[-] Why are there a different number of cells in a nickel cadmium battery compared to a lead-acid battery?
The natural electro-chemical voltage of the lead-acid cell is 2.0 whereas for the ni-cd it is 1.2. The number of lead-acid cells in a 24 VDC battery is 24 divided by 2, or 12 cells, while for the ni-cd it is 24 divided by 1.2, or 20 cells.
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[-] Can you determine the state of charge in a ni-cd battery by checking the electrolyte specific gravity?
No. Unlike the lead-acid battery in which the electrolyte takes part in the electro-chemical reaction, the electrolyte in a ni-cd battery merely acts as a conductor without changing its specific gravity. The electrolyte in a lead-acid battery is almost pure water when it is in a discharged state, making it susceptible to freezing in cold ambients.
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[-] Are there any maintenance-free ni-cd batteries, like the VRLA lead battery?
There are valve-regulated (VRPP) ni-cd batteries which are wet (flooded) and which can operate as long as 20 years without the topping up. Unlike the VRLA batteries they are not sealed.
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[-] What is the typical life of a ni-cd battery?
The design life of most industrial ni-cd batteries is 20 – 25 years when properly maintained.
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[-] Isn’t cadmium a dangerous material?
Yes. However the cadmium in ni-cd batteries is bound into the negative plates and so is not accessible to service personnel. However spent batteries should be properly recycled rather than being disposed of in a landfill.
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[-] How often do I have to add water to a ni-cd battery?
Depending on the application and the environment it should not be necessary to add water more than once per year. Valve regulated (VRPP) cells require much less frequent topping up.
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[-] Do ni-cd batteries fail without warning the way that lead acid batteries do?
No. In ni-cd batteries the active materials are mechanically contained in the plates so they cannot shed and cause build up in the bottom the cells thereby causing internal shorts. Further the internal plate connections are all steel which is either welded or bolted together. Lead batteries rely on lead connections that are relatively fragile.
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[-] Why are ni-cd batteries so expensive?
The initial cost of ni-cd batteries is high because nickel and cadmium are expensive and the manufacturing process is more complicated. However, when this cost is spread out over the life of the battery, the annual cost of ownership is almost always less than that of a lead battery that had to be replaced one or more times.
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[-] Why are there so many different kinds of ni-cd batteries?
The different kinds of ni-cd batteries are responding to the demands of the market. Because ni-cd batteries are so costly to manufacture, it is worthwhile making variations that closely match the requirements of the application.
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[-] Who are the major manufacturers of ni-cd batteries?
SAFT (France) and HBL Power Systems (India), which manufactures Standby Power batteries. Saft also sells batteries under trade names of suppliers they have acquired including Nife Batteries (Sweden), ALCAD Batteries (UK and USA), Emisa (Spain).
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[-] Isn’t the nickel cadmium business dying little by little?
While the industrial ni-cd batteries have not shown the explosive growth of lithium and low cost VRLA batteries, new applications requiring the reliability and performance characteristics of the modern-day ni-cd battery are surfacing constantly. In some cases, ni-cd batteries are being retrofitted where other types of batteries did not fulfill reliability expectations or otherwise meet customer needs.
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[-] Are there any recognized Standards for nickel cadmium batteries?
Yes. IEC 60623 and various national standards
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[-] If I am a user of nickel cadmium batteries, how can I be sure the battery manufacturer has provided batteries that meet my engineer’s specifications?
Every battery manufacturer should publish guaranteed performance tables for all of the batteries offered. These tables should include currents available, times of discharge, end-voltages and temperatures.
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[-] Why is it that when I ask a battery manufacturer for his recommendation for a starting battery for my generator he asks me for oil viscosity, battery temperature, number and duration of starting attempts etc. when the engine manufacturer suggests a lead battery with a certain number of cold cranking amps?
Because ni-cd batteries are so well characterized, it is possible to precisely select the correct (and therefore the most economical) battery for that application. The makers of lead batteries do not publish detailed performance figures so their selection is very imprecise.
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[-] Why do I need bigger batteries when I use dual starting batteries with a best battery selector?
Best battery selectors (BBS) utilize a diode in series with each battery thereby adding a voltage drop of between 0.7 and 1.4 volts. If the starting motor requires a minimum of 17 volts, then this voltage drop must be added to the 17 volts to determine the minimum voltage at the battery. A larger capacity battery is required to provide the required cranking current to the higher end voltage. The best battery selector’s supplier should provide you with the worst-case voltage drop of the BBS.
