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Borrego
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# Posted: 23 Oct 2015 10:54am
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I have been delaying my system for a couple years now, mainly due to financial reasons, and maybe that's ok because I notice more new products and lower prices popping up. Lithium batteries may not be new, but they just recently popped onto my radar.
I assume these are the way to go now if one was building an off grid solar system...I've done some research but there is just too much info out there, so I'll ask the experts here..
1) Pros and cons?
2) Any particular brands/types?
3) Any good websites/forums on this?
Don - does your old speadsheet that figures the correct number of batteries work with these?
Thank you all.
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creeky
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# Posted: 23 Oct 2015 01:31pm
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the pros are numerous. 3-5x the life. assuming you take care of them. 90% lower maintenance. I think you can search lifepo4 or lfp lithium and creeky here to find out what I learned.
there are three posts on my blog as well. both characteristics and benefits. including a post by a fellow in Australia who has had a lithium pack for some years. creektreat.ca
but the biggest thing for living off grid is that the batteries are happy being partially charged. if you don't charge lead acid they will sulphate and die. and in very short order. by not needing to get to full charge every single day lithium offers a far superior experience when it comes to the convenience of your power use.
an example of this might be my dishwasher. It uses about 2kw. So I only use it when my batteries are charged and the sun is shining full and bright. that's to protect my batteries from deep, fast discharge. with lithium they don't care. i could run my dishwasher at midnight after a cloudy day (assuming I have a large enough battery bank of course) and then make up the power the next day. or the day after that. so you can see the convenience factor.
also for off grid. as they sustain high discharge more easily than lead acid. the fellow who sent me an article runs an electric stove top. yup. no propane for him.
I like the winston battery packs from Balqon. It's an all done plug and play solution. Plug in your solar controller. Plug in your inverter. Off you go.
I don't know if it's changed. but the solar sites used to be rabidly anti lithium. die hard lead acid heads I guess. I imagine that has changed.
the con: they are a bit pricey up front. expect to pay about half again for the same useful capacity compared to top of the line lead acid. of course. as soon as they hit 10 years old you're saving money.
I find it cool that solar systems can now be built, top to bottom, with a 20 year lifespan.
also note that they are really useful for the part timers. as they can be left partially charged for years without ill effect you can leave them in the fall, come back in the spring, and no worries mate.
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MtnDon
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# Posted: 23 Oct 2015 02:16pm - Edited by: MtnDon
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Other than upfront cost the biggest drawback to me is in freezing weather they must be kept warm; above freezing. LFP can be discharged below freezing but not charged when below freezing. So for me that means re-doing the battery location and some wiring. If it is a new system then just plan accordingly.
Depending on what lead acid you compare to the cost of LFP can be easily 2x+ the up front cost (comparig to golf cart batteries means likely looking at close to 3x the cost). Yes, the LFP should last longer but it is still a bigger up front cost.
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MtnDon
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# Posted: 23 Oct 2015 02:22pm
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Spreadsheet will still get to the battery AH required. But needs some extra thinking as the daily recharge is no longer a big deal (with LFP). No plans to re-do it. Use the upper part for load calculations. If you play with it and learn what is going on adjustments should not be too hard.
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creeky
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# Posted: 23 Oct 2015 02:32pm
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MtnDon, did you bottom balance your batteries first? Or did they come balanced?
what are you running for bms?
(I'm watering my LA batteries every 1.5 months now. and I need to water them. getting close to the end. final planning now in effect. trying to get them through the winter.)
what do you think for AH. 50% dod on lithium gives you 20 years. 20% dod on lead acid gives you 5. So a 9 kw lithium pack would give me almost twice the useable power that my 14 kw LA pack offers (4.5kw vs 2.8 aprox.)?
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MtnDon
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# Posted: 23 Oct 2015 03:14pm - Edited by: MtnDon
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Quoting: creeky MtnDon, did you bottom balance your batteries first?
Some misunderstanding got read into my post. I have PLANS to build a large-ish end table for inside the cabin. It'll be at the couch end near the exterior wall. This will hide the LFP pack. The table top ill either roll out and uncover the cells, or the table top will be hinged to the wall.
That will also entail moving the CC and re-wiring from CC to the batteries. As well The inverter will need moving and re-wiring. Big PITA. But comes with some down the road benefits. I still only water three times a year maximum and get okay readings on the cells with slightly more frequent EQ. So the cabin battery replacement could still be a few years off. Or I could do it next year if I don't spend the money on something else.
I am closer to replacing the travel trailer FLA with a small set of GBS cells from elitepower with their BMS. Maybe a set of 40 AH cells. Maybe 60's. Not that much more $$. ??? At present I'm thinking I would do an initial top balance as I have a suitable variable output Mil-surplus (constant voltage and constant current) power supply that can do that at very low safe rate.
To use the TT as a pricing example... two GC-2's $200. An LFP set with BMS, $900. 4.5X the cost of the FLA. Dang when I do that math I tell myself I am crazy to think about it. But then look at the weight, 20 lbs vs. 140 and a nicer front to rear balance.... The BMS takes up a big chunk of those $$ and stays the same no matter how many AH I decide on. So I may as well go bigger is better. 
I know a local who has taken the risky approach. No BMS. $500+ saved. He spends his time monitoring the cells in his RV.
