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Old 20-12-2013, 12:05   #3361
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

You guys have taken this discussion way past my pay grade but I habe picked up a few things. Some seem to have a concern about charging these batteries at or below freezing.

My yacht club (near Toronto) has about 400 boats in winter storage on the hard. Although it is against club policy, quite a few people leave their boats plugged in to keep their batteries charged (stoopid !). Is it even more dangerous to do this with Lithium batteries due to the frequent below zero temps ?
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Old 20-12-2013, 12:25   #3362
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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You guys have taken this discussion way past my pay grade but I habe picked up a few things. Some seem to have a concern about charging these batteries at or below freezing.

My yacht club (near Toronto) has about 400 boats in winter storage on the hard. Although it is against club policy, quite a few people leave their boats plugged in to keep their batteries charged (stoopid !). Is it even more dangerous to do this with Lithium batteries due to the frequent below zero temps ?

Anyone willing to spend the money on Li should remove them from a winter stored vessel or discharge them to 50-60% and let them sit 100% disconnected from the vessel.
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Old 20-12-2013, 13:11   #3363
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Anyone willing to spend the money on Li should remove them from a winter stored vessel or discharge them to 50-60% and let them sit 100% disconnected from the vessel.

Agreed ! but is it more dangerous than with conventional lead/acid wet cells ?
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Old 20-12-2013, 13:33   #3364
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Anyone willing to spend the money on Li should remove them from a winter stored vessel or discharge them to 50-60% and let them sit 100% disconnected from the vessel.

This was why I said I couldn't understand anyone wanting to put their Li battery on a continuous float charge, it's just not needed. There is some research that suggests float charging reduces cycle life but I think the voltages that are being used for the float charging are more the issue with reduced cycle life.
The reason to discharge the cells to 50% SOC or 60% SOC is to reduce the amount of activity within the cell that leads to the self discharge. The charts provided only give a self discharge to approx. 60% SOC. Looking at the chart, in the first 160 days 20% of capacity is lost, yet in the next 160 days only 10%, then the next 40 days appear to result in around a further 6% capacity loss, yet shipped cells 3 yrs old still have a 50% capacity, so the discharge rate after 12mths is a bit of an unknown for LYP cells, they are shipped with a50%SOC so the factory must know that this is a safe state of charge for long term storage.

For those Dave has made a little uneasy by his claims of large capacity losses below zero deg C I've posted another Winston chart. In the top right hand corner the discharge rate of 0.5C is shown, that is a very heavy load for house batteries and unlikely to be maintained till the battery was fully discharged but it does give you an indication of the likely capacity loss. If you follow the rule of min 2.8v rule you can see where the load would need to be reduced at different temps. probably best not to be sailing at -45 degC, but if you are, then a 0.5C load will only produce around 70% of the advertised capacity so probably best to keep that in mind. The fact only 95% of the capacity is available at 25 deg C says the reduced capacity may also be related to the load.

It is very difficult to almost impossible to surf the net and find information relating to the use of these batteries at house power loads as no one is paying researches to find out that sort of information, so only actual field test observations are available, no lab testing... but then didn't AGM batteries last for 1,000 cycles in lab testing? Maybe that was the result the researches were paid to find

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Old 20-12-2013, 13:37   #3365
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Dave, one of the things I've learn about trying to share learned information, is not good for ones state of mind, so I'll bow out and leave it to you.

