Power P2 with 2X rechargeable lithium AA batteries?
Rayman
Posts: 14,632
in Propeller 2
So appears rechargeable lithium AA batteries are a thing now.
Wikipedia says voltage is regulated at 1.5 V, but another place said it's a bit higher, like 1.6.
These look perfect for directly powering P2 via battery power.
Or, maybe as backup power with Schottky diode in series...
Anybody already tried this?
Comments
seems there are AAA versions too. Don't know why haven't noticed these before...
Seem great for low cost robotics...
I recent got a couple of 9 Volt clip versions. Each has a USB-C charging port on its Smile. Working well so far. Can even charge and use it at once like a little regulated power supply.
I already have lots of the Eneloop NiMH AA and AAA for rechargeable single cells.
Thing is that it appears the lithium version have a built in voltage regulator.
So, one could power P2 with constant voltage without an additional voltage regulator...
Six of one, half a dozen of the other. The regulator in the battery doesn't ever turn off, so it'll go flat while sitting on the shelf.
Read it’s a buck regulator. So should be fine on shelf. But haven’t tried yet…
Problem with nimh is really only 1.2 v or so…. This seems better…
Usual solution is to design the system to work down at 1.0 Volt per cell. Which suits alkalines too.
These might be different …
Seems 1.5 v until the end
Ya, like I said, six of one, half a dozen of the other. The regulator is either inside or outside the package.
Thinking about trying to power P2 board with a 3X AAA lithium.
At 1.5V each, should be 4.5 V total. This should be perfect for only drawing from battery when regular 5V is not present...
I use 4 18650 batteries two in parallel and two in series to power a P2 for about a month.
The P2 is in low power mode and wakes up every hour to transmit voltage, current, light, temperature, and humidity using Cellular card and LoRa.
It draws no more than 10ma.
Mike
The P2 data sheet says: VIO supply voltage minimum 3.15V. So if it's 1.5V per cell it's outside the recommended range and if it's 1.6V it's marginal. However, that is for the full temperature range up to 105°C. I think if you stay at lower temperatures and don't overclock it (PLL output<=180MHz) it should run pretty well even at only 3.0V.
However, keep in mind that the P2 has no internal brown out protection. So I'd add at least an external reset voltage monitor to prevent crashes at the end of the battery life.
I've been meaning to get some of these new fangled 1.5-1.6V Lithium cells and have a play with them. If these batteries can output their normal voltage and also get charged at the same time via their USB-C port then I wonder if they'd charge and survive ok running off an intermittent 6V solar cell supply, probably clamped down to around 5V with a transistor or LDO, assuming total power requirements get met daily. Or whether that'd limit their lives by topping it up daily, or affect internal charge safety timers etc due to intermittent solar nature and applied voltage fluctuations. Be interesting to try it.
I read that some of the 1.5-1.6V Lithium batteries seem to drop voltage near the end of their capacity to around 1.2V or so, which would suddenly occur without notice. That could mess up a P2 running at full tilt. So you'd need some capacity monitor (coulomb meter) rather than just voltage monitoring, or know that you always have sufficient recharging power available to not drain down to that level.