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

[roetter]

Originally Posted by rainmaking

Paralleling two LFP banks is not easy to do safely though. May be easier to stick with just a 1-2 switch without an 'all' position. Hmmm....how long will it take my 200W of PV to charge all three 8400W-hr banks? I think about 30 days with no other load.

On our 950W solar we see about 4000Wh/d in the Caribbean. So filling your three 8400Whr banks with your 2000W of solar should take 1 day each.

[ebaugh]

Originally Posted by rainmaking

Ebaugh- you are right, it will not cross oceans. :-(
It will cruise the Caribbean indefinitely without fuel though. You are also right about diesel-electric. It really doesn't pay to have it on a cruising boat.

You need a 400nm range plus reserves if you want to do the eastern and western Carib. Grenada to Bonaire and Providincia to Honduras. Some of that can be shortened, but then you end up overnighting in ether Venezuelan or Nicaraguan waters. Mexico to the dry tortugas is close...unless you do Cuba, which is OK but then you have to go through the Bahamas to return to the USA. At the moment anyway...

The Eastern Caribbean to Florida does not require the range. 200nm will suffice.

[deckofficer]

But it will cross oceans and already has. A C60 commercial cat ferry was fitted with just 10 KW of panels and 520 a-hr 48 volt lead batteries in each hull. That is just under 50 KW-hr of storage and since they are LA, less than 25 KW-hr usable. Crossed the Atlantic running between 5~6 kt, 24 hours a day.

14 m length
6.6 m beam
24,000 lbs (and this could have been trimmed using LiFePO4 and aluminum instead of steel for the panel's supports)
1 m draft
(2) 8 kw motors.

transatlantic21: Boat

This cat is making due on 8 KW of solar, but is lighter with more efficient hulls. No reason you can't cross an ocean with just 2.5 KW of solar if you don't mind 24 hour runs to drop from 125 nm to 70 nm.

http://www.solarwave.at/project/boat.html

And everyone knows of this current power cat, they just upgraded to Winston cells from the AGM, and using only 6 KW of solar can knock off 85 nm daily runs.
http://dsehybrid.com/

[Saltyhog]

Originally Posted by Maine Sail

Gotta love Donald Fagan.......


He was one half of Steely Dan. That is a lyric from one of his solo songs off "The Nightfly" album IIRC.......

Yep. Now I'll have that song in my head all day.

[goboatingnow]

for those that dont get it , heres the full lyrics

"
Standing tough under stars and stripes
We can tell
This dream's in sight
You've got to admit it
At this point in time that it's clear
The future looks bright
On that train all graphite and glitter
Undersea by rail
Ninety minutes from New York to Paris
Well by seventy-six we'll be A.O.K.

What a beautiful world this will be
What a glorious time to be free

Get your ticket to that wheel in space
While there's time
The fix is in
You'll be a witness to that game of chance in the sky
You know we've got to win
Here at home we'll play in the city
Powered by the sun
Perfect weather for a streamlined world
There'll be spandex jackets one for everyone

What a beautiful world this will be
What a glorious time to be free

On that train all graphite and glitter
Undersea by rail
Ninety minutes from New York to Paris

A just machine to make big decisions
Programmed by fellows with compassion and vision
We'll be clean when their work is done
We'll be eternally free yes and eternally young

What a beautiful world this will be
What a glorious time to be free

"

I presume you see what I mean

DAve

[diugo]

Fagen wrote those lyrics over 30 years ago. Clearly, by "graphite and glitter" he meant graphite---and lithium iron phosphate

[deckofficer]

Gene Roddenberry got it right when he decided lithium crystals would power the Enterprise on Star Trek back in 1966.

[diugo]

Originally Posted by deckofficer

Gene Roddenberry got it right when he decided lithium crystals would power the Enterprise on Star Trek back in 1966.

Umm, IIRC those were dilithium crystals---maybe the secret is Li2Fe2P2O8!

[goboatingnow]

A just machine to make big decisions
Programmed by fellows with compassion and vision
We'll be clean when their work is done
We'll be eternally free yes and eternally young

prescient too, ist that Google.........!!!!
mind you I think he meant "cleaned out when their work is done"
Dave

[bill good]

My old cat does 7kts with 2X 1GM Yanmars max 6.5HP & most likely gets about 3HP at the props anyone wants a good mast & sail set?? (or the whole boat?)

Present weight 5T

[rainmaking]

Sorry, I should have said, 'before my time' instead of 'over my head'. ��
I would like to do 500nm @12kts. Maybe crossing the atlantic is doable at 4 or 5.

