12/12/2002

Battery Technology

 

Portable Power or in this case… "Batteries" play an important part in Amateur Radio as well as many commercial and personal uses. Deciding what type of battery technology to use will depend mostly on the application that you are using it for. For example, if you were looking at a High Current application where Cost is of Prime importance, NiCd would be your obvious choice since it seems to have the best $ to Amp hour Ratio. If you needed the greatest capacity in a given weight/size then you might select Li-Ion.

The information below is presented to help you make your own choices. I have scoured the Internet for information regarding the most popular battery technologies (NiCd, NiMH and Li-Ion) and although there are many other technologies available they will not be presented here.

One of the first things that I noticed while accumulating information from the web is that there are a lot of contradictions. I will first present the three technologies with some of the characteristics as I see them, then I will provide you with some of the information that I obtained with the associated links to the information.

NiCd (Nickel Cadmium) The oldest of the three technologies. It appears that NiCds still have the best price per Ah ratio (see NiMh below). NiCds generally have the greatest amount of recharge cycles available, however this is dependent upon proper maintenance. NiCds must be fully discharged or a regular basis and then fully charged.

I have personally found that after leaving a NiCd sitting for several months much of the capacity is lost. Fully Discharging and Recharging the cells 2 to 3 times normally brings back most if not all of the capacity. This along with the total amount of capacity that you can provide from a NiCd are the main disadvantages of this technology.

If you don’t mind recharging often and you are not going to let your batteries sit around for a long time… this may be the battery for you.
Check out this link for some Great info on NiCd's http://www.repairfaq.org/ELE/F_NiCd_Battery.html

NiMh (Nickel Metal Hydride) Generally it seems that NiMH has 30% to 50% greater capacity than equivalent sized NiCd’s. For example… some of the newer NiCd’s are rated at 1200mAh and the equivalent NiMh batteries are rated at 1800 mAh. This comes at a cost though as the NiMh are generally 50% more expensive than NiCds (though I think that the prices are starting to come down).

Actually, after checking the prices on the Radio Shack Web site… 2 NiCd’s are running $6.99 as compared to 2 NiMh batteries at $9.99. The cost per Ah is actually lower with the NiMh batteries (the mAh ratings are 1000 and 1600 respectively). However for the full life of the battery the NiCd will still be slightly in the lead.

NiMh batteries are not able to provide as much output current on a continuous basis (as NiCd or Li-Ion batteries) and the amount of recharge cycles are limited to between 300 and 500. Also, the charging requirements are a little more strict and a charger designed for charging NiMh batteries will need to be used.

Li-Ion (Lithium Ion) has the highest power density of the three types of batteries. It is also the most expensive. Many devices (Laptops, Cell phones, etc) have starting using this technology. Li-Ion has the best shelf (on shelf discharge rate) life and is also capable of providing High Current to applications (as is the NiCd. Additionally, you are not required to provide full discharge/recharge cycles as is recommended for NiCds and NiMh cells.

Those being the main advantages here are the disadvantages:

Higher cost

Reduced capacity at High discharge rates.

Life of Cell – I have found topics relating to cell life of Li-Ion batteries and it appears that once the battery is activated the cell begins to degrade. From my research I would suggest that a Li-Ion cell will diminish to 80% capacity within 2 to 3 years after first use. This appears to be dependent on the chemistry in the cell and not the number of charge/recharge cycles.

Another issue with Li-Ion batteries is that they do not come in the Standard sizes. i.e. you will not be able to find a AA, AAA, C or D size Li-Ion batteries. Li-Ion cells have a voltage of around 3 Volts and others (AA, AAA.. etc) have a cell voltage of 1.5 Volts and 1.2 volts for NiCd)

That being said… below I have provided some of the information that I have obtained from the Web including sources. I will try to update this page in the future with new information as I get it.

 

Battery Characteristics as reported on http://www.idxtek.com/runtime_compare.htm

(for use with cameras)

Type

Weight

Recharges

Memory

Total W/H

Li-Ion

1.56lbs

Up to 500

No

82

NiMh

1.5

Up to 300

Moderate

50

NiCd

1.5

500+

High

20

 

 

 

Rayovac http://www.rayovac.com/busoem/oem/specs/ren5.shtml

 

Recharges

Cont Output Current

Capacity

Self Discharge Rate

Akaline

100+

600ma

1600mAh

.01% per Day

NiMh

300+

2A

1100mAh

1% per Day

NiCd

200+

5A

750mAh

4% per Day

Another comparison from Cadex Electronics in Canada:

http://www.buchmann.ca/chap2-page2.asp - A note from the bottom of this page:

Observation: It is interesting to note that NiCd has the shortest charge time,

delivers the highest load current and offers the lowest overall cost-per-cycle,

but has the most demanding maintenance requirements

 

Recharges

Con Output Current

Self Discharge Rate (Room Temp)

Li-Ion

500-1000

1C

10%/Month

NiMh

300-500

.5C

20%/Month

NiCd

1500

1C

30%/Month

 

Discharge rates of batteries (on the shelf) vary dramatically with Temperature as shown on

the Dedicated Digital website (http://www.rayovac.com/busoem/oem/specs/ren5.shtml). Here

are the Discharge Rates per month based on Temperature and type of battery:

Degrees Centigrade (C)

Li-Ion

NiMh

NiCd

20

5~8

30

15

40

10~30

70

60

 

 

 

 

 

Here is a good overview of battery technology although I believe that this presentation

may have been biased towards NiMH technology.

http://www.txobattery.com/pdf/presentations/intro_to_nimh_bat_tech.pdf

 

Lithium Metal???

Here is a great background on Battery Technology and introduction to Lithium Metal Technology.

http://rf.rfglobalnet.com/library/Papers/files/8/howtochoose.htm