Lithium Batteries (for the rest of us)

[manitu]

A lfp battery bank is charged basically like a la battery, alas , a certain number of cells in series, depending on voltage, plus a number of cells in parallel, depending on capacity. Since a serial string of cells is charged together, there is no way to "cut off" charging to a single cell in a string. What the BMS does is to bleed off a bit of the charge, trough a resistor in paralell with the single cell. This happens inside the BMS. It basically senses the cells with lowest voltage, and bleeds the rest. Several cells in paralell cannot be individually controlled and balanced without cutting the connection. But they will be kept at the same voltage, being paralleled.

Two extremes:

1:Connect cells directly in parallel up to capacity, then 4 or 8 of those in series, for 12 or 28 volts.

2:Make strings of 4 or 8 cells, and connect as many as you need to get the capacity you need.

With the first method, your bank is practically 4 or 8 BIG cells in series. The big advantage is that you only need a 4-1 or 8-1 BMS system, like a celllog8. The disadvantage is a bit more complicated. If one single cell in a parallel cell goes bad, this cell has less capacity than the others in that string. This parallell cell will charge at a different rate than the rest , leading to a need for constant balancing. Not too hard do find the bad cell though, but a bit of work to exchange it.

The other extreme is just opposite.. gives you absolute control over individual cells, but requires a nightmare of a BMS.
Or at the very least, one cell-log8 and a rigorous balancing routine.

Somewhere in the middle is what most will end up with.. small enough cells, not to ruin you when they go bad, and few enough to be monitored with relative ease. A modular design allso enables you to carry a couple of backup cells, preferably enough to make a complete emergency battery (4 or 8)
.manitu

[nimblemotors]

Here is an idea. Use a lead-acid battery as a buffer between your systems and the lithium battery. This should isolate the LiFe, and be compatible with all existing LA systems. Someone can work out the details or create a product that does it.

[goboatingnow]

Here is an idea. Use a lead-acid battery as a buffer between your systems and the lithium battery. This should isolate the LiFe, and be compatible with all existing LA systems. Someone can work out the details or create a product that does it.

Thats like teh idea of a man with a red flag in front of a horseless carriage idea

[JayH]

Originally Posted by nimblemotors

Here is an idea. Use a lead-acid battery as a buffer between your systems and the lithium battery. This should isolate the LiFe, and be compatible with all existing LA systems. Someone can work out the details or create a product that does it.

I think you've got that backwards. The high acceptance rate and high cycles of the lithium makes it the better candidate in a buffer application.

[nimblemotors]

Originally Posted by JayH

I think you've got that backwards. The high acceptance rate and high cycles of the lithium makes it the better candidate in a buffer application.

This is an equipment/technology buffer. All existing lead-acid battery charger can be used as-is, AC connections, fuses, solar chargers, wind generators, blah blah.
The lithium system is much simpler, only deals with lead acid battery as input and output source, and can simply "drop in" without any FUD.
Can be sold by West Marine.
I think its a good solution for an upgrade, which frankly is almost 90% of the market has existing lead installed, who wants to do a complete refit of the electrical system to swap batteries or worry if their wind generator will work right or not.

[hellosailor]

"Small format LI /Li polymer is everywhere "
But that's very different. Those small ubiquous batteries are single-cell batteries with a nominal voltage around 3.6 volts. All of the issues about runaway from one cell in a battery, balancing, they just don't exist when the battery is in fact just one cell.
On the next step up, series-parallel arrays in laptop batteries, lithium has shown some ugly sides. First, there is the expensive electronics array controlling the cells. Literally sensing and charging every cell pair in the battery separately, making the batteries radically expensive. And the performance has been either amazing or abyssmal, often limited to 500 charge cycles or 4 years, and failing totally and without warning at the four year point. Of course the battery makers say this is not relevant since the big batteries for cars and boats are totally different compositions and constructions.
If lithium batteries really can use cells that operate perfectly anywhere between 2.6-4 volts (which is about what they all claim) then a 4-cell lithium battery should be a perfect drop-in replacement for the nominal 12v car battery, where it never will be overcharged (14.4 volts max versus 16v battery rating). And the car makers should be killing themselves since they can save weight, which saves more vehicle weight (lighter springs, etc.) and raises fleet fuel mileage and lowers emissions--all goals they radically pursue. Patents? More than one maker has proudly boasted, perhaps in mistranslation, that they have exclusive patents "in China" meaning, they haven't got them for the rest of the world.
Nah. They sling too much mud. They need to learn "pull together".

[daddle]

Originally Posted by goboatingnow

* easier to charge , different then LA yes, but actually technically easier

* less complicated , yes it is . It just we have grown used to LA systems, that are actually quite complex

You will need to define "easier" and "complex". I presently have four LA batteries that I can source easily almost anywhere (Trojans T-105). A simple 100A alternator (rarely used), four solar panels controlled by a simple MPPT unit. No battery monitors, nothing but a voltmeter (mostly ignored) on the panel. The batteries get water a few times per year. After 5 years of daily deep cycling they have reached their end ... about 30% C.

