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Ni-Fe Batteries

Q23:Adding fourth MPPT, facing EAST

Begin with setting up steel frame, and placing the panels in place.

Than crimp/cut and join the panels together

I join the =ve and -ve into the Anderson Plug, but cut the other Anderson plugs and crimp and join them (cheaper option).

Two in series and two in parallel.

Next wire the leads to the Mppt on the board, with 30Amp fuse.

Ensure blankets cover the solar panels to prevent shocks (ie 70V DC at 9 Amps).

Switch on the fuse to set battery voltage to Mppt.

Than wire in the wires from the solar panels into the MPPT.

Install the ammeter (Halleffect) and I name this MPPT "Canada", after the manufacturer.

The bluetooth APP allows you to wirelessly connect and update firmware.

Join the MPPT to the existing network (do not touch leave network)


70Volt 6A changed 29V 14A FLOAT


30Volt 10A changed 29V 12A on FLOAT


74Volt 5A changed 29V 11A on FLOAT


75Volt 1A changed 29V 2A on FLOAT

Notice the fourth MPPT box (red arrow).

MPPT Canada, faces due EAST, on FLOAT.

Notice the fourth string of solar panels faces direct EAST and the main strings (3 of them) face NORTH.

A proposed fifth string will face due WEST.

How the solar panels look on the ground facing EAST.

OK so what is the battery up to?

Switched OFF all solar panels at noon,

The voltage is 29V and all loads are ON (fridge, water and bore pumps)

See how long this medium loading lasts

Going to flog the Ni-Fe to death 'so to speak'.

Summary for first flogging day:-

Time VoltageAmp Out Cell V
12:00 2943 1.43
12:06 2843 1.40
12:08 2743 1.37
12:10 2644 1.36
12:15 2644 1.35
12:17 2645 1.34
12:25 2546 1.33
12:30 2546 1.33
12:33 2449 1.31
12:50 2350 1.28
12:58 2252 1.26
1:05 2154 1.25
1:10 2056 1.23
1:13 1958 1.21
1:16 1861 1.21

Switched the solar panels on, but they went to FLOAT...bother (fuse in wrong place).

One needs a fuse before the MPPT for all incoming solar wires as well.

The total discharge of the Ni-Fe batteries was 1600 W or 66Amp/hr

Will repeat this tomorrow, and try to flog batteries, hence increase capacity.

First day for Canada, my EAST facing system, and I got 7 amps at just 6:30 am on a cloudy morning. Great. Was able to power the water pump from 6:40 am. And hold the voltage up.

Since my flogging yesterday, I have at ABSORB (11am) 1.59V on my Ni-Fe cells !!

I am so excited!!!

Can't wait until they all reach float, and test my battery capacity again, by 'flogging them to death' with turning OFF the charging and run a medium load of 43 amps again.

Loading 40 amps is medium, I have read Ni-Fe at 500 amp/hr can handle up to 120 amp discharge.

But hey, a great sign of recovery so far...


Some maintainence on my batteries:-

Notice some pitting of the positive end cell, the vertical pipes remove the misting and H2 gas, but while removed for adding water, causes misting (splashing of the KOH).

The shunt I added, cutting the negative copper plate into two, ( a cheaper alternative than bus bars, $500 etc. My idea cost $40)

The brass bolt and nut is coming soon. The entire -ve current runs through this single wire, from the shunt, a 200 amp cable?

The only load on at the daytime, is the fridge, mere 6.6 amps.

Apart from my water pump loads, the system is too light for 500 amp/hr Ni-Fe.

I need to daily or weekly it seems to flog the batteries with a 100Amp load.

Notice the halls effect ammeters are cheapest alternative to get facts about every wire.

Far quicker looking at 12 ammeters, than a Victron BMV 712, plus MPPT displays.

I get both forward or reverse current (ie charge or discharge) plus voltage.

Looking into the cell to check water height.

Notice the big cable end to join the two battery banks together, rated at over 350 amps (I got it second hand from metal recycler for $10, it's 10mm diameter or 150mm2).


Voltage cells climbed to 1.61 but fell to 1.43 at float. Never had 1.61V before :)

It took 9400W to charge or 400 amps. Let's see if I can get 400 amps out of the batteries, first switch off solar panels, and than switch on medium loads.