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Old 20-12-2013, 13:41   #3366
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Terry & Mainesail, I do appreciate your taking the time to respond but I still don't know if it is dangerous (moreso than lead acid) to leave these units on a charger through repeated cycles of below freezing temperatures.
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Old 20-12-2013, 14:13   #3367

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

boatpoker-
If there is an insurance mandate, or a fire code (I've seen both) that "nothing stays plugged in" during winter storage, it is plain foolish for the club to allow members to leave things plugged in. Simply because the whole yard could go up in flames, and the insurers could walk away scott-free and say "Well you know, you violated the terms. Its your problem now."
So that might be something to bring to the attention of your club, as storage yard fires DO happen every year.
Our yard used to shut the main breakers at 5pm in the winter, then walk around yanking out any cords they found and having strong words with the owners, because the fire marshal had laid down the law.
If folks are worried about keeping their batteries trickled during the winter, let 'em buy solar panels. The self-discharge rates even for WLA are so easily matched, that costs are not a valid argument any more.
Since solar starts up "gently" with sunrise...I would expect it to also gently warm any batteries that did freeze up during the night, for that matter. Don't know for sure.
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Old 20-12-2013, 14:32   #3368
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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boatpoker-
If there is an insurance mandate, or a fire code (I've seen both) that "nothing stays plugged in" during winter storage, it is plain foolish for the club to allow members to leave things plugged in. Simply because the whole yard could go up in flames, and the insurers could walk away scott-free and say "Well you know, you violated the terms. Its your problem now."
So that might be something to bring to the attention of your club, as storage yard fires DO happen every year.
Our yard used to shut the main breakers at 5pm in the winter, then walk around yanking out any cords they found and having strong words with the owners, because the fire marshal had laid down the law.
If folks are worried about keeping their batteries trickled during the winter, let 'em buy solar panels. The self-discharge rates even for WLA are so easily matched, that costs are not a valid argument any more.
Since solar starts up "gently" with sunrise...I would expect it to also gently warm any batteries that did freeze up during the night, for that matter. Don't know for sure.
I am aware of all of that and completely agree but it still does not answer my question.
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Old 20-12-2013, 14:43   #3369
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Terry & Mainesail, I do appreciate your taking the time to respond but I still don't know if it is dangerous (moreso than lead acid) to leave these units on a charger through repeated cycles of below freezing temperatures.

IMHO they should NOT ever be left on a charger unattended, if you value your wallet. Leaving them charging when there is ZERO need to do so, let alone at sub 32F or 0C is just plain crazy. Doubtful it would pose a safety problem other than a massive hole where your wallet used to be.......

These batteries are not lead acid and thus they should NOT be treated the same way as lead acid.

A horse and buggy is not the same as a internal combustion automobile. Feeding your horse gasoline will have a similar result to feeding your car hay. They both get you from point A to point B but they need different care & feeding....
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Old 20-12-2013, 14:54   #3370

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

OK, boatpoker, let me rephrase this as a direct answer.

"is it more dangerous than with conventional lead/acid wet cells ? "
Probably, yes. Since you don't know if all the scofflaws are using LiFePO4 cells or more explosive chemistries, that's one danger. Since you don't know IF the batteries will drop below the danger point, that's another danger. And since you don't know what the exact chargers are, or how they will react in the batteries in those temperatures, that's another danger. Since charging in cold temperatures will apparently foster dendritic growth, which does lead to cell failure and in some chemistries will lead to fire, there's also a danger being created that is not immediate, but is a permanent added risk for the entire lifetime of the batteries.

IS it more dangerous? You don't have enough specific information to get your question answered. You do have enough information to know that several more potential dangers may exist.

And perhaps more importantly, you knew before you started that the question is a moot point. Those scofflaws are endangering everyone in the yard, by nullifying the fire insurance for the yard. That's the biggest and most definite danger of them all.

If the manufacturer said "Don't charge below zero C" (or whatever specific recommendation) and someone was found to be charging without monitoring, and violated the manufacturer's safety warnings? Yeah, you know what comes next. That changes the action from "negligence" to "gross negligence" and I have to suspect Canadian liability law follows the same logic as US law. Gross negligence gets a much stiffer treatment.

