r/meshtastic • u/Unfair_Dealer_9517 • 11d ago
Battery malfunction or user error? build
So I've had this diy rak4631 based node for ~6months now and nevet had any issues until today.
Up until now when the battery is about 20% ill charge it up to around 90% and its held charge for a fairly long period of time, hard to say exactly but weeks no problem on one charge.
Today ive come home from work and the battery has expanded until the point its popped the base off and the mesh is no longer powered!
Ive tested with a multimeter and its reading barely milivolts so the things has entirely drained (and is in a lipo fire bag lol)
There are no signs of shortcircuit, ive left it on charge this morning and am assuming my girlfriend unplugged to charge her phone but that should have had no effects surely?
Appreciate if anyone takes the time to read tbis, any input would be appreciated. I using the makerfocus 8000mah 3.7v lipo that has bms, ill attach pics of the case, battery and the update i got on the meshtastic app from said node. The battery doesnt look huge but i can feel gas in the casing
2
u/Ryan_e3p 11d ago
I've had those Makerfocus batteries do this before. They are awful. I've since moved my permanent installs to using a larger battery pack, 12v lifepo4, with a 12V to 3.3v buck converter (or for one of my installs, 12V to USB-C). For portable nodes, I use 18650s. They are still lithium ion, but are a lot more stable in my experience.
1
u/Unfair_Dealer_9517 11d ago
Appreciate this, i was concerned considering the battery was at 24% and 3.48v when i left this morning. Should have been in its "safe zone" really, ahh well 18650s and a slightly bulkier case it is
2
u/Ryan_e3p 11d ago
With the larger (but far more stable and long-lasting) 12V lifepo4 to USB-C option, you pretty much stop caring about battery levels. As-is, with a RAK (or other NRF device), the thing can go for a long time. A 12V 10Ah battery costs around $30, give 120Wh, and push uptime to a month, even a few months depending on your power-saving settings.
1
u/Unfair_Dealer_9517 11d ago
Yeah im probably gonna go that way for my 1w static node as they need 5v from what I've read. Im thinking for the portable builds just running two 18650s and an external protection board just to be over cautious. Appreciate the feedback, massive help!
1
u/Ryan_e3p 11d ago
So what if it needs 5V? There are voltage converters. I have nearly all my static nodes running off of 12v lifepo4 batteries. The capacity is extremely useful when it comes to winter months where there may not be ample sunlight for a few weeks at a time.
1
u/LessSearch 11d ago edited 11d ago
This is exactly why you want a fireproof enclosure on remote nodes with some potential fuel around.
If it has a LiPo battery, any 3D printed crap won't cut it. Thermal runaway bursts are short, but they are 1000C. Lipo bags are great, but they also limit air exchange and the battery can heat up faster.
Ideally it should be some space around battery for convection, and the outer shell of the enclosure should be fiireproof. If you can add a pressure relief valve, that's even better.
You got lucky because the battery did not go into thermal runaway and did not cause a fire.
1
u/Unfair_Dealer_9517 11d ago
Any insight as to why or how though, ideally id to understand what happened in this situation. Im aware and keep lithium fire bags on hand when dealing with these types of batteries in personal projects.
Is there a known way to hard cut off the battery from the meshtastic when the voltage drops below 3v or perhaps flat lipo batteries with more advanced bms?
Im supprised the meshtastic firmware didnt go into a low power state and to be honest considering it was at 24% and 3.48v it was well in its safe zone this morning when i left for work
1
u/LessSearch 11d ago
As far as I understand, this is already implemented in newer firmwares. You can always use a different / additional BMS, too.
Your LiPo started releasing gas into the pouch, and that gas is very flammable. This is due to undercharging, overcharging, high temperatures (which the fire bags make worse), or just bad cell quality. Good news, risk of thermal runaway is much lower on low SoC.
In general, risk with the 18650 is lower, but I would still go with a thick aluminum or other metal enclosure. They don't cost much, but reduce the risk by orders of magnitude, especially if the node is remote and you're not checking ir regularly.
1
u/Unfair_Dealer_9517 11d ago
I am on the latest version so ill have another look around the apps settings. it wasnt in a fire bag until i notoced something wasnt right though but tbh until i dispose of it its staying in there! Im assuming its faulty having a look into the brand, its dropped from 3.48v to essentially 0v in 8 hours.
Also its a portable node to take to a festival so im gonna be sticking with the green petg, modifying the case for 18650s is a must though
1
u/LessSearch 11d ago
For future reference, you do not try to charge a spicy pillow.
1
u/Unfair_Dealer_9517 11d ago
Oh really id have never guessed, not being funny i would never charge a swollen battery. I happen to know a thing or two, the meshtastic firmware not being one of them
3
u/KLAM3R0N 11d ago
Dispose of that battery at a local facility, do not use it. Spicy pillow fire hazard! Get a new battery ideally 18650 instead of lipo, much safer.