Charging at High and Low Temperatures

Rechargeable batteries operate in a wide temperature range but this does not give license to charge them at extreme temperatures. Extreme cold and high heat reduce charge acceptance, and the battery must be brought into moderate temperature conditions before charging.

Older battery technologies, such as lead acid and NiCd, have higher charging tolerances than newer systems and can be charged below freezing at a reduced 0.1C rate. This is not possible with most NiMH and lithium-ion systems. Table 1 summarizes the permissible charge and discharge temperatures of common lead acid, NiCd, NiMH and Li‑ion. We exclude specialty batteries designed to charge outside these parameters.
 

Battery Type

Charge Temperature

Discharge Temperature

Charge Advisory

Lead acid

–20°C to 50°C
(–4°F to 122°F)

–20°C to 50°C
(–4°F to 122°F)

Charge at 0.3C or lessbelow freezing.
Lower V-threshold by 3mV/°C when hot.

NiCd, NiMH

0°C to 45°C
(32°F to 113°F)

 

–20°C to 65°C
(–4°F to 149°F)

 

Charge at 0.1C between –18 and 0°C.
Charge at 0.3C between 0°C and 5°C.
Charge acceptance at 45°C is 70%. Charge acceptance at 60°C is 45%.

Li-ion

0°C to 45°C
(32°F to 113°F)

–20°C to 60°C
(–4°F to 140°F)

No charge permitted below freezing.
Good charge/discharge performance at higher temperature but shorter life.

Table 1: Permissible temperature limits for various batteries. Batteries can be discharged over a large temperature range but charge temperature is limited. For best results, charge between 10°C and 30°C (50°F and 86°F). Lower the charge current when cold.

Low-temperature Charge

Fast charging of most batteries is limited to a temperature of 5 to 45°C (41 to 113°F); for best results consider narrowing the temperature bandwidth to between 10°C and 30°C (50°F and 86°F). Nickel-based batteries are most forgiving in accepting charge at low temperatures, however, when charging below 5°C (41°F), the ability to recombine oxygen and hydrogen diminishes. If NiCd and NiMH are charged too rapidly, pressure builds up in the cell that will lead to venting. Not only do escaping gases deplete the electrolyte, the hydrogen released is highly flammable. The charge current of all nickel-based batteries should be reduced to 0.1C below freezing.

Nickel-based chargers with NDV full-charge detection offer some protection when fast-charging at low temperatures. The resulting poor charge acceptance mimics a fully charged battery. This is in part due to the pressure buildup caused by gas recombination problems. Pressure rise and a voltage drop at full charge appear to be synonymous.

To enable fast-charging at all temperatures, some industrial batteries include a thermal blanket that heats the battery to an acceptable temperature; other chargers adjust the charge rate to prevailing temperatures. Consumer chargers do not have these provisions and users should make all attempts to only charge batteries at room temperatures.

Lead acid is reasonably forgiving when it comes to temperature extremes, as we know from the starter batteries in our cars. Part of this tolerance is their sluggish behavior. The recommended charge rate at low temperature is 0.3C, which is almost the same as under normal conditions. At a comfortable temperature of 20°C (68°F), gassing starts at 2.415V/cell, and by lowering the temperature to –20°C (0°F), the gassing voltage rises to 2.97V/cell.

Do not freeze a lead acid battery. This would causes permanent damage. Always keep the batteries fully charged. In the discharged state the electrolyte becomes more water-like and freezes earlier than a fully charged battery. According to BCI, a specific gravity of 1.15 has a freezing temperature of –15°C (5°F). This compares to 1.265 of a fully charged starter battery. Flooded lead acid batteries tend to crack the case and cause leakage if frozen; sealed lead acid packs lose potency and only deliver a few cycles before a replacement is necessary.

Li‑ion batteries offer reasonably good charging performance at cooler temperatures and allow fast-charging in a temperature bandwidth of 5 to 45°C (41 to 113°F). Below 5°C, the charge current should be reduced, and no charging is permitted at freezing temperatures. During charge, the internal cell resistance causes a slight temperature rise that compensates for some of the cold. With all batteries, cold temperature raises the internal resistance.

Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a subfreezing charge. The plating is permanent and cannot be removed with cycling. Batteries with lithium plating are known to be more vulnerable to failure if exposed to vibration or other stressful conditions. Advanced chargers, such as those made by Cadex, prevent charging Li-ion below freezing.

