NiMH batteries (idle thoughts)

[David Paste]

Everyone goes on about lithium batteries as the goal for cars, etc, and whilst they have a higher energy density, that 'ultimate' performance isn't always needed. Milk floats got by on lead acid batteries, so surely they would be a fine candidate for NiMH replacement (I'm thinking of smaller batteries for a greater load of milk or whatever). Also, speaking to the local Evri delivery guy, he does about 20 miles a day in his Ford Transit, surely that would be an ideal vehicle to be electrified, and NiMH would surely be 'better' in terms of cost and environmental issues than lithium batteries?

So, what I have I got wrong? Is there anything obvious that I am missing / don't understand?

Is Lithium worse to mine and process than NiMH? What about the recycling of each? Other than capacity, are there any operational downsides of NiMH? (I think Toyota use them in their hybrid vehicles)

Thanks in advance,

David Paste.

[alan_m]

The milk float crawling back to the depot at 1 mph at the end of the round?

Some of the current crop of electric vans have a range much less than than cars and with centralised delivery hubs many delivery companies around my way are doing 60 miles to and from the hub before considering the mileage covered delivering 100+ packages.

[Rod Speed]

No, but the problem is where its mined. Not a problem for Australia given it has lots of those metals, but it is one of the few first world countrys with much lithium.

The detail is less clear yet with recycled lithium batterys.

Yes, Li ion works a lot better in cordless tools and laptops etc.

[Paul]

Rather than using spider diagrams, they use a plain table when comparing battery chemistry here.

For some reason, the manufacturer of NiMh, makes small cells, and packs multiple of them, into larger casings. There are larger NiMh packs available (larger than car battery), but it is not clear what the internal composition is.

I expect for more than one battery chemistry, there is an issue with making the cells too large for safety.

Lead acid isn't like that. We had "cells" at work, which were as large as an entire room. The battery backup system, was in an underground hallway, and that hallway went out beside the building. Presumably, to change the cells, they would dig up the ground and pull the cells with a stout crane.

NiCd swells when it charges, and this is a major nuisance. This could also be why batteries are packaged in weird ways (pouch cells).

You can see one spider diagram on this page, and the spiders are overlaid, for easy comparison. Notice how the titanium cell has huge charging current capability, and the Proterra transit bus uses those and it charges at 500kW. You can drive the Proterra all day long, as long as you charge for ten minutes, drive for fifty minutes. As transit buses go, the Proterra is kinda small.

If NiMh was "the best", wouldn't they all be using it ?

The solid electrolyte batteries aren't on any charts yet, but they also don't have the charge cycle count to be practical. Give them time.

*******

Every day, there is a more and more expensive car, with a larger and larger range.

112 kWh 830 km on a single charge starts at $138,000 USD

You will be knackered, when it is time for a recharge. Climb in the back and go to sleep.

Paul

[Animal]

yes, where it wasn't too hilly, and they didn't need to run for long each day. They were awful performers, I wonder why they didn't use Nife cells.

they're very heavy, have far less capacity per weight, have very long charge times, and love to die young. Oh, the latter also makes them cost more per mile than lithium.

batteries are the expensive part of EVs, so tiny vehicles are the better ones to electrify. Vans are designed to work all day, something no battery vehicle can do. So companies would pay far more & get far less. Not my definition of ideal.

if so we'd be using them

maybe now you do.

You can run a car on lead acids, people used to over a century ago, but don't be surprised if you get the performance of a milk float.

[Thomas Prufer]

The german Post Office needed a vehicle: large capacity, electric, relatively slow, short range, city use to deliver parcels.

They built their own, eventually,

They also make a "Work Trike": pushbike, tricycle, 90 kilos load, 25 km/h top speed, "push help" (i.e. moves without pedaling) at 4 km/h, range 30 km. This is for letter carriers on their rounds, in town, i.e. houses with multiple letterboxes.

The vans are lithium batteries, the pushbikes don't say -- I'd expect Li because of weight considerations on a pushbike...

Thomas Prufer

[Jeff Layman]

They didn't. They used NiFe batteries. Those batteries are still around today:

[Tim+]

First I’ve heard of it. Got any links to milk floats with those batteries?

