FAQ
INDEX
Litco SystemsAlpha4 FAQ | |||||||||||||||||||||||||||||||||||||||||||
FAQ
INDEX
Additional information is often added to this section so please check back frequently.
1.1 ABOUT ALPHA4
"V" DEVICE
1.2
WHY MUST ALPHA4 BE CONNECTED DIRECTLY TO
THE
BATTERY?
1.3
WHAT TO DO IF YOU DO NOT KNOW CAPACITY OF YOUR
BATTERY
1.4 WHAT TO DO IF YOU OBTAIN "V.LO"
MESSAGE ON ANY
OF THE DEVICES.
1.5 UNDER WHAT CONDITIONS SHOULD
18 GAUGE 36 INCH
ADAPTER CABLE BE
USED?
1.6
CAN I CHARGE AND CYCLE RAYOVAC RENEWAL CELLS ON
THE ALPHA4?
1.7 WHAT ALPHA4
DEVICES SHOULD I USE FOR CYCLING AND
CHARGING NIMH
BATTERIES?
1.8
WILL REVERSE PULSING OR "BURP" CHARGING REJUVENATE MY BATTERY?
1.9
WHY CAN CHARGERS USING TIMERS DAMAGE
BATTERIES?
2.0 USING "N" DEVICE WITH NEW NICADS
2.1 WILL ALPHA4 CHARGE LITHIUM BATTERIES?
2.2 IS MEASURING INPUT CAPACITY DURING CHARGING OF VALUE?
2.3 WHAT FAST CHARGE CURRENTS ARE RECOMMENDED FOR FAST CHARGING TX AND RX.
2.4 ADDITIONAL INFORMATION ABOUT USE OF ALPHA4 "I", "A" AND "V" DEVICES.
2.5 ABOUT CHARGING WET AND GEL CELLS
2.6 TESTING ADAPTER CABLES WITH ALPHA4
2.7 WILL CONTINUOUS TRICKLE CHARGING HURT BATTERIES?
2.8 BATTERY CAPACITY MEASUREMENTS
2.9 SURFACE CHARGE VS ACCEPTED CHARGE.
ABOUT ALPHA4 "V" DEVICE
As a rule most ESV's other than "V" device on A4 have a very small load such as 100 mA, which is almost the same as no load at all. This is because they cannot handle the power dissipation that a large load such as 1000 mA on A4 will dissipate. For this reason the voltage reading on these ESV's will be close to noload reading on A4. The large load of 1000 mA is necessary because if a servo stalls due to jamming or high air load it will typically draw stall current of about 1000 mA. The 1000 mA load of the A4 "V" device is not constant but pulsed. The load voltage reading is taken during the 1000 mA load pulse. The average current is only about 150 mA depending on how many ports are programmed. This high load not only allows for testing batteries but also connectors and switches.
The pins in a typical connector are crimped to a stranded copper wire that is not normally solder plated. In time corrosion develops at the joint causing higher than normal resistance which results in excessive voltage drop across the joint. This results in lower than normal voltage to be available to the rest of the airborne system which could cause a failure. This failure would most likely occur during periods of high current load such as when the aircraft is diving and up elevator is applied. This high air load on the servo could result in a servo stall condition and high current draw.
Using the "V" device
The A4 instruction manual explains
the use of "V" device under the
heading:
"PROGRAMMING VOLTMETER ("V" ON THE KEYPAD).
First program a Voltmeter ("V") on one of the ports and connect battery to be tested to that port. Next press and HOLD a key on the keypad that corresponds to the number of cells in the battery that you are testing. If the battery has 4 cells then press and HOLD key "4". If there is no message on the screen the battery is OK. If V.LO flashes the battery fails under load ( the battery is below 4.72 V if the pack has 4 cells). If V.LO is steady the battery fails under both load and noload.
Note that A4 allows the battery to go to 1.18V per cell under 1000 mA load before flashing V.LO warning message. With typical ESV you would normally go down to 1.175 V per cell under very light load (100mA for instance). This would not leave any margin for problems such as a stalled servo. You should not take chances and when A4 flashes V.LO message you should put the battery on "A" fast charger and continue flying after "A" switches to trickle.
