I made this test / discharge rig for about $25. It uses these bulbs to discharge batteries when necessary. They come in a two pack:
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Low Voltage led Light Bulbs AC/DC12-48V E26 White 6000K 9W 720lm for Off Grid Solar Lighting Marine Boat RV 12v Interior Lighting 2 Pack for Camper - - Amazon.com
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They are rated at 12 - 48 volts but I doubt 52 will harm them.
I screw them into this standard (medium base) bulb test socket:
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I use the alligator clips on the socket wires to connect it to the battery lugs. The process is simpler if you can find a connector for your battery and just plug it in.
The bulbs draw less than 10 watts so discharge may take a few hours.
You can speed it up a bit by using the second bulb and this "Y" adapter:
Sunlite's Medium (E26) base light bulb Y socket adapter is the ideal tool for the professional photographer and artist in need of that extra bit of illumination on a subject. Not only will it work perfectly for professional usage but it also works fantastically for general purpose lighting in...
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