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Old 30-04-2010, 21:34   #301
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Originally Posted by electric1 View Post
Those 12V batteries are meant to replace car starting batteries, where brief high current surges are accompanied by long charging sessions via alternator. That is why individual cells are not exposed just like in Lead Acid batteries. If you use these for propulsion or house power, you will quickly kill them since you have no way of monitoring individual cells. Most Lead Acid batteries die prematurely because you can't cater to individual cells, but no one cares since they are cheap to replace. In LFP we care for each cell because the batteries cost $$$$.
electric 1, I (respectfully) disagree. This is not quite true.
Many of the Chinese LiFePO4 manufacturers are starting to copy our original engine starting/cranking batteries which we have been producing for close to 3 years already.
12V cranking batteries are simply made up of 4 LiFePO4 cells in series to provide the nominal 12V. There is no such thing as a 12V LiFePO4 cell!
A 12V LiFePO4 battery is equally well suited to engine starting as it is for house power. This is why these batteries are so wonderful since these are a truly "multi-application" battery.
The critical factor is the C-rate. The cell must be capable of providing the peak discharge current as per the cell manufacturers specifications.
This is why the low C rate cells ie less than 5C such as all the brands commonly made for the DIY market are best suited for house power. Only if the battery bank is of sufficient size should it be used for engine cranking. For engine starting applications is is far better to use a high power cell or specific engine starting LiFePO4 battery made especially for this purpose.
In most of these packs a BMS is not used. Generally only LVC protection is used to prevent damage due to accidental over discharge. There is no need for cell balancing since very high quality "matched cells" are used (also sometimes known as "racing cells"). Since these cells are virtually identical to each other in terms of internal impedance and actual capacity they have very little tendency to become out of balance.
I will have more to say about this issue shortly.

Our primary manufacturing plant is in Taiwan and we have been supplying high power engine cranking batteries for the Taiwanese fishing fleet for 2 years now and a much smaller and lighter engine cranking battery can be used to provide the same power as a lead acid engine start battery. The Taiwanese fishing boats are powered by a 380HP marine diesel engine and the original lead acid battery they used was rated at 12V 240Ah.
We supply them with a LiFePO4 battery one third the capacity (12V 80Ah) and less than half the weight (less than 34lbs). This battery does an equally/better job compared to the original lead battery.

In another case my own Toyota Camry has had a 12V 20Ah LiFePO4 engine starting battery which weighs 9lbs fitted for nearly two years (two years in June 2010). It has worked faultlessly day in, day out and has saved me a considerable amount of fuel in that time.

Neither the Taiwanese boat batteries nor my car battery contain a BMS!
It all comes down to the likely hood of cells becoming unbalanced. There are a few factors for this which I will explain in much greater detail shortly.

Nor do our LiFePO4 booster/jump starting lithium packs (pictured below) contain any cell balancing and we provide 2 years full warranty on these packs. We wouldn't be providing this warranty if we thought that cells would be getting out of balance and failing!

As you can see below this is what two BMI 12V 10Ah LiFePO4 batteries look like-almost identical. The battery on the left with the battery data interface connectors fitted has a BMS fitted internally while the engine cranking battery on the right with the clamp type auto terminals has no BMS (only LVC).
Both battery types are a direct drop in replacement and have no external BMS components. All the battery management electronics (where required) are built into the battery case.
Both batteries USE THE SAME CELLS.
So lithium batteries are different to lead acid batteries in respect that lead acid battery cells for engine cranking and house power are distinctly different from one another while with LiFePO4 batteries they are the same.

I have just ordered a small but very high power (35C peak) LiFePO4 engine cranking battery for one of my major electric boat projects. This battery which weighs in at 13.4lbs will be the cranking battery to start the 20kVA Yanmar diesel engine/generator for charging the main LiFePO4 propulsion battery bank when there is insufficient solar power on cloudy days and for extended run times with all motors at full power. The same battery will also be used to power the anchor winch as well as be a source of emergency 12V power in the unlikely event of a DC/DC converter failure for house power.

If there is anything which is not understood please let me know so I can explain in greater depth.
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Old 01-05-2010, 08:47   #302
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Before I go into great depth in explaining what a BMS is exactly, its functions, where it is required, where it is not required and alternatives to using a BMS I would like to ask if anyone is completely confused about this subject or has any questions on this topic then please ask so those who are informed about this subject such as myself and electric 1 can answer your questions?
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Old 01-05-2010, 09:25   #303
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C Rate

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The critical factor is the C-rate. The cell must be capable of providing the peak discharge current as per the cell manufacturers specifications.
This is why the low C rate cells ie less than 5C such as all the brands commonly made for the DIY market are best suited for house power.
I have been following this thread from the inception and learning lots so thanks to all the contributors. I may have missed it but can someone explain what the C of C-rate means. I assume it is part of the LVC or Low Voltage Charge?
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Old 02-05-2010, 07:16   #304
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LVC is the abbreviation for Low Voltage Cut-off.

