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Author Topic: Nickel Iron Cells, Charging circuit needed for one cell only  (Read 8700 times)
electricme
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« on: February 15, 2011, 08:00:29 AM »

Hi all,

I know there are other forum posts on the topic of Nickel Iron batteries, extrahappy  I came to post on one of them and it said it would be a better idea to make a new topic so I have.

This is what I have and what I need.

I have 40 Nickel Iron Cells, each one is rated at 300 amp hours, half of them went through the last floods we had in Queensland in Australia, so they will have suffered some deterioration.
Before this occurred, I noticed that there were a couple of cells that needed to be boosted, and I thought, has anyone built a battery cell charger for NiFe cells.

These cells are capable of being really abused (do this with Lead Cells and you will need to buy one again) and still recover from that treatment, I am hoping to do this just to see if I can recover the cell, in other words, over charge the cell, stress it and see if it will recover, nothing ventured nothing gained. If you are a Lead Acid battery chap and have great knowledge on these Nife cells then please put in your 2 bobs worth.

What do I need? a electrical circuit to make a single cell charger, and it must be able to put out 30 amps at least at 2 volts max.
 
I am willing to kick it off by suggesting I use a MOT transformer, pass two turns of heavy duty starter motor battery cable through the MOT as the secondary, what type of diode arrangement should I use? feed 240volts into what was once the HV windings to power the thing, after isolating the last turn that usually goes to the earth connection and connect that to the Neutral side.

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Alan
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« Reply #1 on: February 15, 2011, 08:25:56 AM »

If you use a toroidal transformer.

Any thing like this ( Ex equipment )

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2238320

Just wind a couple of turns of chunky cable
round the transformer, feeding the wire
through the middle.

Use any diode ( Ex equipment ) large.

More turn = more amps.

Use a heat sink on the diode.

Probably bits from an old battery charger
will do, you could even use the amp meter.

Regards

Alan
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rogeriko
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« Reply #2 on: February 15, 2011, 03:12:17 PM »

I have made several 2 volt chargers from old transformers. First find a big old transformer size is everything the bigger the better then remove the secondary winding whatever it was. Rewind a new secondary with heavy duty wire until you get about 5 volts ac, then wind another secondary the same number of turns and connect the windings in parallel this will give you more current. If you want wind another secondary for more amps. The output goes to a high amperage bridge rectifier 50 amp at least and then on to the battery.


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* 2vrsml.jpg (35.65 KB, 819x614 - viewed 654 times.)
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Philip R
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« Reply #3 on: February 15, 2011, 08:10:38 PM »

Always use a full wave rectifier arrangement, not half wave,  otherwise the transformer core will saturate and burn out the primary winding.

Can you access any good stud mounted diodes, something like a 25G80 from international rectifier or some equivilent, these are a bit overkill but they can take some serious current (abuse). Something like a diode from a rotating rectifier assembly.

Philip R
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electricme
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« Reply #4 on: February 16, 2011, 09:12:06 AM »

Hi all,

Thanks for the posts and I will answer them in turn Cheesy.

alan,
I have a toroid core with no 240 volt primary so I guess it rules that one out, but I still have my original MOT, it's been through the flood water, but it should have dried out by now. I agree with using chunky cable.

rogeriko,
First I can see you have a nice set of cells there, what capacity might they be? Paralleling windings is OK as long as the length of the wires around the core bobbin are the same length and they are in phase. Do I see a paralleled bridge rectifier setup in the photo? Nice.
I see some liquid on the top of the .......... where you have setup the transformer diode assembly, did you need to do some rapid cooling ha ha.

Philip R,
That's right about the half diode, usage, I have experimented using this to try and get a economical way to heat oil for a simplex heater, but that's a tale for another day.

I haven't thought of using stud mounted rectifiers, and may do so another time, in the mean time as I have bridge diodes I will use them.

I tried answering this morning but I added to many photos and stalled the thread, hopefully this will send and I will follow it up with some jpgs of my setup..

Thanks everyone for the advice.
 
 

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electricme
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« Reply #5 on: February 16, 2011, 09:34:51 AM »

Some of my ALCAD NiFe cells


* Photo0311.jpg (38.15 KB, 320x240 - viewed 707 times.)

* Photo0313.jpg (47.74 KB, 320x240 - viewed 574 times.)
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rogeriko
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« Reply #6 on: February 16, 2011, 09:43:54 AM »

My battery bank is made up from used 1000Ah cells from the phone company. The phone system runs on 60 volts or so and every 12 years they have to replace them whether they are good or bad. I live in Greece and because they havnt heard of recycling here yet they just chuck em out back. Now 18 years old but work fine, maybe you should visit your telecom company??  

