Solar Lora
Powering nodes in sub-zero temperatures: Which battery should I choose? Lithium?
Meshtastic is an open-source project designed to enable users to build low-power mesh radio networks using affordable hardware. Most deployments consist of small "nodes," each equipped with a microcontroller (such as an ESP32, nRF52, or Raspberry RP2040), a LoRa radio module, and a battery. In many use cases, these nodes are deployed outdoors—perhaps on mountaintops, in remote areas, or anywhere else where stable, long-term coverage is required.
However, using devices in cold weather presents its own unique challenges, particularly when it comes to battery selection. Sub-zero temperatures can significantly weaken or even destroy certain types of batteries—problems that are particularly acute if they are charged (or, in some cases, discharged) outside the recommended temperature range. Battery capacity decreases significantly at lower temperatures, and the risk of permanent damage or shortened lifespan increases.
In this series of blog posts, we will explore the pros and cons of common rechargeable battery types used in Meshtastic nodes, including common Li-ion batteries (such as 18650 batteries), NiMH (nickel metal hydride) batteries, and more specialized battery chemistries such as lithium titanium oxide (LTO).
We’ll also reference several Reddit community discussions – especially the firsthand experience of user KBOXLabs , who has been conducting long-term testing of high-altitude mountain solar nodes in extreme cold conditions of -40°C.
“We currently have several solar nodes at over 7,500 feet in the Rocky Mountains.
They’ve been running for almost a year in -40°C, using an unprotected 18650 battery…”
By understanding these real-world scenarios, combined with some basic battery science, you will be better equipped to choose the right power solution for your cold-climate Meshtastic deployment.
Why low temperatures affect battery selection
At first glance, any rechargeable battery designed for consumer electronics should be able to operate in outdoor nodes. However, harsh low-temperature environments—especially those with prolonged periods of below-freezing temperatures during winter—often present unexpected challenges.
lPerformance degradation in low temperatures :
When the temperature drops, the chemical reactions within the battery slow down. The internal resistance of most batteries increases, resulting in a drop in voltage and a reduction in available capacity. You'll often find that a battery that works fine indoors may quickly deplete or even cease to function in the cold outdoors.
lRisks of charging and discharging :
Discharging a battery in a cold environment primarily results in decreased performance (reduced usable life). However, charging a battery in sub-zero temperatures can cause permanent damage, such as microcracks or the formation of dendrites. This can accelerate capacity degradation and even pose a safety risk in the long term.
lDifferences between different battery chemistries :
Different battery chemistries exhibit significant variations in their performance at low temperatures. For example, lithium-ion batteries perform relatively well in low-temperature storage, but charging below 0°C can damage the battery. Nickel-metal hydride (NiMH) batteries tend to perform better in sub-zero environments, retaining some usable capacity and being more tolerant of low-temperature charging. Lithium titanium oxide (LTO) has garnered significant attention for its exceptional performance in low-temperature discharge and charge cycles.
lReal-World Example - Canadian Rockies :
In a Reddit discussion, a KBOXLabs user mentioned using standard lithium-ion (18650) batteries to power Meshtastic nodes at an altitude of 7,500 feet and temperatures of -40°C. While the nodes continued to function normally, they acknowledged that prolonged charging in low temperatures shortened battery life. While actual results vary across different environments and configurations, this real-world example highlights the importance of selecting the appropriate battery for the temperature range.
Batteries are the lifeblood of any off-grid system—they're responsible for keeping your Meshtastic nodes running smoothly through the day-night cycle and the long winters. Therefore, choosing the right battery chemistry is one of the most critical decisions you'll make when deploying nodes in cold climates. In the following sections, we'll explain how common Meshtastic battery types perform in low temperatures.
