BU-106: Primary Batteries

The growth has been in secondary batteries (rechargeable) but non-rechargeable or primary batteries are equally important. They continue to fill an important niche market in applications such as wristwatches, remote controls, electric keys and children’s toys. Primary batteries also assist when charging is impractical or impossible, such as military combat, rescue missions and forest-fire services. Other applications of primary batteries are tire pressure gauges in cars and trucks, transmitters for bird tracking, pacemakers for heart patients, intelligent drill bits for mining,as well as light beacons and remote repeater stations. High specific energy, long storage times and operational readiness make this battery well suited for such applications. The battery can be carried to remote locations and used instantly, even after long storage. Most primary batteries are inexpensive, readily available and environmentally friendly.

Carbon-zinc, also known as the Leclanché battery, is the least expensive battery and comes with consumer devices when batteries are included. These general purpose batteries are used for applications with low power drain, such as remote controls, flashlights, children’s toys and wall clocks. One of the most common primary batteries for consumers is the alkaline-manganese, or alkaline for short. Lewis Urry invented it in 1949 while working with the Eveready Battery Company Laboratory in Parma, Ohio. Alkaline delivers more energy at higher load currents than carbon-zinc. Best of all, alkaline does not leak when depleted, as carbon-zinc does. On the negative side, alkaline is more expensive than carbon-zinc.

Primary batteries have one of the highest energy densities. Although secondary batteries have improved, a regular household alkaline provides 50 percent more energy than lithium-ion. The most energy-dense primary is the lithium battery made for film cameras and military combat. It holds more than three times the energy of lithium-ion and comes in various blends, such as lithium-metal, lithium manganese dioxide, lithium-sulfur dioxide, lithium-thionyl chloride, lithium oxygen and others. Figure 1 compares the typical gravimetric energy densities of lead acid, NiMH, Li-ion, alkaline and lithium primary batteries.

Specific energy comparison of secondary and primary batteries

Figure 1: Specific energy comparison of secondary and primary batteries
Secondary batteries are typically rated at 1C; alkaline uses much lower discharge currents.

Courtesy of Cadex

Specific energy indicates the energy a battery can hold. This, however, does not guarantee delivery. Primary batteries tend to have high internal resistance, which limits the discharge to light loads such as remote controls, flashlights and portable entertainment devices. Digital cameras are borderline — a power drill on alkaline would be unthinkable.

Manufacturers of primary batteries only specify specific energy; the specific power (ability to deliver power) is not published. While most secondary batteries are rated at a discharge current of 1C, the capacity of primary batteries is measured by discharging them at a very low current of 25mA, or a fraction of a C. In addition, the batteries are allowed to go down to a very low voltage of 0.8 volts per cell. This evaluation method provides impressive readings on paper, but the results are poor under a more demanding load.

Figure 2 compares performance of primary and secondary batteries on a discharge of 1C. The results are indicated in Actual and Rated. Actual is the Wh/kg derived at a 1C discharge, Rated is the Wh/kg the manufacturer specifies when discharged at a much low current.  While the primary batteries do well on a discharge representing entertainment device, secondary batteries have lower capacities but are more resilient at a load of 1C. 

Energy comparison under load

Figure 2: Energy comparison under load. ”Rated” refers to a mild discharge; “Actual” is a load at 1C. High internal resistance limits alkaline battery to light loads.

Courtesy of Cadex

The reason for the sharp performance drop on primary batteries is the high internal resistance, which causes the voltage to drop under load. The already high resistance increases further as the battery depletes on discharge. When the battery goes flat on a digital camera, for example, precious capacity is often left behind. A spent alkaline can often power a kitchen clock for two years. Figure 2 above shows the largest discrepancy between “Rated” and “Actual” on alkaline. A long-life alkaline (not shown on chart) will deliver better results.

Table 3 illustrates the capacity of standard alkaline batteries with loads that are typical of personal entertainment devices or small flashlights. Discharging at fractional C-rates produces high capacities; increasing the discharge rate would drastically reduce it.

Alkaline specifications
Table 3: Alkaline specifications.
The discharge resembles entertainment devices with low loads.

Courtesy of Panasonic

The use of primary batteries can be expensive, and the inability to recharge increases the cost of power by about thirty fold over secondary batteries. The pricing issue becomes even more acute if the packs are being replaced after each mission, regardless of length of service. Discarding partially used batteries is common, especially in fleet applications and critical missions. It is more convenient and safer to simply issue the troops fresh packs with each call rather than estimating the remaining state-of-charge. A US Army general once said that half of the batteries discarded still have 50 percent energy left.

