Got started on mounting the parts into the battery driver box today. With still no sign of the LED’s or drivers I can only work on the batter’s and charger for the moment. I wasnt a fan of the original flat gray color of the box I intend to use so I changed it to mat black. Into that I have put the home made battery charger.
The flat Aluminium section is there it help dissipate heat from one of the charger components to the box. The Blue heatsinks will be rather useless once the lid is closed but I had them laying around, and so, threw them in anyway. During testing no parts got above warm to the touch. The ad-hock battery holder on the left is a temporary solution.
On the left is the 12 NiMh cell’s I will be using. Total capacity is rated for 35Wh, but in reality is around 30Wh. Should be enough for 2 hours run time with all 4 LED’s on at 1A.
Towards the front of the box I have added the 6pin female connectors and some fuses. One fuse is for the charger onto the batter while the other is for the battery to the LED lights. The two different fuses are required as the charging current is at 200mA while with the lights on it will run at around 4A on high.
With the batteries installed its now ready to charge. When the 16V AC power supply is attached the charging light comes on. I also tried to include a voltage indicator of the cells. When the voltage gets to around 16.5V a green LED comes on. This is the LED thats off in the picture above.
Unfortunately due to the chemistry of the NiMh batteries the voltage isnt a true indication of their level of charge. That is, the cells may only be 2/3 full but already at 16.5V.
I may come up with something more definitive in future such as a fast smart charger, but this a lot more complex to say the least. As it is a full charge at 0.1C takes around 12 hours, so its an over night charger.