Manufactures continue to seek ways to charge Li-ion below freezing and low-rate charging is indeed possible with most lithium-ion cells; however, it is outside the specified (and tested) limits of most manufacturers’ products. Low-temperature charging would need to be addressed on a case-by-case basis and would be manufacturer and application dependent. According to information received from university research centers, the allowable charge rate at –30°C (–22°F) is 0.02C. At this low current, a 1,000mAh Li-ion could only charge at 20mA, and this would take more than 50 hours to reach full charge.

Some Li-ion cells developed for power tool and EV applications can be charged at temperatures down to –10°C (14°F) at a reduced rate. To charge at a higher rate, Li-ion systems for automotive propulsion systems require a heating blanket. Some hybrid cars circulate warm cabin air through the batteries to raise the battery temperature, while high-performance electric cars heat and cool the battery with a liquid agent.

High-temperature Charge

Heat is the worst enemy of most batteries, including lead acid. Adding temperature compensation on a lead acid charger to adjust for temperature variations prolongs battery life by up to 15 percent. The recommended compensation is 3mV per cell per degree Celsius applied on a negative coefficient, meaning that the voltage threshold drops as the temperature increases. For example, if the continued float voltage were set to 2.30V/cell at 25°C (77°F), the recommended setting would be 2.27V/cell at 35°C (95°F) and 2.33V/cell at 15°C (59°F). This represents a 30mV correction per cell per 10°C (18°F). Table 2 indicates the optimal peak voltage at various temperatures when charging lead acid batteries. The table also includes the recommended float voltage while in standby mode.
 

Battery status

0°C (32°F)

25°C (77°F)

40°C (104°F)

Voltage limit
on recharge

2.55V/cell

2.45V/cell

2.35V/cell

Float voltage
at full charge

2.35V/cell or lower

2.30V/cell or lower

2.25V/cell or lower

Table 2: Recommended voltage limits when recharging and maintaining stationary lead acid batteries on float charge. Voltage compensation prolongs battery life when operating at temperature extremes.

Charging nickel-based batteries at high temperatures lowers oxygen generation, which reduces charge acceptance. Heat fools the charger into thinking that the battery is fully charged when it’s not.

NiCd has the largest pool of published information on this subject, and Figure 3 demonstrates a strong decrease in charge efficiency above 30°C (86°F). At 45°C (113°F), the battery can only accept 70 percent of its full capacity; at 60°C (140°F) the charge acceptance is reduced to 45 percent. NDV for a full-charge detection becomes unreliable at higher temperature and temperature sensing is essential for backup. Newer type NiMH batteries perform better at elevated temperatures than NiCd.

NiCd charge acceptance as a function of temperature.

Figure 3: NiCd charge acceptance as a function of temperature. High temperature reduces charge acceptance. At 55°C, commercial NiMH has a charge efficiency of 35–40%; newer industrial NiMH attains 75–80%.

Courtesy of Cadex

Lithium-ion performs well at elevated temperatures; however, prolonged exposure to heat reduces longevity. The charge efficiency is 97 to 99 percent, regardless of temperature. In fact, high temperature increases charge effectiveness slightly by improving the internal resistance.

While other chemistries can tolerate stepping outside set boundaries once in a while, there are limitations with Li-ion. Safety concerns dictate that Li-ion remains within specified limits because of possible thermal runaway if stressed. A fully charged Li-ion is more sensitive to a thermal runaway than an empty one; the thermal runaway temperature moves lower with higher charge. In spite of this, specialty Li-ion batteries serve in applications that go to momentary high temperatures, and surgical tools that undergo steam sterilization at 137°C (280°F) are such an example. Other uses that reach similar temperatures are batteries in drilling bits for mining.
 

Caution:  In case of rupture, leaking electrolyte or any other cause of exposure to the electrolyte, flush with water immediately. If eye exposure occurs, flush with water for 15 minutes and consult a physician immediately.

              

Comments

On January 12, 2011 at 11:02pm
Girish.K wrote:

How to calculate the connected load of battery chargers
360V-150A-80% efficency

On August 24, 2011 at 10:33am
Janusz Konopka wrote:

Battery means several cells connected in series.  I the course of work (after several charging and discharging cycles) one may note important differences between particular cells.  Despite of   monitoring particular cells during discharge it chappens that battery become useless because e.g. one cell is much weaker. I founfd it in the case of my electric bike. After, say, some 30 cycles battery become usless. When I performed separate charging of weaker cells the baterry recovered and could be used again.
Plese give me the approximate internal resistance of Li-Ion cell (dV/dI).  This parameter will may be decisive in controlling quality of each cell.