Main battery chemistries considered
Lithium-ion, or LiPo, batteries are very common in portable electronics due to their high energy density, affordability, and widespread availability. For off-grid Meshtastic nodes, the popular 18650 cell size generally provides good capacity (2000–3500 mAh per cell) in a compact package. However, lithium-ion chemistry is particularly sensitive to low-temperature charging: while discharging at subzero temperatures is not a problem, charging below 0°C can cause microcracks and accelerate overall wear. Despite this limitation, many users report that these batteries can be sufficient for small solar installations where the housing can warm slightly in sunlight.
Nickel-metal hydride (NiMH) batteries are not commonly found in many new consumer devices, but they remain reliable in harsh environments. NiMH batteries are less susceptible to permanent damage in cold environments and typically retain a considerable amount of capacity. Compared to lithium-ion batteries, they have a lower energy density, so to meet the operating voltages of many Meshtastic development boards, multiple NiMH cells are often connected in series. Recent reports from Texas Instruments and others have explored the feasibility of charging series NiMH batteries using standard lithium-ion charging circuits. However, using NiMH batteries in extreme cold still requires certain optimizations in charging and voltage control.
Lithium titanium oxide (LTO) has attracted considerable attention for its exceptional performance in extreme temperature environments. LTO batteries exhibit minimal long-term degradation during discharge and recharge in cryogenic environments and boast a considerable cycle life, making them suitable for remote locations or those requiring extreme reliability. Their primary disadvantage is the low nominal voltage of a single cell (typically around 2.4 V), requiring specialized charging or boost circuits to meet 3.3 V or 5 V power requirements. The added circuit complexity and cost make LTO relatively unsuitable for general applications, but LTO may be worthwhile for deployments where maintenance is difficult or safety risks are high.
Other chemistries are occasionally discussed in the Meshtastic community. Some prefer LiFePO₄ (lithium iron phosphate) batteries due to their relative safety, stable output voltage, and a certain degree of low-temperature resistance. Others have tried small lead-acid (SLA) batteries, especially for larger fixed installations. Although heavy and bulky, lead-acid batteries have a long history of use in off-grid solar applications and, if properly selected, can withstand severe cold temperatures to a certain extent. In summary, there is no "one-size-fits-all" battery solution; the required chemistry must be determined based on the budget, performance goals, and deployment environment of each project.
Charging module and temperature management method
Meshtastic nodes typically use a small solar charger or MPPT module to charge their batteries during the day. Common ICs include the CN3791 or CN3795, which typically feature constant current/constant voltage charging. While most of these integrated circuits are designed for lithium-ion battery voltages, some can be adapted to other battery chemistries by changing the sense resistor or reference pin. For NiMH or lithium-titanium oxide batteries, it is crucial to ensure that the charger's cutoff voltage and float voltage are consistent with the safe charging parameters of the specific chemistry.
Battery temperature management is also a major challenge in sub-zero environments. Even high-quality lithium-ion charging chips can be damaged if they are used to charge the battery in an icy state. Some users add a small heating mechanism inside the casing, or use the heat from sunlight to raise the temperature inside the casing to above 0 °C during the day. If there is sufficient sunlight, the temperature inside the casing will usually be above freezing around noon, allowing charging to be completed safely and quickly. In more severe cases, some people have explored attaching a thermistor to the surface of the battery to monitor the temperature and cut off charging when the temperature is too low to protect the battery life. This method can protect the battery, but it also means that charging efficiency is reduced in severe winters.
Since Meshtastic nodes themselves consume very little power, another approach is to keep the charging current low. For example, the maximum charging current can be controlled at around 0.02C (2% of the battery capacity) to keep the chemical reaction acceptable at low temperatures. While this method slows charging, it is often sufficient for devices that only require intermittent radio signal transmission rather than continuous high loads. By carefully selecting the charging module and charging current, users can significantly reduce the risk of battery damage and extend the overall life of solar nodes in cold climates.
Real field data and user experience sharing
For many Meshtastic enthusiasts, actual deployment experience is often more convincing than technical manuals. The most frequently cited case comes from Reddit user KBOXLabs , who deployed outdoor nodes in the Canadian Rockies at an altitude of more than 7,500 feet and temperatures as low as -40°C.
