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

[mrm]

Originally Posted by Maine Sail

I have reached out to both Winston and CALB regarding cells up to 400Ah about vibration testing and stability and both companies stated their 400Ah cells are built to the same standards for vibration as the smaller cells. Neither manufacturer had any qualms about cells between 200Ah & 400Ah for use on boats.

When I asked what the specific testing was (which standard they were tested to) neither company replied other than to say they are tested to our own high standards for vibration.

CALB did say that one competitor has been know to spread rumors that are unfounded and they through perhaps that is where this started. [...]

What follows is pure speculation, assumptions and hypothesis. If you feel this does not belong to the topic feel free to flag this post to the moderators for removal, I won't be offended.

Anyway, working with the assumption that there may be some truth in reports/rumours of problems with large cells in marine applications I thought about a possible reason given the information manufacturers were willing to share with Maine Sail and here is my reasoning and hypothesis: every mechanical component/part has its specific mechanical resonance frequency. Usually larger and/or heavier components have that frequency lower than smaller/lighter components. Components subjected to vibrations in their resonance range are known to deteriorate in an accelerated (pun intended) manner. Perhaps hull vibrations in marine environment (from engine(s), wave action, etc.) have a frequency component which corresponds to mechanical resonance frequency of large cells?

Again, this is only a hypothesis subject to verification.

[stanhoney]

Originally Posted by evm1024

As that this is the Prime LiFePO4 thread I thought I would post this here.

In the various lithium threads we always measure the voltage of the cells. In the thousands of post we have only talked about what we measure the voltage with a (very) few times. As I recall, Mainesail did point out that he used a calibrated Fluke multimeter. And that is the point of this posting.

Perhaps you are like me and have 5 or 6 handheld multimeters ranging from a really poorly performing model that I picked up in Ukraine (Chinese copy of a fluke) to 2 Tektronix bench models to a rather nice Fluke handheld.

When I started on my LiFePO4 install I decided that rather than send the Tek modules off to Tertronix to be calibrated I would buy a new Fluke 87-v that had been calibrated and use that to calibrate the Tek and other DVM that I had.

https://www.amazon.com/Fluke-FLUKE-8...multimeter+87v

I can say that all of the multimeters that I have were 10's of mV off and in the case of the fluke copy 100's of mV off. My Mytex meters were not too bad.

Accuracy (reading the correct "true") in voltage is important and that is where calibration comes in. But, in the case of measuring the difference in cell voltages precision is very important too... My less expensive meters often would read 3 or 4 mV different second to second. (measure, wait a second measure the same cell and see a difference).

So the bottom line is that you should take a look at your meter and decide if it is up to the task. See if you can get a guestemate of it accuracy by comparing to a meter of known accuracy. Also, check its precision by repeatedly measuring a cell and see if it reads the same each time.

If you have any doubts consider upgrading your meter. You do not have to spend $400 to get a good meter. But having known accuracy and having 4 or 5 digits is oh so nice.

If you DO want to spend $400+ on a DVM for use on a boat, consider the Fluke 28-II. It is identical to the 87-V, but is waterproof to IP67.

[evm1024]

Originally Posted by stanhoney

If you DO want to spend $400+ on a DVM for use on a boat, consider the Fluke 28-II. It is identical to the 87-V, but is waterproof to IP67.

Good info, too late for me...

[OceanSeaSpray]

Originally Posted by Maine Sail

I have reached out to both Winston and CALB regarding cells up to 400Ah about vibration testing and stability and both companies stated their 400Ah cells are built to the same standards for vibration as the smaller cells. Neither manufacturer had any qualms about cells between 200Ah & 400Ah for use on boats.
...
CALB did say that one competitor has been know to spread rumors that are unfounded and they through perhaps that is where this started.

CALB right now is not currently building 400Ah cells (lower demand for sizes above 200Ah and high demand for sub 200Ah cells)...

Originally Posted by mrm

...Anyway, working with the assumption that there may be some truth in reports/rumours of problems with large cells in marine applications I thought about a possible reason given the information manufacturers were willing to share with Maine Sail and here is my reasoning and hypothesis: every mechanical component/part has its specific mechanical resonance frequency.
...

