Nickel Hydrogen Batteries by NASA | Hacker News Reader

Nickel Hydrogen Batteries by NASA

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138 pointsel_snark95 comments

I visited the NASA campus in Cleveland, OH many years back and got to talking to one of the engineers who worked on this tech for the ISS. The batteries they use up there run $10k a piece, but he stressed how rock solid the chemistry and design is.

Nickel hydrogen has incredible endurance, but the part that really struck home with me: they measure the state of charge with a pressure gauge.

It's strange they didn't compare these batteries to lithium titanate, which is the other chemistry that can do 30,000 cycles and is something anyone can buy right now. They have extremely high charging C rates and sit somewhere between normal batteries and full capacitors in what they can do. They end up being about 50% more than LiFePo batteries in cost.

The numbers thrown out for this (~$60/kWh) are comparable in price to what LFP might cost in the next couple of years, the C rates for these are much lower (C/2).

This sounds great on paper but there’s a couple of questions left hanging:

> We take the battery, put it in an open fire, and watch it continue to heat up. What ends up happening is that the pressure above top charge will force the hydrogen back into water. And then we have a release valve designed into the unit so at a predesigned pressure and temperature that will release, and you’ll get a steam vent.”

But what about the hydrogen ? doesn’t that risk getting vented out with the steam ? into the barbecue ?

What’s the self discharge characteristics ?

A hydrogen fuel cell also vents and you can ignite the concentrated stream like a blow torch. At 5% the pressure of a H fuel cell, the battery probably vents less hydrogen.

How are today's batteries doing when put in the barbecue fire? The new ones only need to not do (much) worse.

How batteries do when placed in a barbecue is, for most applications, much less important than how often they spontaneously initiate a barbecue.

I laughed, but is that really true? You're going to have a lot of batteries/cells in one place, and one will inevitably start barbecue. Isn't the question whether the rest joins?

I suppose it is probably hard to engineer a battery that is prone to spontaneous barbecues but resistant to the influence of outside barbecues. But I'm not sure I agree that it's just a numbers game that if you put enough of something in one spot, some of them are bound to suddenly catch fire without outside intervention.

> But what about the hydrogen?

Doesn’t it say the hydrogen is vented as H2O?

I think the parent is assuming that there isn’t conversion. In the same way that electrolysers electrodes also have H20 in addition to O2 and H2.

Re-reading the article, it sounds like maybe the venting happens at some pressure high enough above the point at which H reacts back to H2O that there’s none left ?

Can anyone comment on the design of the cell, specifically why it is long and thin, which would work against the square cube law. Is a large surface to volume chosen for thermal reasons?

As I understand it, something like a lead-acid battery using volumes of acid and volumes of reactants so a cube gives them more power with the same surface area. NiMH batteries use boundaries between states instead of acid. Therefore, you want long thin batteries of alternating materials to make them more efficient.

Or, to put it a different way, NiMH batteries require a large interior surface area, and so the square/cube law forces them to look longer and thinner as they get larger.

As per the article, these Nickel Hydrogen batteries are very different to NiMH

> Nickel-hydrogen batteries look and work unlike any other battery. They consist of a stack of electrodes inside a pressurized gas tank. The cathode is nickel hydroxide while the anode is hydrogen. When the battery is charging, a catalytic reaction generates hydrogen gas. During discharge, the hydrogen oxidizes and converts back to water.

Sorry, yes. I was, however, describing my understanding of Nickel Hydrogen batteries' relationship with the square-cube law. Not NiMH.

See this diagram: https://en.wikipedia.org/wiki/File:Nickel-hydrogen_battery_N...

The cells are pressure vessels, so normal cube-square scaling laws don't apply. Instead you need to use pressure vessel scaling laws, which also account for the needed wall thickness.

Pressure vessel scaling laws say that all cylinders have the same mass efficiency, and making long thin cylinders is easier than making short squat cylinders.

> So far, EnerVenue has been operating a pilot production line that can manufacture 100 megawatt-hours’ worth of batteries per year—and they’ve deployed small-scale test systems. But, says Heinemann, the company already has over 7 GWh, or about 400 million dollars’ worth of purchase orders...

We should soon see if this is a viable business then.

> 7 GWh, or about 400 million dollars

This implies a bulk cost of about $57/kWh which is slightly cheaper than present day LFP (the primary competitor for grid-scale battery storage). IMO, it needs to be no more expensive than LFP, because LFP cells can be spec'd for ~8 years and it's hard to get people to invest on timescales longer than ~10 years.

There are many grid battery technologies common on right now, liquid metal battery, IronAir battery and many more. And all of those have lots of 'orders' that they brag about.

I enjoyed this video about this topic: https://www.youtube.com/watch?v=2zG-ZrC4BO0&t=189s

I'm curious how they solved the hydrogen leakage/seepage problem through the walls. Even though it is designed for many (daily?) cycles and not long-term storage, it seems that H2 is in the tank anytime there's a charge ready or building. Maybe the pressures are low enough that it's insignificant even over 30k cycles?

Or does it just require occasional recharging with water or H2, and if so, what is the value of "occasional"?

Since it's relatively low pressure (5% of a hydrogen fuel cell), couldn't they have larger batteries for grids? The current size would be great for homes.

That looks suspiciously similar to a standard gas tank size.

Generally you make a battery by combining cells - they have a 1-1.5V terminal voltage. The image lower down shows a rack of them in a warehouse. I suspect you'd stack them up to a few hundred volts and plug them into an inverter.

I wonder if they require the same balancing as more delicate chemistries.

EnerVenue's website has some claims that imply (but do not state, and remember this is marketing material!) it is much less delicate:

1. No thermal runaway and "phenomenal overcharge, discharge and deep-cycle performance"

2. "Flexible charge and discharge rates"

3. "Vessels can discharge to 100%"

4. Specified charging rate of C/12-C/2 (i.e. can be charged at rates from 1/12 the capacity per hour to 1/2 the capacity per hour)

They do require usage of a tiered BMS though: https://enervenue.wpenginepowered.com/wp-content/uploads/202...

This video discusses that: https://www.youtube.com/watch?v=2zG-ZrC4BO0

But, keep in mind that Undecided is overly optimistic about pretty much every emerging technology.

30 years lifetime sounds great. But doesn't hydrogen diffuse through metal? Can it be contained such a long time?

The use case for this is to charge the battery during the day and discharge it during the night. It is not for seasonal energy storage. There are no batteries that can be used for seasonal storage, nothing comes within a factor of 100 of being economical. But batteries for seasonal storage requires very few cycles, one per year. This battery here can go through many thousands of cycles. If you don't use it for daily storage, you are paying for something you don't need.

When they are at full charge, they have H2 at 300PSI. Assuming they spend a significant fraction of a day at full-charge, after 10 years they will have totaled a significant fraction of 10 years at 300PSI.

GP's question is "Will the H2 migrate through the pressure tank after such a long time?"

So all these years we've been looking for the anti-gravity chamber and they had this!?

The edited headline (Nickel Hydrogen Batteries by NASA) is incorrect; the technology is from NASA, but the batteries are from EnerVenue.

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