[chala]

Originally Posted by daddle

This link (from a CF post back around 1250) clearly shows that a LFP prismatic "cell" is actually a "battery" made from many flat pouch cells in parallel. However for a cruiser this does not result in increased reliability because defective cells cannot be easily removed.
Li-Ion BMS - Prismatic cells

From the link:
“”Prismatic cells
Structure of a prismatic battery cell: A prismatic Li-ion cell consists of multiple flat-wound, Li-Ion cells enclosed in a plastic case and connected to 2 large terminals.
Shandong HiPower cell
We cut open a Shandong HiPower, 160 Ah, Li-ion, prismatic battery cell. (This cell is similar to a Thundersky / Winston / Sinipoly cell, and to a CALB / Sky Energy cell.)
(Cell courtesy of Peter Oliver of Make Mine Electric.)
The cell consists of:
A plastic outer case (possibly PVC)
Two sets of flat-wound cells (similar to pouch cells, except not sealed in a bag)
Each set has about 24 foils coming out of it, for each of its 2 terminals
The negative terminal (shown) uses copper foils; the positive terminal (not shown) uses aluminum foils
The foils are 0.05 mm thick (0.002 inches)
Two aluminum terminals (only the negative terminal is shown)
M8 bolt for terminal connection to the bus bar
A 20 mm nut to secure the terminal to the case
Internally, the foils are held against the terminal by two clamp pieces, and two sets of screws, washers and nuts
It appears that, in this particular cell, the clamp pieces on the negative terminal have dissolved, resulting in heat damage
Across the 51 mm thickness of the cell:
4 mm (8 %): air space for cooling
6 mm (12 %): case
41 mm (80 %): cells””

Of no great importance but it can be assumed that each “set” contain 24 cells in a prismatic formation on an other hand, some one may see the “set” as a one cell concertina folded or whatever.
Of a greater importance is that as quoted “the negative terminal have dissolved”.
Fairly common in the electrical industry copper to aluminium connections can cause problems. Any cruisers that own an aluminium boat may have an idea that leaving copper remnant in the bilge is not a good idea. The problem is recognised.

Originally Posted by T1 Terry

probably a bad contact where the tabs bolt to the terminal blocks.

.
If that type of connection may last only few years and the connection is inaccessible and cannot be easily observed then the reliability of such battery is in question.
It is easy to understand the consequence of charging a battery in which a one cell capacity may have been halved due to one set in that cell being disconnected by a “dissolved connection”.
Proper monitoring of a battery should be able to detect a fault, raise an alarm if required and prevent injury to people and damage to property by automatic isolation of the fault.

Originally Posted by T1 Terry

We have had a few members put in side issues to create doubt in the safety of these cells for what ever reason they have, view them for just what they are, attempts to create doubt by mass hysteria, nothing more. If they can come up with verified instances where lithium ferrous cells have internally dead shorted and created a fire problem then it would be something to become concerned about, but that is not the case, so unless they can provide evidence of such cases, just put them down to troll posts and return to life as normal, ignore them

So you reckon we should ignore among other, posts 2356, 2379, 2382.

On the same above link the following can be found:
“””Thundersky cell
Otmar Ebenhoech cut open a Thundersky cell (which apparently had bloated from being fully charged while not constrained).
Again, note that the positive terminal uses copper foils, and the negative uses aluminum.
(Picture courtesy of Otmar Ebenhoech of Cafe Electric.)”””

Apparently the casing of that cell as not bulged because the cell was

Originally Posted by T1 Terry

simply sitting on the shelf in warm to hot weather

It easy to understand that trying to reshape a “bloated” cell and mostly one with a partial bulge due to inadequate “strapping” may cause some internal damage.

Originally Posted by chala

Good luck but be careful

The warning given is not there “to create doubt in the safety of these cells” but to circumvent the possibility that the operator by is ignorance “create doubt in the safety of these cells” in fact most of the incidence that “create doubt in the safety of these cells” to the extent that some members are

Originally Posted by daddle

reading CF with my goggles on

are due to some poor experimental practices.
“””come up with verified instances””” You and I do live in a regulated country where some prefer to remain discreet.

Originally Posted by Zil

What exact reshaping is referred?

The cell had been dropped; the operator used a large vise to reshape it. The fire that did occur did not happen during the reshaping of the cell but more than 7 days later.

Originally Posted by roetter

Roetter,
This thread is great but hard to weed through a lot of the crap people want to stir up.

I would not use that language but if you are referring to post 2490 you may be right.

[chala]

Originally Posted by ebaugh

I won't

The way I see it: a cell issue may blow all the nine parallel fuses.
A serial fuse opening without any cell issue will also and should blow the relevant parallel fuses (the serial fuse fault current should also be rated for 3 series strings in parallel)
Depending on what the cell issue is, the serial fuse may still allow current from the other strings to flow into the faulty cell.
What is necessary is not to allow reverse current to flow into a series string when discharging. For AC reverse power relay are common. DC reverse current detection may be available or could be made. In this case the relay should operate to completely isolate the relevant series string (that include isolating all relevant parallel lines).
I understand why (as per post) when charging you wish to have parallelling lines but do you require them when discharging the bank? After all if (as per drawing) a cell become faulty you loose a quarter of the capacity of the bank whatever configuration you have.
Of course, and the sky may come crashing, you could use blocking diodes in the series strings to stop reverse current. They will also allow easy detection of a cell issue.

Originally Posted by daddle

Paralleling batteries would be prudent for cruisers.

You think so.

Originally Posted by chala

then enjoy

[goboatingnow]

I have to say Chala, I dont quite get the point you are making , even if you are writing quite lengthy pieces to make it.

Dave

[Zil]

Perhaps in trying to compare such different chemistry we need a different term than cell for Lithium. Or a different or specific definition of lithium cell. It does seem silly to argue, but does get confusing when counting cells.