Lesson Learnt: Use quality battery with BMPCC 4K

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Dalavi Tang

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  • Joined: Wed Jun 24, 2015 2:40 am

Lesson Learnt: Use quality battery with BMPCC 4K

PostTue Jan 15, 2019 10:17 am

I noticed a significant rate of battery drain on my F970 batteries that came with Aputure lights (7200mAh rated, and I thought they would be just fine) when powering the Pocket 4K, so much so that I can merely get 1 hour of run-time.

So I bought a custom-made F990 (8 x Panasonic NCR18650b cells, 2s, 13600mAh rated) and a dummy load to test the discharge. And here are the discharge curves and tested capacity under a constant 4A current draw and cut-off at 5V (if a Canon LP-E6 lasts half an hour, then probably 4A is a good guess for worst-case) with similar ambient conditions.

Screenshot (7).png
Screenshot (7).png (242.6 KiB) Viewed 366 times

Above is the discharge curve of Aputure F970 which lasted 54.5 mins. 3623mAh tested, 50.3% of the claimed capacity. When the current is cut, the voltage of the battery slowly returns to around 7.4v again, but it drains immediately empty again under 4A load.

Screenshot (6).png
Screenshot (6).png (250.53 KiB) Viewed 366 times

Above is that of the custom-made F990 which lasted 198.5mins. 13240mAh tested, 97.4% of the claimed capacity.

But I haven't tested the battery on camera yet, it takes ages to recharge. I don't know if the camera voltage read-out is flawed or not because I've been suspecting that it might be inaccurate since I measured different voltages with a multi-metre from in-camera read-out.

I guess the same is happening for those third-party LP-E6 batteries that doesn't last - the cells just cannot handle the massive current draw and they drop voltage so rapidly that at the end of the discharge curve the voltage just plummet - and the camera just shut off without warning. At least this can be one of the contributing factors.

(Not paid by Panasonic to say their battery cells are good)

Denny Smith

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Re: Lesson Learnt: Use quality battery with BMPCC 4K

PostTue Jan 15, 2019 6:31 pm

Good point, and the high current draw is the reason the cheaper batteries fail sooner, they were not designed for s high current load application. Most DSLR Cameras, these batteries were designed for, are not high current loads, but lower intermittent loads.
Denny Smith
SHA Productions

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