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Old 20-11-2017, 16:04   #16
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Re: lithium batteries or AGM

I'm not paying any attention to 5-yo opinions.

Neither solar nor off-grid forums are RV oriented.

And no way I'm frequenting a place SunKing is allowed to remain the way he abuses people.
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Old 20-11-2017, 16:08   #17
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Re: lithium batteries or AGM

As a middle ground, consider Firefly. (assuming the size works for you)

It will be my next battery after the current AGM's die. They are a drop-in replacement for other AGMs. Same chargers same settings. Because they can be cycled much lower than 50% you can also consider buying fewer batteries.

https://www.bruceschwab.com/advanced...asis-group-31/
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Old 20-11-2017, 16:21   #18
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Re: lithium batteries or AGM

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Originally Posted by john61ct View Post
I'm not paying any attention to 5-yo opinions.

Neither solar nor off-grid forums are RV oriented.

And no way I'm frequenting a place SunKing is allowed to remain the way he abuses people.
Fair enough.. Not sure anything I say or post would change your opinion... Nor do I care to..

However... Can I ask.. Do you have Lifepo4 batts? Do you know anyone personally (not here on CF) that is running them in a liveaboard scenario?

Its clear our opinion will continue to differ no matter what.. My boat, my bank, my life... Take it for what its worth, or not IDC...
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Old 20-11-2017, 16:25   #19
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Re: lithium batteries or AGM

OK, read the whole thread and nobody says stay above 70% SoC. And there's nothing conflicting with the threads I posted and Maine Sail's guidelines as I understand them.

Maybe you got confused and mixed up SoC and DoD? The main rational poster in that thread uses 80% DoD as a lower limit, but that is 20% SoC.

If that's it, that's fine, a bit (IMO way) conservative, but I'd have no problem with someone making that tradeoff.
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Old 20-11-2017, 16:27   #20
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Re: lithium batteries or AGM

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Originally Posted by CarlF View Post
As a middle ground, consider Firefly. (assuming the size works for you)

It will be my next battery after the current AGM's die. They are a drop-in replacement for other AGMs. Same chargers same settings. Because they can be cycled much lower than 50% you can also consider buying fewer batteries.

https://www.bruceschwab.com/advanced...asis-group-31/
Great batts and a great direct replacement for AGM.. However, they are expensive and have ZERO weight advantage. We have also heard of a couple of "quality" issues... But in their defense, they stood behind their product and made the customer happy (even down here in the Caribbean).

I looked VERY hard at those batts when we began cruising and was inches from pulling the trigger. In the end I felt (just my opinion) that they were too expensive for the advantages.

If they could bring the price down by %20-%30 then it would be much more attractive. For me, at their price point, LFP made more sense.
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Old 20-11-2017, 16:28   #21
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Re: lithium batteries or AGM

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Originally Posted by CarlF View Post
As a middle ground, consider Firefly. (assuming the size works for you)

It will be my next battery after the current AGM's die. They are a drop-in replacement for other AGMs. Same chargers same settings. Because they can be cycled much lower than 50% you can also consider buying fewer batteries.

https://www.bruceschwab.com/advanced...asis-group-31/
Yes, FF is a great in-between compromise, unique among lead batts for withstanding PSOC (what would otherwise be) abuse.

And only $500 per 100 AH, so a relative bargain.

At this point I would only recommend the 12V G31, and they're back-ordered many months last set I bought.
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Old 20-11-2017, 23:18   #22
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Re: lithium batteries or AGM

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And only $500 per 100 AH, so a relative bargain.
That's ~50% more expensive than a quality gel/AGM. Since well kept AGM-s also live long, I don't see the bargain here. Invest the difference in 3-4x 100W solar panels and you won't have to worry about partial state of charge/deep discharges.
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Old 20-11-2017, 23:45   #23
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Re: lithium batteries or AGM

As opposed to 5-7 times more expensive than LFP, which was the topic.

And poor weather, latitudes near the poles, not enough room, aesthetic issues,

Not to mention my 1100AH once drawn down are going to need more than your 400W.

Just saying, there are use cases. . .
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Old 21-11-2017, 00:51   #24
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Re: lithium batteries or AGM

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Originally Posted by Giannisailing View Post
hello everyone
I have 1000 AH on my Cat and recently noticed that voltage was dropping very rapidly from fully charged. When inspecting the battery bank I found that one of the 4 batteries was quite warm. Proceeded in disconnecting it and with 750AH the voltage drop was diminished. Nevertheless I think that the bad battery had spoiled the other 3.
The batteries are Deep Cycle AGMs and I think need replacing unless I can improve performance somehow.
I am also planning to install some solar panels. 900W perhaps
What is the general opinion regarding Lithium?
Ive checked some suppliers and have seen 150AH at $560 which looked very competitively priced to me...perhaps too competitively.
What should I look for when shopping for Lithium and, what is the trend now days? replacing AGMs with other AGMs or with Lithiums?