The LVC is the minimum voltage a lithium battery needs to be disconnected or "cut-off" from its load so as to prevent cell damage due to excessive discharge.
This can be achieved automatically by the BMS (Battery Management System) or manually by physically switching off of disconnecting the load at the point where the battery is close to fully discharged. An external Ah/counter meter can also achieve the same function and disconnect the battery at any preset/programmed level.

With lead acid batteries we use the term CCA (Cold Cranking Amps) when comparing different brands of batteries side by side to compare the discharge power of each type.
With lithium batteries the most meaningful term for comparing the discharge power between different brands is the "C-rate". This is the current (amps) the battery or cell is capable of discharging at a specified cell or battery capacity in Ah.
So if we use the example of a 10Ah cell and if it was rated by the manufacturer at 3C this would mean this cell can discharge at 30amps ie, 10 x 3 = 30
The same cell rated at 8C could provide 80amps.

Most of the LiFePO4 cell manufacturers specify two C rates. Both "continuous discharge" and "peak discharge" rates are normally specified. The peak rating is only for a very short period of time and can be either a matter of seconds (or less than a second) . So for instance Thundersky cells are rated at 3C continuous and 5C peak.
Therefore the user can determine the amount of current a battery will provide continuously such as for house power as well as the amount of discharge power the battery can provide for a short burst (for example this might be useful to know for the start up/burst power requirements for an inverter etc).

The following 3 general power classifications of lithium batteries are sometimes used when discussing C ratings.
Low power LiFePO4 = 1-5C
Medium power LiFePO4 = 6-10C
High power LiFePO4 = greater than 10C

The C rating of the other lithium chemistry types such as Li-Co, Li-Mn and Li-Po will vary from one family to the next and are not the same as the C rates for LiFePO4 batteries. We are only discussing LiFePO4 batteries here since these are by far the most suitable type for use aboard boats and are non hazardous as are some of the other types.

With individual LiFePO4 cells which are used to make up battery pack by connecting multiple cells, the cells will most often not have written on them the C rate so the manufacturers data/ cell specification sheet needs to be consulted for this information.
Complete LiFePO4 battery packs which are designed as drop in replacements for lead acid batteries often have the C rate marked on them. Generally with lead acid batteries the most common voltages available are 6V and 12V. With LiFePO4 common voltages are 12V, 24V, 36V, 48V and several other voltages of up to around 350V in a single battery pack are also available. These high voltage batteries cater to the electric vehicle market (most often high voltage AC motor drives).
For example the photo below shows a BMI 48V battery. The top of the label clearly shows it is a "LiFePO4" battery and at the top left of the label its rating of 20C is also stated.

I trust this will clear up any confusion related to C-ratings of lithium batteries.
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Old 02-05-2010, 08:49   #305
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LiFeTech,

Thanks for a very well written explanation of the terms for these batteries. I too was becoming confused. Look forward to more information like this as I learn the applications of this technology

John
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Old 02-05-2010, 09:20   #306
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I've been following this thread from the beginning (thank you, Jallum, for starting it; and certainly to electric1 and LifeTech for their technical expertise) and certainly appreciate the education that I've received, even though much of it quickly gets over my head.

It seems that in the cruising world, there are two market areas for this technology. One of them is for those electric drive boats out there. There are (I'm guessing) probably around 200 Lagoon hybrids running around now. One of the problems with those boats is that they are hauling around tons of lead acid batteries and the additional weight aft penalizes the sailing performance. For those owners, being able to cut that weight to one-third would be a major benefit.

A far larger market would be in house bank conversions for everybody else. What seems to be missing are some fairly definitive, spec'ed out and priced options for those of us interested in converting our house banks. Is it possible yet to get that specific, realizing of course that as more factories come on line that prices will change, hopefully downward.

As you know, the house banks in cruising boats come in either 12v or 24v configurations. Within each of those, there are small (< 300 amp/hr), medium (400 - 800 amp/hr) and large (1000+ amp/hr) configurations. Obviously, I'm generalizing a lot, but this seems to be the case. While there are lots of charging options, most folks use a combination of engine alternators, shore power (or genset) based chargers, and wind/solar.