Summary for second flogging day:-

Time VoltageAmp Out Cell V
3:50 2744 1.38
4:00 2744 1.37
4:10 2744 1.36
4:25 2642 1.34
4:30 2642 1.34
4:40 2643 1.32
4:50 2548 1.31
5:00 2548 1.31
5:15 2449 1.29
5:20 2450 1.29
5:30 2351 1.28
5:45 2252 1.24

I will stop it here, leave a bit for tonight The results are amazing.

Compared to yesterday it took more time to reach a low battery voltage level. About an extra 30 minutes. The total discharge of the batteries was 2300 W or 95Amp/hr

Based on yesterday, compared to the second flogging, my battery capacity has increased by at least 150% !!

I think we are onto something here.

The drainage on our batteries during the day and night is far too low.

They need flogging some more.

Soon we are getting a 1500W water distiller, that should 'flog more stuff'.

Maybe we should get an airconditioner as well for 'night flogging' too.

And even an electric toaster would be nice for breakfast time.

I will have to get a second hand 4000W Victron Multiplus Inverter (a family friend gave it to us) and run a special 15 amp cable from this to the house, for the BIG loads.

This shows the increased capacity of battery (shaded blue).

The lines show the difference between the first day of flogging and the second day of flogging, for a discharge of over 40 Amps.

From Internet Ni-Fe data :Source

Battery charging must be between 10 Amp and 125 Amps.

Maximum continous charging to 200 amps.

Optimum discharging of current is 125 Amps.

No wonder I have not been getting my capacity, I need to flog my batteries more with bigger loads, even much greater than 40 amps.

This is outside my design, I wanted a smaller drain on current (40 amps) with two, to three days of storage. For cloudy or rainy days.

What I will have to do is have a massive 100 amp load on standby and switch it on every now and than, maybe this will work ensuring the capacity and health of my batteries is maintained.

Last night the voltage climbed to 25V despite being flogged down to 22V.

So I ran the fridge and fan loads to midnight before going flat.

This is an additional 136 amps or (3300W/24), The batteries gave us as power.

The total current drawn on the second flogging was 230 Amp/hr


Do not lose your confidence in Ni-Fe and you will be richly rewarded. These are forgiving Ni-Fe batteries.

Looked for more loads, water pump (20A) bore pump (20 A) washing machine (7 A) fridge (3 A) as many as I have for now, the draw ranges from 43 Amps to 56 Amps.

Summary for third flogging day:-

Time VoltageAmp Out Cell V
4:20 2940 1.41
4:30 2741 1.38
4:40 2656 1.35
4:50 2743 1.3 5
5:00 2653 1.34
5:10 2652 1.32
5:20 2643 1.32
5:252644 1.32
5:30 2544 1.31
5:40 2545 1.31
5:50 2445 1.30

Total discharge for the 1 hour 30 minutes was 70Amp/hr

Switched on small loads, solar panels on, at 6:05pm, the batteries have +8 Amps coming in, no loads, with Voltage of 27, or 1.35 cell voltage. ( Big loads gone onto mains power).

What does this look like as a graph compared to the other 2 days of flogging?

Looking at the graph, the increase in the batteries is still increasing, but the affect is slowly down, the voltage drop is lesser over time, and the current increases less. The batteries are holding their reserves of current better too.

Even though the batteries went down to 1.31 cell voltage under a big load, under a small load the batteries recover.

So with monitor clear history again, I will see how much more discharge the batteries can take under the night loads. ( I have removed the bigger loads from the battery, and placed them on mains power).

The batteries only have to contend with a load of 6 amps into the night for now.

The batteries reached 19 Volts at 4 am, so I turned off the fan (1.5 A), but the light load of 6amps (fridge) I left still on.

The total consumed so far is (138 + 70 ) 208 Amp/hr.

This is getting close to the second day of flogging. Overall, about the same.

Some good advice from David Bartlett, Iron Core Batteries, a great person of experience, who sold me the batteries from Victoria:

"Just because someone has put up details on the internet doesn't mean it's correct.

To get the electrolyte and battery temp to 46 degrees would be a challenge in it self. We have cells in far north Qld, Darwin and top end of WA working fine.

Overcharging does not shorten the life of the battery.

I have a set of 12v X 400ah cells that directly connected to a 24 volt wind generator and were regularly charged at 34+ volts for months and are now over 11 years old and still working fine. Delft University bought some of our batteries a number of years ago and on purpose significantly overcharged them for testing purposes. They proved nickel iron batteries work better when overcharged. The negative is you need to top them up more often. Discharging the below .9 volt per cell turns them from a secondary cell to a primary cell and does slowly damage them. This was identified by University of Southern Queensland who bought some cells from us and provided us with results of their testing.

