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

[ColdEH]

Originally Posted by FlyingCloud1937

My preference exactly, well almost. You can order multi-links, so that you don't have to stack.

Lloyd

Hey Lloyd

Where did you source those multi link braided connectors .?? I contacted my source and he doesn't have any thing like that .

Regards

[FlyingCloud1937]

I have to say that is just em-bare-assing for any reputable manufacture to send a product into the MARKET like this.

I wouldn't give a nickle for any boat factory wired like this. WOOOOOW!!!!

Lloyd

Originally Posted by markv

Rolf

thanks for the info...starting to make a bit more sense now. Took some pictures, you will probably remember this as the setup that comes from Lagoon. I think we will have to put the bus bars on the opposite side of the switches, and the Flexmax MMPTs and BMS modules on in the space where the Victron is currently.

The Victron is connected to the Load as far as I can see.

[FlyingCloud1937]

Storm Copper, the source for busing.

Lloyd

Originally Posted by typhoon

Hey Lloyd

Where did you source those multi link braided connectors .?? I contacted my source and he doesn't have any thing like that .

Regards

[ColdEH]

Originally Posted by FlyingCloud1937

Storm Copper, the source for busing.

Lloyd

Perfect , thanks Lloyd.

Regards

[roetter]

I am sorry you get so much critique. I think your job is better than most production boats.


Rolf

[Beccara]

Originally Posted by FlyingCloud1937

I have to say that is just em-bare-assing for any reputable manufacture to send a product into the MARKET like this.

I wouldn't give a nickle for any boat factory wired like this. WOOOOOW!!!!

Lloyd

I'm still getting upto speed with marine electrical work vs land electrical work, Whilst the cable looks like it could be supported better in places whats wrong in that picture?

[markv]

We've added a couple of L shaped wooden strips along the long edges of the battery bank, so the straps are now 1 inch higher and clear of the batteries and terminals. We also added a couple of switches, one for the alternators and one for the solar panels, in the same area as the other switches are. This way, we can manually switch off the charging from solar panels or the alternators. So far it's going well - we don't have MK2-USB to program the Victron, using the Assistants and VE Configure, which is what I need to open the charge relay at 100% SOC and then connect back again at 80%. I can rely on the BMS to switch it off at HVC, but I would rather do that via the Victron. I cannot find where to set the Peukert to 1 on the Victron either...still learning..:-)

We set sail tomorrow for Cascais and Gibraltar, and hopefully can get our solar panel arrays fabricated there. Everyone in France is off now for August...if not Gibraltar, then Smir Marina in Morocco perhaps.

And thanks Rolf......the new setup is not as nice as it could have been, but limited time.. - we will see how it goes.

[mrm]

Originally Posted by markv

We set sail tomorrow for Cascais and Gibraltar, and hopefully can get our solar panel arrays fabricated there. Everyone in France is off now for August...if not Gibraltar, then Smir Marina in Morocco perhaps.

Smir is a nice place of a tourist resort type with somewhat 'artificial' feel to it. Good to visit, good to get cheap(er) diesel, but do not expect to be able to have a lot of fabricating done there, unless you bring all materials with you.

[ColdEH]

Originally Posted by Maine Sail

Mark,

Please do yourself a favor and convert those alts to external and use a Balmar MC-614 regulator or better yet get alternators that are designed to handle this type of abuse.

Your alts are most likely internally temp compensated and your LFP bank will drive the voltage down to try and save the alt from cooking itself, not a good set up for LFP.. LFP should really be designed as a "system".....

Hey Maine Sail

I just read your article on LifePo4 batteries on your web site. Fantastic!! As all here will echo my thanks on your hard work and posting your findings , Thank you Thank you.!!

I am pretty much using it as a manual and building my bank with the same equipment, I just ordered my bench power supply for my initial top balance.

The only difference is that I am am using a single source for charging and I am using 8 Sinopoly 300ah cells built into a single 12v bank .

Just a couple of questions , would I top balance my cells at the same level as yours, and would I set the cut off charge voltage on my alternator the same as your Winston cells . Eco Tec modified my alternator with a potentiometer for a variable voltage cut off set point .

Regards

[hellosailor]

Panbo: The Marine Electronics Hub: The DIY lithium battery bank; Bob Ebaugh has 330 cycles so far

Interesting post from Bob Ebaugh on Panbo's web site this month. His tentative results with a LiFePO4 bank that was cycled 330 times indicate a possible loss of 15% capacity in a year. That would come out to a 48% loss over five years, i.e. only 52% of capacity left. Which might not be so shabby, but is still significant. Pretty much still a "replace batteries in four or five years" situation, I'd think.

Very different from MaineSail's testing, where there's been little if any loss IIRC?

Attributable to the brand? Or the use pattern and environment?

[OceanSeaSpray]

Originally Posted by hellosailor

Panbo: The Marine Electronics Hub: The DIY lithium battery bank; Bob Ebaugh has 330 cycles so far

Interesting post from Bob Ebaugh on Panbo's web site this month. His tentative results with a LiFePO4 bank that was cycled 330 times indicate a possible loss of 15% capacity in a year. That would come out to a 48% loss over five years, i.e. only 52% of capacity left. Which might not be so shabby, but is still significant. Pretty much still a "replace batteries in four or five years" situation, I'd think.

Very different from MaineSail's testing, where there's been little if any loss IIRC?

Attributable to the brand? Or the use pattern and environment?

Recent research shows that capacity loss in LiFePO4 cells is essentially proportional to the amount of use the cell has had, i.e. the more energy you have consumed and replaced since the battery was new, the more capacity you have lost. Depth of discharge in itself, on the other hand, is not a key factor for operation at low C-rates.
From memory, Bob performs significant and sustained cycling and the results he reports make complete sense. From discussions we had in the past, his test methodology and equipment are also excellent.

