Discharging Sodium Batteries to 0V! Useful or just a marketing gag?

In the last test with the Sodium 18650 cells, we want to follow THE feature we all know about: discharging the cell to 0.0V. I want to measure the capacity gain from 1.5V down to 0.0V and if it is worth discharging that low. Not that this is even possible with any inverters out there, but just for the sake of testing...
Unfortunately, the test failed because none of my testers could actually measure that low, but I accidentally found another interesting feature of these Sodium batteries. This questions though, if the whole 0V feature is nothing more than a marketing argument...

GEB Sodium 18650 and prismatic Sodium-ion cells (scroll all the way down on the following website):

DL24P Battery tester, review and product link:
DL24P 185W/20A Battery and Power Tester:

ZKE-Tech EBC-A20 (charge with 5A, discharge with 20A), USB output to PC software for processing data and creation of detailed charge and discharge curves:

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[andrewsweet]

The UREG message means Unregulated. The electronic load tries to tell you that it can't handle itself and stay in CC mode while the battery voltage is that low. It started doing that at 0.6-0.7V battery voltage, which seems awfully close to a standard diode voltage drop!

[anthonyrstrawbridge]

Wow! The depleted cells were automatically converting the sodium ions back to sodium. This phenomenon occurs within the sodium rich state; it likely doesn't occur in the initial uncharged non cycled cell: it likely stops occurring after multiple cycles as the sodium rich state decreases. So, likely they can be shipped at Zero voltage uncharged.
Here we have a cell which repairs itself, has no thermal runaway, and can be discharged and charged easily at 5c. What more? Berlin and Prussian white has been perfected giving increased cycle life and greater energy density so we're in for pleasant surprise as China's largest energy cell manufacturer invests 1.5 billion into manufacturing of SIB'S. Low temperature capabilities is significant too. This technology doesn't abruptly shut off power but rather slowly tapers off. Excellent video Andy. Lindt Lindor Milk chocolate truffle bar❤

[sreekumarUSA]

0314’24/1455h 🇺🇸\ 0315’24/0755h 🇦🇺 Guten Tag Herr Andy. Danke scheon for reviewing/ testing discharge sequence in Na cells. Perhaps about 07 years ago while discharging Li-ion cells, I experienced the similar result, though I was unable to discharge to 0.00V. But found the similar result of voltage rebounding to, even to 3.2V from 2.8V. Sounded / felt like some thing to do with Chemistry. I Terminated test and kept quiet about it.
Thanks for your Na cells test, that opened my eyes. Danke Mein Freund. Have a great day ahead.

[sventenraa]

Hey Andie, Developer/code owner (sfstar) of the home assistant victron integration here. I'm sorry to hear that the integration isn't working correctly for you. Starting from the end of march I will have time to improve the integration and resolve some of the backlogged issues. Are there specific problems for which you have opened an Issue?

[teardowndan]

Being able to discharge Na-ion batteries to 0V supposedly without harm has nothing to do with gaining additional capacity. This is all about being able to ship large batteries fully discharge to make them effectively inert and intrinsically safe - no chance of them starting a fire no matter how much physical abuse is applied during shipping. The voltage may creep back up due to galvanic voltage intrinsic to the cells' construction but there is hardly any energy at play there: 1.8V @ 0.000A is 0W, 230mA @ 0.00V is also 0W.

UREG on your tester likely means that the voltage is too low to regulate load current.

[voort]

Sooo curiuos to your findings on the diybms. Nice work Stuart!

[FutureSystem]

Thanks Andy, as always appreciate your hard work. Cheers. 👍

[SolAce-nwhf]

It's about being able to fully deplete a battery without any damage. So the fact that it is bouncing back after a full discharge is a good sign.
This is also nice for mass transport of batteries, where you want as little energy as possible for safety (yes, there have been fire incidents with battery transport).

Maybe you could do a discharge test with a few of these in series so you can get to a really low voltage per cell?
And after that we need to see if these cells have degraded in any way, but I expect you will show us this in the next video without asking anyway.

[abelramos]

Hi Andy, im a amateur on this, want to ask you, i guess these test are the same results you will get with a sodium "brick shape" battery like the lifepo4 we are using right?

[ajvz]

Hi Andy, thank you for the sodium battery testing thus far. But now what? Specifically for home storage they don't seem much of an alternative to LFP yet. And you would have to wait for cheap big (prismatic) cells to get to market, anyways.
Did you find out the specific chemistry?

[ThanosSustainable]

Next test would be to short a cell in order to KEEP it at 0V for a week and then test to see if there’s any loss in capacity.

[ajvz]

Andy, I just read about LFMP (LFP with manganese), which may actually beat sodium batteries to market.
Any chance you can get your hands on some of those cells?

[teagueman]

I wonder how many cycles these Na batteries can do before they hit 50% of original capacity. That would be a good test Andy.

[StéphaneRivette]

What do you think about MQTT integration with Victron Node-RED? Node-Red in the Large Image can update the integrated MQTT server in Home Assistant. At least, it is incorporated. I may need to be corrected. This is based on a video I've seen.

[r.b.l.]

Now we all have the same question: did the 0-volts excursion reduce the Sodium Cell capacity, SOH or cut life-time cycles ???
We all know the LFP cells can't be discharged below 2.5v per cell without problems, now we need to know for Sodium.

[junkerzn]

Yah, on measuring current with the voltage that low you basically have to connect up a resistor across the battery and you can then calculate the current by measuring the voltage. I = V / R. It still won't be perfect, though, the multi-meters you have do not have a high-enough input impedance.

A regular multi-meter just won't work in this situation... they can measure micro-amps, but only for low-impedance current paths. The discharged battery has a high-impedance current path. The internal shunt resistor in the multi-meter will effect the results and it won't report an accurate value.

By the way, the same effects can be observed when measuring solar panel output at night. Multi-meters have the same problem.

-Matt

[dariomarquez]

Hi! Please, I need to know something about the battery tester product (ZKE Battery Tester EBC-A20) that you use in a lot of your videos before I buy it. Does it have the function of saving the data of the graphs easily? Like a file similar to an excel table with voltage and current value along time in many time points.
Pls!! You would help me a lot answering this question! 🙏🙏🙏

[boringsoftware]

thanks for testing, where did u buy the Sodium 18650 cells? are they ready for real-life-usage?

[somebody]

I am looking forward to your DiyBMS testing. My name is one of those silkscreened on the back :-)

[JdZ-]

I think the load is towards the internal resistance to heavy to see any end curve. On disconnecting the load, the left-over electrons build-up the voltage. Long-term connecting a load will drain the leftovers i presume, like you already mentioned for a testing item.

Using the power in the lower part of the curve is no big advantage, but the main selling point toward LiFePO4 is that it shouldn't harm de battery when it occurs over a longer time.

A great test is to connect the load overnight and then see the voltage on disconnect. Assuming the tester isn't delevering any current to the battery. When the battery arises to a full load when charging and acting normal, then you know for sure it isn't damaged. Hope you can do this test.