“We have been operating these nodes since the spring of 2023, during a winter with extreme temperatures of -40°C for several weeks. All nodes use lithium-ion or LiPo batteries… and
we haven’t had any battery failures so far.”
In such environments, temperatures can remain below freezing for months at a time and often approach -40°C. Despite these harsh conditions, the nodes remain stable operating using standard 18650 lithium-ion batteries.
According to KBOXLabs' experience, cold weather does shorten battery life over long periods of time. However, they have yet to encounter catastrophic failures in the field. This may be due to Meshtastic's low-power design, which allows the battery to charge slowly and gently during daytime sunlight. Even a small amount of sunlight can raise the internal temperature of the housing above freezing, allowing the battery to charge in a relatively normal manner. This phenomenon also illustrates that there is often a balance in actual deployments: even if the temperature is very low at night and during cold and cloudy periods, as long as there is strong but brief sunlight during the day, the battery can complete a certain degree of safe charging.
Other users have also experimented with NiMH batteries, particularly in areas where temperatures can drop to -30°C. They report that NiMH batteries are more resilient to cold temperatures than lithium-ion batteries, though their relative capacity and voltage range are lower. Furthermore, a few users have purchased lithium-titanium oxide (LTO) solutions from niche electronics retailers or community-built boards. While these solutions have generally been positive, their higher price and specialized circuit requirements have limited their widespread adoption.
In some areas, larger enclosures are used to house small lead-acid or LiFePO₄ batteries, particularly for nodes that require year-round power and have slightly higher power consumption. This may be overkill for standard nodes with low data throughput, but large-capacity batteries can provide additional energy storage redundancy during periods of continuous overcast skies or heavy cloud cover. As can be seen, different batteries and charging solutions have their own application scenarios and advantages and disadvantages; most users test various battery chemistries, chargers, and insulation methods in practice, and then continuously refine their configurations based on the test results.
Advantages and Disadvantages at a Glance
When choosing the ideal battery for a Meshtastic node, multiple factors must be considered, including cost, energy density, low-temperature performance, and charger compatibility. While many rely on lithium-ion batteries (especially 18650) for their convenience and higher energy density, others prefer NiMH or LTO for their superior low-temperature robustness. To help sort out these trade-offs, the following summarizes the performance of various battery chemistries in real-world deployments:
lLithium-ion or LiPo (especially 18650):
They offer high energy density per volume and weight, are readily available, and easily adapt to the operating voltage of most Meshtastic nodes. Their primary drawback is susceptibility to damage when charging below 0°C. While users like KBOXLabs have mitigated this issue through careful enclosure design and controlled charging current, lithium-ion remains more sensitive to low-temperature charging than other chemistries. Fortunately, if daytime sunlight can raise the internal temperature of the enclosure above freezing, these batteries often remain the simplest and most viable solution.
lNickel-metal hydride (NiMH):
Performs better in cold environments and is less likely to sustain permanent damage from sub-zero charging. The nominal voltage of a single NiMH cell is lower than that of a lithium-ion cell, necessitating multiple cells connected in series to power a meshtastic node. Furthermore, NiMH's energy density is relatively low, requiring more cells to achieve the same battery life as lithium-ion. Its advantage lies in its tolerance to low-temperature charging and the need for highly sophisticated charge cutoff control.
lLithium titanium oxide (LTO):
Known as a "powerhouse" for extreme low-temperature resistance, it boasts excellent cycle life and performance in cold environments. However, its drawback is that the nominal cell voltage is only around 2.4 V, requiring additional circuitry to meet Meshtastic's typical operating voltage, which also comes at a higher cost. If the node is located in an extremely remote area, maintenance is difficult, and extreme temperatures are frequent, LTO may be a worthwhile long-term solution.
l Other chemistries (such as LiFePO₄ and lead-acid):
LiFePO₄ offers improved safety, a smoother discharge curve, and some tolerance to cold temperatures. While bulky, lead-acid has a long history of use in off-grid solar systems and, with sufficient capacity, can withstand moderate freezing temperatures. However, for typical low-traffic Meshtastic nodes, oversized batteries may not be cost-effective.
