battery bank

Define "better".

This question is badly formed.

Please reform the question so it may be answered.....

Operationaly Ni Cad are more forgiving, longer lasting but more epensive. These will outlast several sets of lead acid if properly maintained, for the long term they are better.

You must remember that most lead acid batteries are not deep recycle, especially the ones in vehicles. You need the type that is deep recycle (apperantely quite expensive) or something more sturdy than lead acid and frankly they're probably the least environment friendly also.

Try to get in touch with battery manufacturers.

Since you are considering an expensive setup it is worth to research into this. You hear fancy talks on batteries but in all honesty the manufacturers themselves do not whish to be too open about it, as in how to prolong the life of a battery or anything like it.

I vaguely recall earlier this year, I think on one of the CR4 forums, an article about somebody in Canada with over 20 years experience on batteries who setup his firm to manufacture battery analysers, chargers and soforth so much so that his now got firms all over in North America and in Europe.

As the man said: define "better". There are lead-acid batteries in use for storage and conditioning of power (no surges or dips) that have been in constantUPS (uninterruptable power supply) use with minimal maintenance for years. The units are sealed, with a fiberglas mat that keeps the electrolyte in nearly a gel state for safety. There are several sources, including Exide/YUASA; I recommend you contact some of them for information. To the best of my knowledge, Ni-Cd would not be an ideal choice for this kind of application, but I do not claim to be the expert, I'm merely describing what I've seen in use.

You need to look at 4 primary factors:

1. Environmental conditions.
2. Voltage range of the motor.
3. Current requirement of the motor.
4. Length of time the motor is required to run while supplied only by the battery.

Environmental: Flooded lead acid batteries can handle higher temperatures better than NiCd. NiCd batteries can operate well at much lower temperatures than Lead Acid.

Voltage Range: NiCd batteries will provide the most stable voltage output of any power battery (I believe Li Ion systems have a flatter voltage curve, but high capacity systems are still experimental).

Current requirements: A series configuration of Lead Acid batteries can provide several thousand amperes. NiCd series systems are limited to several hundred amperes. To compensate, NiCd batteries are frequently found in a series-parallel configuration to allow multiple series sets to supply the load current in parallel. An additional consideration is the starting current of the motor. Lead Acid batteries are better at handling the surge (up to 6x running current) which occurs as the motor comes up to nominal speed.

Time: While NiCd batteries provide a more stable voltage until completely discharged, once the battery is exhausted, terminal voltage drops very quickly, down to 10% or less of nominal voltage. The voltage of a lead-acid battery will continue a gradual decline. If the load is truly critical, and the motor must run (to destruction, if needed) in order to avoid much greater damage to major equipment, lead-acid will provide a better voltage source to the "bitter end".

Without knowing more about the Power Plant, it is not possible to a give more precise answer.

Ni-cd is better because they are able to take repeated deep discharges without much damage. LA's will not last long under those condition but they are the cheaper . Ni-cds also require frequent watering and they gas alot so you need adequate ventilation to avoid an explosive condition in the air around the batteries as they charge

After reading some other posts. here's my bit (keep in mind my experience is mostly in standby batteries, subjected to major surge requirements quite often):

1. For a 48MW plant, consider using a consultant! You don't want egg in your face if the setup doesn't last.
2. Because of environmental issues, we shy away from NiCd batteries, rather concider NiMH.
3. Because of it's simplicity for the whole system (battery & charger), as well as the better early warning of discharge cycle, I prefer lead acid (LA) batteries.
4. There are various types of LA (& NiCd & NiMH) batteries available - I would talk to a few major manufacturers if I were you. They are usually quite good with advice, as they want return business, and must therefore make sure that what they sell will work well.
5. Purchasing cost should not be your major consideration, look at maintenance cost, maintenance expertise available, performance, disposal cost, sensitivity to lack of maintenance (robustness), etc. Look at posts #6 & #7.
6. We usually buy Planté LA cells, and some has lasted over 30 years, most go over 20 years. I don't know if they are suitable for deep discharge. Forklift batteries (& submarine batteries!) are designed for deep-discharge and are sold buy the thousands.
   
7. As a few posters have said, you need to define the word better for yourself in order to make an informed decision.

Let us know what you decided & why!

LAcid batteries "sulfate" quite easily which degrades their performance. You must immediately recharge them to prevent this after each use. For nicd you need to run them down completely and then recharge them. So they have different needs for charge/recharge. If you violate that with nicds you will not have a very good performance *(lazy memory they call it in which if you charge it to 100% then use it for 10 min you and recharge again to 100% , the next time you use them it will only last 10 min? strange but true) . NIMH is said to be unbreakable and doesn't have the lazy memory or the gassing or the watering needs that Ni_Cds have. The main benefit for Ni-cds over LA's is that they can't stand deep discharging alot better. We have drills that are years old and still carry the ball even now using nicds. but we carefully discharge them fully then recharge each time. NIMH beats both nicd and LA. www.peacenikinternational.com has some info on the NIMH you might be interested in.

The only powerplant that i've had the privelige to tour was a hydro plant; they were using Pb/acid to recover from a shutdown (excite the alternator fields)

Did you know that Jay Leno has a 1910 edison electric car that had the lead cadmium batteries.. they still hold a charge !!!! amazing.

There were several makes of electric cars - Baker Electric was probably the best known - and several of them are still roadworthy today using their original batteries. I have a friend in Arkansas that just got one, he drives in tourismos up around St. Louis every summer.

Yes .. thus you lend support to what I thought.. that LAcid batteries are the worst for lifecycle time. Nickel cadmium types seem to last for what 100 years now? Thanks.

Hello TRIPLEBATTERYLIFE,

The Edison Electric Car, would not have used Lead Cadmium batteries.

Well-known in the 1950's, and still used today, are the rechargeable storage cells as invented by Edison himself, with extremely long life, although not as efficient as some other cells.

These were Nickel-iron-potassium hydroxide cells, called NiFe when I first met up with them some 60 years ago.

These were at that time used in railway signalling, and flashing maritime navigation beacons.

For a description of the NiFe cell, and a lovely old picture, have a look here:

http://ieee-virtual-museum.org/collection/tech.php?id=2345874&lid=1

I trust this clarifies any misunderstanding, re the EDISON battery......

Hi Sparkstation,

I fully agree with you I have never heard of a lead cadmium battery.

As I mentioned earlier nickle cadmium cells last indefinitely, the nife cells were very good for this but were heavier and larger than an equivalent lead acid cell. the ones I had in mind are Ni Cads with sintered plates which can stand a discharge rate equal to any lead acid battery.

I am using 10 of these cell in my automobile which are only 27AH rated I have been using them for 10 years in this situation and the cells are actually over 30 years old. I would have gone through several lead acid battery's in this period of time.

Just consider how much pollution these cells have saved, trouble is battery manufacturers would not like the idea of autos using something that lasted that long .

Yep you are right. My mistake (staying up too late.) I think it was as you say Nickel - Iron . And the rumor is that Jay Leno's car still has em and they still hold a charge which gives them a lifetime of about 100 years. Neat!