Please note that charge accepted by nicad and nimh batteries cannot be determined from battery voltage. This can only be determined by discharging the battery on a cycler and noting the capacity in mah.
Determining number of cells in a battery
pack.
The "V" device can also be used for determining a number of
cells in a correctly functioning battery pack. The procedure is as
follows:
-Connect battery pack to a port and program "V" device on that
port.
-Press and HOLD "RUN" key until battery voltage stops rising rapidly
but hold for
at least one minute.
-Release the "RUN" key and quickly
read the load voltage. If the load voltage drops rapidly repeat the procedure
above. This time however hold the "RUN" key longer.
-Divide the load voltage
reading by 1.2. Round off the resulting number to nearest whole number.
Example:
4.33 is rounded to 4
3.87 is rounded to 4
3.45 is
rounded to 3.
-The resulting number represents number of cells in the
pack provided however that there are no shorted cells in the pack.
WHY MUST ALPHA4 BE CONNECTED DIRECTLY TO THE BATTERY?
Many TX's use diode in series with internal battery to prevent
discharging of the battery through the TX charging jack. This is done so
that the TX battery cannot be accidentally shorted through the charging jack
and also to prevent damage from chargers that do not have proper polarity.
There are more sophisticated methods to accomplish this protection but diode
only costs a few cents so it is used.
Diode conducts current only in one
direction and it has a temperature dependant voltage drop accros it. For
this reason it will prevent any cycler from discharging the TX battery. Also
it will prevent sophisticated unit such as Alpha4 from operating correctly
in the charge modes.
A4 needs to measure battery voltage very accurately
at all times in all
modes of
operation in order to follow battery voltage curve and correctly and precisely
switch to trickle. For this reason it must be connected to the battery directly
and not through a diode. If there is a diode in series with the TX charging
jack A4 will display "OPEN" message as it cannot properly read voltage backwards
through
the diode. In this case you can bring leads directly from the battery
to a separate connector on the back of the Tx or in some cases simply remove
the battery and then connect leads directly to it.
It is also possible
in some cases to bypass the diode with a fuse but you should consult the
TX manufacturer before doing it.
Since cycling batteries is now
a universally accepted practice one would think that TX manufacturers would
correct this design problem. We suggest that you complain to these manufacturers
about this situation.
WHAT TO DO IF YOU DO NOT KNOW CAPACITY OF YOUR BATTERY
If you do not know a battery 's capacity, charge it first on "A" charger ( it does not ask for the capacity) and leave it on trickle for 3 hours. Next cycle it on "S" cycler. Enter capacity of 1000mah when requested. The "S" cycler uses peak detector for recharging and termination to trickle, so it does not matter if your guess of 1000 mah is not correct. When "S" completes discharge cycle and switches to "F"(FAST) the true capacity will be displayed. If you now wish to measure maximum possible capacity, charge the battery on "I" charger and after the charger switches to trickle leave it on trickle for several hours. Next cycle the battery on "C" cycler. The charge acceptance of battery is higher at the slower charge rate of "I" charger and leaving it for several hours on trickle puts small additional charge into the battery.
Please note that charge accepted by nicad and nimh batteries cannot be determined from battery voltage. This can only be determined by discharging the battery on a cycler and noting the capacity in mah.
WHAT TO DO IF YOU OBTAIN "V.LO" MESSAGE ON ANY OF THE DEVICES.
The V.LO message means that the battery voltage is below normal. This condition can be caused by a battery that is excessively discharged or a battery with defective separator in one or more of the cells. In critical application such as model aircraft we wish to be aware that a separator failure is developing. Ignoring this condition will lead to eventual total failure of the battery and crash of the aircraft. This is why A4 will not allow you to process a battery that exhibits V.LO message. If V.LO message occurs the battery should be connected to a port programmed with "V" device. Next "R" (RUN) key should be depressed and HELD. When "R" key is depressed and held the load is removed and 1000mA quick charge is substituted as long as the "R" (RUN) key is held. The second four digit reading now represents the battery voltage under charge rather than under load. This reading should be carefully observed. If this voltage reading increases quickly over 1.2 Volts per cell then the battery is probably OK. If the voltage reading hesitates to increase above 1.2 volts per cell the battery is defective.