The issue has never been about vibration, but motion and accelerations. Boats at sea don't vibrate, they roll, slam and get slammed.

When I sent a technical query to Sinopoly some 18 months ago, they called back to discuss the application with me. They specifically advised against using cells larger than 200Ah, stating the large cells were intended for stationary power storage.
The internals of the cells become increasingly heavy, the casing proportionally weaker and it becomes impossible to guarantee that not even minute mechanical motion is going to occur when you keep rolling, pitching and bouncing around at sea with no end to it and it leads to cell damage.

Prismatic cells are just a bunch of plates stacked together and they don't have much structural strength in themselves. Clamping helps and it very important, but it only goes so far. If you want cells you can kick around with no adverse effect, use lots of the small cylindrical cells.

Sinopoly did have the larger cells available at the time, but they still stubbornly refused considering even their 300Ah cells for installation on a boat.
I would also point out that Rolf lost two installations using 700Ah Winstons on catamarans, but this would appear to have been rather quickly lost from sight. To my knowledge, you can't buy a single commercial packaged marine lithium battery made out of cells larger than 180-200Ah either - quite curious considering that most everyone in the market wants them bigger and there are "no known issues".

But of course, it is all a conspiracy to try and cell more cell links while the price of copper is high, discredit the competition and protect the baby fur seals in the port of Shenzhen.

Meanwhile, the shortest path to a sale is still telling the buyer everything he wants to hear, so just go ahead.
At the time Sinopoly also made offensive comments about using their cells without supervisory management, balancing etc, so it would appear I wasn't talking to some clown paid a commission on sales, but those do talk much more nicely.

[Maine Sail]

Originally Posted by OceanSeaSpray

I would also point out that Rolf lost two installations using 700Ah Winstons on catamarans, but this would appear to have been rather quickly lost from sight.

I would love to know more on the specifics of those failures. It is frustrating when folks who DIY don't also discuss the failures. Perhaps he did and I just missed it? Some do discuss it, others won't, and that does not help us learn.

To date I have yet to hear of a failure of any 400Ah or smaller cells that have been well installed on boats and then charged and discharged correctly. My own cells (2009 vintage) are purring along so nicely I forget they are even there.

Interestingly I have seen failures of factory made LFP systems, which use sub 200Ah cells, when they did not construct the end plates well enough and then told owners to charge them at 3.65VPC.

I have a totaled 10K battery in my shop made by a "well respected" company who's engineers got far too much wrong on that battery..

[OceanSeaSpray]

Originally Posted by Maine Sail

I would love to know more on the specifics of those failures. It is frustrating when folks who DIY don't also discuss the failures. Perhaps he did and I just missed it? Some do discuss it, others won't, and that does not help us learn.

To date I have yet to hear of a failure of any 400Ah or smaller cells that have been well installed on boats and then charged and discharged correctly. My own cells (2009 vintage) are purring along so nicely I forget they are even there.

Interestingly I have seen failures of factory made LFP systems, which use sub 200Ah cells, when they did not construct the end plates well enough and then told owners to charge them at 3.65VPC.

I have a totaled 10K battery in my shop made by a "well respected" company who's engineers got far too much wrong on that battery..

I would agree with you about reporting failures as I see and hear about a lot more of them than what is apparent here.

Rolf was reporting insanely high rates of self-discharge on two cells out of four and those were making the bank impossible to keep in balance. Both installations had been taken ocean cruising.

I haven't heard of failed 400Ah cells either, but it doesn't mean yours would keep looking good if you gave them a good thrashing while crossing the North Atlantic. If we want to discuss resilience to motion, then the only data points of relevance are from boats that actually spend significant time at sea. Even then, a configuration seemingly for Trade Wind passages might not fare too well in heavy weather - yet design and construction should be adequate to withstand it.
The word from the manufacturer was "200Ah max, 100Ah better, the small cells are much stronger". I also sail in ugly weather at times and I would rather be on the conservative side than tease the limit.

