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Always On Current Draw without load

Ross Oct 15, 2014 12:46AM EDT

We plan on using the 3.5W or 6W kit with V15 Battery to power some very low-power sensor stations which connect via WiFi(pinoccio), once per minute or so. Pinoccio have their own small lithium battery too.
I just discovered the voltaic battery "always on" mode.
I'm wondering what the current draw is for the battery charge circuitry itself in "always on"? Say, if I have nothing connected to the USB 'A' connector.
Is there a minimum current draw to keep my load charging.

Also, when "always on" is disabled, what is the approximate current at which the battery curtails output?
thanks,
Ross

Up 2 rated Down
Voltaic Support Oct 15, 2014 09:48AM EDT Home Agent

Hi Ross, great questions.

The internal draw to keep the chip running while in always on mode is enough to maintain the operating state of the battery for at least 24 hours after it goes flat. So for a low powered sensor, you might be able to get 3-5 days from battery run-time alone, then an additional day when the battery is not supplying power to the sensor but if it gets charge at all from the solar panel, it will wake up and resume powering the device. After that time-frame, it will wake up in auto-off mode and the power button will need to be manually pressed to begin repowering your device. Meanwhile, the solar panel should be continually charging the battery, so as long as you get about 2 good days of sun per week, you should be fine with a low powered system. As always, it’s best to err on the side of caution and get a solar panel larger than you think you’ll need, that way it can charge the battery faster in bright conditions and rely on less sunlight to keep the system running.

Our batteries are designed to provide the same voltage throughout the entire discharge cycle, and almost the same possible current. For the grand majority of the discharge cycle the V15 can output up to an Amp if that is what the device is drawing, then for the last 15-20 mins of the discharge cycle the current output is reduced down to about 500mA before it shuts off.

Since every sensor system is so different, we’ve found that there’s really no alternative for an empirical test to see how our battery responds to your specific sensor. I’d recommend buying a V15, charging it up to full, and seeing how long your system stays on from the battery alone. If it’s less than 3 days, consider ways to reduce the power consumption of the system, or consider buying an even larger panel like a 7W system, or a larger battery like the V39 which has more than double the capacity of the V15.

Regards,

Tony

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