If the battery appears OK, hold the "R" (RUN) key for another 30 to 60 seconds and then press "P" key and reprogram the port to desired device or simply switch the battery to a port that has been previously programmed with the desired device.
UNDER WHAT CONDITIONS SHOULD 18 GAUGE 36 INCH ADAPTER CABLE BE USED?
If the adapter cable is used for charging and cycling batteries from 2 to 12 cells the length and gauge of cable is not critical.
Only 18 gauge or heavier and 36 inches or shorter cable should be used with "V" device. This is necessary because the second four digit reading of the "V" device is taken under heavy 1000mA load and thin long cables will have a large voltage drop. This will result in voltage at the battery being higher than at the Alpha4 port jack. This will cause flashing V.LO message to appear at a higher battery voltage prompting you to charge battery more often than necessary.
If single cell is being discharged on one of the A4 cyclers
a short heavy well connected cable must be used or discharge current regulation
will not be maintained and capacity reading will be higher than normal. If
the combined voltage drop across the connectors and the cable is higher than
0.1 Volt the constant current discharge will not be held.
Since this
will result in lower than rated discharge current it will cause the capacity
reading to be higher than normal. This
does not apply to batteries consisting of 2 to 12 cells. For charging 1
to 12 cells cable and connector voltage drop is not critical.
CAN I CHARGE AND CYCLE RAYOVAC RENEWAL CELLS ON THE ALPHA4?
These cells must be charged individually and not in packs. Also they require different cutoff voltage than either nicads or wet and gel cells. Their internal resistance is much higher than nicads. The short circuit current of individual cells is about 6 to 8 Amps and rapidly drops with each recharge. The short circuit current of nicads of equivalent size is several times higher and is approximately constant over hundreds of cycles. For this reason the Renewal cells are not recommended for higher current drain applications. In RC applications they might be OK for TX's but marginal for RX packs. The airborne pack has potentially a drain of about 1000 mA per stalled servo plus small RX drain. (servo at rest has very small current drain, while servo actuating nonbinding load might have a drain of about 100 to 300 mA). A positive feature of these batteries is very small self discharge current and high capacity when new and when lightly loaded. We felt that it was not worthwhile to include special charger on the Alpha4 for these batteries especially since only one cell could be processed per port. Also cycling of these batteries would only cause premature loss of capacity. Furthermore Rayovac offers special chargers for these batteries starting at about $14.00.
WHAT ALPHA4 DEVICES SHOULD I USE FOR CYCLING AND CHARGING NIMH BATTERIES?
Nimh batteries do not
develop pronounced voltage peak as nicads do. For this
reason
nimh batteries cannot be charged on "A" and "S" devices. These
devices
terminate on the onset of negative slope of the voltage versus
time curve. They are
therefore peak detectors.
The "I" and "C" devices
terminate ahead of voltage peak on the zero slope portion
of the voltage
versus time curve. These devices are therefore suitable for processing
nimh
batteries.
The "F" and "R" devices are fast charge devices which begin
to taper down at 80%
capacity. In theory they should work fine with nimh
batteries provided however
that charging nimh batteries at rates above
C/10 is recommended by the battery
manufacturer.
To be on the safe
side you should use only "I" and "C" devices with nimh
batteries.
Please note that nimh batteries have much higher internal
resistance than nicad's.
For this reason we do not recommend batteries
in the lower capacity range for use with airborne packs.
A stall current
of a servo can be as high
as 1000 mA. Under high air load or with binding
linkage a servo could
stall. This might cause excessive nimh battery voltage drop and
system
failure. Furthermore nimh batteries exhibit temperature dependent high
self-
discharge rates, have lower longevity than nicads's and present
safety issues. Finally, in comparison to newest nicad's, nimh batteries
no longer offer significant energy density
advantage.
WILL REVERSE PULSING OR "BURP" CHARGING REJUVENATE MY BATTERY?
This "technique" involves periodically reversing current flow during
the charging process. Since 1960 claims were made that this technique would
rejuvenate batteries of varied chemistries. Attempts to market this technique
to battery manufacturers failed as technical tests revealed that this technique
had no beneficial effect on the batteries.
