LiFePO4 - The future for off-grid battery banks?

[PNjunction]

It's because most of the posters here do not have a functioning PV system using LFP batteries, unless you count a golf cart or a couple bench top battery packs. The people that do have a functioning system don't seem to stay long and are not interested in arguing about gnats on pinheads.

It's all relative and scalable. That charge has been levied against me elsewhere, from those who have no intention of EVER looking into lifepo4. At least we are on the field, apples-to-apples (one is just bigger than the other!) It is almost as if in the Pb world, that a guy with a flooded battery on a bench top is irrelevant unless he starts out with a 10Kw bank of Rolls-Surrettes as his first project.

The cost is 3 times as much as FLA, so unless you have a weight issue or storing them inside they do not seem to be worth it.

True enough, but the worth is far more than mere upfront cost, or weight, even in a fixed installation. It has to do with operational freedom.

No sulfation, so no need to keep or desire them to be fully charged.
PSOC operations are not only totally possible, but from a lifecycle standpoint, encouraged!
Ability to walk away from them in a discharged state and return a year or more later at nearly the same SOC. (no parasitic draws of course)

So IF that operational freedom is important and represents a big break from maintaining a lead-acid based project badly, this could be a major turning point for many.

A bench-top project or Golf-Cart provides the hands-on that is so important, but the biggest thing about it is that unlike mere talk, experience even at the small level, breaks the so-called "lead-acid" operational mentality and prepares you for the bigger stuff should one want to go there.

Put it this way - I'd first trust the guy with a bench top flooded, rather than a guy whose only experience is with AA flashlights merely *talking* about wet-cells.

Anyway, all of this is old news and has been hashed to death since 2008 or so in most forums. I think many are just burned out of repeating the same thing over and over, or more likely, going lifepo4 has turned the corner into being a commodity product. If you want it, it is easy to get these days.

[Bala]

Living off grid is not as simple as saying I use X Kwh per month on grid so what do I need to supply that with off grid solar.

For off grid you need to consider when you will use that power.

If you want to use an air con, washing machine, clothes dryer etc at night then your system will need to be huge or run a genset a lot.

If you want to use a welder then you need a genset to suit.

If you are home all day you can take advantage of the sun, when we are both working full time we burn a lot more diesel to do washing etc at night.

So as well as a realistic energy audit that I think was suggested earlier you need to get your head around the fact that off grid is a lifestyle, not just a different place to get electricity from.

[jedics]

Take it easy man - perhaps turn off the argumentative bolding

Ha, you guys really dont like it, I was just using it to make it clearly defined what I was saying against what I was quoting is all.

The more I read the more I see conflicting opinions and for someone like me who is brand new to all this its become more confusing than clarifying which is one of the reasons for salesmen I guess

Ok, perhaps I should broaden my questions a little. So as I said I am going to build a living space in a 12 meter refrigerated semi trailer and I have a site in mind but I have to negotiate with owners more before I can be sure it will happen. I have to plan for the fact I dont know where I will put it hence my desire to go off grid, then I can pretty much put it anywhere. Also if I get the solar set up first we can use the power for out tools for the build.

So apparently my assumptions about how long it takes to charge AGM to 100% against lithium are wrong, so this comes down more to the type of AGM and the chargers capability to provide enough power to a large bank of AGM's?

Even if I do decide to go AGM I definitely want a charger/Inverter capable of Lipo for down the track, as I see prices dropping hugely in the next few years with what Tesla is doing.

I have a friend who works at Tindo Solar, they make aussie made panels that are tested to give a true 250 watts of power with enough light and say that a lot of imported panels can sometimes be only 80% or 90% of capacity of what they claim, Tindo also say theirs are more efficient under high temps because most imported panels are made for much cooler climates. However Tindo panels are more expensive, about 300 au per 250watt panel. I can get something that 'seems' comparable on ebay for 250au per panel. If I bought say 12 panels thats a 600au saving, I could just buy 2 more panels which would more than make up for Tindo's more efficient panels, is this sound thinking?

If you guys have some reading/video material that would give a beginner a head start it would really be appreciated, as Im afraid of boring this forum to death with my 101 newbie question that will likely follow ...... perhaps Im down to 98 by now!

[Willy T]

What a Hack.

There you go again with your name calling, grow up.

[Sunking]

It's because most of the posters here do not have a functioning PV system using LFP batteries, unless you count a golf cart or a couple bench top battery packs. The people that do have a functioning system don't seem to stay long and are not interested in arguing about gnats on pinheads.

