New lifepo4 batteries

[vicv]

Teslas and other are starting to use LFP batteries in their packs. Do you think we'll start to see 18650s and 21700s available soon that are better than the previous ones we had? I still have a couple Samsung 18650s that are only 1100mah. I'm hoping to see higher capacities

 

[jtr1962]

There are already 18650s of 1800 mAh and 26650s of 3800 mAh.

Maximum theoretical capacity of an LFP 18650 is around 2000 mAh IIRC, but use of graphene could potentially bump that by about 20%.

 

[vicv]

I've seen those on battery space. Don't think I'd trust an unbranded cell though. I mean you can buy "9000" mah 18650s. I'd want to see something from lg or Samsung or someone

 

[jtr1962]

Well, this move by Tesla might spark some R&D to get the capacity up. That said, I don't think there's that large a market for LFP 18650s. Maybe things with very high discharge rates which currently use ~1,500 mAh li-ion, such as power tool packs, might be a possibility. At least here an 1,800 mAh LFP would offer improved safety without sacrificing energy density.

 

[Lynx_Arc]

Well, this move by Tesla might spark some R&D to get the capacity up. That said, I don't think there's that large a market for LFP 18650s. Maybe things with very high discharge rates which currently use ~1,500 mAh li-ion, such as power tool packs, might be a possibility. At least here an 1,800 mAh LFP would offer improved safety without sacrificing energy density.

I've heard that the Dewalt Powerstack uses a new pouch battery tech in it that is safe.

 

[vicv]

Interesting. Ya they're claiming double the cycle life. LFP would do that. It would quadruple it probably

 

[Lynx_Arc]

Interesting. Ya they're claiming double the cycle life. LFP would do that. It would quadruple it probably

I'm guessing that is compared to lithium ion 18650 and 21700 cell packs.

 

[jtr1962]

Good review:



Stacked pouch cells, versus cylindrical ones, makes for a more compact battery, partially offsetting the lower energy density of LFP. The real kicker though is despite the lower Ah rating (1.7 versus 2.0), the Powerstack actually has more useable energy in real world use. The li-ion battery got hotter during use, meaning more power was wasted due to internal resistance.

To get 20V nominal I'll guess they're using 6 cells in series (versus 5 for standard li-ion).

 

[Lynx_Arc]

Good review:



Stacked pouch cells, versus cylindrical ones, makes for a more compact battery, partially offsetting the lower energy density of LFP. The real kicker though is despite the lower Ah rating (1.7 versus 2.0), the Powerstack actually has more useable energy in real world use. The li-ion battery got hotter during use, meaning more power was wasted due to internal resistance.

It does excel under heavier loads but under light use the lower capacity per cost ratio is not worth it. I saw a bunch of youtube vids comparing the battery in 20v circular saws and impacts and large drills. I think when/if they come out with a 3-5Ah powerstack battery we could see a lot more people investing in them but the small mah size cannot compete well with the 5A and larger batteries in continuous heavy use the powerstack can put out more power but for less than half the runtime of the larger capacity batteries of which Dewalt has up to 12Ah now. Personally if these batteries were equal in price per Wh to the 18650/21700 counterparts they would likely replace a lot of 3A and less batteries used in many devices. I think I saw a video of them putting a nail through one of the power stack batteries somewhere so they are safer but all in all tool battery safeness is excellent.

 

[jtr1962]

Like anything else, the price will drop as more are made. For now early adopters who might need the sustained current output, or who benefit from twice the cycle life, are buying them. I personally think LFP will start taking over for the simple reason cobalt and nickel are going way up in price. I'm happy to see this because about ten years ago I honestly thought this technology was dead. It limped along for a while. Now it's apparently seeing a resurgence.

 

[DIWdiver]

So...

Most phone and tablet batteries are pouch cells, laptops are a mix (recently mostly pouch) and until recently most or all tool batteries were cylindrical. The only fires that I hear about are in phones and tablets. Do tool fires happen and I just don't hear about them? Or are tools for some reason safer? Or do tool users "just deal with it" instead of getting hysterical and posting on the net?

 

[vicv]

Tools generally use high current batteries. Laptops and phones use as high capacity(energy dense) as possible. They have thinner separators Ect. So they're more fragile. And their electrolyte is more flammable.

I am also glad to see lifepo4 on a comeback. I'm just waiting for good brands to make them. Even though I'm not sure how useful they will be to us. Leds are getting lower vfs, but not low enough yet for a single cell to power them well. Would be nice to get some higher capacity LFP 16340s though for 2 cell tactical lights. In series they work great

 

[idleprocess]

The only fires that I hear about are in phones and tablets. Do tool fires happen and I just don't hear about them? Or are tools for some reason safer? Or do tool users "just deal with it" instead of getting hysterical and posting on the net?

Two things come to mind. Tools are built using high-current cells - and generally cylindrical cells at that - knowing that they're going to get hot and designed to accommodate. They're also generally used to provide short bursts of power on a low duty cycle.

 

[HarryN]

Usually the reason that companies shift toward LiFe is to reduce liability, as (often) they have less fire risk.

This is especially true of cylindrical cells. I am still not a big fan of pouch cells, especially for applications with vibration involved.

This is why LiFe pretty much dominates industries like RVs.

 

[vicv]

I'm just thinking the high cycle count and flat discharge curve. Not to mention low Damage with deep discharges

 

[jtr1962]

Usually the reason that companies shift toward LiFe is to reduce liability, as (often) they have less fire risk.

More like virtually no fire or explosion risk. That's why I like them for personal projects.

I am still not a big fan of pouch cells, especially for applications with vibration involved.

Meneither unless they're contained in a solid enclosure. Prismatic cells are probably the best choice for robustness, safety, and energy density.

 

[Dave_H]

Not using any large LiFePO4 batteries yet but found 18500 cells used in garden lighting fit some small 3xAAA flashlights with round cell holder which are too short to take 18650. Lower capacity is a drawback but taking what I can get, and I found a decent charger for them.

Dave

 

[HarryN]

More like virtually no fire or explosion risk. That's why I like them for personal projects.

Meneither unless they're contained in a solid enclosure. Prismatic cells are probably the best choice for robustness, safety, and energy density.

The risk is definitely very much reduced, but not zero. I do some work in conversion van electrical. There are some fires reported on self built larger prismatic packs. ( ~ 4-8 kw-hr). For my van build work, I will only use commercially produced batteries that are cylindrical based, and only ones from a supplier that I have qualified.

Yes, it has costs me some work due to pricing but I am ok with that.

Nice to see that you are still out there posting.