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Canon 600D (T3i) dummy battery not working

Started Oct 30, 2015 | Discussions thread
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Slowpoke69 New Member • Posts: 2
Canon 600D (T3i) dummy battery not working

I am having trouble trying to build a dummy battery powered by a 12 V marine battery for my long astrophotography sessions.

First of all, I built a step-down circuit out of this schematic http://www.astrofototecnica.it/images/stories/alimentatore350dschema-2.jpg, using a 7808T voltage regulator, with a measured output voltage of 7.94 V.

Then, I got a cheap LP-E8 Chinese battery from eBay, disassembled it and removed the internal lithium battery, replacing its output to the battery circuit with the output of my circuit. The tester confirmed a voltage of 7.94 V between the + and - pins of the battery, and also a 7.86 V voltage between the + and T pins (which is the only other used by the camera).

As a comparison, the original battery shows a voltage of 8.18 V between + and -, and 8.09 V between + and T.

However, when I inserted the dummy battery in the camera and turned it on, the display showed the message “change the battery pack” (in Italian in the picture).

Thinking the disassembled battery circuit could be the problem, I ordered a DC coupler from Amazon (http://www.amazon.it/gp/product/B00WX2TAX6 ), connected it to my step-down circuit but got the same exact result.

Therefore the only problem could be the step-down circuit. I supplied the dc coupler with a 8.02 V - 500 mA power supply (the only suitable I own), but still got the same message.

I don’t know what else to try. It is worth to mention that any regular LP-E8 battery works perfectly (both Canon and compatible ones)

 Slowpoke69's gear list:Slowpoke69's gear list
Canon EOS 600D
Canon EOS 600D (EOS Rebel T3i / EOS Kiss X5)
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