Do RAK nodes always need manual reset after battery drain?

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I know this has been talked about quite a bit with regard to solar nodes, but in my experience every Rak node I own, regardless of solar or battery, will enter brownout-protection mode when the battery drains completely. This requires a manual power reset every time.

Now, I’m a technical person and tend not to let my devices drop to zero battery, but I’ve recently started giving a few handheld, battery powered, mobile nodes out to trusted neighbors as a way to grow the local mesh. These people are generally not technically minded, so they will let their nodes’ batteries go completely dead from time to time…and every time they do, they have to bring it to me and have me open the case and reset it.

Short of installing a physical switch to sever connection to the battery, is there any way around this phenomenon? I know I could use an external battery management system. It feels like this is a fatal flaw in the RAK designs, though, as it makes the units inappropriate for non-tech savvy users…which in my experience is most users.

When I start to explain you have to use a screwdriver, open the case, manually pull the connector form the board and re-seat it…they just say they’d sooner bring it back to me for that “service” for fear of breaking something or not being able to put the case back together.

Are Rak boards really that “fragile” with regard to power and not being at all able to come back from battery drain, even when powered through USB? I’m not talking about solar charging at all, I’m not plugged into that. I used an 18650 connected to the JST battery port on the board. The solar JST connector is unused. When trying to revive from zero battery, I use a USB connection to the board via a pigtail surface mounted to the case.

What’s worse, I’d estimate 20% of the time when this happens the firmware is corrupted and the whole thing needs a re-flash. None of that speaks well to ease-of-use or consumer adoptability.

I know there are other options out there beyond Rak boards, but this sure seems a fatal flaw in Rak’s architecture.

Hoping for someone to tell me I’m missing a critical device setting or something along those lines!

Thanks in advance!

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You need to be using a protected cell

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This was the issue that wasted me several months tinkering. Obviously a solar battery powered node that needs a manual reset when drained is utterly useless and annoying. To eliminate this problem I use the Waveshare D solar power manager ( Solar Power Manager Module (D), Supports 6V~24V Solar Panel and Type-C Power Adapter, 5V/3A Regulated Output | Solar Power Manager (D) ) and my tests show it restsarts after brownout. I think the Waveshare D device will also let you work without solar and just charge the battery via the board so then it also springs back on when you recharge via USB, but this needs a test. Yes it is more kit but this solves the fundamental problem using off the shelf bits. (There are DIY solutions… ) And BTW I do not know if using protected batteries alone solves the RAK issue … but I use protected battteries as well as the Waveshare D solar power manager especially if I am thinking of putting a node in someone else’s house because it is a big responsability to hand over a li-ion powered device to another person in case of fire. In fact, some folks add a temperature cut-off device also e.g. https://amzn.eu/d/0fOf8utj
The BQ24074 and BQ25308 uses a NTC for temperature protection. But I read the spec of the Waveshare D and it says it already has these temperature and voltage protections… but I am not sure if it suffices. I would do both and also place the batteries / node in a metal child-proof housing preferably with a sand layer so it could burn and not cause anything else it touches to catch fire. This is of course a totally hard build so I don’t give DIY nodes with li-ion batteries to friends: they have to build them themselves. Never use broken batteries.

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Thanks @garth and @adingbatponder …I’ve got a few protected 18650’s on the way…I had no idea that was a “thing”…though it seems curious to me that the Rak boards lack the basic architecture to work correctly without a “helper” hardware…that still feels like a faulty or incomplete design on the part of the Rak developers. Easy enough to work around if it means having to buy a $9 battery instead of a $6 battery, but it still feels like a gross oversight on the part of the Rak folks not to design something that can sustain so much as a battery loss without manual intervention.

I’ll report back my experience once I’ve received those protected cells later this week. Appreciate the advice, but disappointed at the lack of design resilience in the Rak product.

Thanks again!
Pol

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It’s not entirely RAK’s fault. It’s the CPU. Where I blame RAK is in not making the power supply shut off on low battery, then turn on after the battery is recharged above that point, with a bit of hysteresis. Also in putting a solar and battery connector on their wisblock as if that was sufficient. Also in selling a box designed for a wisblock with a totally inadequate solar panel. Also in charging me a total over $100 (plus battery) to find that out. So yeah…

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There is an interesting paragraph is this post about the brownout issue:

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This thread also has info on this topic: RAK 4631 Solar Repeater

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This might solve the problem too, but I have not tested it. https://amzn.eu/d/08G8EMo6 Recommended by this thread Solar charge controller for the WisBlock Unify Outdoor Enclosure - #3 by eastsanmiguel

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Thanks, I’m still stymied by the fact that I’m not at all trying to use solar charging, just a straight up battery connected to the JST battery connector. This isn’t a solar charging issue, it’s a “how Rak boards use batteries in general” issue…

My protected cells should be arriving this coming Saturday, and I’ll be glad to put them through some test runs and report back findings. These claim to do low and high voltage cut-off, along with current and temp protection, so I’m hoping they’ll just shut down power delivery above whatever threshold the brownout protection engages. It still strikes me as odd to have to supply additional hardware solutions to overcome a deficiency of the underlying hardware…but the price isn’t objectionable and the Rak boards are really good to work with in lots of other ways…

More to come!

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I understand fully that you do not use solar but these boards allow for usb charging and might achieve the avoidance of brownout reset problems. If the protected batteries do the same thing that super - please do post here. That would be a real result for everyone. (I do not think it is about the voltage levels but the neatness of the voltage step on switch-on… see https://www.youtube.com/watch?v=BqwUNOHiZ9k ). Good luck.

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Back to report some findings! Good news, the protected cells are keeping the Rak4631 from entering brownout mode…sincerely appreciate the learning opportunity here. I ran multiple nodes through multiple charge/discharge cycles and they all booted back up correctly once connected to USB 5v.

I’ve got a good number of plain old unprotected 18650’s though, and didn’t like the notion of just not using them anymore so I did some more homework. Ended up with these little beauties.
image
At $0.70 (USD) each, I was admittedly skeptical. After having installed 6 of these now, and gone through at least one charge/discharge cycle per battery, I can say they’re doing the job nicely. All nodes boot right back up, having maintained their configuration and histories up to the point of shutdown.

Sorry none of this speaks to the solar charging question, but at least we can say with some assurance there’s a reasonably affordable solution to the question of whether some protection is necessary…it is, but the good news it seems there are minimalist solutions that aren’t terribly expensive or intrusive.

Thanks again for the nudge in the right direction!

Sincerely,
Pol

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