FMA Direct SuperNova 250S
For a long time, electric-power enthusiasts have been
looking for a sophisticated, fast charger/discharger cycling unit with
a reasonable price tag. At around $140, the new FMA Direct* SuperNova 250S
is such a unit.
[The price now (Aug 00) has now been dropped to $129]
You can operate it off a car battery or an AC to DC power
supply with a nominal 12V DC output at around 20 amps.
The SuperNova is capable of charging or discharging from
1 to 25 cells Ni-Cd or NiMh) and can also charge lead-acid batteries of
up to 6 cells or 12 volts nominal but can not discharge them; and it can't
be used to charge lithium batteries. [Actually you can fool the SuperNova
into discharging a 12 volt lead acid battery. Set for Nicad – 13 cells,
which will give a cutoff voltage of 11.7 volts. With the discharge current
set at 1 amp this will not discharge the lead acid pack to a dangerously
low level. Be sure however to recharge using the Lead Acid (Pb) set up
immediately
Output fast-charge current levels can be set from as low
as 0.10 amp (100mA) to a claimed high of 5 amps for all packs from a single
cell up to a total of 25 cells. This means you can charge packs with as
little as a 50mAh capacity and up to 1700mAh at a 3C rate (20 minutes to
reach full charge!). At above 17OOmAh capacity, the 5A charge limit will
extend the charging time some- what; for example, a 3000 mAh pack would
take 35 to 40 minutes to reach a full charge, at which time an alarm sounds.
(If you prefer, you can turn off that alarm
Discharge current loads for Ni-Cd and NiMh cells can be
adjusted from 0.5 amp to 3 amps. I found the O.5A minimum discharge current
a little too severe for the smaller packs up to about 275 mAh. It would
have been better to set the minimum discharge down to 0.1 amp for those
tiny battery packs. [This reviewer has little problem with this, 5C is
not an abusive discharge for small capacity packs. It may result in a lower
than actual capacity reading, however when one considers that many small
packs are used in electric flight applications, then this range of discharge
is typical of the application.]
Discharging will typically continue down to approximately
0.9 volt per cell. There is also a trickle charge setting exclusively for
lead-acid batteries. When charging Ni-Cd or NiMh cells, a trickle charge
doesn't follow a fast charge. [This has been since clarified by Fred
Marks of FMA, who tells us it does have trickle charge. It is a very short
pulse every few seconds and one has difficulty seeing it unless a storage
scope is used. ]
The issue of trickle charge is still a mystery.
No one has been able to verify with storage scopes etc. (RS 3-22-01)
To protect the unit, charge and discharge currents are
automatically limited. A warning sounds whenever the input volt- age drops
below 9.5 volts or exceeds 15.5 volts. If the DC input voltage is hooked
up backwards (reversed polarity), the charger won't operate, but nor will
it be damaged. In the same vein, if a battery is connected to the output
with reversed polarity, the LCD screen will warn: 'Output battery- reverse
polarity.' When it's first connected to the output, a battery pack is automatically
checked, and if there is a problem, you’ll see: "Output battey —connect
polarity error." And as if that weren'’t enough, the charger will actually
'Pause' (it says so on the LCD) or stop if it begins to get too warm when
it's charging or discharging. Then, after cooling down for a short period,
it automatically resumes the charging or discharging
The FMA Direct SuperNova charger is housed in a rugged
aluminum case that’s 5 1/2 inches long, 3 1/3 inches wide and 1 5/8 inches
thick. Two side mounting brackets are supplied; if they're installed on
each side of the case, they elevate the charger to a convenient angle [and
allow air to circulate over the heat sink]. A miniature internal fan
helps to keep its temperature down, as does a thick aluminum heat-sink
plate that runs along the top [and back side] of the case. The output
connectors require standard banana plugs, which are not supplied [but
readily available at electronics outlets such as Radio Shack]
On the input side, the cables are 36 inches long with what appears to be an in- line fuse that's inserted into the cable. [Fred solves this mystery….This unit, as any uP unit, has to meet CE and FCC unintentional radiation requirements and that is a filter to keep clock freq from radiating off the input power leads. Its only useful function as far as the unit is concerned is that the filter probably helps keep some trash from auto systems, including embedded processors, from getting into the charger from the input power lines when running off the car electrical system with the engine going. FRED] The output cables end in two large, color-coded, alligator clips. [I cut the alligator clips off and replaced them with banana plugs, then made up short adapters for cigarette ligher plug, and for alligator clips. Use 5/32" ID brass tubing covered with heat shrink to mate with banana plugs.] There is no main power switch, so when you connect it to a car battery, there will be an initial spark. I'm not fond of that feature in any charger, so I usually insert an in-line switch in one of the input leads [Good idea]. After doing that, it is easy to first attach the alligator clips to the car battery and then flip the switch to turn on the power-no sparks!
