LiFePo4 House Bank Using SmartHousePower BMS

[electric1]

As I promised in the other LiFePo4 discussion thread, I am starting a new thread to focus specifically on details of my new BMS designed for LFP house banks. Going forward I will use common abbreviation LFP instead of LiFePo4 because its shorter, both are equally used and refer to the same battery type/chemistry.

A little background for those who didn't read the other LFP thread. I come from DIY EV world where I have been involved in EV conversions using LFP batteries. I drive my own EV conversion for couple of years now and have over 10,000 EV miles on my LFP pack. During this time I have been designing and producing LFP BMS systems for EVs, but recently I also got involved in marine house bank market and it brought me to this great forum.

With help of forum members here I was able to formulate technical requirements for marine house bank BMS using LFP battery cells, and I designed new BMS specifically for house banks. I called it SmartHousePower BMS. BMS is a Battery Management System, which is required on LFP banks to protect them from overcharge and overdischarge, to prolong the battery life. LFP battery has tremendous advantages over Lead Acid and recently large AH capacity cells became available/affordable and now compete with Lead Acid considering their long lifecycle, high performance, high efficiency and low weight.

My goal is to produce effective, reliable, easy to install BMS and make it affordable for those who aren't afraid to upgrade their house banks on their own. BMS can be a separate enclosed unit which is wired to LFP cells purchased separately, or it can be integrated in a box with LFP cells for a simple drop-in solution. Since LFP cells are relatively large and heavy, I want to give customers the opportunity to source and purchase LFP cells locally or from their preferred source and then attach my BMS to those cells. This will avoid multiple shipments of cells, which increases cost.

I also welcome professional marine electricians to source cells locally and use my BMS to offer their local customers complete turn key solutions. This could create new business opportunities and help promote new technology among boating community.

Lets try to keep the focus of this thread on specifics of my BMS. The other more generic LFP thread can be used for general LFP discussions.

I hope I am not violating forum rules by starting this thread. I sincerely hope to help forum members adopt LFP technology and kick Lead Acid to the curb.

[electric1]

Here is the white paper draft for my new BMS.

SmartHousePower BMS.pdf

[electric1]

To make a prototype of a complete drop-in solution I purchased 4 200AH cells from LFP manufacturer called HiPower. These cells fit perfectly into standard 4D marine battery box made by Todd, with room available to place BMS electronics inside the box. As I make progress I will share more pictures. In parallel I am also building a prototype of the same BMS in its own small box for those who buy cells on their own. I will have more pictures soon.

[Tinkerer007]

I like it. A number of features I didn't even know I wanted.

I like the visual and audible indicators for action conditions. Does it use the same signals for all conditions, or are there different LEDs, or pattern of flashes?

I also like the power off feature for storage.

Is there a snooze button on the warning modes? I can imagine the audible warning could be annoying if you are in a stressful situation and need to discharge the battery to 80%.

I am curious about the 1C charge disconnect. I thought LFP batteries could provide 1C charge and discharge without problem. Some boats have 200 AH or more alternators.

[electric1]

Originally Posted by Tinkerer007

I like the visual and audible indicators for action conditions. Does it use the same signals for all conditions, or are there different LEDs, or pattern of flashes?

There are different patterns to distinguish different conditions. Audible signals start with short and less annoying beeps, then grow into longer and more annoying beeps as battery gets lower and lower, culminating in a solid beep once power is cut off to protect the cells. LED signals are designed to pinpoint specific problem. This will all be documented in a user guide, along with wiring diagrams and all other details.

Is there a snooze button on the warning modes? I can imagine the audible warning could be annoying if you are in a stressful situation and need to discharge the battery to 80%.

Initial alert is not annoying and I don't think snooze is appropriate action when your battery is about to go dead.

I am curious about the 1C charge disconnect. I thought LFP batteries could provide 1C charge and discharge without problem. Some boats have 200 AH or more alternators.

LFP can take up to 3C charge rates, but its not advised to go over 1C charge rate regularly to prolong battery life. I imagine that boats large enough to sport 200Amp charging source will likely have house bank larger than 200AH, which means each 200AH string will only see a portion of that 200A charge current. In any case, I can easily adjust alert levels in the software if customer wants to deliberately abuse his/her LFP bank.