In real life the efficiency is not all that great with a normal PV to battery capacity ratio. Those that data log find the I/O is about 94-96 % efficient and the charging time is almost the same using a 3% ending amps in the saturation phase as FLA. The cost is 3 times as much as FLA, so unless you have a weight issue or storing them inside they do not seem to be worth it.

What a Hack.

[PNjunction]

I'd of thought it would be the best way to see what results in efficiency versus cost is the best solution, Id really like for people to chime in on this as I know batteries and inverters are not created equal but price is a factor of course

I turned off the bold for you. Thanks.

Without knowing your actual power needs, all this leads to is endless speculation for a proposed system that may never see the light of day. In some circles, that would be seen as a trolling maneuver.

In addition to knowing your actual power needs, you should also provide your location - at least geographically close. There is the issue of solar-insolation to be taken into account. Solar insolation hours are far different than just sunrise-to-sunset and are critical unless one wants to wing it.

Thus, a proposed system might work in Arizona, but be a total pipe-dream and waste of time and money in the pacific northwest, unless you have an unlimited wallet. You know that going off-grid with batteries is about 10-times the cost of your local poco on average right?

For a place you intend to live in, you have to take it seriously. We can get away with winging it with camping and so forth, but for permanent living quarters it is a different story.

These two requirements - your power needs and your solar insolation - stated up front, are what makes the difference between just throwing things at the wall and seeing what sticks, to doing it right.

[Willy T]

I noticed there isnt much of people posting what components they are actually using in their system here, is that because moderators dont want the site turning into a sales place?

It's because most of the posters here do not have a functioning PV system using LFP batteries, unless you count a golf cart or a couple bench top battery packs. The people that do have a functioning system don't seem to stay long and are not interested in arguing about gnats on pinheads.

In real life the efficiency is not all that great with a normal PV to battery capacity ratio. Those that data log find the I/O is about 94-96 % efficient and the charging time is almost the same using a 3% ending amps in the saturation phase as FLA. The cost is 3 times as much as FLA, so unless you have a weight issue or storing them inside they do not seem to be worth it.

[Living Large]

I noticed there isnt much of people posting what components they are actually using in their system here, is that because moderators dont want the site turning into a sales place?

I'd of thought it would be the best way to see what results in efficiency versus cost is the best solution, Id really like for people to chime in on this as I know batteries and inverters are not created equal but price is a factor of course

Will you please not post in bold? See how much easier it is to read your post when it is not in bold? You're hurting people's eyes - not the same as upper case, but just as annoying.

I was not assuming I could use 80% of AGM's capacity the same as LFP, as Sunking mentioned above. I also wanted a battery with no out-gassing, so maybe that was the chief criteria that caused me to move to LFP. I do recall my gen run time was going to be longer, for whatever the reason. It may have had to do with float or having to equalize on occasion.

[inetdog]

I noticed there isnt much of people posting what components they are actually using in their system here, is that because moderators dont want the site turning into a sales place?

I'd of thought it would be the best way to see what results in efficiency versus cost is the best solution, Id really like for people to chime in on this as I know batteries and inverters are not created equal but price is a factor of course

There is no policy against describing or specifying in as much detail as the poster wants the equipment they are using or are evaluating.
What the Forum does not generally allow is clickable links to those components on a retail site or FleaBay. Links to the manufacturer's site are usually just fine.

Take a look as multiple members signatures that describe the exact components they are using.
Other members give detailed lists of proposed components from quotes received.
If members do not list specific components it is more likely because they were not asked.

And please take it easy on the bold. If you are visually challenged, you can just increase the font size in the formatting tools bar.

[jedics]

This was a big factor in my choosing LFP. My location has poor insolation, and I didn't want to have excessive gen run time and the maintenance that comes with it to fully charge my batteries. I believe the run time difference in my case was a factor of two to three to one.

I noticed there isnt much of people posting what components they are actually using in their system here, is that because moderators dont want the site turning into a sales place?

I'd of thought it would be the best way to see what results in efficiency versus cost is the best solution, Id really like for people to chime in on this as I know batteries and inverters are not created equal but price is a factor of course

[PNjunction]

Concorde Lifeline says they can be charged up to 5C.

Yes, but Mr. Puekert is still hanging around in bulk. While getting up to the absorb point very quickly is a good idea, now your absorb will be longer. At least thats what I have observed when having fun like this.

