I’ve done many tests of 12-volt Sealed Lead Acid batteries with the Pocket.
When I got frustrated with $15 internal 800mAh EN-EL20s lasting as little as five or ten minutes, I began to wonder about cheap SLA batteries. Looking at the Pocket specs, seemed like they would work. I started with an eight-dollar 1.3-Amp-Hour SLA. I made a cable with the Pocket connector on one end and two F2 connectors on the battery end, being sure to match F2 positive and F2 negative with center pole positive and outside pole negative of the Pocket connector.
Naturally, I was terrified the Pocket would fry, but when I hooked up that first 1.3AH battery, it worked. Run time with mostly continuous recording: About 28 minutes with the 1.3AH SLA alone and 80 minutes with both the fully charged (12.65 volts) SLA and fully charged (8.2 volts) internal EN-EL20. With dual batteries, the camera quit recording when the external SLA battery ran down to 8.2V and the internal EN-EL20 ran down to 7.4V.
I tested the SLA alone to see if it made a difference in noise; a theory was going around that when the internal battery heated up the camera, you’d get more noise. My testing was inconclusive. But with the SLA alone, the camera quit recording sooner, when the SLA discharged to 10.8 volts, rather than 8.2V. I decided that the longer run time with an internal battery present, 80 minutes vs. 28 minutes, might outweigh any extra noise. But I also had a couple of internal batteries that started to swell over time and were difficult to remove. That was a reason I later leaned toward using an external SLA alone, despite the shorter run time. My theory (never tested) was that if I left an internal battery in place, continuously being charged for eight hours by an external SLA, it might heat up and swell. My recurring nightmare: A dead, swollen battery stuck inside the camera.
That first 1.3AH SLA gave me a taste; it was my gateway battery. Next experiment: a 5 Amp-Hour SLA for about $10. It worked. Then I mainlined a 9AH SLA for $20. It worked. Bigger batteries, longer run times. It was pleasant. But I continued to be terrified and thought I should check myself into Anton Bauer rehab. Becoming ever more paranoid, I constantly monitored the voltage of these batteries with a multi-meter. My testing showed that all these batteries were similar: They would be "fully charged" at around 12.65 volts, they would self-discharge to around 12.3 volts over a period of a couple of days if you didn’t use them, but stabilize at 12.3V. When I later began powering the Pocket with them, they would run the camera (in recording mode) until they discharged to around 10.8V and the camera would quit (Note: This is with no internal battery). The camera would remain powered up in standby and play clips back at 10.8V or less, but not record. Conclusion: Higher voltage is required for recording.
One thing I never understood is why an internal EN-EL20 will run the Pocket until it discharges to 7.4 volts, but an external SLA that discharges below 10.8 volts will not. Could the Pocket have two “baseline” recording voltages, one for internal power and one for external? I’m guessing Denny could answer that.
Further testing results: I found that when you have an internal battery present, the 12-volt SLA will discharge deeper, to 8.2V, as it continues to charge the internal — but that's a bad idea. The nice thing about having the 12-volt SLA quit working at 10.8 volts is, that’s about as far as you should discharge an SLA, to give it longer life. Simple rule: When using an SLA by itself, it’s time to recharge when the Pocket quits recording — that means the SLA is down to 10.8 volts. And to prevent overcharging, recharge the SLA with a “float charger” that regulates the “full charge,” which seems to be around 12.65V. Another recurring nightmare: Exploding batteries!
Big negative with SLAs: Weight. The 9AH weights 5.5 pounds. So I made a fanny pack that I carry this battery in, and a longer cable to reach the camera for hand-held stuff. On a tripod, I mount the 9AH on the sticks. Big positive: the 9AH will run the Pocket for a long time. My guess, based on rate of discharge, would be eight hours of continuous recording if you also had an internal battery present. But I have not tested this on a continuous "record" cycle because I'm terrified the Pocket might get tired and fry. Or hit a wall in the land of physics. I like to test, but I'm not willing to fill up cards running the camera continuously for eight hours pointed at a physics wall.
Anatoly nicely lays out the risks of using SLAs. I agree with everything he says. I would add one more: With a cheap SLA battery, you are always terrified your camera is going to fry. It hasn’t happened to me in two years of using them, and my Pocket is now going on four years old, but I expect it to happen the next time I power up. Probably tomorrow. If I had an extra $284 lying around, I would check into Anton Bauer for the peace of mind.
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