[Dave]

Hi Kevin-

You’ll probably want to keep the batteries either all in series or all in parallel to keep them charged correctly. I haven’t done a lot of work with batteries, but what I’ve seen seems to have them either all in parallel or all in series. There’s a pretty similar circuit here

http://www.evilmadscientist.com/2008/simple-solar-circuits/

with some nice discussion below. Based on reading that, it looks like your system will work OK, but it’s pretty inefficient, and not something that will scale up really well. There’s some interesting reference information here

http://www.powerstream.com/tech.html

[Dave]

Neil-

I don’t have any current active projects, I’m pondering an open source lagrangian drifter for stream flow measurements, but nothing build yet. You’ve written up some nice installation instructions to keep in mind.

Regards

Dave

[Dave]

That’s a great summary of things. Doing both sides of the link is both an advantage and disadvantage for these approaches. There’s also no re-occurring charges for service, although the up-front cost is probably higher.

[Dave]

Stephanie-

This is independent of a cellular carrier, you use unlicensed ISM bands for communications. You can sort of think of this as very long distance Wifi. The sensors communicate with a separate base station that you configure. The Datarates you can get over this are somewhat dependent on the distance between the sensors and the base station, so it’s good for transmitting data, not good for web pages. I haven’t used it, but I’ve spent 6 to 10 hours looking at it.

Dave

[Dave]

One technology that’s become recently available is LoRa, which is a ISM (900 MHz) band system that’s optimized for data transmission. More details at https://www.lora-alliance.org/ but PCB’s with LoRa radios on them are available from Tindie.com at reasonable pricing (sub $20 ish). It looks like these would require a base station to complete a network, but they claim 5 to 10 km of coverage, which might be sufficient for may applications. I’m not affiliated with them, I just find the technology interesting.

[Author]

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