Winter kills more remote monitoring stations than wind, water, or vandalism, and it usually does so through a mechanism the buyer did not know they had bought. This piece is about that mechanism, and about the specification choices that avoid it.
The two temperatures, and why the gap matters
Almost every integrated solar power system datasheet lists an operating temperature range. Many also list a charge or charge/discharge range, in smaller type, further down. They are different specifications describing different things, and the second one is the one that decides whether the station survives.
| Specification | What it means | What it does not mean |
|---|---|---|
| Operating temperature | The ambient range in which the equipment can be installed and can run | It does not mean the battery can be charged across that whole range |
| Discharge temperature | The range across which the battery can deliver current, usually wide | Capacity is still reduced at the cold end, sometimes substantially |
| Charge temperature | The range in which the battery can safely accept current | This is the one that stops at or near 0 °C for most lithium chemistries |
Charging a lithium cell below freezing causes lithium plating on the anode, which permanently reduces capacity and creates a safety risk. A charge controller that refuses to charge in the cold is doing its job. The design error is upstream, at the point where someone assumed an operating range implied a charging range.
What actually happens to a battery in the cold
- Sealed lead-acid loses a large share of usable capacity below freezing — commonly cited around 30-50% at and below 0 °C. It will accept charge in the cold, which is its one advantage here, but the capacity you sized around is not the capacity you have.
- LiFePO4 holds far more of its capacity in the cold, typically 70-80% at −20 °C on discharge, and offers much better cycle life. Its constraint is the charge window: without a heater or a purpose-built low-temperature variant, it should not be charged below 0 °C.
- Ternary lithium (NMC) behaves broadly similarly on the charge side. Chemistry choice changes discharge performance and cycle life more than it changes the freezing-point charge limit.
Chemistry comparison across cycle life and temperature is covered in more depth in our battery chemistry notes for remote monitoring, and the derating arithmetic for line-monitoring sites specifically in our cold-climate battery field notes.
Winter is not one problem, it is four
- Fewer peak-sun-hours. The obvious one, and the only one most sizing exercises account for. At high latitude the worst month can be a fraction of the annual average.
- Lower sun angle. A panel at a summer-optimised tilt is badly aimed in December. Steeper winter tilt costs summer output that you have in surplus anyway, and buys output in the month that decides the design.
- Snow cover. A panel covered in snow produces nothing. Steeper tilt sheds snow better; a shallow-tilt panel can stay covered for days after a fall.
- The charge window. The one described above, and the one that turns a marginal design into a dead station rather than a slow one.
Four ways to design around it
1. Steepen the tilt
Set tilt for the worst month rather than the annual optimum. It captures more of the low winter sun and sheds snow more readily. On a monitoring station, summer surplus is worth nothing — the design case is the month the station might die.
2. Oversize the array rather than the battery
A bigger battery stores more energy but does not generate any, and in the cold it also cannot be recharged during the hours that matter. Extra array capacity converts the few usable winter hours into charge more effectively than extra storage does.
3. Specify a heated or low-temperature battery
Packs with integrated low-temperature charging support draw a small amount of power to warm the cells before accepting charge. This costs energy, which has to be in the budget, and it is the correct answer for sites that are genuinely below freezing for extended periods rather than occasionally.
4. Reduce the load for the season
Where the application allows it, cutting reporting frequency in winter is the cheapest capacity you will ever buy. A station reporting hourly instead of every fifteen minutes through January may be entirely acceptable operationally, and it changes the sizing case completely. This is a firmware decision with a hardware-sized effect.
Field details that decide a winter
- Snow shedding is a mounting decision. Tilt, panel surface, and clearance beneath the module all affect whether snow slides off or sits. A panel mounted flat against a structure with no clearance will hold snow the longest.
- Condensation is worse in winter. A sealed enclosure cycling through a large daily temperature swing pumps moist air in and condenses it inside. An IP-rated breathable vent plug is a small part that prevents a common failure.
- Cable and connector behaviour changes. Cable stiffens and becomes easier to damage during a cold-weather service visit. Leave service loops and expect to handle wiring gently at low temperature.
- Access is seasonal. On many northern sites a fault in January cannot be fixed until March. That reality, more than any datasheet, is the argument for margin.
- Trail and wildlife cameras have their own pattern. Battery drain in the woods during winter is a well-documented failure mode; our trail camera battery sizing notes cover the canopy and cold combination.
Questions to ask a supplier before ordering for a cold site
- What is the charge temperature range, separately from the operating range? If only one number is given, ask for the other in writing.
- Does the battery include low-temperature charging support, and if so how much energy does that consume?
- What is the battery chemistry, and what is the rated capacity at −20 °C rather than at 25 °C?
- Is a low-temperature variant available, and what specifically differs in it?
- What tilt is the mounting hardware adjustable to, and can it be set for winter rather than annual optimum?
- What is the low-voltage disconnect setpoint, and can it be configured?
A supplier who answers question one with a single number has not thought about your site. That is a useful filter early in a sourcing conversation.
Where LinkSolar fits
We supply the power layer — panel, battery, controller, enclosure, mounting hardware — sized for the season that actually threatens the station rather than for an annual average. On cold-site projects that means we will ask about the charge window before quoting, and we will say plainly if a standard configuration is wrong for your latitude.
- Low-temperature variants available where the site genuinely requires them, specified rather than assumed.
- Custom electrical specification: panel voltages from 3 V to 48 V, configurable disconnect setpoint, multi-rail outputs.
- Samples in 7-10 days for custom mini panels; integrated-system lead times confirmed at quote.
- MOQ from 5, so a winter can be proven on a pilot before a network order.
- Components sourced from ISO 9001, CE and RoHS certified partner factories, with pre-shipment QC evidence on every batch.
FAQ
Can lithium batteries be charged below freezing?
Not without a heater or a chemistry specifically rated for it. Charging a standard lithium cell below 0 °C causes lithium plating on the anode, which permanently reduces capacity and creates a safety risk. Charge controllers correctly refuse to charge in that condition, which protects the battery but leaves the load drawing from a pack that is no longer being replenished.
What is the difference between operating temperature and charge temperature?
Operating temperature is the ambient range in which the equipment can be installed and run. Charge temperature is the narrower range in which the battery can accept current, and for most lithium chemistries it stops at or near 0 °C. A system rated to −25 °C operating may only be able to charge above 0 °C, which is the specification gap that causes winter failures.
Is lead-acid better than lithium for cold sites?
It has one advantage — it will accept charge below freezing — but it loses a large share of usable capacity in the cold and offers far shorter cycle life. For most remote monitoring applications LiFePO4 with either a heater or a low-temperature variant is the better system-level answer. Lead-acid can make sense where the site is only occasionally below freezing and the replacement interval is acceptable.
Should I use a bigger battery or a bigger panel for winter?
Usually the panel. A larger battery stores more energy but generates none, and in the cold it also cannot be recharged during the few usable hours. Extra array capacity converts those hours into charge more effectively. Battery capacity should be sized for autonomy, not used as a substitute for winter generation.
Does panel tilt matter that much in winter?
Yes, on two counts. A steeper tilt captures more of the low winter sun, and it sheds snow far better than a shallow one. Setting tilt for the worst month rather than the annual optimum costs summer output you already have in surplus and buys output in the month that decides whether the station survives.
Speccing a monitoring station for a cold-climate site?
Send your load list, the site latitude, and the lowest expected sustained temperature. We will size against your worst month, confirm the charge window that applies, and tell you plainly whether a low-temperature variant is needed — RFQ response within 24 hours, custom panel samples in 7-10 days.