The same paper also highlights that this capacity loss mechanism changes and accelerates when charging below some temperature threshold, somewhere between 15degC and 0degC.

There is a lot of hype along the lines of "as good as new after so many years cycling", I think those are primarily subjective opinions in the sense that there is no perceived loss in performance yet, but the first failures with properly managed LiFePO4 banks will look like increasingly frequent and unexpected LV alarms and cut-outs due to insufficient remaining capacity.

[roetter]

I have seen a presentation of research at U of Toronto that shows that most of the "cycle" loss happens above the upper "knee". Seems like staying out of that range may increase cycle life substantially. So the recommendations from Main Sail and others to not charge above 13.8V will likely see you wear out your own life cycle before the battery does.


Rolf

[OceanSeaSpray]

Originally Posted by markv

If we need to replace the alternators we can do that later, as I am not sure we can get Balmars here in Les Sables in time, for now I will need to get voltage regulators on them so the voltage hitting the charge bar is 13.8... I tested the voltage coming out of them just now and it's 14.3v.
I was going on the advice of Rolf, who has Mitsubishi alternators, which is what I thought was going to be on when we bought the boat, but Lagoon seems to have changed to Valeo...

If I can get what I need from Defender, we can order it for arrival in Gibraltar when we get there in a couple of weeks..we are ordering some other stuff, so that would work out. What alternators would you recommend to buy exactly?

Pretty dubious advice regarding alternators if you ask me. The difference between the 14.3V you are measuring at the alternator and the 13.8V you are getting on the charge bus is the loss at high current through the cable from the alternator output to the charge bus.
As charge current tapers down, this difference will taper down to zero and if the regulated voltage is still 14.3V, it is going to be too high on the long run for a LiFePO4 bank, especially if you motor for extended periods.

Internally regulated alternators like you have are also suitably thermally protected and trying to get rid of this feature by fitting some external regulator is an open pathway to a burnt-out unit. Don't go and spend money to lower reliability.
Temperature compensation, on the other hand, is a term that relates to correcting the output voltage according to ambient temperature. Built-in alternator regulators cannot (and do not) do this, as they can't sense ambient in the environment they operate in.
Temperature compensation must not be used with lithium batteries, they will under-charge in hot weather and get severely damaged in the cold.

If alternator charging is going to be a primary source of power, best option by far is using a heavy-duty unit with a built-in, adjustable regulator. This also makes external voltage sensing unnecessary in most instances. Set it for 14V max at the alternator output post, or whatever you personally deem suitable!
In the past I have installed Electrodyne units in heavy-duty commercial marine applications and we never looked back. I keep well clear of all the gadgets sold for the pleasure boat market.

If your Valeo units have external voltage sensing, then solutions like implemented by Rolf are very acceptable. If your alternators get too hot, they will likely cut-out, cool down and kick-in again.
In the past, I described mods you can consider to de-rate them if they systematically overheat and you don't want or can't replace them.

[OceanSeaSpray]

Originally Posted by roetter

I have seen a presentation of research at U of Toronto that shows that most of the "cycle" loss happens above the upper "knee". Seems like staying out of that range may increase cycle life substantially. So the recommendations from Main Sail and others to not charge above 13.8V will likely see you wear out your own life cycle before the battery does.


Rolf

There is no doubt that a lot of damage takes place above the upper knee, because this is where all the heating takes place when charging and staying away from high end-of-charge voltages certainly improves the situation.

However, the authors of the paper I referred to above found a clear correlation between energy throughput and capacity loss, not number of cycles and capacity loss. End-of-charge damage would be proportional to the number of cycles and they performed deep cycles, shallow cycles etc, so I would assume they were using sensible charge termination.
All scientific information available today points out that, no, LiFePO4 cells don't and won't last forever, except maybe if they are not being cycled at all and stored at 20degC!
It will be interesting to see what "conservative" users eventually get by the time plain aging catches up maybe, but those who are happily cycling heavily today may get a prompt to recalculate their anticipated whole-of-life cost a little earlier than expected. Which doesn't automatically mean it will come out unfavourable by a long way.

Eric

[hellosailor]

"Temperature compensation, on the other hand, is a term that relates to correcting the output voltage according to ambient temperature."
Although, as I've heard the term used, the question is very much not ambient temperature, but the temperature of the battery/bank itself. That's ambient when the charging starts, but the battery temperature goes up as charging occurs at high rates, and it will not be the same as ambient. Ambient beats nothing--but when a temperature sensor is installed, it is usually on the battery positive post, not just "ambient".

"Built-in alternator regulators cannot (and do not) do this, as they can't sense ambient in the environment they operate in."
They may not, but with hundreds of designs out there, I wouldn't bet on absolutes. And I think they could make a very close approximation to ambient temperature sensing. Consider, if you will, that the alternator frame's temperature will be based on the cooling airflow, which is a fixed function of the fans and speed by design, relative to the ambient temperature, and the heat created by the load, which can be sensed by comparing temperature at the diode frame to the alternator frame perhaps, or by sensing the load and making an approximation based on that.
Not ideal ways to second-guess the ambient temperature, but I suspect some clever electronic engineer could come pretty close in some similar way. At least close enough to know if the ambient temperature was 20F (winter day in the yard) or 185F (summer day engine running). Or of course, they could always put two thermistors in the alternator, one in the airflow, the other on the frame, and start working from there.

If no one is doing it yet--that doesn't mean it can't be done. Just that they haven't felt a need to spend the extra buck on parts yet.

Very interesting that lithiums don't need thermal compensation though. In all the messages and all the propaganda, ergh, ah, DATA sheets I've read, I hadn't seen that mentioned before.