Ok I retrieved the node today for charging as I wasn’t able to ping it anymore. Looks like we got just about 2 full months out of 42v 560 watt hour battery. Kinda feeling like it should have gone longer. I’m updating to 1.1.8 and setting router mode. I’ll put it back in the tree next weekend and see what’s she does from there.
Do you have the data sheet for the buck converter? It may not be as efficient as it could be.
I bet that’s absolutely the issue. So I still have the lora device connected to it’s own 18650, wonder if I could trigger a relay every 3 days or so to turn on the buck converter for 4 hours to charge the battery.
I mean I bet that would work right?
Didn’t really see any consumption data on the amazon page
Do you have access to a bench power supply and a multimeter with a DC current measure feature (most multimeters can do this)?
If so, set your bench power supply to the nominal voltage of your battery.
Connect the step down supply to that.
Then connect your multimeter set to measure current in series between the geri module and your lora module.
On the bench power supply, multiply the voltage * amps to get the wattage drawn from the bench.
On the multimeter set to measure amps, multiply that by 5 to get the watts drawn by the lora device.
Subtracting the two watts will give you the inefficiency of the step down module.
Here’s something that jumped out at me:
That’s based on the LM2596 switcher by Texas Instruments.
The data sheet ( https://www.ti.com/lit/ds/symlink/lm2596.pdf?ts=1606577586355&ref_url=https%3A%2F%2Fwww.google.com%2F ) says it’ll take a max of 45V.
Page 8 of the data sheet shows the efficiency graph of 5v and 3.3v outputs. Looks like a worse case of about ~80%. That’s pretty good.
I looked at your picture a little closer. The way that’s wired, you’re regulating down the big battery down to 5v and then there’s a regulator from that on your lora board to bring it down to 3.3.
You’ll get more efficiency if regulate your battery down to 3.3v and go straight into the 3.3v pins of your lora board.
At least after that, the next place to gain power savings is to use the router mode on the module.
You may also be losing power from the self discharge of your lithium pack. That’d be something you can also test with a multimeter.
yes i agree with all that, I have a bench supply that can measure everything down, but the point is moot as this is the hardware I have at the moment, and honestly 2 months isn’t that bad. When I’m back from work travel next week I’ll perform the tests and reinstall it in the tree with the router mode set and see what happens.
Really I should be hiking up to this park more than once every two months.
can a 42v - 3.3v regulator even be found?
also, thanks for taking the time to consider my problems. its pretty cool of ya
Excuses to hike are aways good!
The LM2596 will go down to 1.5, so 3.3 should be easy.
Anytime mate. Reading your updates are always fun. Wish I could reach you from where I am, but I don’ think Lora can easily go through half the state.
appreciate that! ok so i actually have a bunch of Lm2596’s and I’ve tried them before on the 42v (technically 36v)batteries and it blew it out. I’ll try another one as maybe that time was a fluke. Here in LA, lets say there is a “large supply” of “low cost” scooter battery packs with charge controllers built in, so I’m pretty motivated to make it work this way. I mean i guess i could just put 6 packs together… lol
Our cities have the same surplus.
Could also be that the Lm2596 has been faked. Digikey has them for about $2 / ea if you buy 10,000.
aight let me grab 20k real quick
< sarcasm > Cool. Let’s do a group buy, I could use one or two. < /sarcasm >
I’ve got my giant battery node refreshed and now on the default #LongSlow-1 channel. If you are in the LA area anywhere close to my range map drop me a line!
Is your node still up and running? Will try to hit it again soon.
@datadrian Have you considered upgrading the antenna from the stock “rubber duckie” to a dipole antenna with better gain?
Something like this: Dipole Antenna 915mhz
yes my main node is still up! the Getty and North Hollywood repeaters are going back up on Thursday.
wow awesome! I’m surprised its making it down there, wonder if you were bouncing off the Getty repeater.
I’ve considered it, but I’ve got excellent coverage over the LA basin (20+ miles) so I’m not really needing to upgrade at the moment.