Estimating the battery state-of-charge would help, but such instruments are expensive and inaccurate. The most basic method is measuring the open circuit voltage and reading the internal resistance by applying a brief load and checking the voltage drop. A large voltage differential would relate to rising resistance, a hint to the end of life. A more accurate way is to count the out-flowing energy, a measurement that is also known as coulomb counting, but this requires expensive circuitry. See How to Measure State-of-charge. Due to high cost and inherent inaccuracies, fuel gauges are seldom used on primary batteries.

Comments

On April 6, 2011 at 8:20pm
Ramesh wrote:

supperb

On December 14, 2011 at 8:47am
Stephen J. Nichols wrote:

I beg to differ on alkaline batteries not leaking when. I have had a couple of flashlights that were used only a few times for brief periods and six months later would have to have the batteries almost driven out and yes they were turned off. Also televison remotes that worked a few minutes ago, and won’t now. When you go to change the batteries you have to clean the crud and corrosion out before installing the new batteries. From the looks of the amount of leakage and corrosion it had been going on for some time.
Do keep Battery University updated and on the web it does have a world of good information. An extremely handy reference.

On December 18, 2011 at 4:50pm
Mike wrote:

However Secondary cells are very poor to useless for long life low power consumption or device used intermittently with gaps of months (or even a few weeks for higher capacity NiMH) between use.  I recently had application for 80V at 5.5mA. The most economical and long use between replacements was 6 stacks of 26 x CR2032 Lithium coin cell parallel with 6 x 1N4148 diodes. About 6x capacity of Alkaline PP3 and recharging such a number of NiMH or Lithium ion in series is problematic as well as avoiding reverse charging a cell.

On February 14, 2012 at 7:57am
Nick wrote:

How I can measure the capacity of Zinc-carbon 6V battery ? I can discharge the batt by resistor f.e. 100ohm/1W. What are the formulas to calculate the capacity/Ah if I have cut off voltage f.e. 3.6V and know the discharging time in hours to achieve 3.6V.

On December 23, 2012 at 1:21am
Vipin wrote:

Can I use lithium and alkaline batteries together in one device?

On July 17, 2013 at 6:09pm
Kaz wrote:

The article is correct; alkaline batteries should not normally leak, whereas for zinc-carbon batteries, this is practically an expected behavior.

The reason why zinc-carbon batteries leak is that the casing of the battery serves as the negative terminal. The casing is consumed as the battery drains, and can perforate!

This is not true of alkaline batteries, whose casing is not one of the electrodes.

That is not to say that the casing cannot fail, but it’s not expected that mere discharge of the battery will “eat” through the casing.

On July 17, 2013 at 6:15pm
Kaz wrote:

You can use lithium and alkaline batteries in the same device, but not on the same circuit. They have different discharge rates.
 
The device has to have some separate circuits with separate power sources. This happens. For instance, a device that draws the bulk of its power from AAA batteries could have a coin battery on its circuit board (on a dedicated circuit) which maintains the contents of a non-volatile static RAM (NVRAM) chip. So that’s an example of one device with two kinds of batteries. A much more ancient example of multiple batteries are portable vacuum tube devices, which used three separate batteries: a battery for the vacuum tube heaters, another one (high voltage, 30 or more volts) for the plate, and a third battery for the grid bias!

If different types of batteries are connected in parallel, bad things will happen as one type of battery discharges to a lower voltage than the other (or is that way initially) and tries to charge the other.

In series, it is even worse, because a good battery in series with a dead one will reverse-bias the dead one (impose a reverse polarity on it).

Even new and old primary batteries OF THE SAME TYPE should not be put in series; you should change series battery packs at the same time.

 

On October 29, 2013 at 4:24pm
chloe wrote:

can you tell me information on a great value battery, a family dollar battery, duracell battery and a energizer battery. if you can that would be great !! im in the 7th grade and im doing a science project on battery life!!! if you can do this that would be great!!!

On December 14, 2014 at 9:42am
arsalan wrote:

I have fujitsu ah530 laptop i tried to replace the battery cell of my old battery with the same voltage and amphere cells but I failed the battery’s Positive terminal does not have any charge. I arranged another old dead battery from my friend but same results. in both senario the +ve terminal is not having any charge, when placed to laptop it does not
start on battery showing error “0% charge plugged in charging consider replacing your battery”. how to on solid state switch so that their would be a charge on +ve terminal and how can I resolve the issue please help me