Thanks for your feedback!

[electric1]

Sorry for slow progress, there aren't enough hours in a day to get all the work done

The drop-in unit is now completed and ready to be put on a boat!

Here is what it looks like. Standard 4D box housing 200AH 12V LFP battery with BMS. Power switch and 5 LEDs are on the top panel, as well as terminal strip for optional control circuits and 3/8" power posts.



I am now working on "BMS-in-a-box" unit, I found real nice plastic waterproof enclosures that I will use, got most of the parts I need, its just a matter of putting it all together with whatever little free time I have these days.

[LiFeTech Energy]

Originally Posted by Tinkerer007

I am curious about the 1C charge disconnect. I thought LFP batteries could provide 1C charge and discharge without problem. Some boats have 200 AH or more alternators.

We have to be clear in distinguishing between LiFePO4 batteries made for the DIY market and professional grade LiFePO4 batteries.

Low power batteries made for the DIY market typically are rated at low C rates for both charging and discharging.
By contrast high performance LiFePO4 batteries typically are rated at 10C - 35C for discharging and 5C charging.
If we use the example of 100Ah capacity then at a charge rate of 5C means we are charging at 500A.
It is easy to see the charging limitation in most cases will be due to the power available from the alternator rather than the current the battery can safely accept.
This is why high power LiFePO4 batteries can be recharged to more than 90% capacity in as little as 15 minutes.

[Steve_C]

What would be the approximate cost for the 200AH drop in unit not including shipping costs? I am just looking for a rough point of reference here.

Also what would be involved in a remote monitor for a bank of these?

Interesting thread, thanks.

[electric1]

Originally Posted by LiFeTech Energy

We have to be clear in distinguishing between LiFePO4 batteries made for the DIY market and professional grade LiFePO4 batteries.

LiFeTech, this statement doesn't make any sense and with all due respect you are putting down your competition in every post you make with very little facts, mostly just empty phrases of how superior your Taiwan production facility vs. mainland China factories. Since I started this thread focusing on particular system I am building, I'd like to ask you to take your commericals elsewhere.

To clarify, your company only makes small cylindrical cells, which are designed for high power high C rates, but cost a lot more. Then you package many of those cells in a box to get larger capacity. Please correct me if I am mistaken. Show me any large prismatic cell that your company makes if you have it.

As a result of grouping small cylindrical cells you end up with high power battery, excellent product, no doubt, but much more labor intensive to build, thus much higher cost. There is a market for it, obviously, and its an awesome product for that market.

Other companies choose different route, they make large prismatic cells, with high capacity, but lower power lower C rate. Does that make them inferior? Absolutely not!!!! For applications like house power and even most of long range propulsion, large prismatics are perfect. Their lower cost and simpler handling make them very attractive not only for DIY, but for many professional products.

You keep painting a picture for this audience that high C rate is somehow better than low C rate, that is absolutely wrong. Its just like saying that oranges are better than apples.

I really don't want to turn this thread into another LFP discussion, there is another thread for it already. This thread assumes that reader is already aware of LFP benefits and wants to see how large prismatics can be used as a house bank using specific system that I have developed.

[electric1]

Originally Posted by Steve_C

What would be the approximate cost for the 200AH drop in unit not including shipping costs? I am just looking for a rough point of reference here.

Also what would be involved in a remote monitor for a bank of these?

Interesting thread, thanks.

Steve,

this system would retail about $2500.

Any battery monitor which counts AmpHours in and out will work perfectly with LFP banks. Many DIY EVs use Xantrex battery display and other similar products. My company is also developing EV Display which can be used just as effectively for house banks or propulsion banks. It will be available in about a month and will be priced under $200.

BMS in a box will be priced around $600 if you want to buy your own cells and put the bank together yourself. It will require no special skills.

Thanks for your interest.

[LiFeTech Energy]

Originally Posted by electric1

LiFeTech, this statement doesn't make any sense and with all due respect you are putting down your competition in every post you make with very little facts, mostly just empty phrases of how superior your Taiwan production facility vs. mainland China factories. Since I started this thread focusing on particular system I am building, I'd like to ask you to take your commericals elsewhere.

