2022-01-14 at 3:39 PM #16265dan@wachusettParticipant
Can anyone recommend a good 12v deep cycle battery for use with the Mayfly 0.5 board. I have a station that gets very little sun and would like to be able to power it for long periods of time and swap out the battery a couple times a year. I did some looking around and the variation of specs and pricing made me unsure of which would be the most appropriate 12v battery for the Mayfly.
Thanks for your help!
2022-01-14 at 4:41 PM #16266CalParticipant
After struggling with power problems for years and buying several brands of 12v batteries and also using multiple batteries in parallel, I discovered I was looking in the wrong area. The solution for me was to find where power was being used and replacing inefficient modules with efficient ones. And the problems I found were surprising and probably NOT what you would expect. You really have to measure the current drain on all your devices to see where the problem lies – and it’s NOT going to be the Mayfly. In my case, the problems were:
- The 12v to 5v converter. Don’t believe the advertisements – measure it. I found cheap small buck converters are the best, but they vary widely.
- The solar panel charging circuit (if you have an external module) or the solar panel itself (if the charging circuit is built in). There should be very little current drain when the sun is not shining. BTW – bad charging circuits can kill a good battery too.
- A defective 10 year old SDI-12 sensor that was still working but using more and more power.
After fixing these problems, my stations need very little sun to keep the single 12v battery charged. I can even run my stations with no sun for months. Of course you should be putting the Mayfly, Modem and other devices to sleep between activities. Good luck.
Ps. you don’t need a LiPo battery on the Mayfly if you are powering it from the USB 5v. The LiPo’s cause problems too.
2022-01-14 at 10:03 PM #16267neilh20Participant
I’m also deeply into power analysis as the way of keeping everything going. I was working with some engineering students and got them to do a spreadsheet, which I modified and added and can be used to build a budget for the power that you think you need, and what the power consumers might be. I then look for the major user of the power, and let the project be driven by that. ie if its a sensor that needs 12V and consumes a lot of power then you need to have the large battery.
I also reduce the power by changing how often it turns on the cell modem. ie from 15minutes to 60minutes. The project with students we are only talking about turning it on every 24 hours. However this is a lot of software that I’ve added to my fork.
I also have a battery threshold that I stop any transmission, and then when there is enough solar power harvested start transmitting the stored readings and then the new readings. Its not trivial software to do this, but it has now been well tested.
Happy to share more about power savings if its of interest.
One idea that I’ve seen with the Mayfly 1.0 and the new power routing, is that there can be the LiIon battery plugged in, with solar panel, and then a top up USB Battery pack plugged in.
However I do have to say that the Mayfly 0.5 and also 1.0 battery measurement is challenging, and I’ve tried to phrase it here. IHMO its a really basic issue, and has caused me no end of technical headaches. Mayfly 1.0A3 is more of problem than 0.5 https://github.com/EnviroDIY/EnviroDIY_Mayfly_Logger/issues/32
2022-01-15 at 3:52 PM #16269neilh20Participant
edit to the above email: Sorry I don’t have any experience with the 12V batteries, or 12V to 5V.
I would note that the Mayfly1.0 charger is different than 0.5b, and I’m seeing that it wants a slightly higher+5V than the Mayfly 0.5b for it to do a 0.5A charge of the LiIon battery. I am using USB charging monitor “USB Meter” to monitor the charge rate.
I definitely agree with @ckillen that whatever methods’ are used, some monitoring is required to figure out where the power goes and is it working as expected
2022-01-25 at 1:10 PM #16305dan@wachusettParticipant
Thanks for your input Neil and Cal. I pulled my station from the field where the battery was not recharging so I could do some testing. I’ll report back with my testing results to see if anyone has any advice. I would still be interested in the 12 v battery option if anyone out there uses one successfully with their Mayfly board v 0.5.
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