That is quite easier and anything but quite complex.

Otherwise, I eagerly await the day that LFP technology makes practical sense for me. And doesn't cost quite so much up front. I especially like the weight savings:

Delivered from respective distributors in Manila, PI:

(4) Trojan T-105, 464 A-h @ 12V, US$683
(8) Winston LYP160AHA, New, Jumpers, 320 A-h @ 12V, US$2863

[Khagan1227]

Originally Posted by ebaugh

Maybe 10x a group 27 "deep cycle" battery from Sam's Club. I will be happy to see 3x my old Trojan golf carts. And there may be little additional cycle life compared to real 2V traction cells (forklift batteries).

Anyone who can say 10x without any qualification is drinking kool aid.

I'm not even close to being an expert, so I can only tell you what I read in the funny papers.

www.bruceschwab.com/uploads/li-vs-la.pdf

[daddle]

Originally Posted by Khagan1227

I'm not even close to being an expert, so I can only tell you what I read in the funny papers.

www.bruceschwab.com/uploads/li-vs-la.pdf

Wow. What a surprise! A glowing breathless completely un-referenced analysis from a LFP vendor. Hits all the "talking points".

[nimblemotors]

Originally Posted by daddle

(4) Trojan T-105, 464 A-h @ 12V, US$683
(8) Winston LYP160AHA, New, Jumpers, 320 A-h @ 12V, US$2863

However, at 50% DOD the Trojan delivers gives you about 200 AH.
65lbs each = 260lbs, let's call it $500.

So I'd compare more to 8 CALB 130 Ah, round it to $1500,
10lbs each = 80lbs
Or 12 100 AH Sinopoloy (300Ah) $130ea = $1560
7lbs each = 84lbs

Sinopoly 100 Amp Hour Lithium Battery

So roughly 3x cost, and 1/3 weight.

Big question is cycle lifetime. T-105 say 650 cycles. If lithium really is 3000 cycles, cost is a wash, any better, lithium wins and saves weight, higher charge rates, doesn't need watering, spill, outgas and corrodes.

[ebaugh]

Originally Posted by nimblemotors

This is an equipment/technology buffer. All existing lead-acid battery charger can be used as-is, AC connections, fuses, solar chargers, wind generators, blah blah.
The lithium system is much simpler, only deals with lead acid battery as input and output source, and can simply "drop in" without any FUD.
Can be sold by West Marine.
I think its a good solution for an upgrade, which frankly is almost 90% of the market has existing lead installed, who wants to do a complete refit of the electrical system to swap batteries or worry if their wind generator will work right or not.

I think you are right, but perhaps even simpler than you think? The LA solves the alternator problem with an abrupt cutoff for overcharge, keeping the LA in the loop and not frying the diodes. Further, a simple voltage management system can pull the LFP as needed to prevent overcharge or over discharge. I would make this based on LFP cell voltage, but it could arguably be done at the pack level for a 12V system.

It's similar to what I do, keep a 225 Ah of AGM in parallel ALL the time with 1200 Ah of LFP. But it could easily be smarter with simple electronics to add the AGM>13.2V and below 12.8V. The LFP would be added/in between 12.6 and 13.4V. The values could be tinkered with, but the idea is the AGM are in outside of the flat parts of the LFP operating range as a fail safe. This battery can be pretty small.

This means no worries about overcharge, or fancy alternator controllers. You do need to manage alternator temperature. That's about all that's left. The discharge side saves the expensive battery in a situation that should never occur.

I like it.

[s/v Jedi]

Originally Posted by daddle

Wow. What a surprise! A glowing breathless completely un-referenced analysis from a LFP vendor. Hits all the "talking points".

Are you disputing it?

[Khagan1227]

Originally Posted by daddle

Wow. What a surprise! A glowing breathless completely un-referenced analysis from a LFP vendor. Hits all the "talking points".

I would have thought that while Bruce Schwab is a vendor, his sailing resume would at least give him a bit of credence.

Since he has circumnavigated alone and non-stop, he might have a pretty good insight to what works or doesn’t work when it comes to energy storage and management on a sailing vessel.

[s/v Jedi]

For readers who don't exactly know what this is about or don't really believe these batteries perform like claimed: this short video from Canada is a good eye opener, showing how a very small battery can be very powerful:

https://www.youtube.com/watch?v=qcvmvrmTMMk

[goboatingnow]

You will need to define "easier" and "complex". I presently have four LA batteries that I can source easily almost anywhere (Trojans T-105). A simple 100A alternator (rarely used), four solar panels controlled by a simple MPPT unit. No battery monitors, nothing but a voltmeter (mostly ignored) on the panel. The batteries get water a few times per year. After 5 years of daily deep cycling they have reached their end ... about 30% C.

Yes of course, thats because you already have the complex equipment, already, but LI is technically easier to charge, its basically a 1 stage Cv charger.