We have also conducted our
own tests. The technique is trivial to implement. In case of Alpha4 it is
costless as it involves insertion of a few commands into the EPROM. Unfortunately
the technique is useless and potentially harmful. If the current reversals
are at sufficiently slow rate and the duration of the reversal is sufficiently
long the batteries under charge undergo in effect continuous shallow cycling
and the battery capacity is prematurely decreased. At higher rates the effect
is reduced. In any case no rejuvenation of any kind is observed.
Claims that a "burp" charger will substitute for a battery cycler are simply
false. A simple charger with couple of LED's on the front panel will not
measure the capacity of your battery.
"Burp" charging is mainly used
in situations where an attempt is being
made to market an otherwise unsophisticated battery charger at an excessive
price.
WHY CAN CHARGERS USING TIMERS DAMAGE BATTERIES?
Most nicad and nimh batteries are designed to accept overcharge at
C/10
rate or lower without immediate damage. C/10 current rate equals battery
capacity divided by ten. If these batteries are overcharged above this
rate
then gas pressure buildup and venting will occur which will lead to premature
loss of capacity. To obtain full service life, batteries should be switched
to trickle when they are fully charged and not by a timer.
All
unsophisticated cycler/chargers and some supposedly sophisticated cycler/chargers
use timers to terminate
to trickle. If the battery capacity divided by 10 is the same or less than
the charger current rate no immediate damage will occur. Since most
cycler/chargers have only a few current ranges the selection of proper current
rate is often not possible. A higher current rate than C/10 is often selected
leading
to battery damage. If lower current range is selected the timer will switch
to trickle before the battery is fully charged.
In some very high priced
cycler/chargers a timed charge
of as high as C/5 is used. This is totally unacceptable as it will lead to
certain loss of capacity with most nicad and nimh batteries. These high priced
cycler/chargers should use a slope following technique not timers for proper
termination to trickle.
Alpha4 does not use timers for termination to trickle. Accurate analog
to digital converters are used to measure battery voltage in all modes of
operation. From these measurements Alpha4 calculates the slope of the voltage
versus time curve of the battery.
"I" and "C" devices terminate to trickle
in the zero slope region ahead of the peak at 95% capacity.
"A" and
"S" devices terminate to trickle at the onset of negative slope at the peak
at 100% capacity.
"F" and "R" devices begin to taper down at 80% capacity.
USING "N" DEVICE WITH NEW NICADS.
New nicads should be left on "N" device for a couple of days before
processing with other devices. This will properly "form" new batteries. The
"N" device charges at C/10 rate and does not terminate to trickle. At the
C/10 rate batteries will not be damaged or lose capacity over this short
period of time.
New batteries often have been sitting on the shelf
for a long time and due to self-discharge exhibit lower than normal voltage.
If this is the case these batteries will generate "V.LO" message on all devices
except the "V" device. Please see FAQ paragraph 1.4 above for instructions
how to proceed in this case.
WILL ALPHA4 CHARGE LITHIUM
BATTERIES?
At the present time Alpha4 cannot process
lithium rechargeable batteries. As the demand increases, and numerous technical
issues are resolved we will consider firmware change for Alpha4 to accomodate
these batteries. At this time it is totally impractical to implement this
change for many of the following reasons.
Many of these batteries require
battery specific
charger. Standardization is a problem as some battery packs include internal
circuitry. Need to monitor individual cells when cells are connected in series
presents a problem. Inability to accept a fast charge at higher current rates
limits their appeal. The maximum current available would also be of concern
if one or two servos stall. With some of the battery types there are unresolved
safety issues and the number of cycles available relative to cost is not
competitive. On the other hand low weight per energy stored and low selfdischarge
rate are big pluses.
Since the safety issue is of extreme importance
in
consumer applications the following is a review of rechargeable lithium
technology from safety viewpoint.
-Lithium metal with liquid electrolyte. Highly reactive liquid lithium presents unacceptable safety hazard for consumer applications.
-Lithium metal with polymer electrolyte. Again presence of metalic lithium is a very serious safety hazard.
-Lithium ion with liquid electrolyte. Free flowing electrolyte is highly flammable.
-Lithium ion with solid polymer electrolyte. This is the safest technology and the only one recommended for consumer applications.