Are we to the point yet where you can price out packages for the most common configurations? That would certainly help those of us who may be looking at conversions or new banks consider whether to go in the LiFePO4 direction. I think most of us understand the many benefits, but sailors tend to be both conservative (tried and true preferred) and stingy, but also practical. If it is possible to get to those bottom lines, that would be greatly appreciated.

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Old 02-05-2010, 11:02   #307
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LiFeTech,

Thanks for a very well written explanation of the terms for these batteries. I too was becoming confused. Look forward to more information like this as I learn the applications of this technology

John
Dido...Thanks as well.

Jack
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Old 02-05-2010, 16:26   #308
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Gord, i don't say trolleys were killed entirely and solely by disinformation, but it was a primary tactic of the conspirators. They painted trolleys are dangerous, potential sources of electrocution, inflexible, old fashioned...you name it. They didn't just buy 'em and bury 'em, they convinced the public that they were doing a Public Service in doing so.

Kinda like Archer-Daniels-Midland telling us all how corn ethanol is really saving us from gasoline. (Ahem)
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Old 02-05-2010, 16:38   #309
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"12V cranking batteries are simply made up of 4 LiFePO4 cells in series to provide the nominal 12V."
Just what voltages are you working with? I'm seeing nominal voltages reported as a maximum 3.8V charging voltage, 2v maximum discharge state, and 3.2V as a normal "fully charged and rested" voltage, comparable to the 2.2V for a wet lead cell.
So, a 4-lifepo4-cell "12v" battery would actually be...a native (3.2x4=) 12.8 volts if a matched charging source was being used? As opposed to 12.6-12.7 for typical lead acid batteries?
Happily charging to a full charge state on the usual 13.8-14.4V auto/marine alternator then, without any extra consideration for the slight voltage difference, and the LiFePo4 cells are quite happy to function in that range?

By the way, how do they take to prolonged non-use, i.e. storage discharge damage? Can they be left on a shelf for six months (unlike wet like) without capacity loss?

And, if one cell DOES develop a defect...without a BMS to prevent that one cell from overcharging and overheating, just how is (pardon the phrase) fire control accomplished in this situation?
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Old 02-05-2010, 16:58   #310
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lifetech,
on the C ratings, low, med & hi cells. Are they the same chemistry & manufacture & just a "Select On Test process" that results in your different model of what appears the same cell?
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Old 04-05-2010, 08:03   #311
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Are we to the point yet where you can price out packages for the most common configurations? That would certainly help those of us who may be looking at conversions or new banks consider whether to go in the LiFePO4 direction. I think most of us understand the many benefits, but sailors tend to be both conservative (tried and true preferred) and stingy, but also practical. If it is possible to get to those bottom lines, that would be greatly appreciated.
ID
As much as I would be more than happy to provide specific pricing information you require I am not permitted to provide this information here due to the rules of this forum. I do not want to be banned by the moderators so I am afraid I will not provide any specific pricing information directly.

My main aim in being here is to provide as much technical information and educate as many interested boat owners as possible regarding LiFePO4 battery technology and how it can enhance and make your boating experience more enjoyable.
There are many electric boat projects underway all around the world and several I am directly involved with. As some of these projects are completed over the next 12 months and more is written about them, more people will learn about the fascinating possibilities due to the performance characteristics of LiFePO4 batteries.

I will limit discussion to different brands/manufacturers in broad terms and of course feel free to further verify the information I provide from additional sources or ask for further clarification. I will let you know what to look for in a good LiFePO4 battery and what to be wary of. As with all products there are those that are very good and others which are a complete waste of money and basically junk (I have learned this the hard way myself in the early days).

I will do my best to answer questions in as much detail as possible and I would ask that the moderators go easy on me if I unintentionally push the limits at times.
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Old 04-05-2010, 08:23   #312
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Quote:
Originally Posted by Intentional Drifter View Post
I've been following this thread from the beginning (thank you, Jallum, for starting it; and certainly to electric1 and LifeTech for their technical expertise) and certainly appreciate the education that I've received, even though much of it quickly gets over my head.
....
Are we to the point yet where you can price out packages for the most common configurations? That would certainly help those of us who may be looking at conversions or new banks consider whether to go in the LiFePO4 direction. I think most of us understand the many benefits, but sailors tend to be both conservative (tried and true preferred) and stingy, but also practical. If it is possible to get to those bottom lines, that would be greatly appreciated.

