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

[bcn]

Originally Posted by OceanSeaSpray

Not only this has been explained over and over again, but I had posted the graph showing that just a few pages up,.

Can you please give the link to your relevant post, refreshing memory?

Thanks

[OceanSeaSpray]

Originally Posted by bcn

Can you please give the link to your relevant post, refreshing memory?

Thanks

Sure: this one. It was only 3 weeks ago...

Regards,

Eric

[bcn]

What I would take into my books then:

It is a misconception to believe that SoC can be controlled using voltage. 3.4V will still charge a LFP cell to 100% given enough time and 3.3V will struggle to achieve 30% no matter what. The transition is so steep that it makes voltage unusable.

perhaps: to believe that SoC can be controlled using voltage alone
so:

What would better control SoC is using the combination of end voltage and residual current

When your system is ready, please give me a shout...
Two 24V (8S) /160Ah banks here.
The BMS we use is connected to the 12V starter battery and eats it when connected permanently. The idea was to have the power for the BMS independent from the bank it controls.
BlueSea latching relays.

Hubert

[SV THIRD DAY]

Originally Posted by OceanSeaSpray

Precisely NOT. I am talking about charging once to 100% full for balancing and while terminating the charge manually.

And here we go with another instance of the ******** shovelled with no end in this thread, because there is no such thing as a magic voltage that will charge, but not overcharge.

Not only this has been explained over and over again, but I had posted the graph showing that just a few pages up, so when it comes to the period of decay of information here... sad state of affairs.

Are we really surprised that someone designing a solution for a "problem" would think the "problem" could only be solved by his engineering solution? Of course what I'm shoveling is ******** to someone who hates a manual shovel over his electronically controlled computer interfaceable shoveling drone that he is selling...surprise...surprise...well not really. I'm not selling a shovel and have nothing to gain by telling folks what has worked for not just my battery bank but other cruisers as well. All I have is downside risk in sharing actually, but here I am...taking the bullets nonetheless with a smile...

What I'm being told to believe is that the 400AH LiFePO4 system I have been running now for nearly 3yrs in the real world on a boat (not on a test bench or theoretical) and the other dozen systems I have helped set up are in fact not actually working, when my eyes and data shows they are....hello McFly...

My system and the others, have seen no capacity loss, have seen no overcharging issues, have seen no individual cell drift, they are all working like a dream currently on full time cruising/liveaboard boats, not on a drawing board. So do I believe a chat room internet expert building something to sell and rip out my death system or do I trust my lying eyes and real life data from 13 LiFePO4 battery systems? Sure, I may just be a self described Cruising Bozo, but I didn't retire at 38 and go cruising by being stupid.

Now we are going to add a starting battery charger to the BMS for added hupla when an off the shelf battery-to-battery 20A charger will work as a simple solution? See where we are going folks? Why not add an espresso maker to it or Bluetooth connectivity for your Iphone...ya...that's the upsell marketing ticket! We are making this way to complicated so that WHEN your electronic black box fails you are stranded at the dock. Overly integrated systems works great in theory but try fixing that from a 3rd world Country. That's when an off the shelf solution even if not as "cool" is worth it's weight in Coconuts.

Lets drill down a bit and see what we can learn:

Originally Posted by OceanSeaSpray

It is a misconception to believe that SoC can be controlled using voltage.3.4V will still charge a LFP cell to 100% given enough time

So I assume you have ran tests to tell us what "given enough time" actually means? Or is this "given enough time" a laughable number that disproves your argument that using voltage to assess SOC can't work? I noticed the data you show on the graph wasn't from your testing, but from other sources that you put together to illustrate. Can you share with us your field test data...and just how long does it take to overcharge a bank when charging at 13.6v (3.4/cell)? I by the way have done those tests which is why I'm not worried....

[SV THIRD DAY]

I hate this crap where we can't edit posts after 30 minutes to correct typos or to clear things up on second readings. Since terms and words matter, I need to clarify this.

Originally Posted by SV THIRD DAY

using voltage to assess SOC can't work?

Lets change that to:
using voltage to limit charging can't work?

That's what I was trying to say and is more accurate.

[exMaggieDrum]

Originally Posted by OceanSeaSpray

Charging and top balancing is simple and easy. I have disagreed and explained why in the past, but repeating the same over and over again gets tedious, and even more so when the same people keep throwing the same claims and misinformation into the thread with no end to it to try and become less isolated with their brilliant achievements.

Charging your cells right up and leaving them results in slow electrochemical degradation. You certainly won't have "lost" them, but you should rectify ASAP, because you are very, very slowly damaging them and losing capacity and this is irreversible.

Now, more specifically to your case, you keep talking about controlling the "current", but current just does what it wants to do when you are balancing. Forget about the current. The only thing that matters at the end when balancing is cell voltage and the tell-tale that you have reached full capacity is when that cell voltage holds up after disconnecting. Don't bother about trying to reach zero current, but you will - naturally - if you are able to control the maximum voltage, like with a small, good quality PSU.

