Rising Internal Resistance

High battery capacity is of limited use if the pack cannot deliver the stored energy effectively. To supply power, the battery needs low internal resistance. Measured in milliohms (mΩ), resistance is the gatekeeper of the battery; the lower the resistance, the less restriction the pack encounters. This is especially important on heavy loads such as power tools and electric powertrains. High resistance causes the voltage to collapse on a load, triggering an early shutdown. Figure 1 illustrates low and high resistance batteries in the form of free-flowing and restricted taps.

Effects of internal battery resistance

High resistance

 

Figure 1: Effects of internal battery resistance

A battery with low internal resistance delivers high current on demand. High resistance causes the battery voltage to collapse. The equipment cuts off, leaving energy behind.

Courtesy of Cadex

Lead acid has a very low internal resistance, and the battery responds well to high current bursts that last for a few seconds. Due to inherent sluggishness, however, lead acid does not perform well on a sustained high current discharge and the battery needs a rest to recover. Sulfation and grid corrosion are the main contributor to the rise of the internal resistance. Temperature also affects the resistance; heat lowers it and cold raises it. Heating the battery will momentarily lower the internal resistance to provide extra run time.

Alkaline, carbon-zinc and other primary batteries have a relatively high internal resistance, and this limits its use to low-current applications such as flashlights, remote controls, portable entertainment devices and kitchen clocks. As these batteries discharge, the resistance increases further. This explains the relative short runtime when using alkaline cells in digital cameras. 

Comments

On December 12, 2011 at 10:16am
Guillaume wrote:

If anyone could provide me with a link of a lead-acid battery internal resistance vs temperature, it would be awesome.

On December 13, 2011 at 6:37am
girish yadav wrote:

lead acid battery performs better at low intl resistance at low temperrature intl resistance rises while at higher temperature vice-versa.

On December 13, 2011 at 12:40pm
Guillaume wrote:

@girish

I should have been more explicite in my question. I already knew that a colder temperature meant a higher internal resistance (yeah, I know I should have mentionned it).

What I would like to know is by how much the internal resistance is affected by a change of temperature. For instance, take the internal resistance of a battery at 30°C (say 4mH).

What will it be at -40°C ? 2 times 4mH ? more than that ?

On November 28, 2012 at 11:48am
danwat1234 wrote:

Why is is that cheap aftermarket lithium ion polymer camcorder battery packs often, over time, get high internal resistance to the point where you can’t record that long in 1080p before the voltage lowers too much and the camcorder shuts down. If I wait a few minutes I can then do some more video.
Eventually though, internal resistance gets so bad that the battery just can’t deliver a large load for any amount of time.

This has happened to me with many aftermarket DB-L80 batteries. The charge cycles is something less than 100, probably around 75, and they aren’t exposed to high heat all that much except for summer.

What changes in a li-ion battery to cause it to wear out in the form of rising internal resistance instead of just reduced capacity?

On December 5, 2012 at 11:37pm
Tysen wrote:

danwat1234, the Batteries in question were most likely rated at a high Capacity but have very poor Discharge Rates. for instance the OEM batteries in a Li-ion drill are rated at only 1300-1500 mAH of storage, but are Capable of Delivering 10-15x their capacity (18amps) for a few mins. this is Just Like a starter Battery. Most Laptop batteries are rated around 2400-2600mAH and can Deliver usually 2x their total Capacity in amps which results in a 30 min Battery life when playing games (5200/0.5 =2600mah). now the aftermarket maker prob tried to sell you on a Larger cell. you did indeed get a larger cell but the Battery is unable too keep up with the demands of your camcorder.

On December 5, 2012 at 11:47pm
Tysen wrote:

Sorry to further Add onto this. Generally with the 18650 cells (most laptops use) the larger the Mah rating the lower the rate of Discharge. one of the things ive found from these cells is
1300 +/- 18 amps discharge rate
2000 +/- 10A
2200 +/- 6.5A
2400-2600 5A
2700+ 0.5-2A in a perfect world. and I have seen a Samsung 2900 mah cell with a 3A discharge rate. but it required a hobby charger to take it to the rated 4.35 volts and in standard systems it only ran 2640mah

On December 6, 2012 at 12:07am
danwat1234 wrote:

No they are regular sized DB-L80 polymer single cell batteries. They have just about the same capacity as OEM but internal resistance is higher. It’s just 1 of those things you have to look at when you buy $3 aftermarket 2.5 watt-hour batteries.
Thanks it’s interesting how higher density batteries can’t put out as much energy at once.

On April 14, 2014 at 3:28am
MUZAMMIL SALEEM wrote:

I want to deseal/open a lead acid battery without damaging. Is it possible? Is there any machine or specific tool available for this purpose.