Recommended Practices and Summary
Combining real data and field test reports from Meshtastic users ( KBOXLabs is particularly prominent), we can conclude that, in fact, for most sub-zero temperature Meshtastic deployment scenarios, lithium-ion batteries are still the mainstream and reliable choice.
Although chemistries such as NiMH and LTO are more robust in cold environments, lithium-ion batteries are also sufficient for most practical needs. The main reasons include:
First, Meshtastic nodes generally consume very low load power, placing much less strain on batteries than other power-hungry devices. Low power consumption can prevent serious failure or rapid degradation of lithium-ion batteries. KBOXLabs' ability to maintain stable node operation at -40°C using 18650 batteries is a prime example.
Second, even though lithium-ion batteries experience accelerated capacity degradation in extreme cold, they can still last for years. For many Meshtastic projects, even replacing batteries every two to three years is acceptable. This makes the simplified design offered by using a single 18650 battery and a small solar charger even more attractive. If the deployment site is easily accessible, the operational cost of replacing batteries is also not prohibitive.
Third, maintaining long-term stability in lithium-ion batteries depends primarily on controlling the charging current. By choosing the right solar panel and charge controller, the battery can be protected from excessive charging power at low temperatures. In most cases, the battery enters a safe charging range only when the housing, exposed to sunlight, warms to near or above freezing. At night or during periods of prolonged low temperatures, solar output decreases, mitigating charging risks.
Taking these practical factors into account, lithium-ion batteries are very attractive for most Meshtastic nodes in terms of simplicity, energy density, and cost. Although NiMH and LTO are more reliable in very extreme or unmaintainable deployment scenarios, community data shows that lithium-ion batteries are quite successful in most cold region use cases.
References and Further Resources
If you're interested in topics like battery chemistries, low-temperature charging, or specific charger designs, the following key resources are helpful for further reading. Many of the insights in this article come directly from discussions on Reddit, where enthusiastic Meshtastic enthusiasts share their real-time experiences.
Here are some relevant links and documents mentioned in the article:
lTexas Instruments published an application note that discusses how to use a specific Li-ion charging circuit to power NiMH batteries. This research is often cited in the community and covers the theoretical basis for using a Li-ion charger with three NiMH cells in series:
https://www.ti.com/lit/an/slyt468/slyt468.pdf
lThere is a discussion on Reddit about NiMH batteries in low temperature environments, with user comments. The discussion also compares NiMH and Li-ion batteries in Meshtastic nodes:
https://www.reddit.com/r/meshtastic/comments/1i2unza/you_can_use_nimh_batteries_with_liion_charger_for/
lFor more details on how 18650 batteries perform in cold environments, see this Reddit discussion, which includes actual results from using the node in extremely low temperatures:
https://www.reddit.com/r/meshtastic/comments/1f51cli/comment/lkq6jzr/
l If you’re interested in lithium titanium oxide (LTO) as a more weather-resistant option, you can find some user-made charging boards and LTO batteries on Etsy that support a wider temperature range:
https://www.etsy.com/ca/listing/1616711365/lithium-titanate-oxide-batteries-lto
https://www.etsy.com/ca/listing/1609406536/mppt-solar-battery-charger-and-regulator
Finally, for those who want to build a new node, the case column of the MeshCN community is a good starting point:
By reading these community discussions and technical documentation, you can gain a deeper understanding of how different batteries actually perform in low-temperature environments, and also learn from other users' valuable solutions for charging, heat preservation, and overall power management. We wish you success running your Meshtastic node in cold environments!
Author: Hays Chan | Community blogger
Translator:Joe Tan | KEEPTEEN | meshtastic node repeater
Website: https//www.keepteen.com
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