NiCad versus Lead

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natfuelbill

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I am trying to learn more about NiCad compared to Lead acid batteries.

Yes, I know that the NiCad is much more expensive, but is it worth it?

I understand the NiCad is advertised as also much longer lived than the lead, is that your experience?

Is one NiCad the same as another? I am being presented with SAFT and EnerSys NiCad battery companies.

Applications are DC power plant 24V, and emergency lighting.

Have your emergency lighting systems, been run on 24Vdc loads, 110Vdc loads or 120Vac inverter fed?

Bill
 
I don't know if it makes much difference in this application. If I had to choose one or the other, i think I might go with lead-acid gell cells, but Ni-cads would not offend me a whole lot.
 
The use of one over the other depends on the application. Ni-Cad will tollerate high temperatures better and are less affected by cycling than lead-acid. For example, an outdoor battery/equipment cabinet without environmental controls would be better off with Ni-Cad. All lead acid batteries live best at or around 77 degrees F.

Ni-Cad batteries come in dfferent flavors as does Lead-acid. Flooded, sealed, valve regulated, High Rate, Deep Cycle, gel and so on. Proper care and maintenance are the key to battery life.

An indoor 24vdc power plant located in an air conditioned space might use VRLA (valve regulated lead acid) batteries and depending on the brand, could last well over 10 years.

Lower voltages such as 24vdc lighting applications are affected greatly by distance due to voltage drop in longer circuits runs. Consider using emegency lighting fixtures with LED's to save energy and a reduced load for the 24vdc plant circuits.

Remember. Most local fire-life-safety codes will require a 90 minute run time of lighting inverter systems to meet UL924 requirments.

I could go on and on...but remember that all compents in a public area emergency lighting system must be UL rated for this application.

Scott
 
I have been in the Telephone electrical design biz for about 30 years now and designed hundreds of DC plants.

Short story is no one in the biz would touch a NiCad battery for a DC plant, VRLA if space is a premium but no NiCad. Fact is a pure lead wet design will retain 80% of its capacity 50-years down the road, and NiCad and VRLA will have to be replaced in 5 to 7 years.
 
natfuelbill said:
I am trying to learn more about NiCad compared to Lead acid batteries. ...
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For your application, the lead acids, the main types are: (Yes I know I left out a batch of types)
1. wet lead-acid (with fill caps)
2. VRLA/AGM (valve regulated lead acid/Absorbed Glass Mat)

Each have different internal designs depending on the application. And get this - "Mfg color glossies from the marketing dept LIE" - Even the reputable ones. Disgusting but true. However, their tech depts tend to tell the truth.

So, when SAFT and EnerSys are giving their presentations, pay attention to what they are comparing their product to.

natfuelbill said:
...Yes, I know that the NiCad is much more expensive, but is it worth it? ...
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Depends on the application (I won't say this again - I promise) The cell voltage on ni-cads stays up clear to the end of the discharge curve. You can suck them clear down and not hurt them. Lead acids don't like to be pulled down at all. 20% is good, 50% is generally okay. Ni-cads shine where a high energy density is required - W-h/lb or W-h/cu-in.

Another issue is end-of-life disposal costs. Ni-cad disposal costs are really high - but I don't know how high, last ni-cads I dealt with was 20 years ago.

Charging thermal runaway is an issue with nicads (also with large VRLA banks). Should consider the charging system cost along with the batts.

natfuelbill said:
...Is one NiCad the same as another? I am being presented with SAFT and EnerSys NiCad battery companies. ...
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I have persomal experience with EnerSys industrial grade wet lead acids and they have a good quality product and tech dept. I don't have any experience with SAFT, but from what I have heard they are an equally high quality industrial grade mfg.

natfuelbill said:
...I understand the NiCad is advertised as also much longer lived than the lead, ...
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If you are comparing ni-cad to wet LA, as dereck said, wet LA will last 25 years plus. But, I've seen ni-cads still cooking along after 20 years as well - but I don't have much experience with ni-cads.

natfuelbill said:
...Applications are DC power plant 24V, and emergency lighting....
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Both applications off the same bank? I ask, cause emergency lighting comes in two flavors. One is about the same as the 24V power plant application, maybe 4 hours. The other is egress, 10 to 30 minutes.

natfuelbill said:
...Have your emergency lighting systems, been run on 24Vdc loads, 110Vdc loads or 120Vac inverter fed?...
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All the above except 125VDC instead of 110VDC and also a 4' fluorescent with a third tube and battery powered ballast (egress only)

I pretty much agree with dereck:
1. Wet lead acids (calcium based), low specific gravity, is first choice. Ventilation may be required, watered once a month, cleaned and tested twice a year.

2. VRLA/AGM if I can't use wet LA. If ventilation is a problem, or maintenance is a problem, or space is a premium. Figure on repalcing in 5 - 7 years.

Take a look at NFPA 70E for ventilation requirements.

Get your fire reg whiz to tell you about smoke detector requirements for battery rooms.

carl
 
Ryan -

I've never seen lithium-ion used for stationary service batteries. I'm really interested. Do you have any references or data?

carl
 
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