Sorry to be such a bother on all this. I just read your blog about balancing which you linked. I had not gone to that (for whatever reason) before. It is well organized and very useful.

I used your first method for top balancing exactly, EXCEPT I did do the cells individually first and the first ones did sit at the higher voltage for a few days before I got them all in parallel to finish. I can see how keeping them at too high a voltage could degrade them, or least without seeing the results in controlled conditions with sacrificial cells and results backing that up. I'll take it as correct as no reason not to and you probably have done it yourself or read about it being done.

In any case, I finished the top balance with all cells in parallel to 3.650v and when I disconnected them they stayed at 3.5+v for a day and then slowly dropped to the high 3.46+ range over the next two days.

I put a little inverter powering a 60W bulb yesterday and got the voltage down to 13.23v (3.308v per cell). The cells arrived to me with the same exact 3.29v so they seem to meet your criteria for new cells.

Thanks for passing on the link. This must be very frustrating for you but thanks for your contributions anyway. The fact of the matter is that this is uncharted waters for most of us. As usual for the wide-world public there are disagreements, some based on the National Enquirer, and some based on real experience. For whatever it is worth, I value your contributions the most. I always try to determine, in my own mind, how a particular individual might be biased. Your contributions and those by Maine Sail and Martin on Entropy, and Rich on Third Day (even though he disagrees) seem to me to be the least biased and most informed.

But, it seems there are many (based on testimonials) who believe that much of this is overkill. I'm OK with some overkill right as it doesn't seem to hurt anything other than my time and pocketbook and at least it seems as if it will prevent some issues down the road until it is proven which way is the best.

It seems like many of the threads on anchors and hull forms in some ways, with vociferous claims for one side or the other, based on individual experience and limited experience with actual controlled side-by-side comparisons. The service providers with experience with the most installations, and the most experience with down-side issues, have a lot of credence with me. I suspect in the end it will all settle with something in between.

So I am moving on with the installation of my own system, hopefully with cells which are only slightly degraded. I think they will work as well as I will ever be able to determine as I don't have the luxury of a perfect test system to compare to. And mine may or may not be overly complicated but it is where I will be. If it turns out with the preponderance of experience that some of it is unneeded, it can be easily simplified and the used bits sold in a garage sale.

BTW, I talked about "current" because it came up many times in discussions of how to do it by others. I described what I did, and why, on purpose to get feedback as there are disagreements. I think I have ignored current as it was all I could do anyway with my equipment and it turns out that is OK. I certainly was not trying to add to the confusion and have no predisposition on theory and practice nor an ax to grind on the issue.

[SV THIRD DAY]

I think some of the headache comes from the difference in designing a system to Sell to Cruisers vs Sharing Experiences with cruisers about what works for me. There is a HUGE Difference because as I know first hand from doing 7 day a week customer service, there is a very wide gap in knowledge and skills in the cruising fleet. I get questions ranging from how to use a Volt meter to "how do I get my wire to fit on your provided male pointy thing" (male spade connector). When I first bought 4 cells for my boat and a duplicate set for lab/bench testing I had the idea of putting together system for sell. But after using the system myself and helping others set up a system, I've bailed on the idea. Why...liability and seeing what would be a much too difficult job of being an expert on all the different boat set-ups and charging devices. As a test, ask a few friends what size and brand of batteries they have and some will just say "I don't know". Same with battery charger, alternator, etc. There is a general lack of boat systems knowledge that makes the DIY LiFePO4 battery system unrealistic, at least in my view. Sure it works Great for me and for those that know the status of their systems by the sound of the boat but for Joe Q Public...na...go with an off the shelf made for you system.

So I'm in the process of adding the bench test battery bank to my boat and writing it all off as a failed R&D LiFePO4 project for Mr IRS...ha ha ah. That's the advantage of being in the marine industry I guess...

[OceanSeaSpray]

[QUOTE=bcn;2234923]What I would take into my books then:
perhaps: to believe that SoC can be controlled using voltage alone/QUOTE]

Because the state of charge you eventually reach is really a function of what absorption voltage you are using, how long you are holding it (in the simplistic case where you can hold it and power doesn't go out on you) and what the charge rate was earlier during bulk (which is in fact all over the place on a boat), playing with the voltage equates to tweaking the knob with a blindfold on. It is ultimately hopeless, but you can devise a recipe that works reasonably for a fairly constant usage profile.

If you just want to stop short of overcharging, then you need to be measuring the battery current as well. If you want to control the SoC and not charge more than required, then you need to track battery capacity as well as doing everything else.
Preventing overcharging is the first thing that comes to mind of course, but if you use SLA gear, it doesn't matter how you tweak and adjust it, if you walk away and leave it, it invariably overcharges the battery in very short order.