I CAN find links to them having lead acid batteries.

Tim

[The Natural Philosopher]

Er sorry, the original milk floats of my youth were definitely lead acid.

[Theo]

Today's lithium ion batteries are lithium + nickel/manganese/cobalt, which are designed for energy density in phones and laptops.

The new generation are lithium iron phosphate. Less energy density but more robust and harder to catch fire, so you make back some of the energy density by not needing as much fire protection.

Iron and phosphorus are abundant, so the constraint is only on lithium. Lithium is abundant too - in seawater. The challenge is how to extract it in usable amounts. Progress is being made:

Lithium mining is just digging up places where sea water has historically collected and evaporated, much like the way we harvest table salt in salt pans from the sea.

There are also sodium ion batteries, which replace the lithium with more commonly available sodium:

Lithium is easier to mine than nickel. You can pump water into boreholes and extract brine, whereas with nickel you need to dig out the ore.

The 'metal' in NiMH can be fancy too. Wikipedia:

"The metal M in the negative electrode of a NiMH cell is an intermetallic compound. Many different compounds have been developed for this application, but those in current use fall into two classes. The most common is AB5, where A is a rare-earth mixture of lanthanum, cerium, neodymium, praseodymium, and B is nickel, cobalt, manganese, or aluminium. Some cells use higher-capacity negative electrode materials based on AB2 compounds, where A is titanium or vanadium, and B is zirconium or nickel, modified with chromium, cobalt, iron, or manganese.[18]"

Recycling is pretty similar. Grind them up and separate the materials. There's a lot of copper (for electrodes) and graphite in there.

Cost per kWh is a big issue. The hybrid vehicles typically have 2kWh of NiMH or less.

Theo

[John Walliker]

It is also possible to dig up a Li ore called spodumene. There are large deposits in Canada and the USA which are being, or soon will be, mined. After refining the Li is shipped as lithium carbonate or lithium hydroxide.

John

[Jeff Layman]

It was a lot more difficult than I thought! At

: "Practical Traction Batteries

For over a century Lead Acid batteries have been the prime source of energy for traction applications because they are both robust and relatively inexpensive. For fork lift trucks, milk floats and similar applications Nickel Iron batteries, which are almost indestructible and have a lifetime of up to ten years, have also been used successfully."

That's the only link I could find. Perhaps because a milk float is a uniquely British thing it's almost never mentioned elsewhere. There are quite a few mentions of them being used in forklift trucks. I can remember talking to a guy in the early 70s who was driving a pretty clapped out milk float used as a vehicle on a big site to help move stuff around. It was probably at least 20 years old then. When I commented on the big batteries, asking if they were used in lorries, he said that they were NiFe cells, which I hadn't heard of.

[Brian Gaff]

I think the issue is the number of cycles and what happens if you flatten them too much and their tendency to have weak cells that get reverse charged, though a lot of this could be fixed by some electronics, I'd suggest. Brian

[RJH]

30% discharge per month, and a maintenance cycle every 3 months? Not my expereince of NiMh . . .

[Paul]

That table does not include the LSD variant.

What we don't know, is whether you can make large cells with LSD behavior.

Paul

[Theo]

I don't think there's a technical reason why not, but the question is whether you can do so economically. Also, consumer LSD cells are cylindrical, whereas EV cells are typically prismatic.

Theo

[Tim+]

Try telling that to Elon!

Tim

[David Paste]

Interesting link, thanks!

Do you know what the costs of each are by any chance?

That'll be optimal situation though, right? I.e. not in the middle of winter with the heater on. I'd love an electric car but other than the cost, it's the true range that would be important: 200 miles in winter at night with no charging stops.

I know a guy who has an electric Vauxhall tranny van converted into a family car (to take his son's powerchair) and it gets half the rated range in cold weather, even when driving carefully. I know some electric cars are better than others, but it's the optimism of the ideal situation range versus the realistic range which bugs me in the marketing.

Cheers!

[David Paste]

Ah, I didn't know they died young.

[David Paste]

Ah! Thank you!