On the face of the SuperNova charger are three push-button switches designated 'Set stop," 'Discharge (down)' and 'Charge (up).' They enable you to select and set the charger/discharger inputs and other parameters. Control commands and inputs are monitored on a front panel (two line) LCD measuring 2 1/2x 9/16 inches.
WHAT MAKES IT SPECIAL?
Beyond its being inexpensive, this unit's software is
unique, to say the least. It will allow you to connect any battery-within
its acceptable parameters-and will automatically charge or discharge it
without your having to set any input commands. So if you aren't sure which
charge or discharge current to select for any pack, just call up the 'Automatic'
mode and simply press 'Charge' or 'Discharge,' and the SuperNova will do
the rest automatically. If you select Charge, the battery will be fully
peak-charged and the unit will cut off.
By switching to a
sub-menu-'Reference data'- you will be able to call back any parameter
that interests you such as peak voltage at full charge, the capacity in
mAh put back into the battery, the average charge current, to mention a
few. If you are discharging, it will tell you the battery capacity in mAh.
Those parameters will remain on the LCD until you have disconnected the
battery pack from the charger.
If, in the automatic mode, you first choose ‘Discharge,’
the proper load current is selected for you and discharging begins. It
continues until the pack reaches approximately 0.9 volt per cell, at which
time it stops discharging and automatically charging. At the completion
of charging, you will be able to recall all of the attained during both
the discharge and charge portions the cycle. You will have no control over
this automatic charging after discharging, so your choices are charge only
or discharge, after which charging occurs automatically This charge-after-discharge
sequence occurs in the manual mode as well
In addition to the automatic mode, the SuperNova also
has a very extensive manual mode that can be set up to do just about anything.
To make life even easier for you at the flying field, FMA engineers established
a series of preset battery charging/discharging conditions for many popular
combinations of battery cell count, capacity and cell type. Ten preset
conditions are permanently stored in the SuperNova's microprocessor. You
can temporarily alter any these for a one-shot charge or discharge "modification",
or you can establish your own preset for a battery pack in your inventory
and store it permanently in the SuperNova's memory. If you ever want to,
you can return all of the presets to their original factory settings.
In a typical manual mode charge/discharge sequence, attach
the battery pack to the output connectors; press the set/stop button to
scroll to "Battery" (which will be flashing). Press set/stop again to get
to '"Select" (flashing). You can now select a preset and go immediately
into charge or discharge, or you can go into '"Set" (flashing) and from
there go down the menu and make your changes to battery type, battery cells
(number of), battery capacity, charge current, or discharge current, and
then go back to "Set" and then "Exit". Having made these modifications
to a preset, you're assured they are now stored in the SuperNova's memory.
You can then proceed with manual-mode charging or discharging or both
The one thing you must learn right from the start is that in manual mode, you can't just set a charge or discharge current value and hit the start button; it isn't quite that simple. You must always first call up a preset and then modify it, though there is one slight variation on this routine: let's say you selected a preset and started charging. Early on, you realize that you have the current set too low and that it will take too long to reach a full charge. While in the charge (or discharge) mode, you can increase current or reduce it as a 'one-shot' deal. So if I start a 12OOmAh pack at 1.2 amps (which might take an hour), I can easily boost the charge current up to 3.6 amps (3C rate) and have the battery at full charge in just 20 minutes. That option is always open to you
As originally conceived, the SuperNova was not intended
to perform C/10 or overnight charging, but Fred Marks of FMA Direct suggested
something I'll pass on to you: if you select the lead-acid battery, you
really don't have a peak-detect circuit in effect; you can set the average
voltage for your pack and the C/10 charge rate, and it will continue to
charge indefinitely. I tried this with a 6-cell 1700niAh pack The voltage
was set at 8, and the charge rate was set at 0.2 amp (200mA). You can set
the current only to 100 mA, so the 0.2 was as close as I could get to the
0.17 amp that I wanted. Under these conditions, the SuperNova did work,
so this is an option you might want to try
My final test was to see whether the claimed charge rates could be actually attained. If the specs call for 5 amps at 25 cells, you should be able to obtain that charge level and cell count when operating off a standard car battery. I didn't quite have a 25-cell pack handy, but I did manage 21 cells at 17OomAh. I was able to obtain 3.2 amps with the 21 cells, but I couldn’t get to the specified 5 amps. Was I disappointed? Not really, since I usually charge packs of 10 or fewer cells. When I do have to charge 32 cells for a 1/4-scale model, I break the battery into two, separate, 16-cellpacks and use two chargers, so not being able to reach 5 amps at 25 cells isn't a problem for me.