There is a reason why the thread is so old and so long and keeps going: it never delivered any proper solutions. All of the problems from Day 1 are still here.
I wrote about some aspects of working with LiFePO4 batteries elsewhere some time ago, but there are areas I haven't covered, because some of the house bank-type issues are presently unsolvable with what is on the market.

Industrial BMS solutions as found in production EVs are pretty sophisticated products with a lot of R&D going into them and they target the needs of the application. Two years ago, I designed a BMS mistakenly assuming I just needed to provide good and very reliable protection. As I wrote earlier, it did that very well, but it left all of the real issues on the table, because if you want a proper solution that fully looks after itself, all aspects need to be dealt with in an integrated way.
So I have kicked the ball again now, it is a R&D project, but because it benefits from that previous experience and feedback from a number of installations and users, I am quite positive about it.

Now, regardless of what happens, some people will keep smashing smoke alarms and plugging them into Junsi CellLogs or dropping bare cells into their boats, talk about The Voltage with no end to it and make a tremendous noise, but that's perfectly fine by me.
I just want the hardware I need so - when I build a system - I don't have crazy unsolvable issues, I know it is as good as it can be and the bank will last as long as it possibly can, deliver best value and require zero user intervention/specific knowledge.

All the components are sitting here in a box now, but I will be hauling out next week, so will carry on with writing the firmware until this is behind.

[grjfield]

Apologies if this is the wrong thread for my inquiry..

I have a 40' sailboat which I converted to electric a while ago. I currently have 235AH of lead acid batteries and for my needs it works quite well.
My intention was always to upgrade to LiFePO4 when the price improved.

I recently came across a vendor (ELECYR) in the eastern US who carries a LiFePO4 product I'm considering. Apparently the batteries are Chinese and the US company has a proprietary BMS. They have positioned themselves as an alternative to the Tesla Powerwall.
I noted in their 'Marine' Application page that one of the owners had undertaken a conversion to a Hybrid Electric Propulsion System on his sailboat..hence my interest.

Their battery is called SmartBattery, 7.5 Kwh for ~$4900US.
The battery has a max output of 40A @ 48V, so to make it viable for my setup, I would need 3 or 4 set up in parallel to achieve close to hull speed.

They also have a product called the Daily Sun, also 7.5 Kwh for $5900US, which has a built in 1500 inverter.

My question is...
Have any forum members come across this product/company and would care to share any insights?

I have attached the website below.
How Does Renewable Solar Energy Work - Elecyr Energy Storage

[lev]

ok...

a wile back i said i would post my experiences dealing with benergy tech "https://benergytech.com/" to get some lifepo4 cells... 16 100amp cells (BSD-LFP-100AHP) to be exact.

i will make it quick...

the contact there is Kevin... he comes across very helpful at first... all the answers are yes and we got what you need! and we can get them to you no problem and fast!... but when it comes to making the final order then things change... they have cells, they do not have cells, they are getting cells balanced and ready for you then they are gone and maybe in a month they will have more cells... you complain and send an email that makes it look like you are done with them and what do you know Kevin sends me an email to say just send your payment and he will ship cells tomorrow!... like a bad joke... and that is very much the short of it....

it is clear that there is a great deal of BS going on in benergy and i will go as far as to say it is clear that they will lie to you point blank as they clearly did with me... i was so desperate for cells i really let this kevin get away with way to much... very luckily i did not loose any money on it but i clearly lost a great deal of time on trying to deal with these people...

so i clearly recommended staying away from benergy! at this point i really question if payment was made, if i would even have gotten the cells at all.. and since it is only payment by wire that would have been bad... but i really can not say, and would never risk it... one thing is clear if they would have come at all it would have been a very long wait...

[svGenesis]

Can we start a sticky post at the top for battery suppliers, pricing, reviews ect.

[lev]

that is a very good idea...

Originally Posted by svGenesis

Can we start a sticky post at the top for battery suppliers, pricing, reviews ect.

[billysurf]

We are doing research on lithium batteries for a converted bus (MCI or GM) and can't get the answer to a very basic (although loaded) question. How long can you be without a power hookup. I know the boat community could answer this much faster than the RVers!

For example, running one A/C unit and typical RV needs how much battery power would you need to run a fan or 2, washing machine.dryer once every 2 days, laptop, 40" tv, directv, coffee pot for a week. Just looking for ballparks. No solar at this point. I appreciate your time!!!!

[DotDun]

Originally Posted by billysurf

We are doing research on lithium batteries for a converted bus (MCI or GM) and can't get the answer to a very basic (although loaded) question. How long can you be without a power hookup. I know the boat community could answer this much faster than the RVers!

For example, running one A/C unit and typical RV needs how much battery power would you need to run a fan or 2, washing machine.dryer once every 2 days, laptop, 40" tv, directv, coffee pot for a week. Just looking for ballparks. No solar at this point. I appreciate your time!!!!

Until the battery runs down!

[billysurf]

hahahaha! NICE!