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[-] Why do some engines require a higher minimum voltage during cranking?
The engine’s electronic controls are typically connected to the starting battery. This means that the during engine crank the engine control computer must be able to operate normally when powered by very low voltages during cranking. Most control manufacturers design engine control computers to operate down to below the breakaway voltages specified in EGSA 100B Standard  (e.g. 13 volts in a 24 VDC system). Some engine controls companies, however, ignore the EGSA standard and provide engine control computers that must be kept above the EGSA-specified standard values. This design oversight requires a larger battery than is actually required to crank the engine – just to keep the controls operating properly. Find out from the engine manufacturer what minimum voltage engine’s control computer can tolerate. If it is above the values specified in EGSA 100B let us know the minimum tolerable voltage so we can size the battery properly for you.
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For engine cranking applications, select 10 cells for a 12 VDC system and 20 cells for a 24 VDC system. For 125 VDC switchgear either 92 or 95 cells are usually chosen depending on the maximum permissible float voltage. The Standby Power OptiSize program selects the proper battery in accordance with IEEE-1115 – 2000 Standard.
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[-] How do I determine the minimum voltage which is acceptable for my application?
The minimum voltage for any application is determined by the load that is connected to the battery. For engine cranking the minimums for a 24 volt system are usually 13 volts and break-away and 17 volts cranking unless there is a best battery selector or the controls manufacturer has designed his equipment for higher voltages. For 125 VDC switchgear, the minimum is usually 105 volts unless otherwise specified. The manufacturer of the equipment being powered is the final authority on both minimum and maximum voltages his equipment can tolerate.
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[-] What is the correct way to charge my ni-cd batteries?
Typically a ni-cd battery can be charged with any source that can put current into the battery – trickle charge, constant current, constant voltage or any combination thereof. Most real world applications require automatic re-charging and this is best accomplished by the use of a multi-mode charger which charges the battery at constant current until it approaches full charge and then switches to constant voltage to maintain the charge. Some manufacturers produce sophisticated chargers that periodically boost the voltage of the battery to achieve 100% charge.
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[-] How long does it take to charge a ni-cd battery?
The general formula for battery charging is:
I (recharge) = 1.4 x C / T where
I = Re-charge current in amps
C = Ampere-hours to be replaced
T = Time in hours to recharge
This formula will provide a rough answer.
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[-] How can I tell if my ni-cd battery is going to fail?
Instead of failing catastrophically, ni-cd battery performance gradually diminishes over their life of 20 – 25 years and end-of-life is assumed to be when performance is 80% of original
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[-] Do ni-cd batteries work in extremely cold or hot temperatures?
Yes. Operation in extremes of temperature is one of the great advantages of the ni-cd battery. They will operate in temperatures of –50 F (with artic electrolyte) to + 140 F
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[-] The recommended charging voltage is too high for my connected loads – what can I do about this?
The options for dealing with this are either to use a DC-DC converter upstream of the load, or use what are known as “dropping diodes”. These are series-connected diodes (chosen for the correct voltage drop) connected between the battery and the load. During the time the battery is being discharged, these diodes are shorted out by solenoids controlled from an automatic voltage regulating circuit
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[-] Are ni-cd batteries any good for cycle service?
Absolutely – ni-cd batteries have a much better cycle life than any other battery
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[-] Do ni-cd batteries need ventilation?
Yes – ni-cd batteries emit a small amount of hydrogen and oxygen during charging. Under normal circumstances the normal ventilation in a room is adequate the disperse these gases, but ni-cd batteries should not be installed in sealed housings (such as NEMA 12) unless special provision is made.
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[-] Do ni-cd batteries emit any dangerous fumes the way lead acid batteries do?
Other than the small amount of hydrogen and oxygen as noted above, ni-cd batteries do not emit the fine spray of acid that vented lead cells do
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[-] Do your ni-cd battery factories have recognized quality standards
Yes – to ISO 9001, certified by third-party assessors
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[-] Do your ni-cd battery factories have recognized approvals for environmental protection?
Yes – to ISO 14001, certified by third-party assessors
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[-] What happens when I need an emergency replacement cell for one damaged in transit or during installation?
Standby Power maintains an extensive stock of most of the batteries it supplies and can therefore replace batteries from its stock. When batteries are not in stock, replacements can be obtained on an emergency basis within 2 – 3 weeks.
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[-] Why do you refer to your nickel cadmium batteries as ni-cd instead of “nicad”?
“Nicad” is a registered trade name owned by another company – we use the generic ni-cd that describes the active elements in the battery.
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