A VERY SMART charger

Charger ready for testing
I have built  A&A Engineering's 1 amp Smart Battery QRP charger mainly for my Elecraft K2's internal battery. This very much is a smart charger and here are a FEW reasons why.....

1. The charger can be connected to the battery indefinitely and no harm will come to the battery. Once the battery is fully charged the Smart charger will remain in maintenance mode delivering a float charge. Therefore the battery cannot be over charged.

2. The charger can stay hooked up to the battery while operating the radio if you so choose to do so. The charger will enter the bulk mode to help with the load of the radio operating.

3. When the charger is connected it automatically determines the type of charge the battery needs.

Close to done but no heat shrink on LED
 The charger can either be ordered fully assembled and tested or as a kit.....yours truly held true and strong the the QRP spirit and chose the kit. The kit did arrive very fast and all parts were checked and accounted for. If you are a first time builder of  kits this may not be the one for you as the instructions are vague at times. I did get myself into problems after  realizing I had missed part of the assembly and had to go back to add parts and two jumpers. The kit does not give you the "standard" step by step instructions regarding assembly. It's more or less tells you too "install the components according the the pictorial diagram".  There are even little side notes here and there one in particular relating to jumper installation that I totally missed. I did get the charger all together and it was time to check the unit out. So I plugged the charger in, turned it on and ........no 12 volts DC from the leads on the charger!!!!
Top view with no jumpers or D1 ops

Fried resistor
 It was time to check the board to see if parts were installed according to plans and if all solder joints were good and soldered. All seemed to be good so it was off to the internet to see if anyone had the same troubles. It was on the internet I found a test procedure for the kit version of the  charger from A&A Engineering. For some reason beyond me I am not sure why this was not included in the kit!!! Anyway.....one of the things what was emphasized was if the charger is not hooked up to a load you will NOT get any output. Well that solved the problem of no output and things now seemed to be "normal" There was a test procedure in the text that
Decided to use Anderson conn's
allowed you to see if parts of the charger were working as they should. It involved removing the IC and shorting legs of the IC 16 pin socket to certain areas of the circuit board. When this was done certain voltage reading should be observed or LED's should turn on. Here is my BIG problem with this type of testing......when you short things out things can go WRONG and they DID!!! I guess I was not paying close attention and I shorted the wrong pin on the IC to ground and I FRIED a resistor on the board. When you short out to test I call this a destructive way of testing I much more prefer using a meter to look for certain voltages. If  you either don't get the right voltage or a down right outrageous voltage you understand
1. You are in measuring in the wrong place.
2. You have made a mistake in the assembly.
In either case nothing has been toasted
Some heat shrink fun
In the end all checked out ok with the Smart charger and it working great to charge my Elecraft K2.  Over all this is a great unit even with the hiccups that I had. Some of the things that are not clear in the instructions are as follows
1. The heat shrink tubing is very clearly stated to go on the transistor but it also should go on the leads of the LED's...that was not so clear and I have redo the LED's.
2. Make sure you add the jumper J1 to J2 in my case it is mentioned but off to the side of the instructions
3. There is no diode to be installed in D3 position, instructions just say install parts and there are is D1, D2 and D3. Just install the diodes (both are the same diode) one in D1 the other D2.
D1 needs to have the diode not D3

4. If  you ordered the QRP version of the charger as I did you will get a separate kit that allows the charger to switch between two charging currents. Read those instructions and install the resistors they tell you too or you will end up removing resistors if you follow the main instructions then move to the add on kit instructions as I did.
5. When done remember the output leads will SHOW NO VOLTAGE UNLESS A LOAD IS APPLIED.
6. The document required to test the unit can be found at the link above under "test procedure". BUT when  you do it be very careful!!!
Mike Weir, VE9KK, is a regular contributor to AmateurRadio.com and writes from New Brunswick, Canada. Contact him at [email protected].

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