I need to power a device to which I can not bring a power line. I need somewhere between 6.5 V and 12V. I would actually prefer 9 - 12V. I would prefer Li but NiMh could work. I am in northern Washington so it can get to zero F in the winter. It will also be in the sun. Capacity can cover a range. I would like to replace battery packs as seldom as is reasonable. The current drawn by the device is 0.006 A/min. There is a one second 0.055 A pulse every minute and a constant 0.005 A.
I have been looking around and the only ones I have seen are on Alibaba. Too risky, and most have minimum quantities greater that I am interested in (2).
I really would prefer something that I know from users that they are good quality. A possible alternative would be to find some battery holders that take 1860s, add a box, and make my own. It would simplify things if I had an assembled unit with an internal charger. But I could work with the individual cells if I have to.
Just FYI, the device being powered measures the depth to water in a well to within between 0.1 ft and 0.05 ft (depending on the quality of my setup). It sends a pulse out every n seconds. I am going to use 1 pulse per minute normally and maybe less frequently as I gain experience. I want to know the draw down when the pump is running. And track static water levels throughout the year. I will eventually add something like a Raspberry Pi with WiFi. I have no way at this point of knowing how much power that will take. I would try to make the add-on system to sleep as much as possible.
Those devices have issues that concern me. The first one seems to require pushing buttons after power-on to set voltages. Not really OK for a permanent supply (in my opinion). There is also the issue of minimum current shutdown. As I noted in my post, the current drain is way under the cutoff. The second one (and probably the first as well) use a buck/boost converter to supply higher voltages. The converter will most likely use an order of magnitude or more power than the load.
Reorganizing my thoughts a bit. The voltage output needs to be directly from the batteries. So 7.2V - 7.4V would be good. There should be at least 2 cells in parallel. Otherwise I am schlepping out to the well more than I would prefer.
A solar panel with a charge controller would be a potentially useful choice. That I can do. It is getting a charging circuit that properly handles the proper balancing and protection of cells. It is the charger for series/parallel cells that I was after by getting a power bank. We tend to have rather limited supplies of sunlight around here, and the location would only get about 1/4 to 1/2 a day of direct sun. I am in a valley with forest on all sides. Everyone else gets sunlight at least an hour and a half before and after I do. I would need to do some measurements, but it would be far handier to never have to change out the batteries/bank. Properly done, that could also remove my dismissal of a converter. But not the push button when powering on and minimum current cutoff.
I have just ordered a couple of these for charging my camera batteries with aftermarket adaptors designed to run from 12V. Can't comment for sure on the quality as it will probably take a couple of months for them to arrive but I don't expect any problems at a low 12V current draw.
Maximum rated current is only about 500mA but this could be a very simple solution for you. You can use any quality USB power bank capable of a decent 5V output, but preferably one with a physical switch so that the light load does not cause it to auto shut off.
Advantage of this idea is that there are plenty of small solar 5V chargers already available to keep the USB bank topped off. Just calculate or test the draw over a couple of days and buy a panel of an appropriate size based on your load and available sunlight.
Thank you. That is interesting. Never thought there would be such a device.
I did a google search and found a semi-infinite number to 5V to 12 V converters. lots of uncased boards with various connecters. That is really what I need. Thanks again. Now I need to find a power bank. I will probably need to get one from the US. I can't wait months to get it.
based on both a good review and the fact that I had a visually identical one I got about two years ago from Cottonpickers (CPF)
This one is rubbish! Terminates the charge early, cannot deliver the rated 2A and when used in pass-through mode (charging while outputting the way you want to use it) the USB voltage drops to the battery voltage rather than holding the 5V spec.