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

[thomasow]

It is good to see your are making progress on your BMS, am looking forward to the results of your effort over the years.

Originally Posted by OceanSeaSpray

Beware of power requirements, it is one thing to run a NMEA2K bus on a boat in use with everything going and another to have the bus active 24/7: not an option. There are a lot of things to think about in terms of CAN integration and operation.
I can see an avenue to leverage off the reliability of CAN and output battery data, but by using a strategy keeping the transceiver in standby most of the time. My initial consideration was using I2C through a P82B96, which can be run at low bit rates and doesn't have any clock requirements. I have started to think that CAN would offer more possibilities, but it comes with its own issues.

The consumption of an alternator regulator is essentially a moot point, but it is very different for a BMS or even a MPPT converter (or it will become useless/harmful in low light).

CAN need not be an excessive power drain, there are many examples of low-energy CAN products including several BMS’s as well as many more devices likely sitting in your driveway.. You are correct though that one needs a mindful hardware / firmware design to prevent undue overhead as well as not requiring 'near continuous' packets while at rest. I2C: Perhaps you have already concluding this, but I2C combined with a bus extender would be a very poor choice for device communications. Its lack of common-mode rejection combined with its susceptibility to ground offset alone would result in a highly unreliable architecture; if simpler serial comms is desired perhaps something like RS-485 would be a better choice.

Originally Posted by OceanSeaSpray

If you focus on your alternator controller, I will provide the BMS. The last thing we need I think is yet another one of those systems where nothing can work unless everything is interconnected with digital coms all over the place.

Today there is the regulator, a demo porting for a MPPT controller is underway for additional proofing of the prioritization portion of the protocol as well as remote instrumentation across multiple charging devices. I am developing a simple battery monitor, more likely used for lead-acid technologies, would be nice to see a proper BMS included as well.

An overall philosophy is: Devices should work well all alone, and work better / simpler when talking with each other. Not only as a growth path, but also as one of the reliability / fall-back strategies.

Originally Posted by OceanSeaSpray

An alternator controller for lithium should be able to limit the battery voltage, limit the maximum alternator current and stop charging when the current has decayed down to a limit. Stop charging just means try to regulate at a level that is at or lower than the desired final SOC when the engine is stopped. It is pretty simple, it doesn't require "zero current control" and the like. You get that for free and you don't need CAN to get there.

Ideally, it should do just that "out of the box" and it would be in a good position to displace the Balmars and others, which are unable to provide that.

Having a COM port on it could allow the BMS to send a setpoint to the alternator, rather than use the same all the time, and modify the operation based on the battery management strategy.

Thanks for the advice -- I think if you look at the current regulator you will see all your thoughts are covered. And I know you are a fan of the fixed voltage ‘float’ for LFP, and that is OK – the protocol as developed allows for which every approach to managing the battery deemed appropriate.



And again I will say: If there is broader interested in this forum around an open coordinated systems architecture, perhaps we should start up a different thread as such conversations could get rather detail for the current topic.

[OceanSeaSpray]

I was considering a point-to-point link from the BMS to a display unit with power and comms on the same cable, so not much of a problem and even quite large I2C networks are very feasible this way.
CAN has excellent characteristics, but they are partly obtained by pumping plenty of power into the cable. 3.3V CAN would be superior in this regard.

Quiescent current is precisely an issue nowadays in driveway devices... and it is a far more acute issue for a LFP BMS on a boat that could remain unused for months or years. 1mA of consumption without charging means 1Ah gone every 42 days. A lot of engineering has to do with minimising and being able to eliminate consumption.

I did look at your alternator controller, but not at the code. What matters in the end is what it actually does, out of the box, not what could be done by changing the firmware. I think it is important to remember that electronics enthusiasts are the minute fraction, people need/want a product they can use, not a benchtop experiment that keeps changing and this is what my comment was directed towards.

Last thing, "float" means nothing and creates confusion. I call it "hold" by lack of a better term. It is a voltage control strategy that mitigates battery discharge when relevant.

A new thread would be great if enough interest was there to discuss hardware development.

[OceanPlanet]

heh heh, OSS, well said, and funny joke about the wire colors. Fortunately they haven't actually done that (yet).

And good move on the temp sensors...;-)

[john61ct]

Originally Posted by john61ct

known LFP prismatic cells, actual manufacturers, all from China:

CALB
A123
Winston
Sinopoly

Adding GBS

Winston (as Thundersky OR Voltronix)

Also recently came across on eBay "Lishen", apparently supplies Apple, Samsung, LG, HP, Dell and Lenova?