ID
Yes, this is a great thread! Perhaps the most informed posters of LiFePO4 marine applications available online. Electric1 and Lifetech are fantastic sources of info.

Regarding your question about pricing for common configurations, some of us are doing that every day now, and a great many comprehensive LiFePO4 systems are getting out there. Genasun, Mastervolt, Valence, RaceCell, of course Electric1 & Lifetech, Corvus, Enertek, and others all offer systems/prices.

I think it would be fun to have a list of boats with current LiFePO4 systems here (and new ones on the way?)...I'll through out a few, and I'm sure Electric1 and Lifetech will have some very cool projects to let us know about! I think posting prices here may not be allowed, but it is great to know what is going on out there.

In no particular order:

"Zogo" 29ft hybrid launch (Maine), 320Ah x 48V, RaceCell

"Ginger" 50ft spirit of tradition performance sloop (Maine), RaceCell

"Brainwaves" J35C (Calif.) 200Ah x 12V, Genasun

Huckins 45' powerboat by Yachting Solutions (Maine) 720Ah x 12V, Genasun

Gunboat 90' 1800Ah x 24V (Holy Moly!!!!) (South Africa), Genasun

Morelli & Melvin cruising cat (Westerly marine) 720Ah x 24V, Genasun

"Mala Conducta" 60ft Morrelli/Melvin by Lyman-Morse (system size unknown), Valence

"Ocelot" 45' racing sloop (Calif.), RaceCell

I'm know there are many more, these are just some I'm either involved with or know about.
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Old 04-05-2010, 08:41   #313
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lifetech,
on the C ratings, low, med & hi cells. Are they the same chemistry & manufacture & just a "Select On Test process" that results in your different model of what appears the same cell?
Bill, there are a few factors involved here.
One factor is the construction type of the cell ie, whether it is prismatic or cylindrical in form factor.

Low power cells are always prismatic in construction and are generally of high Ah capacity. The high capacity is required due to the low discharge rate which can be drawn from these cells ie, usually around 3C.

Low power cells can also be made as a cylindrical form but most commonly most cylindrical cells you may encounter will be either medium or high power types.
Many cylindrical cells (because of their high power discharge capability) are used in small battery packs used for engine cranking and other applications where very high currents are required for short periods of time.
For example in the photo below you can see the latest battery (LiFePO4) as a lead acid battery replacement which is supplied as an original starting battery for Porsche sports cars. You can see behind the opaque outer battery case the battery is actually made up of four cylindrical LiFePO4 cells which are connected internally in series to provide 12V (actual nominal voltage is 12.8-13.2V).

The most important factor which determines the C rate of a LiFePO4 battery is the formulation/blend of the LiFePO4 powder used in the manufacture of the cell. Manufacturers of this powder often produce several formulations depending on the application of the battery. For example a low C rate blend with high energy capacity might be used for batteries suitable for house power on a boat whereas a high C rate formulation would be used for a high power battery for engine cranking.

The lithium battery manufacturers (particularly between the few manufacturers of the highest quality batteries) are very secretive about their formulations and manufacturing practices. The very best powder is manufactured under license from the company which holds the patent rights from the originator and inventor of the Lithium Iron Phosphate battery (Dr John Goodenough from the University of Texas). This company is Phostech Hydro-Quebec Canada. Phostech manufactures very high quality LiFePO4 powder which is supplied under strict licensing agreement to a handful of battery manufacturers.
You can be sure that no matter what battery brand you choose, if it uses genuine Phostech powder it will be amongst the very best LiFePO4 batteries available.
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Old 04-05-2010, 09:00   #314
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Great info Lifetech!!

Do you happen to have a list of the cell manufacturers that you know are using Phostech powder? Thundersky, Sky Energy,...others? I hear that Valence is doing something a bit different (Li-Mn?) as is Corvus (Lithium NMC?), what are their respective advantages/disadvantages vs. LiFePO4?

From the marine safety perspective, I never considered the early Li-Co systems a good idea when they showed up on boats. Now I've been convinced that LiFePO4 is good and am recommending it, but would like to know more about the alternatives touted by Valence/Corvus/others.

Info greatly appreciated!
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Old 04-05-2010, 09:03   #315
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Yes, this is a great thread! Perhaps the most informed posters of LiFePO4 marine applications available online. Electric1 and Lifetech are fantastic sources of info.
Perhaps we should separate boats into two categories-
1) those boats using LiFePO4 batteries for house power (since this will be of interest to most boat owners) and
2) boats which use LiFePO4 batteries for electric propulsion (either pure electric or hybrid).
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