Im currently setting out a new project, and am concerned that im going about things the wrong way from the outset, so asking for advice, rather than just ploughing on..
So the mission brief:
Provide a charging case/station to safely charge lipo batteries in parallel.
Why?
Parallel charging with a high power charger/balancer allows quick preparation of batteries for model flying.
Whats wrong with what I have?
My current setup is a little clunky and has no built in safety.
Current setup:
2 x server PSUs, one with a floating DC earth, running the DC in parallel to give 24V output at up to 63A constant current draw
Fan speeds controlled via a dual gang potentiometer as a voltage divider across the correct pins on each PSU.
The 24V supply then supplies a lipo charger (Revolectrix PL8).
Output from PL8 into a home made balance board (10 x main battery connectors, and 10 x JST balance connectors)
Current problems:
There is no monitoring or self regulation of the PSU temperature. So by default to be safe you have to manually set the fans running too fast, which is noisy and doesnt adapt to the loading of the PSUs, so at the end of the charge, which can take 15 minutes the current draw is low, but the fans are still going at high speed which isnt required.
There is no way of detecting (other than the charger throwing off an error) of a pack failing during the charge. When lipos get angry during a charge this can result in a fire, and given that these are pretty high power batteries (25V, 5Ah) these fires tend to get big quickly.
The install looks bad. really bad.
Solutions:
I have a nice charging case to be building.
I want to: individually monitor the temperature of each battery (so thats 10 at a time). The batteries will be on charging 'pads' (essentially just a marked area on a perspex board). If the temp of any one of the batteries rises significantly above ambient (say 5 degrees C (another input)) then the power to the PSUs should be cut, and an alarm sounded (so thats one output) I also want the device to indicate which battery has triggered the alarm, so that this can be looked at carefully before further charging.
I want to be able to monitor the charger output power (by means of a hall effect current sensor(another input)) and use this to vary the fan speed (driving the fans independently of the PSU controller (another output)), with an override if the output air temperature gets too high (another input).
I want a 'control panel' to be able to monitor all of the above, and plan to use an LCD display.
I want a way of controlling where the PSU power goes to as I sometimes would want to use a different (non hard wired) charger), so thats two more outputs driving two relays, and also control whether the PSU's supply 12V (one PSU) or 24V (the two in series), so thats 2 more outputs to drive 2 x 240V relays, and of course 2 inputs to decide what voltage and where the current goes...
So to cut a very long story short (I thought it would help if I laid out why I needed these things), I think I need:
10+1+2+1+2 inputs = 16 inputs
2+2+1+1 = 8 outputs
plus of course the outputs to drive an LCD screen (ideally 20x4)
So my question - how on earth do I get all these inputs/outputs. I cant see this happening on an arduino UNO board.
Can some clever people help me?..
Thanks
James