The transformer is from an old 1600kva UPS with 2 parralled full wave rectifiers 50A (ebay) and the water is just from the rain,I left it outside but a little rain dosn't hurt. I use it to boost 1 cell if it drops behind the others instead of having to equalise the whole bank.
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electricme
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« Reply #7 on: January 09, 2015, 10:51:52 AM »

Hi Roger and any one reading this thread,
It's been a long time since I have been back here, my wife died in 2012 and so I had my mind on other things but in the last couple of months I have rebuilt my solar system and have had the electrician around to wire it back into the switch board to run everything except for the big airconditioner, electric stove and the hot water system. I ditched the Gas stove as I hear Gas prices will be going to 3 times what we paid for in 2010.

I have 12 x 80 watt panels (Pannel A)outside wired in series parallel, in full sunlight it's putting out 25 Amps 30 amps Peek at 24 volts DC. This is fed into a Solar60 Solar Controller supplying the DC to the 20 ALCAD 300 Nickel Iron Batteries. As I have another 14 solar panels (Pannel B) in the house ready to connect into the solar array, the present Solar60 will be over powered by 10 amps, (tried looking for a 100 Amp unit but they are scarce as hens teeth).
 I have ordered the Solar80.
There is a Dual 60 amp circuit breaker on the solar board, two strings of Panel A and B can be combined to feed into the Solar80 controller through a much higher capacity copper cable. I can monitor the Current and voltage from the solar panels either in open circuit or connected.
It's quite something to watch the analogue gauges as a cloud comes over so the current drops then returns as the sun hits the panels.

On the Battery side of things
I have a HUGE high current manual main cut off switch between the battery bank that feeds the CASA 6Kva Inverter, electrician put in a heavy AC cable from the generator room back to the 240 mains meter box, in the meter box there is hard wired a 64 AMP 240 volt change over switch, so if the solar system goes down for any reason then all I need do is switch back to town power.

The batteries feed into a KASA 6KVA Pure sine wave inverter, there is a disconnect switch wired in line for any emergency cut off in needed.
Bought a 8Kva generator which can feed directly into the KASA 6Kva to recharge the batteries if needed.

So far I can power the big computer and printer and run both fridges in the kitchen, as long as the sun shines I got free power  Grin
When I get the second lot of solar panels up I should be able to run the Air conditioner....... we can hope LOL

Essential Items one may need
Battery capacity LED Tester for 24v Batteries, connected across the battery it will tell me how much charge is avaliable.
20 AMP circuit breakers, each one to be connected between each 24 volt panel on the back of the panels (connected in series) output.
4 x 24 volt DC computer power supply fans, I want to argument the flow of air through the 6Kva Inverter
On the way is a Universal 24 Volt to 12 volt 60w/45Amp Car Power Converter, I have a number of emergency lightning lights under the house and a 12 volt window opening electric motor to supply power to. The extra capacity will come useful one day no doubt.
On the way is a Hantek 365A long time record voltage, current, resistance and capatance Data Logger, I want to record how much sunlight falls on the panels outside, seems to me there is data out there but I prefer to roll my own so they say.

Also getting 12v/24v Large screen LED Digital Volt meters so I can keep an eye on the voltage from a distance, there is nothing worse than having to get up real close up to a display to see what is happening with the system, large gauges are definatly the way to go.

I also have bought 2 more Charge Controllers, one for the wifes Gopha keep on forgetting to recharge the batteries so solar will do it for me, same for the ride-on mower, been too many times it was flat so the sun can keep them going.

Oh yes, I have got all this stuff off EBay, have to go cheap as I'm an Invalid Pensioner.
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bxman
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« Reply #8 on: January 09, 2015, 02:25:15 PM »

Have you considered changing the electrolyte in the 2 cells that do not come up to the mark  or at least check the specific gravity of the badly performing ones against the others .
 I am sure new electrolyte it will rejuvenate  all of your cells and will have a good chance of sorting your problem .

It seem like   according to
http://ftp://metalab.unc.edu/pub/academic/environment/alternative-energy/energy-resources/homepower-magazine/archives/15/15pg23.txt
1.19 - 1.22   is what you want

Testing this myriad of cells started with adjusting the electrolyte
of each cell to a specific gravity of 1.190 gr./ml..  This was accomplished
using a high quality hydrometer.  Use only a brand new hydrometer
that has NEVER been used to test lead-acid cells.  All cells that
were not yet reconditioned were filled with distilled water to the
maximum level mark on the cell's case.  The specific gravity was
then adjusted either by adding distilled water or more highly concentrated
electrolyte.  The concentrated electrolyte is a solution of KOH in
water with a specific gravity of between 1.19 and 1.22 gr./ml.. 
The cell was then charged and gassed for about 15 minutes in order
to completely mix the solution.  After another 10 minutes of charge,
the specific gravity was measured with a hydrometer.  It took several
such episodes to achieve the desired value of 1.190 gr./ml., approximately
40 minutes per cell on average.  Excess electrolyte was then removed
from each cell to bring the level to the maximum mark.

good luck you will not be wanting to replace with new I am sure .
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