Trail camera

A few years ago we bought a trail camera to leave around the garden. It has a movement detector and worked pretty well. It takes 4 or 8 batteries and 4 decent alkalines last a few days. I quickly made an adapter for a 12V SLA battery, as it has a 6V external input but this was pretty inconvenient. The battery died, so I thought I'd check the power consumption.

20mA is taken, even in the off position, which is about 0.5Ah/day.

200mA whilst taking a photo 

Assuming 30s of photos/video, 10 times/hr = 300s x 24h = 7500s = 2hr x 0.2A = 0.4Ah.

Say 1Ah/day in total

By removing the 4/8 battery divider and some of the battery supports I found space to fit 2 lion batteries in series, a regulator set at 5.8V for the camera, and a charger, set to 0.75A. The charger needs to be > 9.5V in.

2 batteries in series are better than 2 batteries in parallel due to the larger losses in the step up converter.

As 18650 battery capacity tops out at 3.6Ah, even if you can buy 8Ah ones from some places, I picked some at 2.9Ah as they're half the price of 3.6Ah ones and only extend the camera life 12 hours or so. 

Using 2 x BAK N18650CL-29 should give nearly 3 days. Charge time from empty of about 4 hours. Battery protection with a small 2s pcb. Some notes as specs in the electronics folder.

It's a bit tight on the height, but it closes.

Original

At the top CC/CV charger, middle buck converter
2 batteries with the 2S protection pcb
2.1mm power connector