To clarify, your company only makes small cylindrical cells, which are designed for high power high C rates, but cost a lot more. Then you package many of those cells in a box to get larger capacity. Please correct me if I am mistaken. Show me any large prismatic cell that your company makes if you have it.

As a result of grouping small cylindrical cells you end up with high power battery, excellent product, no doubt, but much more labor intensive to build, thus much higher cost. There is a market for it, obviously, and its an awesome product for that market.

Other companies choose different route, they make large prismatic cells, with high capacity, but lower power lower C rate. Does that make them inferior? Absolutely not!!!! For applications like house power and even most of long range propulsion, large prismatics are perfect. Their lower cost and simpler handling make them very attractive not only for DIY, but for many professional products.

You keep painting a picture for this audience that high C rate is somehow better than low C rate, that is absolutely wrong. Its just like saying that oranges are better than apples.

I really don't want to turn this thread into another LFP discussion, there is another thread for it already. This thread assumes that reader is already aware of LFP benefits and wants to see how large prismatics can be used as a house bank using specific system that I have developed.

Electric1, I felt I should come in here since the information presented in this forum should be factual/truthful. If I read something which I know to not be the truth of course I feel the need to come in and set the record straight. Just as I would expect you to also come in and challenge me if you believe something I have said is not correct.

Earlier in this thread you clearly stated that- “LFP can take up to 3C charge rates, but its not advised to go over 1C charge rate regularly to prolong battery life”.
This is simply not true! Perhaps you should have clarified this statement by saying your comments only applied to the low C rate DIY LiFePO4 batteries because this comment certainly does not apply to the high power LiFePO4 battery products available in the market place.

You say I “make with very little facts”. What leads you to this conclusion since I try to include as much hard data where possible. You will see my most recent comments on the dedicated LiFePO4 thread I have included the LiFePO4 cell self discharge curve. I will present hard data where ever possible.

We manufacture medium size cylindrical cells in 38123, 40152 and 40176 sizes which all have threaded terminals. “Small” cylindrical cells are most commonly 18650 and 26650 sizes, ie, the cell sizes used in the manufacture of laptop computer batteries and power tool battery packs which do not have threaded terminals and require spot welding cells together to make battery packs.

You also say- “Other companies choose different route, they make large prismatic cells, with high capacity, but lower power lower C rate. Does that make them inferior? Absolutely not!!!! For applications like house power and even most of long range propulsion, large prismatics are perfect".

The Chinese battery companies make large prismatic low power (low C-rate) cells for the simple fact the Chinese battery companies don’t have the technology to make a good quality, high discharge rate LiFePO4 battery. If they could then why aren’t you selling high C rate cheap Chinese LiFePO4 batteries?
The Chinese merely copy other people’s inventions and ideas without any recognition to the rightful owners who invented the technology in the first place. I will always be a strong supporter of the US inventors and rightful patent holders of the LiFePO4 battery. I am not afraid to say I am proud to be an official licensee of the genuine US patented product!

You further say (referring to large Chinese prismatic cells)- “Their lower cost and simpler handling make them very attractive not only for DIY, but for many professional products.”

How is there “simpler handling” of your product when this whole topic is about adding a BMS to individual cells to make a workable product, not to mention that the manufacturers of the larger Chinese cells (Thundersky in particular) state that their cells must be installed upright at all times so as to prevent leakage of the cells and thus prevent early cell failure?
I would of thought a complete packaged battery which includes the BMS already built in and which can be fitted in any orientation (as in the case with complete LiFeTech battery packs) thereby making the battery a true “drop in replacement” for lead acid is the simplest solution.

Of course you are absolutely correct as far as the initial cost of your product is lower.
But that goes without saying when you consider all the corners the Chinese battery manufacturers take such as minimal testing and quality control of their finished product, inexpensive/low grade LiFePO4 powder used to manufacture their cells and the fact they don’t pay any royalties to the rightful American owners/inventors of this product!