Tianjin*Lishen Battery*Joint-Stock Co., Ltd

A supplier from Russia had little (tiny) cells he claimed were new 20AH, but the discharge graph was at 40A (2C, 30 min!)

$150 for packs of four @ 12V delivered

[john61ct]

Can't locate any info about this, suspicious

http://www.ebay.com/itm/201920802328

[Hoopla]

Originally Posted by OceanPlanet

FWIW...if any on this Li battery Forum are in or near Hawaii... We have a client who is replacing his 5yr old Genasun battery system with a new OPE-Li3 system for his next cruise. The Genasun kit was originally two 24v banks of 360Ah, each bank being two 12V/360Ah packs in series. One of the 24V banks is testing out great (will have a capacity test done soon), however one bank has a cell pair that appears to giving up the ghost.


So the one higher-performing bank could remain a 24v bank, or could become one or two 12V banks (twice the Ah's, half the voltage). The other bank could be one 12V bank, half the size of the other. The weaker pack could be kept for spare cells.


These aren't new, and are long out of warranty, however could be a heck of a bargain. If you're cruising near HI, drop me a PM if interested. Packing & shipping these batteries is not really practical. But moving them to another boat in HI is something that could be done.

OceanP that is a great buy for someone, wished I was in HI..even if cells are shot they can be replaced longer term with CALB CA's, unfortunately with Genasun out of the LFP business nothing else is replacement generic, so needs some longer term cell board/BMS spares planning from what is there today according to voltage.

IMHO Genasun's BMS is the the marine standard still to this day some 6 years after their introduction being alternator friendly and with individual cell pair voltage and temperature monitoring, not daisy chain monitoring...with deference OceanP to your OPE-Li3 system which has clearly stepped up and into the space left by Genasun and with their own US made cells to boot. It is a shame Genasun stepped out of the room it just means mainstream acceptance of properly engineered LFP systems for those that can't do the DIY route may now take longer.

[Hoopla]

Originally Posted by OceanSeaSpray

DNV-GL released guidelines for marine Li-ion systems long ago, no big deal in there. I had to request the document via e-mail, but it is otherwise free. I have uploaded it here for now and will leave it for a few weeks.

OceanS thank you very much for that. I found it a great read. For anyone worried about resale value with a LFP system they have put in, be it DIY or a system, you should carefully read the documentation bits of this publication, albeit big boat commercial and having regard for it then prepare an appropriate document for your boat in conjunction with anything else that pops its head up in due course in the LFP arena like ABYC.

Do that and I suggest you will satisfy any insurer, any broker and any potential buyer and in doing so get a large part of your LFP investment back on re-sale by having a very positive marketing point of difference to other comparative vessels on the market at the time.

In fact you if your interested in maximising re-sale return all systems on your boat should be documented accordingly. Seldom do that where modifications have been made no matter how good they are since time of build/original boat documentation and those sellers wonder why potential buyers and or brokers are so luke warm to their handiwork.

[Maine Sail]

Originally Posted by Hoopla

OceanS thank you very much for that. I found it a great read. For anyone worried about resale value with a LFP system they have put in, be it DIY or a system, you should carefully read the documentation bits of this publication, albeit big boat commercial and having regard for it then prepare an appropriate document for your boat in conjunction with anything else that pops its head up in due course in the LFP arena like ABYC.

Do that and I suggest you will satisfy any insurer, any broker and any potential buyer and in doing so get a large part of your LFP investment back on re-sale by having a very positive marketing point of difference to other comparative vessels on the market at the time.

In fact you if your interested in maximising re-sale return all systems on your boat should be documented accordingly. Seldom do that where modifications have been made no matter how good they are since time of build/original boat documentation and those sellers wonder why potential buyers and or brokers are so luke warm to their handiwork.

I don't know why I would ever sell our boat with the LFP battery in it. My own system is designed to be removed and re-converted to lead in a few hours, if that. Slap in a few hundred worth of brand new lead acid batteries and a buyer is happy cause he/she has a "brand new" bank...

The LFP is not going to add any value to my vessel on resale, but it certainly could detract from it. It will certainly add value to the next boat though, for my own use....

[Hoopla]

Originally Posted by Maine Sail

I don't know why I would ever sell our boat with the LFP battery in it. My own system is designed to be removed and re-converted to lead in a few hours, if that. Slap in a few hundred worth of brand new lead acid batteries and a buyer is happy cause he/she has a "brand new" bank...

