Free NiCd Batteries

[Yianie123.]

Hello, still new so here it go's.   I currently have 1400w of solar panels on grid tie inverters.  My problem is that I make way to much power during the day, and return about 4kw back to the grid.  Not getting paid for it because there is a premium cost to me for the utility company do to the math.  So they sell my power extra power and I get nothing.  I have run across batteries where I work that will soon be disposed of.  They are 60AH 1.2V NICD, used to start a large generator.  I would like to somehow use these batteries.  There is enough for a 12V system, but I always thought a 48V would be better.  The idea would be to get off the grid, charge the batteries with solar, build a wind turbine 48V tie everything into an inverter to the main breaker box.  Tie the utility grid also to the inverter as a back-up.  Thought one day of living off the grid and this would be a stepping stone.  Please give me your opinion on the best usage for these batteries and please tell me what most off grid house use for voltages 12, 24 or 48V.  Have this crazy idea of living near the beach off the grid either in the USA or back where my mothers from, the island of Mytelene, Greece.

[Frank S]

Since you are currently grid tied. You  will find that going off grid is going to be both expensive and will initially at least cause you a lot of headaches.
  I think most here will say it would be better to create a dedicated off grid subsystem with storage to use your solar. With that you could use the grid as if it were generator support Via a battery charger for the times when RE could not bring the bank up to float.
 Since you would no longer be grid tied you would still have power when the grid goes down
 The subsystem would have to have its own panel as well that in no way would be connected to the mains at least that is how I interpret the way the electrical service provider demand things be done in my area.
  But before doing anything you need to know just how much energy is being used by which appliances + their high time overlap usage start up watts and so on. This would give you an idea of how many circuits could be removed from the grid and installed in the subsystem.
 I have 1100 watts solar 850 Ah of storage in my RV it is off grid but when we need to switch on the air-conditioning we have to start the generator. otherwise on good RE days the solar can power everything including have a little left over for me to run my lathe   

[Bruce S]

To answer your question about the NiCd batteries. The short answer is; yes!
At my former employer I used to get NiCd battery packs that were taken out of service as well.
Do a search for a long time forum member " Norm" he is the guru of putting that packs to some great uses.
Now, the 60Ah ones are much more useful.
There is some things you will need to find out and let us know too.
Are those batteries solid types or wet? There are some considerations both.
Another great member and former Moderator "TomW" has posts about his large NiCd packs too, so you might want to read up on his as well.
When you say there is enough to make 12Vdc, how many is that specifically?
NiCds both wet and dry are when fully charged and resting at 1.36 - 1.42 per cell and quickly drop to the 1.25 per cell when under a load.
You can quickly see that these voltages are under the normal voltages for LA based batteries, so you will need to make adjustments for the differences. Most of the larger inverters will complain about this.
The packs I use are solid and only 16Ah max, but they are great for heavy or high drain situations as they hold their voltage until nearly dead.
NiCds can also take a nearly complete drain and bounce back like a happy puppy :-).
IF you have 11 or 12 of the NiCd batteries, you could actually mimic a L.A. system by using them to account for the lower voltage or what I know of as voltage sag.
Just know that NiCd are constant current charging batteries so you will need to adjust your thoughts on a charging circuit.
A picture of on of the batteries would be great.
Still,,, with the little amount of mental change, those are a could be a great addition
Cheers
Bruce S
       

[dnix71]

Like Bruce said, 10 cells will look low to devices run from 12v nominal systems. 11 is better under load, but you can't fully charge 11 cells to 1.35v/cell or you will go into what most inverters consider "overvoltage."

16v is a common capacitor rating so somewhere close to that is the absolute limit for a battery powered "12v" inverter.  My Prosine squeals at me and will not operate above about 15v. Blowing a large electrolytic cap is like setting off a grenade.

24v inverters are common because that's the nominal voltage for trucks. 21 cells of nicads is a much closer match for 24v lead-acid chemistry voltage range than 11 nicads is for 12v systems.

36v inverters are rare.

48v inverters are the limit for home brew in the US, as the NEC considers 60v to be high enough to require permitting and inspections, meaning your insurance won't cover you if something goes wrong and you ignored the NEC requirements. A fully charged nominal 48v lead-acid string is 56.8v but to properly equalize the string would require going over 60v. At 48v nominal, 42 nicads fully charged to 1.35v/cell would be 56.7v, and under load would drop to 50.4v. That "48v" nicad arrangement is an exact match for the range of lead-acid.

[Yianie123.]

Picture file is to large.  Send you email address to john dOt vasos  AT gmail DoT com and I will mail picture

[DamonHD: don't put email addresses here in plaintext or you'll be SPAMmed to death.  Also, can't you just shrink the image first then upload it?]

[Yianie123.]

Thank you everyone for commenting on my question.  I spoke to the manufacturer service tech on these batteries and here is what he told me.  These batteries are used for quick discharge.  There application is for starting large generators.  Each cell is 1.2V -60h and should be charged hard for 2 hrs with 1.56V.  When the cell is at 1.52V stop charging and float on 1.42V.  They are considered drained at 1.0V and can be recharged to 100% at that point.  He also said that  these batteries  require a quick and hard charge and quick discharge to stay alive.  At the end of there life, it will cost about $.40 a pound for disposal.  After considering the requirements to keep the battery in tip top shape, my best judgment is to pass on it.  Am I being foolish?

[dnix71]

If they cost $0.40 to get rid of, they are not free. A 1.42v float is high. They must have been designed to sit for long periods. The hard charge churns the electrolyte. NiCads have toxic cadmium, but they also can withstand a dead short better than any other common battery type. That's why they still find uses. Nickel metal hydride would be worth money for recycle because they have no cadmuim, but they won't put out the dead short current that a nicad wil.