So again...dangers, yes, and moot points.
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Old 20-12-2013, 15:56   #3371
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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I am aware of all of that and completely agree but it still does not answer my question.
The correct answer is no. LFP is less dangerous than lead acid because a proper LFP installation should include a charger that is smart enough not to try to charge a lithium ion battery at low temperatures.
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Old 20-12-2013, 16:04   #3372
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

If you do not have a system that will stop charging if a cell reaches 3.6v then don't leave any charging system connected to unattended batteries. that reads stop charging not holding the charge at 3.6v but stop charging at 3.6v in any one cell and charging not resume charging until the cell has dropped below 3.6v for at least 2 mins.
As far as float charging for long periods, don't do it, float charging on solar as long as the above conditions are met is fine because it's only occuring while the sun shines, but don't float charge Li batteries for a long period, like a mth or so, on a mains charger, there is no need and will not add to the batteries/cells long life.

Is it dangerous to leave a mains charger connected while unattended, most certainly, all electrical appliances have the capability of starting a fire.

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Old 20-12-2013, 16:34   #3373
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Yes it is dangerous to charge Li technology at or below freezing


Why , any examination of Li technology, shows that Lithiation rates are very temperature sensitive. a commercial quality anode hence struggles to accommodate the Li ions at low temperature hence plating occurs which is dendritic in nature , if that material then pierces the separator a short occurs.

Li can be charged at low temperature , but most definitely not with the same charging regime as at room temperatures. This is why Winstons recharge temp range is extremely mis leading.

The bank should be charged to around 40% to 50 % SOC , completely disconnected from the boat and charger and left for the winter.

Despite what T1 Terry says , the ageing process is quite well understood and any search of scholarly material will reveal a considerable body of work. The primary ageing factor is the electrodes / electrolyte interface. For want of a better explanation , the electrolyte " eats" away the electrode over time. Hence a Li battery has a finite life irrespective of cycles.

Tests have shown that the electrolyte is most stable and reaction with the electrodes to be lowest at around 40 % SOC. electrode plating is minimalised as well. Hence this is the recommend storage parameters.

Unlike LA , Li doesn't really have a self discharge component , what actually happens is that actual capacity is lost permanently.

Ps terry I'd take those Winston low temp graphs with a grain of salt. , have a look at some more reliable brands like CALB or even YUASA for example. ( Or panasonic or A123 even ) Winston for all the hype hasn't invented anything different or special.

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Old 20-12-2013, 18:03   #3374
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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any search of scholarly material will reveal a considerable body of work. The primary ageing factor is the electrodes / electrolyte interface. For want of a better explanation , the electrolyte " eats" away the electrode over time. Hence a Li battery has a finite life irrespective of cycles.
Could you please cite any "scholarly material" on LFP cell aging that did not study cells that were also heavily cycled? My understanding is that the SEI layer protects the anode---and since shallow cycling and/or low currents preserve this protective layer, that may suggest increased longevity.
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Old 20-12-2013, 18:29   #3375
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Hi, all. Iíve read enough of this thread to realize I will have to study the subject a lot more before I put LiFePo4 batteries on my boat. I am not ready for that now, because I have new batteries on the boat (PO toasted his and credited me for the new ones), and I and the boat (2001 EndeavourCat 36 sailboat with 2 29 hp Volvo diesels) live in Rhode Island, where it gets considerably colder than 0 C for weeks at a time. We will head south in a few years.

However, I am replacing the current charging system (a Heart Interface PathMaker and 40 amp charger) because the Heart thing sucks down my batteries and wonít accept more than 100 amps total from the alternators even when I have both engines running, and the charger is undersized and not very clever. I have a 400 AH house bank.

Iím planning to replace this setup with a Sterling Power 210 amp max ProAlt C Alternator to Battery Charger and a Sterling Power 60 amp ProCharge Ultra battery charger. Sterling promises both of these will charge LiPo4 batteries as well as AGMs and LA batteries.

In your learned opinions, are these a good choice for someone who wants to make the switch to lithium down the road? I understand Iíll have to add some other gizmos when the time comes; I am just trying to improve my current situation while keeping my battery options open for the future.
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