On October 31, 2011 at 7:48am
Max Dirnberger wrote:

Dear Janusz,

This will be because your charger is not doing charge balancing. When Li-Ion batteries are in series (most battery packs) this step is often not implemented but must be to avoid the problem you mention

On December 24, 2011 at 9:03pm
Omair wrote:

So basically, if I don’t requite the batteries to fast charge, and since I plug my phone to the charger before bed, I actually prefer it to charge slowly in order to reduce stress, wouldnt cooling the phone to about 15°every night
help elongate my battery life? (Accodibg to your other post, by uptill 15%).
The battery in consideration is a 3.7v 1230mAh Li-ion battery.

On March 13, 2012 at 7:23pm
Happy wrote:

So i have already read all the lesson above. my question is which one is the best metode, charging at the lowest or highest temperature for range 10 - 30C that you mentioned?

thanks for the answer

On June 24, 2012 at 6:45pm
jo wrote:

Hi

On July 20, 2012 at 3:48am
emad wrote:

I connect my phone to my pc ( tethering to get internet ) about 4 to 5 times last weak and i found that my battery is get fully charge after 2hours connecting to the charger instead of 2h 30min as usual .Is that mean that my battery health is affected too much?
and usualy i connect my charger when my battery charge about 25% : 40%
is it okay , or better to leave it to fully discharge befor charge it agail??
please help
my battery is li-ion 1200
the room temp. about 28° : 30°c

On September 30, 2012 at 11:25am
Garry wrote:

So i have already read all the lesson above. my ­question is which one is the best metode, charging at the lowest or highest temperature for range 10 - 30C that you mentioned?

On December 17, 2012 at 8:29am
Dave Dutton wrote:

I have heard lately from Makita salesman that charging warm is best. How warm? I don’t know. I am thinking that since the Lipos like to discharge at near 100 degrees F that charging might be best near that temperature, too.
Anyone with data? Anywhere? I am studying.

On January 14, 2013 at 2:27pm
Pim wrote:

Can I charge a Li-ion above 40C till 50C? With a voltage of 3,92Volt (50%) without damage the battery?

On May 8, 2013 at 8:43pm
Stephen wrote:

Compare to other type of battery, NiCd gives best performance in charging for temperature over 40 degree C.
High Temp NiCd can doing good at 70 degree C. That is why they still use in Emergency Lighting application.
I can also make Low Temp NiCd which perform 65% at -20 degree C. It is heard that some companies can even supply NiCd work at -40 degree C.
My experience is that, Li-ion battery become unstable when over 40 degree C. It could be dangerous of fire if you get products from unprofessional manufacturer.
0 - 40 degree C is the suitable range for most Li-ion.

On May 29, 2013 at 1:33am
praveen wrote:

can anybody tell me how to calculate battery sizing when the load power is 12KW

On June 29, 2013 at 11:52pm
GILBERT M. SAMOITA wrote:

Hi,
I have been a keen follower of your site and i have interests i battery manufacturing. Please advise me on factors influencing charge acceptance.

On September 5, 2013 at 5:24pm
dale wrote:

hi i was wondering about batteries will they be a bomb if you put too much heat on it

On September 18, 2013 at 2:03am
Tom Wald wrote:

Wireless chargers for cellphones increase battery temperature. The third party fonesalesman brand QI charger for my Samsung Galaxy S4 takes the battery temperature up to around 37 degrees, maybe a little more for long charges, whereas charging by plugging it in produces a very small temperature rise.

Are there any safety concerns here? Will the battery life be significantly degraded?

On December 15, 2013 at 4:35pm
Oto wrote:

What about alkaline rechargable batteries and NiZn? What are temperature limits for charging?

On December 17, 2013 at 6:31am
stephen wrote:

Special NiCd battery can be charged at temp up to 70°C, this is so called High Temp NiCd, normally used in maintained Emergency Lighting in Europe regulation, especially in UK.
They are in floating charging all the time, and must be over 70% capacity after working in four years.
Another special Low Temp NiCd can work down to -40°C. This is used mostly in cold storage warehouse.
Anyone want to know more can contact me.

On December 18, 2013 at 1:29am
praveen wrote:

@Stephen you have mentioned they are in float charging all the time, so what would be tha max cahrge and discharge rates it can be operated?

On December 24, 2013 at 11:15pm
muhammadmutlab wrote:

q786 low battre tam

On February 14, 2014 at 6:36am
William wrote:

I have a lithium battery in my laptop, I lost my dell charger and have a rocket fish charger which allows my computer to run but it has 0% charge. If my plug is pulled out of the outlet the computer shuts off.

Would putting my battery in the freezer for a couple days be a good idea, pointless, or a terrible idea? A friend told me it can bring back some battery life that has been slowly degrading, is this true?