The LFP is not going to add any value to my vessel on resale, but it certainly could detract from it. It will certainly add value to the next boat though, for my own use....

But where do you stop at re-sale MaineSail..put back all those winches sitting in the garage which are in perfect condition, but you just didn't like their size at the time etc...MaineSail your at the front end of LFP so you need to pass that LFP bank baby of yours and IP attached to it on for others to enjoy and learn...bit like letting children leave the nest and do their own thing....and your batt bank/boat aint that big so a LA swap back pretty easy :-)

[Maine Sail]

Originally Posted by Hoopla

But where do you stop at re-sale MaineSail..put back all those winches sitting in the garage which are in perfect condition, but you just didn't like their size at the time etc...It's not really about the resale it's baout the whack you'll take on it after scaring 98% of the buyers away....



MaineSail your at the front end of LFP so you need to pass that LFP bank baby of yours and IP attached to it on for others to enjoy and learn...bit like letting children leave the nest and do their own thing....and your batt bank/boat aint that big so a LA swap back pretty easy :-)

Sadly I have learned over the past 8+ years that the vast majority of boaters are not well suited for LFP because they can't lose the lead acid mentality...... Just look at how many folks, whom after thousands & thousands of posts, are still asking about "float voltages" for LFP....

Heck I just had an RV'er (called himself a "boondocker" ??) email about his great successes with his LFP bank. Course at the end he admitted his bank is dumper dive trash now, after just a year and a half, because he chose to use "human monitoring" rather than an actual BMS. Apparently humans are forgetful.... How he defined his $4000.00 pile of LiFePO4 rubbish, as a success, is beyond me....

To my way of thinking success with LFP will be definable at the 10+ year mark as I already have deep cycle lead acid batteries lasting that long (mostly GEL and industrial flooded).

Heck I have been busting my hump to break 1000 cycles and am still not there yet.

[senormechanico]

Did the boondocker give you any clues as to what he did to his bank "forgetful" wise to trash it?

[Hoopla]

Maine Sail the 10 year anniversary for LFP in this format becoming commercially available must be approaching soon?

If the test results achieved by you and Terry todate with fractional use , care and attention are any guide, then it is difficult to imagine they will not reach the 10 year/3500 cycle mark still going strong.

Your probably right about the wider acceptance of LFP not being overwhelming in the foreseeable future. The negative experiences that have to emerge from those treating them as "drop ins" is not going to help their reputation either.

[john61ct]

Biggest factor is the unfair fire-risk connotations of the umbrella term "Lithium batteries"

[senormechanico]

As a former president of the local chapter of The Corvair Society of America, and having lived through the associated B.S. presented by Ralphie Nader, I can certainly live through all the naysayers misconceptions about lithium cell technology!

https://www.bloomberg.com/news/artic...vair-right-now

[dlentz]

Originally Posted by senormechanico

Did the boondocker give you any clues as to what he did to his bank "forgetful" wise to trash it?

Let's see Maybe tooling down the road all day with an automotive style alternator/regulator pumping in 15+V
What could go wrong?

You don't need a lot to have a safe and reliable Li system. IMHO, pack monitoring and cell level monitoring with HVC & LVC and some quality regulated charge sources set conservatively.
I'm going on 4 years with Winston 700 amphr cells that were slightly used when I got them, and haven't needed re-balancing or any other issues. I even recently went though a survey by the largest and most respected surveyor in San Diego and my Electrical & Battery system was pronounced excellent and I was reinsured with NO problem.
These large format cells have even done the upwind, upswell bash from La Paz to San Diego no problems, no spontaneous combustion!

So what's the lesson/moral to the story? Is that it's just as easy to destroy a Li pack as a LA? Or that Li is safe because this dude didn't burn down his RV while destroying his pack? Or is it; the only safe way to do Li is to buy a fully engineered failsafe system, costing half your boat.

With that said, I get that if you're creating and building LiFePO batteries for sale, you need a whole other set of design criteria to CYA! (and wouldn't that discussion be suited to another thread?)

How about let's discuss our day to day use for those who actually live with or use LiFePO4 and move the engineering theory to another thread.


For instance; Has anyone here actually tried to use the temp compensation on a solar control to shut it down or dial it back in a high voltage event? MorningStar has some directions on their website on this and it seems like an elegantly simple way to deal with the solar in case of a HV event.
Hey, I wonder if you could do something similar with the MC 614?

OK Rip me a new now