More on Nickel Iron batteries….

24 07 2018

You read a lot of rubbish on the internet about batteries. It’s usually written by people who have very little experience with them too… for instance…:

The BIG reason to NOT buy NiFe batteries is they are incredibly expensive, they are charging you 9x the price of a lead acid and guarantying you only 5x the life. 

In reality, a Nickel Iron battery costs about double the price of a good Lead Acid battery. For example, a 12V, 300Ah Giant Power Sealed AGM Lead Acid Battery cost $669.00 online. This battery is rated at 1,850 cycles @ 30% DOD, which is 5 years. A comparable Nickel Iron Battery would be an Ironcore 12V, 200Ah battery rated at 7200+ cycles, which is 20+ years. This battery will cost you $1480.00……  and in reality give you more capacity than the above. It’s difficult to make a proper comparison, because in truth we’re comparing apples with oranges here….

So, if you are off grid and using your battery everyday, over a 20 years period you would have to replace that lead acid battery bank 4 times, and maybe 5 times….. With Nickel Iron you will never have to replace the battery, so over a 20 or more year period, you would have definitely saved money. More importantly, there will come a time it will be impossible to even replace the batteries!

NiFe batteries are VERY inefficient, which means a significant fraction of the energy you put in, does not get stored, something like around 25%. 

I am going to break this down into 2 parts. First, we are going to talk about Nickel Iron Battery efficiency, and then we will talk about Lead Acid Battery efficiency.

Nickel Iron Batteries are about 75% Efficient. The cells have been tested at the National Renewable Energy Laboratory, and below are the results. Overall at normal temps, they out performed their rated capacity between 75-80% efficiency.

Lead Acid Battery Efficiency – Below is a link to the Sandia National Laboratories results on Lead Acid Battery Efficiency. According to this document, they found out that when you are only using the top 20-30% of a battery, it really only has a charge efficiency of 55%.

http://ironedison.com/images/Spec%20Sheets/Test%20Results/Sandia%20Labs%20Lead%20Acid%20Efficiency%20Test.pdf

So after looking at the actual data – the nickel iron battery is more efficient than a lead acid battery in daily off-grid charging, because you can discharge them as much as you like, and as often as you like without causing any damage whatever…. living with NiFe batteries is a completely different mindset that took me ages to get used to!

They are VERY VERY gassy, that is why there is such a huge head space on them to hold SO MUCH extra water, which MUST be distilled water ONLY. 

Nickel Iron Batteries do off-gas a little more than a lead acid battery, but this is because of the differences in the batteries’ chemistry. Both a wet lead acid and nickel iron battery require to be put in a battery box and I recommend using a vent fan or a whirly bird or two as I did in my container station.

The Nickel Iron Battery produces hydrogen when the battery pushes the oxygen from the water molecule to increase the oxygen concentration on the nickel plate. The head space is not huge on a nickel iron battery, but you do want an area for the electrolyte so you are not having to fill the battery with distilled water all the time. In my experience, I have to top my batteries up three times a year which takes about 20 minutes… 1 minute per cell.

A wet lead acid battery produces hydrogen through inefficient charging, when the electricity not used from charging is spent on splitting a water atom.

Both a wet Lead acid battery and Nickel Iron Battery use distilled water only. A sealed lead acid battery does not need water and does not off-gas, but has a much shorter shorter life if cycled everyday…..  or even if not cycled every day. I had sealed lead acid batteries in Cooran that were floated all day long that lasted just long enough to go out of warranty which was two years! A friend of mine in Queensland bought better quality ones that lasted six years….

They have a high rate of self discharge, so if you just leave them there, they can loose 10% or more of their charge PER DAY.

In reality, Nickel Iron Batteries have a 1% self discharge rate, or possibly less. I recently disconnected two cells, out of forty, to force charge the remaining 38 in winter. when I reconnected them four months later, those cells’ voltage had dropped from ~1.6V resting to 1.32V…. thats less than 0.3V in 120 days! If you are wanting a battery that will just sit there and not be used, then you might want a sealed lead acid battery. Sealed lead acid batteries are good for people that are not using their battery and want it to just sit there and hold its power in case the power goes out once a year or so…. personally, I think that’s a waste of time money and resources, last time I did this the batteries lasted just two years….

If you plan on using your battery every day, it really does not matter if it discharges 1%, because you are going to charge up the battery and use the batteries power next day. In my experience, that overnight loss is regained in the first twenty minutes after sunrise, so it’s a non argument……

edison EV

Thomas Edison with early EV

Of late, I have been thinking more and more about an eventual conversion of my trusty 4WD Bravo to electric drive. Never forget that NiFe batteries were originally invented for the very purpose of driving electric cars at the turn of the 20th Century……

Ironcore, from whom I bought the powerstation’s battery bank, sell 12V 10Ah batteries (actually 10 x 1.2V cells connected together) for $270. To achieve 120V por motor power, I’d need 10 of those giving me a capacity of 120V x 10 Ah = 1.2kWh or barely what’s in a litre of petrol! The old ute would go about 10km on that amount of fuel, but as electric motors are twice as efficient (or more) than ICE’s, it’s more likely it would go 20km. Furthermore, because NiFe batteries can be discharged far more than other types, it’s possible the ute would actually go farther, but of course that’s hard to predict…

Image result for 12V ironcore battery

10 of these connected together make a 12V battery

By having two such banks in parallel would double the range, which is probably about as far as I would need to go, especially after everything’s shut down from lack of fuel! Gathering firewood would almost certainly be its biggest task, and the forest is not very far away at all.

Out of the blue, an article about enthusiasts like me converting ICE cars to electric drives came up on out ABC internet website, which is what prompted me to write this while spending time in Queensland, supporting my better half looking after her 94 year old mother while the Tasmanian winter weather does its thing…. and the prime subject of these conversions is a ute, though unfortunately, while the batteries are mentioned, they are not shown, so I have no idea what this guy used… there’s a video at the link.

http://www.abc.net.au/news/2018-07-24/make-your-own-electric-car/9918964