The completely unrelated matter with charging voltage is - again... what charging voltage?? Unless you are charging with a pure, smooth regulated DC source, the peak voltage experienced by the cells can be much higher than what the multimeter is showing.
Cells don't swell and fall apart unless you manage to break down the electrolyte. This requires about 4.2V, not 3.65V. But float your cells at 3.6V with a solar PWM controller, they will eventually get 100% full and unable to absorb any current and each time the controller cuts the panels in, you will be briefly applying solar voltage at 18-22VDC to the bank. That is enough to do it.
Most of the time, we are not charging with smooth DC power - I wrote about ripple voltage some time ago. As long as the cells are absorbing, little concern. But if you fail to terminate and overcharge, you will eventually incur the peak voltage the source can produce, which still won't show on a multimeter at the battery, but can easily ruin the cells. Controlling at 3.45V/cell instead of 3.60V/cell etc ultimately isn't the real answer as it doesn't do a thing about the root cause: overcharging and voltage ripple.

Making the end plates stronger won't be that useful if you are destroying the cells electrochemically anyway...

[transmitterdan]

Some (most) good volt meters will measure ripple if you use the AC mode even on DC systems.

Unfortunately most of the good meters convert the ripple to RMS which tells little about the peak voltage. But a significant RMS reading would be at least a hint that there is ripple. So it's possible to measure something in terms of ripple.

[stanhoney]

Originally Posted by transmitterdan

Some (most) good volt meters will measure ripple if you use the AC mode even on DC systems.

Unfortunately most of the good meters convert the ripple to RMS which tells little about the peak voltage. But a significant RMS reading would be at least a hint that there is ripple. So it's possible to measure something in terms of ripple.

Some (relatively expensive) meters e.g. the Fluke 87-V or the waterproof equivalent Fluke 28-II have min-max modes. In the case of the Flukes you can set them to measure peak voltages as short as 250 uS. Of course it is also possible to measure average voltage with various time constants.

[OceanSeaSpray]

Originally Posted by transmitterdan

Some (most) good volt meters will measure ripple if you use the AC mode even on DC systems.

Unfortunately most of the good meters convert the ripple to RMS which tells little about the peak voltage. But a significant RMS reading would be at least a hint that there is ripple. So it's possible to measure something in terms of ripple.

Yes, ripple shows on the AC range, but it is not good enough to see a solar charge controller spiking a full battery with narrow pulses.

A better way is using an ultrafast diode and a ceramic capacitor in front of the multimeter to sample the peaks. Readings are always unimpressive until the battery gets near full.

[senormechanico]

One of these days when I get time, I'm going to slap my Fluke Scopemeter on the bank and leave it in the "Record" mode to see what it looks like when near full.
I never bother with shorepower, just solar and BlueSky 2512IX MPPT.
Hopefully, I will get some pics to post here.

[Moonos]

Quick question.

I have been following the progress of lifepo4 but have been out of the discussion for 12 months.

Have there been any real developments in the last 6-12 months, or is it all much the same?

Any real mainstream commercialisation of marine lifepo4 systems?

[SV THIRD DAY]

Originally Posted by Moonos

Quick question.

I have been following the progress of lifepo4 but have been out of the discussion for 12 months.

Have there been any real developments in the last 6-12 months, or is it all much the same?

Any real mainstream commercialisation of marine lifepo4 systems?

Not really...just more DIY guys making, installing and loving their installations. As was recently being discussed, finding systems that have failed it turns out is harder than find folks with failed old school Lead Acid batteries...who would have predicted that? Certainly not the Chicken Littles, that for sure.

[Moonos]

There was a guy on one of the Kickstarter sites wanting to start an open source lifepo4 controller...

From the little info I read it looked like he knew what he was doing.

[ColdEH]

I have 8 x300ah Sinopoly cells , they also have been "purring " right along . 2 Years live aboard 80% of the time, still within 4mv balance .

Regards

[Cottontop]

I am surprised that prices for batteries haven't fallen more, especially with the new entrants into the space (e.g., Tesla).