Safety warning:
Lithium in the
metallic form is highly reactive. This presents difficulties in rechargeable
form. Repeated charge discharge cycles can cause electrode surface
irregularities
called dendrites. These can penetrate the separator and
form a short circuit between
the electrodes causing cell temperature
to rise. If the temperature reaches the lithium
melting point severe
flaming might result. For this reason this rechargeable technology
is
unsuitable for consumer applications.
IS MEASURING INPUT CAPACITY DURING CHARGING OF VALUE?
Unfortunately this measurment is almost useless as the input capacity
is not the retained capacity. Due to both thermal and chemical inefficiencies
batteries require 20 to 60 percent excess charge. For instance if you are
charging 600 mah battery at 60 ma it might take up to 16 hours to obtain
full charge. It will never take just 10 hours since this would require ideal
battery which we do not have.
As the batteries age the internal resistance
increases causing higher thermal loss and the excess charge must be increased.
The above comments apply to fast charging as well. Since thermal losses are
current squared multiplied by internal resistance of the battery the disparity
between input and retained charge is even greater due to higher current during
fast charging.
The thermal losses described above occur also during discharging. At higher discharge current the apparent capacity is smaller than at lower discharge current. The difference will depend again on internal resistance of the battery.
Input capacity measurment should never be used for fast charging at the field for two reasons:
1) The mah usage of the airborne system is not constant and depends
on air loads and
and degree of binding in pushrods.
2) The input capacity is not the retained capacity as described above.
When used repetitevely this method will cause the errors to accumulate which will lead to inadequately charged battery and a crash.
To speed up charging between flights simply fly fewer times between
charging.
Charging with Alpha4 "A" charger until it switches to trickle
will assure fully charged battery and therefore large safety reserve for
the next couple of flights. Use "V" device before each flight to check battery
voltage as additional safety measure.
WHAT FAST CHARGE CURRENTS ARE RECOMMENDED FOR FAST CHARGING TX AND RX.
The wiring and connectors in the RC radio system are not designed for
use with very high currents. Currents in excess of 1000 ma should never be
used as they will lead to equipment damage and/or loss of warranty
coverage.
To speed up charging between groups of flights simply fly fewer
times between charging.
Use Alpha4 "A" charger until it switches to trickle.
After only two or three flights this should not take very long. Use "V"
device before each flight to check battery voltage under load.
Unlike
other peak detectors Alpha4 contains a sophisticated slope detection capability
which will not cause batteries to become hot and overcharge.
There are
numerous special purpose, high current peak detector chargers available for
very fast field charging of electric car and electric airplane motor batteries.
In these applications the concerns are winning races and flight duration
and not flight safety and battery life. Alpha4 is not addressing this market
and should not be compared with these special purpose chargers. Fast charging
is only one of Alpha4's many capabilities.
Return to FAQ index
ADDITIONAL INFORMATION ABOUT USE OF ALPHA4 "I", "A" AND "V" DEVICES.
Charge acceptance of batteries is higher at
low current charge rates so use "I" charger and leave for couple hours on
trickle when time allows.
"I" charger should also be used in the above
manner when testing subsequently with "C" cycler for maximum battery capacity.
Please note that "I" charger terminates to trickle based on battery state
of charge and not a timer. At lower current rates this is difficult to accomplish
since it requires very accurate measurement system. To our knowledge Alpha4
is the only unit with this capability.
At the field use "A" charger, monitor
with "V" device before each flight and charge as necessary. If charging is
done after couple of flights it will not take very long to fill the battery.
You can also use the "F" charger at the field but read the manual, section
"Programming Fast Charger, Trickle" first.
Conservative battery capacity
rating would be at the one hour discharge rate. If you wish to duplicate
this condition use discharge current closest to the battery capacity. For
instance for 600 mah battery use 500 ma discharge rate (two ports programmed).
There is no harm using lower or higher discharge current but at the lower
current rate the measured capacity will be somewhat greater than at higher
current rate due to lower thermal losses. These thermal losses are proportional
to battery internal resistance.
Please note that charge accepted by nicad and nimh batteries cannot be determined from battery voltage. This can only be determined by discharging the battery on a cycler and noting the capacity in mah.
