode - If you plan on storing your batteries for a relatively long period, you should probably use this mode. It will charge the batteries to about 50% of normal capacity.
  • Cold Weather Mode - If the temperature is below 55 degrees F, the 10S will stop the balance charge at 4.10 Volts to protect the battery
  • Safety Charge Mode - If you have a battery in which one cell is seriously out of balance, the 10S will automatically lower its charge current to 0.5A. You may want to treat such a battery with extreme caution!
  • Support for long battery extensions - if your main discharge wires are a little on the long side (up to six feet), the 10S will recognize this and compensate to within 1 mv of accuracy.

Making the Best Use of the Cellpro 10S

The three planes illustrated near the beginning of this review article all use two packs connected in series. What this means is that after each flight, you will have two lipoly packs that have been discharged to approximately the same level. A scenario such as this is where the 10S charger will really prove its value. You can connect the two batteries to the 10S and it will bring both of them back to a fully charged state with haste.

Where this charger will not be as advantageous is if you connect two different sized batteries or two of the same batteries which have been discharged to drastically different levels. The reason it will not operate as well has to do with the fact that it connects the two packs together internally in the charger when the charge cycle commences. As one of the packs approaches the state of being nearly charged, the 10S will switch to balance mode. The second battery will thus take quite a bit longer to finish its charge at this lower rate.

Charge Scenario I

I used each of these two Thunder Power 4200 3S2P lipolys in my E-flite AT6 Texan, one at a time, so they were not discharged to exactly the same level.

Of course, you could always terminate the charge when the first battery is complete and then restart the charge of the second battery which would force it to charge at a higher rate. Doing this will require a slight shuffling of the connections however, as they are a little different when charging a single pack. This is but a minor workaround to implement but it highlights that the real forte of this charger is recharging a pair of batteries discharged to about the same level.

Charge Scenario II

The following scenario involves a pair of Thunder Power V2 Extreme 3850 4S packs that are connected in series and that power a Hangar 9 Frenzy 100 with a E-flite Power 110 motor and Castle Creations HV110 speed controller. These packs were charged in the "Accurate Balance Optimization" mode. They were discharged to within a few percentage points of each other. Within about 27-28 minutes, they slipped into Balance mode. The charge was complete in less than 40 minutes.

Charge Scenario III

This scenario involves the same two Thunder Power 4200s used in the first scenario but this time, they were connected in series and run as a 6S2P pack in a 60 size FW190 with a AXI 4130/16 spinning a 15X10 prop using a Jeti 70 speed controller. The optimization was switched to the "Faster Charge" mode.

The importance of an adequate DC power supply

Input Voltage:85-135 VAC or 170-260 VAC, 47-63 Hz
Output Current:Maximum of 28 Amps, 25 Amps Continuous
Size:7" x 2.25" x 7.5"
Weight:4 lbs)
Protection:Overvoltage and Overcurrent (30 amps)
Available From: FMADirect

While compiling this review and reviewing the many graphs and charge cycles, I came to the realization that my old 12 VDC PC power supply was limiting the 10S charger from achieving its true rated output. At around 8 amps of charger output, the voltage from my 12 VDC supply would start to sag and cause the 10S charger to automatically throttle back. You can clearly see this in several of the above graphs.

I contacted FMA to notify them that my supply was not up to the task of feeding the 10S charger. They suggested I try their new 28 amp DC supply. This power supply is sized to allow the 10S charger to achieve its full rated output.

I agreed to try their 12 VDC Power Supply, which is specifically designed for their 10S charger. The difference was immediately apparent, as the charge graph now showed maximum current levels of slightly higher than 10 amps during the charge cycle.

In hindsight, I probably should have started out this review of the 10S charger by using a better power supply than my old PC conversion supply. After all, who puts regular unleaded gas in their Ferrari?! A high performance automobile requires and deserves the best premium fuel possible. It will only achieve its rated performance on the best fuel and the same is true of the Cellpro 10S charger. The FMA switching power supply is a perfect match for their charger and will let it run at 100% of its rated capacity. It is aesthetically a good looking piece of hardware, designed to match the charger.


FMA has brought to market a charger that stands out for its design emphasis on safely charging the potentially volatile lithium chemistry cells. Prior to releasing this charger, FMA subjected it and its code to an extensive beta test program. The team offered up an endless number of suggestions and data files to help FMA ferret out the bugs and fine tune the charger interface and its charging algorithms. Though charging this type of battery should NEVER be done unattended, FMA’s chargers, and the extensive programming hours put into them, give the end user added peace of mind. The extensive safety features and programming elevate charger technology to a new level. And the use of internal resistance gives users a new tool to monitor the health of their battery packs.

I love the Cellpro 10S charger even more than my Cellpro 4S. It does a superb job of charging my larger packs. I especially like the ability to upgrade the firmware, without having to send it back to the manufacturer. And the Charger Control Software provides a means to maintain a history of my packs by logging and graphing every charge cycle. I do often ask it to charge several packs that have not been discharged to the same level and while it will do it, it will usually take a little longer. I do not think that this is necessarily a design flaw though, as much as a limitation due to the way the charger connects any two packs it is charging in series by means of its internal circuitry.

It is true that the FMA 10S charger is a bit more expensive than many of the "entry" level chargers. Add in the cost of their 12 VDC Power Supply and it can get pricey (FMA has put together some money saving combos that save a few bucks). However, this chargers capabilities set it apart as a charger that you can grow with. I started into electric radio control crafts and at first only used 2S and 3S lipoly battery packs. In short time, I moved into EDFs and started using 4S packs. Next, I moved into larger planes, which have required 5S all the way up to 10S packs. The FMA Cellpro 10S charger is capable of charging all of my batteries. With haste! From my smaller power systems all the way up to my largest ones, this charger has me covered!