As far as your comments about “professional users” goes.
Thundersky, Sky Energy and China Hi-Power and similar batteries made for the DIY market will never be chosen by any of the “professional” EV manufacturers (as far as I can see). I talk to many professional manufacturers and none will remotely consider using these batteries. The professional EV conversion companies I talk to all seem to have similar opinions about the Chinese product with the major comment being along the lines of- the Chinese prismatic batteries look very unprofessional with the live/exposed copper links and “all the little wires” for the BMS on top of the cells. These comments are in addition to the low C rate arguments. These are not my opinions but those of the professional EV conversion companies I talk to.

It is my own personal belief that the current Chinese DIY batteries will slowly fade away and totally disappear from the market in the next 5-10 years. The professional manufacturers of the world ie, the GM, Ford, Toyota and similar companies will be using professional quality products to power their vehicles. As electric vehicles of all descriptions (cars, bikes, boats, buses, etc) become more common place a new market will open up for cheaper used/secondhand LiFePO4 batteries. Just as is the case now where you can buy a new car part or a cheaper used part from an auto wrecking yard those people who now are using the Thundersky or similar Chinese batteries will in the years to come be able to buy good quality used LiFePO4 batteries.
In the past I have already supplied LiFePO4 cells to a company in Texas which I was told was using the cells to re-build defective Honda Insight battery packs.

Just my opinion. You can come back in 10 years time and tell me I was wrong!

So electric1 you are doing good work and anything which gets rid of the lead is a good thing. I just reserve the right to make my own comments known when I believe the facts are not being told.
I don't want people who are new to LiFePO4 or who have some experience (but are not as experienced as you or I) thinking that all LiFePO4 batteries face the same performance limitations which you describe when you are only referring to the battery types you are using.

[electric1]

Earlier in this thread you clearly stated that- “LFP can take up to 3C charge rates, but its not advised to go over 1C charge rate regularly to prolong battery life”.
This is simply not true! Perhaps you should have clarified this statement by saying your comments only applied to the low C rate DIY LiFePO4 batteries because this comment certainly does not apply to the high power LiFePO4 battery products available in the market place.

So, to make you happy, every time I speak about LFP cells I have to distinguish high power cells from low power cells? Well, let me make it easy right now, I never did and I never will use high power cells in applications where high C rates are simply not required, since that would be a waste of money. Since I am not involved in racing or engine starting or any other applications that actually benefit from high C rate, my comments are always toward resonably priced large prismatic cells offering 1C-3C rates, which are plenty for house banks and propulsion systems where people care more about running for more than one hour than ability to dump 1000 Amps in 5 seconds.

And yet again, you keep labeling Chinese large prismatics as somehow inferior and using unbased arguments of Chinese business practices to show your company apparent superiority. All business related claims you make are empty phrases, that is what I was talking about earlier, not your technical data. Your technical data is perfect and I thank you for taking time to share it with the world, but your business attitude and ethics are questionable based on your forum postings. Someone who is proud of their product does not need to bash competition with his tongue in cheek remarks in almost every post.

I repeat again, since you missed it in my last post, large prismatic cells don't need high C rates, it would be stupid to make 10C continuous 200AH cell because no one needs 2000Amp contunuous discharge for 6 minutes when application requires power longevity. These applications need energy, not power, and energy density of your product is not higher than any other LFP product, when you consider the room taken by the box holding smaller cells and all connectors and wires around it. When you need more power you usually need more energy too, so you just add more cells in parallel. Just adding more power by using high C rate cells means you will run out of that power much faster.

What are those EV companies you talk to? Apparently you are talking to people who have no clue at all. Any and every battery needs wires and connections. You hide yours in a box, but the same can be done and in fact is done with large prismatics as well. Chevy Volt and many other EV manufacturers use prismatics and bundle all connections inside some form of casing, obviously no one runs an EV with wires exposed, what kind of argument is that?

Back to your constand talk about patents. Do you have concrete facts that companies like HiPower, CALB and ThunderSky run their operations by violating any patent laws? DO you have any court documents to show it? Are there any active legal suites? Are you privileged to any inside information of these companies that you so easily bash on multiple forums? All we hear from you is how evil Chinese steal everything, this story gets old really fast.

