LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[evm1024]

Originally Posted by OceanSeaSpray

No worries. They won't "converge at the top", the issue you are describing has nothing to do with the state of charge. It is the amount of current you are running that is skewing the voltage differently between cells and nothing is going to fix this.

All you can do now is get organised so it doesn't cause your BMS to trip while charging. Keep your charging voltage down a bit so that cell doesn't read HV at high current. Once the current starts tapering down, the difference will also subside.

When I buy cells, I specify I want them straight out of the factory crate, never touched by anyone afterwards, from the same production batch with consecutive numbers, all voltages reading below 3.300V and none differing by more than 1mV.

I am difficult, but I can get that. You are not the first here reporting getting a complete outlier with Balqon...

I suspected they won't converge but being a research engineer repeating the calibration and repeating the "test" is the first step to figuring out what is happening.

In any case they are top balanced now and I can live with delta V under 100 amp charges. I'll just taper the charge current more aggressively as any cell nears 3.45 vpc.

I have been working on a beaglebone black BMS and I can program this in.

regards

PS I don't consider matching cells to be difficult. This is how we get the max performance and least difficulties.

[donradcliffe]

Does anyone know what kind of batteries the Volvo Ocean racers were using??

This are quotes from the team which investigated the incident where Team Vestas Wind hit the reef in the Indian Ocean during the last Volvo Ocean Race:

LFP Batteries
247. The only point regarding equipment that is considered necessary to raise in this report
concerns the LFP battery(s) catching on fire. The LFP batteries are reported to have started
‘smoking’ shortly before abandoning the yacht. This is believed to be as a result of their exposure or
submersion in salt water. This did raise a concern of fire and was one of the factors that influenced
the decision to abandon the yacht.

106. The next two days were spent by the crew retrieving as much as they could from the yacht
and minimising any environmental risks. One point of note was that the crew discovered that at
least one of the LFP batteries which had been relocated to a beach had burnt and self-destructed.
The removal of the batteries from the yacht had been a sensible precaution.


Edit--I looked further at the report, and they were LifePo4 batteries

[Rimica]

Mastervolt Lithium 24 volt 180 Amp per battery.

[OceanSeaSpray]

Very interesting observation. A quick search leads to Meeting the Ultimate challange in the Volvo Ocean Race | Mastervolt and then Mastervolt Volvo Ocean Race

The batteries would have been Mastervolt 24/5000.

The data sheet is here and states LiFePO4. Standard prismatic cells from close-up photos I saw of the Mastervolt packs. They use inductive charge pumps for rebalancing all the time.

So 180Ah cells as Rimica said above.

[OceanSeaSpray]

After running a few numbers based on the conductivity of seawater, it seems quite plain that there is no way immersion alone could short the cells/battery sufficiently to cause them to smoke or go on fire. In fact, it would be quite hard to draw more than a few amps this way.

So, shorting and failure of the balancing boards sitting on top?



Maybe, but the photo shows a 30A blade fuse on each and the boards should blow themselves to pieces long before passing enough current.

The impact of the grounding could have caused something else, elsewhere, to short the batteries, but a massive short should have blown an over-current fuse. Or did the impact damage the cells themselves, internally?

This could in fact be the most likely explanation, especially as the fault continued after they were removed from the boat and cells even caught fire later while on the beach.

Prismatic cells can be caused to ignite by damaging them on their short sides (by opposition to punching through the thickness of them). It is much easier to create a massive short at the edges of the plates (http://www.prba.org/wp-content/uploa...PA_-_20111.pdf, page 57). This is a rather interesting document by the way!

[hellosailor]

The sudden impact shock of a moving boat slamming into a rock or reef might be enough to cause an internal tear or rupture in a battery pack. If that was just enough to tear one layer of the separator against a post or terminal...then it could cascade from there, with one small internal short being enough to start the whole battery up.


I don't think I've ever seen "g-shock" ratings for lithium batteries. In automotive use, I suspect that's a consideration due to how common crash impacts are. But for boats?

