Charging a Battery in Cold Weather

Many lithium batteries won't charge, or charge slowly, when the air is near or below freezing. That's by design. Charging a cold lithium cell can hurt it, and the electronics built into the battery are there to stop that from happening. Annoying? Yes. Wrong? No.

What goes wrong inside

Battery University lists lithium-ion charging from 0°C to 45°C (32°F to 113°F). Its table adds: no charge permitted below freezing.¹

The reason it gives is reduced diffusion rates on the anode, which is the battery's negative electrode.¹ It also describes plating of metallic lithium on the anode during a sub-freezing charge.

It says plating during a sub-freezing charge leads to permanent loss of performance and safety.¹ It also says the pack can appear to be charging normally while this happens.¹

So the problem isn't just slow charging. It's quieter and worse than that. A cold charge can do lasting harm while the screen shows nothing wrong.

Cold, but above freezing

Between roughly freezing and a few degrees above, things are still slower. The same source says lithium-ion can be fast charged from 5°C to 45°C. Below 5°C, the charge current should be reduced.¹

A maker's guide agrees on the general behaviour. It says charging can slow down, especially if the unit has just come in from a near-freezing space.²

Some batteries have specific cold-charge limits

Look at the numbers in your own manual. One portable power station's published charging range is 0°C to 40°C (32°F to 104°F).² Other models can list different limits. Your maker's manual is the place for that detail, not a general article.

Battery University says specialty lithium-ion cells can discharge down to -40°C, but only at a reduced discharge rate. Charging at that temperature is out of the question.³ It also says some cell makers offer custom cells for cold charging.¹ Those need matching chargers.¹

What makers and references say to do

• Warm it first. One maker says to bring the unit into a dry, moderate indoor room and let it warm naturally before charging or connecting heavier home loads.²
• Don't rush it. The same guide says not to rush the battery straight from cold storage into high-demand use.²
• Stick to the charging range. Battery University says consumer chargers lack the temperature features of industrial ones, so the user is advised to only charge at room temperature.¹
• Read your manual. Your maker's charging range beats any general figure, and if it describes a cold-weather procedure, follow its steps in the order given.

What not to do

Don't try to trick the battery into charging. Don't bypass its protection, and don't open the case to warm it from the inside. Modifying a battery is out. If yours refuses to charge in the cold, the protection is probably doing exactly what it was built for.

To see how charging limits differ from other limits, read Operating Temperature Versus Storage Temperature. If your battery is hard-wired, moving it or rewiring it is work for a licensed electrician.

Different chemistries react differently. See How Different Battery Chemistries Handle Cold for how.