Any tip greatly welcomed.
The financial cost or benefit will depend on what prices you can get batteries for.

In Australia, to replace my 600 ah of AGMs would have cost me about $1800. 400 ah of Winston lithiums cost me $2400.

The AGMs lasted 6 years, so the financial break even for the lithiums is 9 years.

BUT, there are significant other advantages. They're much lighter, much smaller, and noticeably more efficient. It's almost like adding 10% more solar panels.

And everything likes the higher voltages. From water maker to windlass, you notice an extra enthusiasm. They run that bit faster.
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Old 21-11-2017, 06:11   #25
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Re: lithium batteries or AGM

Plus you have the legendary Terry at T1 Lithium in Mannum

I love the idea, visualising an animation of all the load devices getting excited 8-)
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Old 21-11-2017, 08:20   #26
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Re: lithium batteries or AGM

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Originally Posted by travellerw View Post

In a very quick sum up.. The RV crowd now believes LifePo4 should not be discharged below %70. Nor should it be charged over %90 (maybe once in a while when you think it will be cloudy and need the extra capacity you can do the %100 - %20). So if you do the math.. That is %60 of the capacity of the bank that is usable. Pretty much exactly the same as modern AGM. Of course these numbers are for maximum life cycles. If you aren't concerned about that, then %100 charge and %20 discharge are an option, but life will suffer (especially in a hot environment like the tropics).
If that is true then the RV guys are simply misguided on this and not realizing the benefits they paid for. Almost every RV installation I have seen has been rather murderous to LFP batteries in use or execution/installation. This the most likely reason they are seeing capacity fade.

Issues like float charging, charging below 32F, improper off-season storage SOC, incorrect CV duration, incorrectly thinking a lower charge voltage can't over charge LFP, chronic over charging, poor balancing practices, mismatched cells, heat etc. etc. are all major DIY LFP issues I have seen & been emailed about from the RV community.

I had one RV guy who was extremely pissed at his "expensive cells" when he simply dropped them in (no BMS what so ever) and plugged them into an inverter/charger set for GEL. His 28SI alternator was set for 14.5V and when ever the engine was running this was the target voltage. His inverter/charger did a 4 hour absorption cycle at 14.2V and then floated continuously at 13.8V. Even after explaining why his cells were toast in 6 months he was still angry at the cell manufacturer. You can lead a horse to water...

Most of the emails I get have been prismatic DIY builds but I have had a few guys try to build banks out of 18650's too... I won't even go into the guys who've bought "LFP drop-ins", ruined them and now can't get warranty replacements. It's not just RV's though, there are lots and lots of poorly executed marine installations too and I get the emails from both sides plus off-grid and even the occasional EV guy.

Other than a hand full (T1Terry etc.) I've yet to see many good DIY RV LFP installations but, I do keep looking. I would love it if you could lead me to some well engineered/designed, properly used fractional C LFP systems on RV's?

The bank for our boat is about 45 cycles shy of 1000 cycles and there has been no quantifiable change in tested and accurately measured capacity. The cells were made in 2009 and they are still delivering what they did back then 8 years and close to 1000 cycle later..

Almost all cycles have been to at least 80% DOD with a fair number much lower than 20% SOC.. About every 5 or 6 cycles, or when I have the opportunity, I take the bank to 100% in order to reset and have a more accurate Ah counter. Another mistake is folks believing their Ah counter is accurate and will remain so on LFP, they don't.... Otherwise we simply put the energy into the bank for what we need, for the desired run time, and let it go back to approx 80% DOD before recharging.

The issues with most LFP installations is not the cells, it is the owners.

On many cruising boats cycling a lead bank back much above 85% SOC, daily, is the stuff dreams are made of. This results in a usable capacity of only 35% not 50%.

Lead acid and LFP do have some commonalities though. The common denominator in both lead banks and LFP is owners who murder them prematurely..
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Old 21-11-2017, 09:48   #27
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Re: lithium batteries or AGM

So gratifying, thanks for chiming in!

Quote:
Originally Posted by Maine Sail View Post
I would love it if you could lead me to some well engineered/designed, properly used fractional C LFP systems on RV's?
Personally I'd be happy with a link to a single informative discussion on LFP taking place in an RV-centric forum.

Where the main value isn't illustrations of what not to do, or me preaching the gospel of Rod 8-)
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Old 21-11-2017, 09:51   #28
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Re: lithium batteries or AGM

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Originally Posted by travellerw View Post
LifePo4 should not be discharged below %70. Nor should it be charged over %90 (maybe once in a while when you think it will be cloudy and need the extra capacity you can do the %100 - %20). So if you do the math.
The math is easier if the scale / units is made clear, like this

Quote:
Originally Posted by Maine Sail View Post
Almost all cycles have been to at least 80% DOD with a fair number much lower than 20% SOC.
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Old 21-11-2017, 10:26   #29
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Re: lithium batteries or AGM

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Originally Posted by Maine Sail View Post
About every 5 or 6 cycles, or when I have the opportunity, I take the bank to 100% in order to reset and have a more accurate Ah counter.
Q1 Is that *your* custom-safe definition of 100% (and Q2 what V is that, below 3.5Vpc?) or the cell vendors' at a higher voltage?