Back to your own producs, why is that you are so proud of your product but so ashamed to post a clear price list? I was unable to find any online price referenc of your producs. All I found is AliBaba site listing all your batteries, but no prices mentioned? Every other LFP cell or battery can be priced online without having to call or Email someone, why is yours different? And don't give me your usual story of "custom made packs" or "forum restrictions", there is nothing custom about those batteries listed on AliBaba and forums don't care if you type cost per AH or WH. Let me give you an example right here, HiPower cells I bought for this prototype cost $1.45/AH (or $0.45/WH ) from door to door, including all US import duty and shipping to Tampa FL. So, how much I would pay per AH to get my hands on your battery of similar size here in Tampa? Trust me, no one will ban you from the forum if you reveal this well guarded secret.

Back to your terminology. What exactly does DIY mean for you when you say "DIY battery" vs. "professional battery"? Does this imply that battery is hand made in China like they make rugs in India? Chinese large prismatics are made in a factory just like yours are made in a factory, so what makes them DIY? Are you implying that Taiwanese quality is better than Chinese quality? Other than old wives tales youu speak of, do you have any hard facts? I know for a fact that EV Components in Seattle imported tens of thousands TS and CALB cells over the past year, all of which were sold before they even hit US shore, and 99.9% of them are peffectly working product. A handful of defects were promptly replaced under warranty. All of that business was done at $1.3-$1.4/AH door to door. Here, I posted price again.

[MarkJ]

Good discussion lets us have good information to make our minds up.

So I thank you both, and hope you both keep a watchful eye on here


Mark

Anyone who wants to give us 400amp hours to test in a real cruising situation we are ready to help!!!!

[hellosailor]

Originally Posted by electric1

Here is the white paper draft for my new BMS.

Attachment 15921

Well, as of tonight Acrobat said the file is damaged and could not be repaired or opened. Perhaps someone could check on that?

Surette, one of the more expensive brands, charges about $2/AH for 300AH at 12V of deep cycle wet lead batteries. No fancy BM$ needed.

Making LiFePO4 still a niche product for those with the bucks to buy into it.

Sure, I'd like to get the lead out, but trading gold for lead is an old conjurer's trick, isn't it? (G)

[electric1]

Originally Posted by hellosailor

Well, as of tonight Acrobat said the file is damaged and could not be repaired or opened. Perhaps someone could check on that?

Surette, one of the more expensive brands, charges about $2/AH for 300AH at 12V of deep cycle wet lead batteries. No fancy BM$ needed.

Making LiFePO4 still a niche product for those with the bucks to buy into it.

Sure, I'd like to get the lead out, but trading gold for lead is an old conjurer's trick, isn't it? (G)

The file still opens up fine for me, not sure what the deal is.

I absolutely agree that today LiFePO4 is a niche product, but sticker price alone can't be used to judge it. When all benefits are considered, LFP comes out on top of Lead even at today's price. All great new products early on were niche, competing and pushing away at the old stuff, that's just life. I drive EV for 2 years now. What I saved in gas will never cover the cost of EV investment, but that is not the point of doing it, at least not yet. Some of us just like to be on the leading edge and see the future, while others will stick to what worked before until its all gone.

Its funny that Lead Acid is always poined out as not needing BMS, this can't be further from the truth actually. As you know, Lead Acid cells are 2V nominal and ALL batteries have 3, 4, 6 or 12 cells in series inside the box, usually without access to individual cell terminals. Lead Acid cells suffer greatly from imbalance and battery's short life can often be traced to failure of one cell, while others are perfectly fine. The reason there is no BMS is that Lead costs little and no one cares to throw away a battery when one cell inside dies. If LFP cells cost the same as lead and could be as commonly available, then many people would not bother with BMS. We only use it to maximize cell's life and it pays for itself in a long term ( assuming BMS is reasonably priced of course ).

I agree though, today, a regular user who just needs house power and doesn't care to be on the edge, should carefully weigh the pros and cons of LFP investment, cons being high initial cost and pros being everything else

You'd be surprised when all things considered many will see LFP come out on top, but of course considerations differ based on specific power needs.

What works for me may not work for you and vice versa.