  • Recharges a pair of 1S to 5S packs , or a single 1S to 10S pack, quickly, safely and efficiently
  • Charges both lithium and A123 battery chemistries
  • Firmware updates via the Internet - No need to return the charger and suffer any downtime
  • Automatic checking for software and firmware updates when using the PC Interface
  • Charger Control Software allows graphing and tracking of each and every charge cycle
  • Excellent back lit LCD display
  • Display of internal resistance helps monitor the health of your packs
  • Choice of optimization mode, either "Faster Charge" or "Accurate Balance"
  • A charger to grow with


  • Charge times are lengthier when mixing different sizes of batteries or batteries with different levels of discharge
Last edited by Angela H; Jun 17, 2008 at 06:03 AM..
Thread Tools
Jun 16, 2008, 03:37 PM
Southern Pride
everydayflyer's Avatar
One knowledgeable contributor offered up so much criticism, both positive and negative, that FMA decided to undertake a major rewrite of the code resulting in a jump from revision 1.x to 2.x.
Guilty as charged but everyone ended up with a much improved charger due to my constant nagging, grumbling,nick-picking and parade of suggestions for improvements.

Jun 16, 2008, 07:44 PM
The Toy Man
Frisk151's Avatar
Excellent and very detailed review!

Jun 16, 2008, 07:59 PM
Originally Posted by everydayflyer
Guilty as charged but everyone ended up with a much improved charger due to my constant nagging, grumbling,nick-picking and parade of suggestions for improvements.

Ironic, isn't it?
Jun 16, 2008, 09:32 PM
Bajora's Avatar
Thread OP
Thank you for taking the time to read it Frisk151!
Latest blog entry: Updated FMS 1400mm J3 Cub
Jun 16, 2008, 10:29 PM
Registered User
quote..."FMA made several notable improvements to the 4S charger over its life cycle. One was increasing the maximum charge rate from 3.0C to 4.0C. " this correct..? Or did you mean to say that the maximum charge current was raised from 3amps to 4 amps..?

Jun 16, 2008, 10:37 PM
Bajora's Avatar
Thread OP
Good catch Bill. I believe you are exactly right on that one. Got my Cs and amps confused!

You didn't happen to notice any other brain slippages I made did you?!

EDIT: Correction made-thanks Bill!
Last edited by Bajora; Jun 17, 2008 at 08:43 AM.
Jun 16, 2008, 10:48 PM
Registered User
mjemery's Avatar
Great review - I recently purchased the 10S and the new power supply and I'm very happy with both! I have a quick question: if I have an older pack with no balance connector, can I still charge the pack with the 10S?
Jun 16, 2008, 11:09 PM
Bajora's Avatar
Thread OP
If I am not mistaken, you can charge using only the balance connector ...or using both it and the main discharge connection BUT I do not think it possible to charge using only the main discharge connection.
Latest blog entry: Updated FMS 1400mm J3 Cub
Jun 17, 2008, 03:33 AM
Registered User
SteveM732's Avatar
Thank you for the excellent review and thanks to yourself and the other testers for helping refine the 10S. As the owner of a Cellpro 4S I can see where changes and improvements have been made and I feel like every annoyance of the 4S was fixed in the 10S (eg. the beeping when finished can be adjusted). Additionally, other new features like calculating battery impedance and the multitude of plotting options and firmware upgrading are great.

In short, I was about to buy a Hyperion EOS0610iNET but you have won me over to the 10S as I see it will do 260 watts with a DC supply of 15.7 volts and will charge Li-Ion to 4.1 volts in addition of my normal A123 charging needs. Now I just need to find a 15.7 volt supply that will do 25 amps or more...maybe a Mastech.
Jun 17, 2008, 06:05 AM
Dr. Dave
An excellent and comprehensive review Jon. Glad as well you were a part of this project. I too use an old CPU power supply, but as batteries got bigger I had to move up to another power supply. Really, having both is great. Ok, I see your point on unplugging the power supply leads as they may touch each other. I had better pay attention.
Jun 17, 2008, 08:41 AM
Registered User
Very nice review.

Cheap multimeters come with insulated banana jack recepticles. Could FMA consider installing them in the next production run to eliminate the shorted lead potential?

My 10s should be here today!
Jun 17, 2008, 08:56 AM
Registered User
ggcrandall1's Avatar
Originally Posted by mjemery
Great review - I recently purchased the 10S and the new power supply and I'm very happy with both! I have a quick question: if I have an older pack with no balance connector, can I still charge the pack with the 10S?
No. The 10s cannot charge a pack that does not have balance connectors.

However FMA does have connectors with pigtails that you can install on your pack.

Jun 17, 2008, 04:26 PM
"Have Glue - Will Travel"
dawnron1's Avatar
Excellent review, Jon! I know you put many hours into this one and the work really shows. I'm saving my pennies to get one now!

Jun 17, 2008, 04:55 PM
Morning Light Mountain
badbill's Avatar
Uhh... It only charges up to 4 amps? Didn't I see about 8.5 in one of the graphs above?

Where can one buy these chargers other than FMA? Is it possible for local hobby shops to be a dealer? (yes, I already know the answer )

Bill Davenport
AMA 28141

Originally Posted by retiredVTT
quote..."FMA made several notable improvements to the 4S charger over its life cycle. One was increasing the maximum charge rate from 3.0C to 4.0C. " this correct..? Or did you mean to say that the maximum charge current was raised from 3amps to 4 amps..?


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