(Continued from page 4)

The photo shows the display between current pulses.  Note that the pack voltage has decreased to 8.39 volts. This drop in voltage is

sufficient to cause

the charger to pulse

again. This happens

when a cell is not fully

charged.  The  cell (and pack) voltage will start to decrease when no charging current is applied.  The charger detects this decrease and pulses the current on and then turns off.  The intervals between current pulses becomes longer and longer as the cells maintain the voltage .  When the pack is fully charged the charger stops and beeps 3 times loudly. It does this when the battery pack voltage does not decrease with the longest interval the charger has.  The charger then displays:

1. CHRG Done

2. Total charge time

3. Total current put into the pack

Voltage of the battery pack

The uniqueness of the third mode is that it will actually leave the pack about 5% short of what could be put into the battery pack if a true Constant Voltage mode were used.  However, there is nothing wrong with this.  Most users of Lithium packs are now removing the pack from their chargers shortly after the CC (constant current 2C2) portion of the charge as at that point the pack is about 90% charged.  This takes about an hour to do with the current lithium chargers, but that other 10% could take anywhere from 30 minutes to an hour to do!  It is just the nature of the beast.  Plus in addition, once again this helps to eliminate an overcharging condition.

The charger will also warn you if:

· The input voltage is to low

· You try to charge more than a 9 cell pack

· The output is shorted

· It does not detect a battery voltage of more than 3 volts

The charger also has a built in discharge function.  It will display battery voltage, duration of the discharge and amount of total current discharged.  I personally have only hooked up the charger long enough to see that the

 

discharge function worked.  I normally use my Orbit for any discharge function because I can interface it to my PC and get a curve trace.  The discharge function works by discharging a pack down to about 70% of the detected starting voltage.  So, you must start with a fully charged pack to use this feature.  Personally, I could have done without the discharge feature, especially if it operates as I’ve been told.  You could possibility over discharge a lithium pack and ruin it by putting a partially discharged pack on it.

This charger is one of the most straightforward chargers I’ve ever used and so far, has been totally reliable.   I have charged batteries on it about 50 times now and everything works fine.

What I don’t like about the charger...  There is always something.  My pet peeve about it has to do with the AMPS ADJUST knob.  It is always active.  That means at anytime it could accidentally be turned up or down.  Also, if you forget to turn the knob down first before starting the charge, you could feed in quite a current slug before you realized it.  I also wish there was some way to make the discharge function know the number of cells in the pack or set a voltage level to discharge to.  However, these drawbacks will not stop me from using this charger, as it is probably the best value lithium charger currently on the market. 

In addition, these concerns have been passed on to AstroFlight by myself and others, some of whom are well known in electric flight circles and do seem to have more influence.  I have heard that changes in the programming are coming that address these particular issues and should be released in the near future as a programming upgrade. As I mentioned, this requires just the replacement of the EPROM chip usually for a nominal cost.

The only modifications I have made to the unit were to change the output connector to match what I currently use, change the input alligator clip to larger battery clips I got at Radio Shack, and to put some stick-on rubber feet on the bottom of the charger.  There are molded-in feet knobs on the bottom, but these tend to slip in my experience.

I’ve just covered the highlights here of using the charger and tried to give you guys some basic lithium cell information.  As with anything new, the best advise I can give is to research, research and do more research. 

 

 

· All mounting screws including engine to mount, mount to firewall and muffler screws are secured with lock washers and/or “Locktite” on the threads.

· Clevises are secured with ‘keepers’.

· The propeller must be in good condition, balanced, mounted on the shaft with the foil side forward, rotate near the horizontal position on compression, and the mounting nut must be tight. A spinner or smooth prop nut should be used.

· The tank clunk is free to swing, and the correct lines are brought out to the carburetor and to the muffler pressure tap. Fuel tubing connections are secure.

· All hinges are intact with little hinge gap, and will not pull loose.

· The throttle movement fully closes down and fully opens the carburetor intake. The rudder swings to the ‘right’ when the transmitter stick is pushed to the ‘right’, right aileron control makes the right aileron rise, etc. Up elevator (pull back) makes the elevator move up. Control surface movement is smooth.

· The model is balanced at the “GC” and laterally.

· If you are unsure about what these pointers mean, please ask an instructor to work with you.

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