So there is also a practical point to consider when doing super fast charging with pure-leads. For a solar housebank of reasonable financial proportions, you aren't going to be hitting even 0.3C anyway. Genny - sure possibly.

But as Sunking points out - for the neophyte that doesn't know what temp-comp, hot-spots, thermal runaway is, or using the agm pulled from the depths of the garage and hitting it with 5C, NOT a good idea.

[PNjunction]

Yes Im sure I can get some AGM's near by but with the kind of money Im going to be spending for my long term home Im wondering how I might feel about them in 3 years time when they dont hold a charge like they used to.

By the way how long have you had yours? Have they lost any capacity in 'that' time?

5 years on an old Odyssey. Not enough to be consequential in my relatively low-current non-sli applications. I baseline with a West Mountain Radio CBA-IV, and now followup with additional IR check with an iCharger 306B on my 6 other pure-lead's. Not lab equipment to be sure, but good enough for consumer use. Pure-lead only please.

The key is to not undercharge them, which is easy to do with solar if one follows the typical "canned" presets, which are conservative by design, and really intended for float/standby use. "Read CYA".

Yes, you need to do more research. The reason we don't take batteries below 50% DOD is that provides the most reasonable minimum amount of cycle life. HOWEVER, with lifepo4, you don't think in terms like you do with lead, such as from 0-50% DOD scale. It is a sliding window of PSOC operations, and typically for best results one uses a 10-80% DOD scale window.

EVEN THEN, as a wise solar-user, you don't cut yourself short on autonomy, no matter how good the lifepo4 is! Beware of any sales-droid foaming at the mouth talking about taking your bank down to 80% on a *regular* basis. If you do, that means your bank is in fact too small from a day-to-day liveable solar standpoint. One or two days of no autonomy and you are done - unless you want to start burning genny fuel.

Take it easy man - perhaps turn off the argumentative bolding - we're trying to save you money in the long run by not jumping headlong into some foregone conclusions.

My smaller 20 and 40ah lifepo4 banks made from GBS cells are doing GREAT - just to show you that I'm no chemistry bigot. As great as I think they are, lifepo4 such as those from GBS or even Victron, have not reached even a 10 years worth of experience since the large format prismatics got into general public consumption - circa about 2008 or so.

[Sunking]

Concorde Lifeline says they can be charged up to 5C.

Yes I know, some AGM's can be charged in excess 1C as you pointed out with Concorde be able to charge at 5C. I use C/4 because it is a SAFE number and some numb nut may run with it and do no harm. In other words it is the lowest C-Rate which is limited by the slowest charging AGM's out there. I can sleep at night with recommending C/4. If you want to know the real upper limit check your battery manufacturers O&M manual. I will say at least a minor Majority are 1C or higher.

I just wanted to let the OP know he is making a purchase and technology decision based on false data and assumptions. .

[lkruper]

OK no one has caught this, but your assumptions are false. AGM can easily be charged at C/4 or less, just as fast as Lithium. Secondly it would be very doubtful you need batteries that conditions dictate a fast charge from an Over Sized Panel Wattage. So if your justification of going to the expense and complexity to use Lithium because AGM cannot be charged as fast is 100% Completely False.

As for AGM discharge depth is not the same as Flooded, they can easily go to 80% DOD. However if you have a proper design of say 3 full usable days between charges, LFP requires the exact same number of Amp Hours. Example if you need 30 Ah per day, you need a 120 AH battery. Makes no difference if it is AGM or LFP. With AGM has the same usable range of 80% as LFP.

Concorde Lifeline says they can be charged up to 5C.

[Sunking]

After reading about AGM batteries and how long they take to charge to 100% together with the fact they shouldnt be discharged bellow 50% I quickly started to prefer lithium.

The whole reason Im considering lithium, 1/4 of the time to recharge them.

OK no one has caught this, but your assumptions are false. AGM can easily be charged at C/4 or less, just as fast as Lithium. Secondly it would be very doubtful you need batteries that conditions dictate a fast charge from an Over Sized Panel Wattage. So if your justification of going to the expense and complexity to use Lithium because AGM cannot be charged as fast is 100% Completely False.

As for AGM discharge depth is not the same as Flooded, they can easily go to 80% DOD. However if you have a proper design of say 3 full usable days between charges, LFP requires the exact same number of Amp Hours. Example if you need 30 Ah per day, you need a 120 AH battery. Makes no difference if it is AGM or LFP. With AGM has the same usable range of 80% as LFP.