We recommend over 80 amps while charging and while exercising the battery(raising the capacity) long and low discharge (low amps) overnight to get the battery cells down near .95 volts per cell.

When they are getting through the night without the inverter turning off for a week or so, add some more load and when this load makes it through the night for a week or so add some more loads until the cell capacity is reached.

High discharge loads does not exercise the batteries.

Once the batteries are working fully you can put high loads onto the battery but no different to other battery types, the higher the load the less you can take out of a battery. Low discharge can give you more then the rated ah capacity if the battery is at capacity.

I hope this helps."

So it seems flogging helped a little, but it's usefulness is limited. What I require is a system to manually overcharge my batteries, at around 100 Amps, for 6 hours. And than drain them slowly on my inverters through the night until capacity is reached.

Might have to try the gentle touch after the hard charging routine?

Gentle discharging all night (7 Amps) it's nearly 6:00am, the batteries are on 25V still, discharged 108Amp/hr, charged 366 Amp/hr, so should be plenty still in them.

Didn't happen that way. Got little out of them.

Went to town and left batteries to the solar controllers, the only load was the fridge (6 Amps). They only put in 30 amps than went to float. Running a water pump for a few minutes after coming back from town, the batteries went flat (19V 1.32 cell voltage). So I am forced to have no storage for the entire night. Not happy Jane?

We got a new fridge, that runs on between 3 to 6 amps. 900 litre Fridge/freezer. It's night time, voltage is 25V used 104 amp/hr and the batteries received 387 amp/hr of power.

Things seem OK for now.

Too much trouble getting a solar cell and relay to switch ON during light, not OFF during light, as night switches do.

So purchased a cheap ($13) mechanical timer with clock, and with 15 minute switches all around the 24 hours. (96 switches in total)

Hooked up the 240V timer to switch ON between 7 am and 3 pm. This should reduce drain on battery until sunshine hits, though may be bad for a cloudy or rainy day.

Also installing another high pressure low volume pump for water irrigation, with timer. Here the pump only runs for 30 minutes starting at 8:30 am.

This removes the need for the water controllers, and blocked irrigation nipples using bore water. Instead I have a single 600m 32mm water pipe, running in two loops back to the water tank with a gate valve. This gate valve allows me to adjust the pressure and volume flow to 90 (2mm holes) 4mm nipples, which has a larger hole, hopefully not blocked so easily by the bore water. I am trially this new system, that it works OK.

Trees irrigated by small flow (red arrow)

Uphill from water line, flows less.

The 24V pump to run hot water system.

Canada early sunshine capture already on 11 Amps, makes early recovery on batteries.

The Multiplus 3000W Inverter, awaiting installation, for bigger loads.

The big Multiplus Inverter is the same capacity as the five smaller ones.

However during power failure the big one costs $2500 while smaller ones cost $630 each. ( Consider redundancy factor)

Consider maintenance costs for long term.

Same idea with 5 smaller 100|30 MPPT's ($350 each) verses a larger more expensive 150|100 SmartSolar MPPT ($1,300).

Other day, lots of bore pump and water pump, going on holiday, so getting garden ready, noticed the batteries went to bulk in the middle of day. Never happened before. The power consumption out rated the power coming in. So the batteries got charged a second time in the one day, with chargers all on BULK. The night load nearly didn't make it, with 20V 141 Amps removed and only 179 Amps went into the batteries. Looks like that fifth string of panels facing WEST is a must. Also need more panels to build a manual charging system.

That means getting 30 solar panels (second hand with amps ranging 3 to 5 Amps) at say 34 Volts, and 6 0 to 90 Amps. I string them all in parallel, with 35mm cable, and switch them directly unto the batteries for 6 hours, say 6 x 80 = 480 Amp hrs. The one cycle will overcharge my batteries reduce water loss, but give me back my storage capacity. Such a system has no bulk, no absorb and no float, its a pure 60 to 90 Amps for the full 6 hours.

The timer on the bore pump is helping with reducing loads for night use, it switches off the bore pump at 3 pm.

Next we look at running bigger loads, and the manual overcharging of the batteries.

Ni-Fe battery technology

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