A gloriously dumb USB powered NiMH and NiCad battery charger that will guarantee a full charge every time, but only if you're not in a rush. A trashy 500mAh cell will take about a day to charge, while a luxuriously high capacity cell could take most of a week to charge - but will be charged right to the hilt and not be harmed in the process.
The unit uses low current trickle-charging at between 20-30mA to ensure a safe charge at a low enough level to allow the inherent feature of self catalysis of end of charge gas bubbles back into liquid electrolyte with low pressure buildup.
Can also be powered by a 5 or 6V solar panel and will use whatever solar energy there is to put some charge into the cells.
The PCBs can be cascaded with a common power buss to create an array of up to 40 charge positions from a common 1A charger.
Each cell is charged completely independently from the others and has a diode to prevent backfeed when power is removed or there is no solar power available.
Individual LEDs to indicate charging status. Choose whatever LED colour you like. Power indicator LED is optional and can also be any colour of LED.

There are four 3mm mounting holes for feet or for mounting the PCB to a panel. I'd recommend against having the panel loose amongst metalwork on a bench in case the back gets shorted out.

This trickle charging system is perfect for the newer NiMH low self discharge cells. It's basically creating a better than fresh-out-the-pack level of charge.

Here's a link to the gerber zip file for getting PCBs made. YouTube prevents a direct link to a zip file for security reasons, so you will have to copy and paste the link into another browser tab.

www.bigclive.com/NIMH.zip

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