[transmitterdan]

It seems more likely that smoke would be emitted by the electronics than by the battery itself. Are we sure the smoke/fire was really the battery and not the power electronics package on top?

[OceanSeaSpray]

Originally Posted by transmitterdan

It seems more likely that smoke would be emitted by the electronics than by the battery itself. Are we sure the smoke/fire was really the battery and not the power electronics package on top?

LFPs vent quite profusely when abused and it looks like grey smoke, there is plenty of footage of it available around. It is electrolyte vapour and gases. If the internals reach 200degC, then thermal runaway occurs and then they burn fairly hot.

The investigation report says: "One point of note was that the crew discovered that at least one of the LFP batteries which had been relocated to a beach had burnt and self-destructed."

I was told by Sinopoly never to use cells larger than 200Ah on boats due to mechanical strength-to-weight considerations (and commercial marine lithium batteries never are, as far as I have seen). I think we have just had an illustration of this.
Imagine falling off a wave one day with 4 huge cells parked up underneath a bunk. I think it is also a lot more important to seriously clamp them than we have sometimes thought.

[roetter]

Hi, I have not been on this thread for a while. Got too much in electrica car (Tesla) things.

I am preparing an install of LiFePo for a friend. What is the latest for decent prices, reliable customer service and shipping in the US/Canada. We are in need of 800-1000 Ah at 12V.

[Twin Coves]

Hello,
I bought 16 x 200Ah x 3.2V Real Force prismatics on Sept 21. I bought from electric car parts company .com Lithium Car EV Pouch Cell Battery Conversion Kit Company in Utah They arrived Victoria BC in perfect condition Oct 3. Price was UD$3,552 including post bolts and jumpers. Shipping was US$175 to Blaine. Seawings.ca brought them to Victoria for another CA$135.

I was extremely pleased with the service and they even prechecked the resting voltage and confirmed all cells to be at 3.25V at shipping date. The only thing that would have made my order better would have been getting 400Ah cells but they seem to be rare in North America right now. Balqon says they have them but try finding a way to do business with them!!

[ColdEH]

Originally Posted by roetter

Hi, I have not been on this thread for a while. Got too much in electrica car (Tesla) things.

I am preparing an install of LiFePo for a friend. What is the latest for decent prices, reliable customer service and shipping in the US/Canada. We are in need of 800-1000 Ah at 12V.

I got my Sinopoly's from this company , service was great as well as price , shipped right to my door in Toronto Canada.

http://www.canev.com/

Regards

[georgec]

I purchased 8 - 400AH cells from CALB earlier this year. They had consecutive serial numbers and included documentation from the factory of each cell's internal resistance, open circuit voltage and AH capacity. You can contact Keegan at keegan@calbusainc.com

[Seman]

Would anybody know where to buy LifePo4 cells in South Africa? I need 8 x 200Ah Cells. Have searched everywhere, no luck.

[offpist]

Testing out the Balmar AT-200 together with an Balmar 60-150-SR-IG on an Yanmar 4JH4E. Gives me 350A charging power for my 1000AH Lifepo4 setup.

Controlled by two Mastervolt Alpha Pro MB regulators.

As its 10 groove Serpentine on both alternators, i am not too worried about bearings wear on the engine. But maybe I should be?

For now I have limited at 50% output on the regulators, still giving me plenty of power and the alternators are running very cool this way.

If I want full power I can deactivate "small engine" mode.

Balmar is P+ regulated, and Mastervolt is N- regulated, but that was easy to fix.

[OceanPlanet]

Originally Posted by georgec

I purchased 8 - 400AH cells from CALB earlier this year. They had consecutive serial numbers and included documentation from the factory of each cell's internal resistance, open circuit voltage and AH capacity. You can contact Keegan at keegan@calbusainc.com

We used to really believe in CALB, having sold them for many years in the Genasun GLi systems. However have been having issues lately, especially with the new CA cells. Even with supposedly identical specs, there have been differences in coloumbic efficiencies, making them difficult to balance in high-current charging applications. We switching to something else where our mfg has more control of the supply chain to ensure better QC.