ABOUT CHARGING WET AND GEL CELLS
Wet and gel batteries require special charging methods to deliver full service life. Simple chargers nearly always subject these batteries to overcharge. During overcharge the electrical energy rather than being stored in the battery is used instead for breaking down the battery electrolyte into hydrogen and oxygen (gassing). This causes the battery to dry out and lose capacity. If wet or gel cells are left partially or completely discharged or are simply allowed to self-discharge, a lead sulfate compound is formed on the plates. This compound hardens over time and cannot be converted by subsequent charging. The battery loses capacity and is said to be sulfated.
To address the above problems a special charger is required. This charger
first charges the battery to 100% and then switches to float mode. In float
mode the charger supplies only enough current to neutralize self-discharge.
The "W" device of Alpha4 delivers these functions with total flexibility
for wet and
gel batteries from 1 through 9 cells at 2 Volts per cell. It will handle
capacities from 10mAh to very large 1000 Amp/hours. Typical automobile battery
has a capacity of 60Ah.
The "FAST" charge rate is 1000mA divided by the
number
of programmed ports. To obtain maximum charge rate of 1000mA program only
one port. The "FLT" (float) charge rate varies with the type of battery and
could be under 1mA for small batteries. Expect a 6Amp/hour gel cell to remain
on "FAST" for at least 6 hours if completely discharged. Automobile batteries
may
stay on "FAST" for several days.
The "W" device is equipped with
a 4 digit
DVM. Expect the DVM to reach well above 14V for 6 cell 12V wet or gel cell
before switching to "FLT". Expect the "FLT" voltage to stabilize around 13.30V.
Exact voltage depends on battery. Do not expect the "W" device to operate
properly with batteries that are aged, sulfated, dried out, open or shorted.
It will not rejuvenate worn out batteries. Dried out batteries will go to
"FLT" prematurely and not accept full charge. Batteries with partially
or fully shorted cells may never go to "FLT".
The "W" device is intended
for
fresh batteries. If you experince incorrect operation with "W" device obtain
a fresh battery. With fresh batteries "W" device will deliver a full service
life
of about 400 cycles.
TESTING ADAPTER CABLES WITH ALPHA4.
Adapter cables can be tested for lack of contnuity, short circuits
and intermittent connections with any of the Alpha4 devices.
IT IS
VERY IMPORTANT TO TEST THE ADAPTER CABLE AND ITS CONNECTOR FOR SHORT CIRCUIT
BEFORE PLUGGING IN THE BATTERY.
IF THERE IS A SHORT CIRCUIT BATTERY
LEADS COULD MELT AND THE BATTERY WILL BE DAMAGED. EQUIPMENT HOUSING THE BATTERY
SUCH AS PLASTIC TRANSMITTER CASES WILL BE DAMAGED.
YOU SHOULD TEST
ADAPTER CABLES YOU MAKE AS WELL AS CABLES PURCHASED
COMMERCIALLY.
ALPHA4 CANNOT SUPPLY SUFFICIENT CURRENT TO CAUSE SUCH
DAMAGE.
BATTERIES ON THE OTHER HAND CAN SUPPLY VERY HIGH
CURRENT INTO A SHORT
CIRCUIT.
If the leads to your battery pack have melted and /or
heat shrink wrap of your battery pack has split due to excessive heat do
not send Alpha4 for repair.
Check your cables, plugs and connectors for
short circuit using the procedure outlined below. Please note that the short
circuit could be intermittent.
Alpha4 has the following diagnostic error messages:
"OPEN"
"SHORT"
"REVER" (reverse polarity)
"V.LO"
(voltage too low)
"V.HI" (voltage too high)
Of the above five messages only the first two message will be used for testing adapter cables and connectors.
TESTING PROCEDURE
Program "V" (simplest to program) device on port 1 and insert the adapter
cable to be tested into the port 1 jack.
If there is no short circuit
in the adapter cable "OPEN" message will remain on the screen. Bend conductors
back and forth at the connector of the adapter cable to make certain that
there are no
intermittent short circuits.
If there is a short circuit in the cable
or its connector a "SHORT" message will appear on the screen. Correct the
short circuit before plugging any batteries into the adapter cable or meltdown
will occur.
When "OPEN" stays on it is safe to plug in the battery into the adapter
cable. The "OPEN" message must now disappear (and voltage reading appear)
if the cable and connectors have continuity. Bend cable back and forth at
both connectors to make certain that there is no intermittent continuity.
"OPEN" message should not show.
