Dangers include (but are not limited to): very high discharge currents; mildly corrosive electrolyte.
The negative electrode consists of iron (II) hydroxide on an iron conductor, and the positive electrode consists of nickel hydroxide on a nickel conductor. The electrolyte is alkaline, normally potassium hydroxide with about 20% lithium hydroxide in aqueous solution, although sodium hydroxide has been used for high temperature cells.
On discharge, the following reactions occur:-
Positive: e- + NiO2H + H2O -> Ni(OH)2 + OH-
Negative: Fe + 2OH- -> 2e- + Fe(OH)2
Mass of reagents to produce 1 mole of electrons:- (Ni=58.7; Fe=55.8; O=16.0; H=1.0) 137.6g.
Voltage: 1.25v nominal; 1.0v discharged; 1.65v charged
Maximum discharge: ~5C
Cycle Life: 2000+
Nickel cadmium cells may be rapidly discharged and charged. They have a very large cycle life for the flooded varieties, although the sealed cells tend to suffer from dendritic formation. For charging the sealed cells, it is normal to charge at a constant current until the temperature rises. For the flooded varieties, normal CC-CV or CC-ZDV charging techniques are suitable.
The current integration method is perfectly acceptible for this technology. Determining the capacity using off-load voltage is harder as the off-load voltage curve is very flat. It may be possible to use this to estimate discharge states only when very deep discharges have occurred. It is possible to determine battery state quite well from the voltage when discharging into a small load: so for instance a current of, say, C/20 might be used to determine fuel level, by applying the load and waiting for a minute to see what the output voltage becomes.
It is important to factor in self-discharge rates.
| Manufacturer | Part | Chemistry | Voltage | Capacity | Weight(kg) | Dimensions(mm) | Peak Power | Continuous Power | Cost | Cycles | Peukert Number | Energy Weight Wh/kg |
Wear Cost (per kWh per cycle) |
Notes |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Theoretical | Reagents Only | Nickel Cadmium | 1.2 | 26.8Ah 32.2Wh |
0.138kg | - | 161W | 32W | - | 2000 | - | 233.3 | - | 1 mole of electrons |
| Eagle-Picher | ??? | NiFe | 6.25 | 200Ah 1.25kWh |
24.1kg | 261x181x249 | 6.3kW? | 1300W(1h rate) | $284 | >2000 | 1 | 52 | <$0.11 | Reconditioned |
| Edison | A4 Cell | NiFe | 1.2 | 150Ah 0.18kWh |
6kg? | ? | 0.6kW? | 180W(1h rate) | - | >2000 | 1 | 30 | - | 1910 design |
| Suntopway | TN60 | NiFe Pocket Plate | 1.25 | 60Ah 0.075kWh |
3.1kg dry | 134x70x280 | 375W? | 75W(1h rate) | ??? | >2000 | 1 | 24 (dry) | ??? |
This design was originally produced by Thomas Edison in 1910. Some of the original 1910 batteries are still in service: this technology certainly lasts. The original Edison battery was used in a commercial electric vehicle - the Detroit Electric - which had a range of 80 - 200 miles per charge, in the first half of the 20th century! The Dodge TeVan uses the same chemistry (the Eagle-Picher battery above) to give 100 miles range.
This technology is being advanced in various ways, most of them concerned with making good electrical contact with the nickel oxide in the negative electrode. Various approaches, including nickel wire wool and nickel-plating the grains of oxide have demonstrated very improved performance. Some researchers have claimed 95% plus utilisation of the nickel hydroxide electrode, which would lead to very good performance.
There is nothing in these cells that is poisonous, and the component chemicals are made from some of the most abundant elements on Earth.
This page is part of an Open Source Electric Car Project, and is written and maintained by Simon. At this stage these pages are constantly under revision. Thoughts and comments are welcome.