Q3 Does that definition, in above regular usage, include holding that V until A decline to endAmps ?

T1 Terry claims (or at least I believe he used to) that LFP's memory effect causes

if this defined top point is always the same, and you never go above it

that creates a "resistance bump" in the charge curve, in effect walking down capacity, maybe permanently

by the amount of AH between your custom-safe Full and mfg's defined Full

Q4 what do you reckon that difference is off the top as a percentage?

Q5 do you agree with that above supposition? Think there's anything to it? Worth preventing?

His advice was to periodically charge to a higher setpoint, maybe as high as mfg-recommended,

to keep that "bump" from becoming permanent.

An alternative perhaps would simply be to always vary the stop-charging setpoint, keep it under custom-safe Full (mine is 3.45Vpc at .3C no endAmps) most of the time, maybe go over a bit a quarter of the time, and approach mfg Full say 10% of cycles.

I realize this isn't practical for an automated charge cycle, but asking in principle

Q6 What say you?

Any other comments would of course be *most* welcome!

And thanks so much again for all your invaluable contributions to the community.

​Which reminds me, I haven't donated lately to your site maintenance fund (hint hint to any others as grateful to Rod as I am)

https://marinehowto.com/support/

And finally, a reminder of my past offer to help you with the drudgery aspect of transferring your past content

e.g. relevant to this thread http://www.pbase.com/mainecruising/lifepo4_on_boats

to the new site
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Old 21-11-2017, 10:53   #30
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Re: lithium batteries or AGM

Just for giggles, here's my "boilerplate" LFP summary for RVers, mostly from Maine Sail, excuse any repetition wrt this thread

Any and all feedback is welcome!

____
Bare cells: ​Winston/Voltronix, CALB, GBS, A123 & Sinopoly

Systems: OceanPlanet (Lithionics), Victron, MasterVolt, Redarc (Oz specific?)

Note nearly **every** vendor, also those of ancillary hardware touted as "LFP ready", gives charging voltages **way too high** for longevity.

My (conspiracy) theory is that manufacturers would prefer their cells get burned out in under 10 years.

EV usage is very different from much gentler House bank cycling. Most EV people talking "lithium-ion" mean other chemistries not as safe as LFP, much shorter lifetimes, and with completely different setpoints and behaviors.

My charge settings for LFP: 3.45Vpc which = 13.8V max for "12V".

Either stop when voltage is hit, or if you want another couple % SoC capacity, stop when tailing amps hits endAmps of .02C, or 2A per 100AH. Note even at the "low" max charge voltage, letting the charge source continue to "push" even low currents long past the endAmps point is **over-charging, and will** greatly reduce lifecycles.

If you can't then "just stop", set Float at 13.1V, but that is a compromise, and *may* shorten life cycles.

With LFP, you don't need to fill up all the way at all, as far as the cells are concerned, in fact it is bad for them to sit there more than a few minutes. Therefore only "fill up" if loads are present, ready to start discharging, ideally right away.

Store the bank as cool as possible and at 10-20% SoC, or maybe higher to compensate for self-discharge, if not getting topped up regularly (I would at least monthly). Letting the batts go "dead flat" = instant **permanent unrecoverable** damage.

Same with charging in below 32F / 0C freezing temps.

Persistent high temps also drastically shortens life.

Charging at 1C or even higher is no problem, as long as your wiring is that robust, vendors may spec lower out of legal caution.

Going above 14V won't add much AH capacity, but will shorten life cycles dramatically.

The point is to look at the SoC vs Voltage chart, and avoid the "shoulders" at both ends, stay in the smooth parts of the curve. And of course, we're taling about gentle "partial C" House bank discharge rates, size appropriately and be careful feeding heavy loads like a winch or windlass.

Following these tips, letting the BMS do active balancing is unnecessary and potentially harmful, just look for LVD / OVD and temp protection. Multiple layers of protection are advised if it is a very expensive bank, don't rely on any one device to work.

Check cell-level voltage balance say monthly to start, then quarterly, finally every six months if there are no imbalance issues, but only if that seems safe to you.

This thread is long but informative
http://www.cruisersforum.com/forums/...ad.php?t=65069 , make sure to give both Maine Sail and Ocean Planet your close attention.

Also MS' summary notes here
http://www.pbase.com/mainecruising/lifepo4_on_boats

**Everything** at that site is worth reading, very valuable. He also has great articles in Practical Sailor. His new site under development transitioning the pbase content is here

https://marinehowto.com/support , feel free to make a donation to help with those expenses.

Best of luck and do please report back here.
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