If "OPEN" message stays
on or shows intermittently the cable and/or connector have no continuity
and must be
repaired.
Return to FAQ index
WILL CONTINUOUS TRICKLE CHARGING HURT BATTERIES?
Battery manufacturers offer specifications for battery longevity as
related to continuous charge current. At C/50 continuous trickle charge the
battery longevity would be considerably higher than at C/10 continuous charge
but slightly lower than if battery was not continuously trickle charged.
For instance if battery longevity would be 5 years with continuous trickle
charge you could expect 5.5 years if battery was not continuously trickle
charged.
More important than small loss of capacity might be the fact
that continuous trickle charging might mask partial shorts developing in
the separator in one or more of the cells. To test for partial shorts charge
the battery fully on "I" charger and then remove it from the charger and
do not use it for 10 days. Next put the battery on "C" cycler and measure
the remaining capacity. If the battery is down more than 10 percent due to
self discharge the separator might be suspect.
BATTERY CAPACITY MEASUREMENTS
Battery capacity measurements depend on many factors and exact capacity rating as written on a cell cannot normally be exactly duplicated.
The measured capacity will depend to certain extent on the discharge
rate. At lower current rate ( more ports programmed ) the measured capacity
will be greater than at higher rate because of lower thermal losses due
to battery
internal resistance.
You should find out at what discharge rate your
battery was specified (1C rate, C/2 rate or C/5 rate) and then discharge
close to that rate.
Please note that most Sanyo batteries are conservatively
rated and have higher capacity than specified.
Charging at a slower C/10 rate on "I" charger will result in higher charge acceptance than fast charging on "A" charger. Leaving battery on trickle charge for a few hours will result in still higher charge acceptance.
In the discharge mode Alpha4 interrupts discharge current for a few milliseconds and samples voltage readings at no load. The discharge is terminated at 1.00 Volt per cell. This makes the cutoff point independent of connector and wire resistance and results in a deep discharge without cell reversal producing higher capacity reading . Other cyclers terminate discharge at 1.1 Volts with discharge current on. This results in unreliable shallow discharge with capacity readings lower than actual battery capacity and influenced by connector and wire resistance.
Frequency of cycling.
To verify capacity batteries should be cycled every month or perhaps every two months. Since batteries are guaranteed only for 500 to 1000 cycles frequent cycling is counterproductive as it tends to reduce the battery capacity.
Determination of capacity use per flight.
To determine capacity use per flight follow this procedure:
1)
Charge the battery on the "I" charger and leave it on trickle
for
at least 3 hours.
2)
Cycle the battery on "C" cycler. Leave the battery on "C" cycler
until Alpha4 switches to trickle.
Leave on trickle for at least 3 hours.
3)
Write down the capacity indicated on "C" cycler. This is the
maximum
capacity for this battery.
4)
Fly the aircraft with this battery and count the number of
flights.
5)
Cycle the battery on "C" cycler without first charging. Write
down the remaining capacity.
6)
Subtract the remaining capacity in step 5 above from maximum
capacity
in step 3 above and divide the result by the number of flights. This is your
average usage in mah per flight. This applies only to this aircraft. Other
aircraft will have different capacity usage per flight.
SURFACE CHARGE VS ACCEPTED CHARGE
Please note that charge accepted by the battery cannot be determined
by measuring voltage after charging. Voltage right after charging is higher
than normal due to surface charge. This voltage due to surface charge decreases
with time. It rapidly decreases with discharge.
The higher voltage
due to surface charge is generally meaningless except that an unusually
high voltage after charge normally indicates poor quality or dried
out battery.
To correctly determine charge accepted by the battery, charge the battery first and next cycle it.
On Alpha4 follow this procedure:
1)
Charge the battery on "I" charger, leave it on trickle for couple
of hours.
2)
Cycle the battery on "C" cycler. Set the discharge rate as close
as possible to the battery capacity. For instance if the battery capacity
is 1000 mah program only one port to set the current discharge rate to
1000 ma.
If you wish to insert minimum charge after discharge, program the "C" cycler
with the capacity of 0010. This will reduce the charge current after discharge
to 1 ma which will insert minimum charge into the battery.
3)
Write down the capacity after discharge is completed. This is
the charge accepted by the battery.
.
.
.