I mentioned my observation on charge current to FMA president
Fred Marks, who kindly sent me this statement for publication'When charging
up to 21 to 25 cells, the maximum output current may not be 5 amps.The
actual output is determined by the condition and internal resistance of
the cells in the pack and the condition and voltage of the supply battery.
In general, the charge rate will hold as high as 3 amps at the upper range.
It may be more than 3 amps but will not be less. Do not be tempted to start
your car engine to jack up the charge rate, as that might damage the charger
[Interesting
– before reading this I used the SuperNova frequently charging my plane
on the way to the field. I have had the charger on and working at the time
the car was started, and restarted after we stopped for coffee. Nothing
in either the Simprop or SuperNova manuals address this. I think using
the unit in this manner would be a natural occurrence for many modelers.]
Indoors, I used an AC to DC power supply rated at 12V
DC and 10 amps. I charged 10 cells at up to 5 amps. If you must charge
the full cell count of 25 at 5 amps indoors, I suspect you will need a
supply with arated output of at least 20 amps or more.My 10 Amp supply,
by the way, was capable of discharging 25 cells at up to the 3A maximum-load
rating. [The SuperNova only draws about 175 mA in any of the discharge
modes. So you could power it from just about anything….until it goes into
the charge mode]A few words about the instruction manual. It is well-written
and thorough but contains a tremendous amount of information. I read it
several times before attempting to use the unit. At first, I was snowed-
so much so that I exchanged several emails with Fred and Tim Marks of FMA
Direct. They encouraged me to just get into using the charger. In other
words, try it; just don't keep looking at it and reading the instructions.
After a few charge/discharge cycles, it started coming to me; after a week
of using it regularly, it became second nature to me. At this point, I
realized that from a technical standpoint, this unit is sensational and-better
yet-it is not expensive.
The FMA Direct SuperNova 250S may set the pace for battery
chargers in the new millennium. For the money, it can't be beat! Since
it is so computer (software) oriented, I get the feeling this first product
is the tip of the iceberg. I can see many extra features being easily added
as experience builds with this unit. I'm very glad I started at the beginning
with this new product and look forward to using it.
ADDITIONAL TESTING by the Battery Clinic
Input voltage = 13.26
Charge current accuracy 1.2 %
| Supply Current | Curren to battery indicated | Current to battery actual |
| 5.15 amps | 4.96 amps | 5.02 amps |
| 4.18 amps | 3.99 amps | 4.04 amps |
| 2.17 amps | 2.00 amps | 2.01 amps |
Note: current to electronics and controls 170 to 190 mA. The rest goes to the battery under charge.
Discharge current accuracy: 1.3%
| Supply Current | Current to battery indicated | Current to battery actual |
| 168 ma | 2.78 amps | 2.82 amps |
| 167 ma | 2.88 amps | 2.92 amps |
| 166 ma | 3.04 amps | 3.00 amps |
Voltage cut off on discharge: 6 cell pack 5.38 volts (0.897 volts/cell) 0.3% from spec. 0.9 volts/cell
Hi cell count (24 cells) charge from 13.6 V, 12 amp supply:
Source voltage 12.84 volts, current 8.24 amps
Charge voltage 38.00 volts, current 2.47 amps
Hi cell count (20 cells) charge from 13.6 V, 12 amp supply:
Source voltage 12.59 volts, current10.04 amps
Charge voltage 38.84 volts, current 2.92 amps
Discharge (6 cell pack)
Read .520 amps Measured .516 amps
Charge (6 cell 1700 mAh pack)
| Set(amps) | Indicated | Actual |
| 0.1 | 0.10 | 0.121 |
| 0.2 | 0.20 | 0.241 |
| 0.4 | 0.43 | 0.442 |
| 0.5 | 0.53 | 0.541 |
| 1.00 | 1.03 | 1.037 |
| 2.00 | 2.00 | 1.994 |
| 3.00 | 3.05 | 2.968 |
| 4.00 | 4.02 | 3.970 |
| 5.00 | 4.99 | 4.960 |
Capacity measured with SuperNova 250S correlate well when
checked against Alpha 4 under similar charge/discharge regimes.
SPECIFICATIONS
Comments.
Capable of automatic peak fast charging and discharging. The SuperNova decides the proper charge and discharge current. In the manual mode, you can store up to 10 preset charge/discharge cur- rents for your specific battery needs. These presets can easily be modified permanently (stored in the memory) or temporarily.
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