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creeky
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# Posted: 23 Oct 2015 03:17pm - Edited by: creeky
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Quoting: MtnDon may as well go bigger is better
I with you on that one. I can replace my la with a 5 kw lithium and be equivalent. but ... for the extra 40% I get double the power. so...
where are those darn tesla powerwalls. i figured, if nothing else, they'd put cost pressure on other mfcts.
ya. I read about a guy who bottom balanced and is now on two years without a bms. says everything. knock on wood. is going well.
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NorthRick
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# Posted: 23 Oct 2015 03:27pm
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Quoting: creeky what do you think for AH. 50% dod on lithium gives you 20 years. 20% dod on lead acid gives you 5.
From what I've been reading on other sites, there hasn't been any LFP battery banks in use for an off grid PV system for more that a few years, let alone 10 or 20. So, the life span of these batteries is what the manufactures claim, and they would never lie, right?
I've read differing experiences from people with real world experience with these. Some do not appear to be holding up as well as claimed while others do. My feeling is that it has to do with manufacturing quality. It appears to be all over the map and what is currently available to retail (us) is the worst.
It is still very much a developing technology. For me, I think I'll stick with lead acid for now and watch how things shake out.
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creeky
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# Posted: 23 Oct 2015 03:55pm
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no worries. spend your money again and again and again. I've read the posts on early failures too (3 years, now at 80% original ah is the worst I've seen). RV guy. He blamed himself: high storage/use temps ... and as with any battery, multiple high discharge. just like you see guys kill their lead acid packs in a year.
mahself doh; i've had my 5 years of lead acid. never ever ever again. they blow monkey chunks. lousy efficiency. high self-discharge. maintenance. etc.
sure. small system. not full time. not planning to be around.
but if your off grid, full time, and rely on your solar system for power. I can't advise anything but lithium.
and there are guys over 5 years now happy happy happy. (who took mega abuse from the "knowledgeable ones". we'll see who gets the last laugh.)
as for cost. well. I have a sister-in-law showing off her 80k bavarian beasty. her depreciation driving off the lot would have bought an entire off grid solar system with a huge lithium pack. and she doesn't drive any faster than someone her age with a corolla. isn't any quieter. may or may not be a bit more comfy.
value is a tough thing to decipher.
lithium has real performance benefits beyond long life.
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Borrego
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# Posted: 23 Oct 2015 11:11pm
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Why do I keep hearing about Tesla?
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Borrego
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# Posted: 23 Oct 2015 11:15pm
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By the way, I am off grid, but use the system (for now) only on weekends. I do leave for the summers (4 months) and only check in maybe twice...so if that helps your advicement....
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MtnDon
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# Posted: 23 Oct 2015 11:49pm
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Quoting: Borrego Why do I keep hearing about Tesla?
Tesla issues press releases.
Tesla is sexy.
Tesla cars start at $76K. Don't expect bargain prices on their powerwall battery systems. That is just my opinion, mind you. And so far powerwall is still adware, not hardware.
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MtnDon
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# Posted: 23 Oct 2015 11:53pm
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Quoting: Borrego I am off grid, but use the system (for now) only on weekends. I do leave for the summers (4 months) and only check in maybe twice
You still need to size the system for your needs. LFP cells should make it easier to grow the storage; easier than FLA.
What are the desert summer temperatures? The RV guy that was mentioned in this thread, someplace above, cooked his batteries a little and lost capacity. He was somewhere in AZ in summer. Mind your FLA batteries don't fare very well through AZ summers. Two summers out of a set of FLA GC-2's or L-16's is common.
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creeky
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# Posted: 24 Oct 2015 11:39am
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Quoting: Borrego hearing about Tesla
You know the advertising maxim "sell the sizzle not the steak?"
By pre flogging the giga factory and powerwall he does two things. One: creates anticipation which often results in delayed purchasing of a competitors product. Two: makes his product more appealing.
If you look at the business model, Musk makes his money (heh heh heh) off of the SolarCity installs. Have you seen the prices. The markup looks to be 60%. Which is a healthy retail margin. Of course markup doesn't translate into profit.
I just have so much admiration for his marketing.
**
that was a bit off topic
**
I see balqon has dropped their small battery packs. that's too bad. the smallest now is the 5kw. which would give you 2.5kw of useful power (about a 1kw system worth of storage). and, in your scenario of weekend use, probably last 50 years.
as I've mentioned, one benefit of lithium is you don't have to charge it when you're away for the summer. turn everything off the day before you leave. use up some of the power. leave it somewhat discharged (60% is the number is see online). walk away.
that's a pretty handy feature.
you might want to go look at the gbs cells someone else has mentioned.
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NorthRick
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# Posted: 24 Oct 2015 12:25pm - Edited by: NorthRick
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Don't get me wrong, I would love to see LFP pan out and prices come down. They sound great for all the reasons creeky lists. However, it's just too soon for me.
I'd also love to see creeky and Mt Don set up an LFP battery bank and share their experiences.
We're weekenders, so our system can easily get the batteries back to full charge and into float while we are gone. I might think differently on battery type if I had to manage power daily.
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creeky
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# Posted: 24 Oct 2015 02:35pm
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thx NorthRick. I'd love to install a lfp pack too. sadly my la pack continues to rattle and wheeze along despite my worst intentions. maybe it's just ego or the bank account, but I would like to get to 5 years of service.
I had thought it was dying as it was taking 3 kws to keep it charged. but then I cleaned out my fridge. found that the vents in the freezer where covered. did some general clean up and fixed the door gasket and I'm back to 2kw charges the system. which. when you take into account the loads etc. Is bang on. sigh.
if you want to read a few thousand posts about how wonderful lithium packs are ... and view multiple installs, there's a yachting lithium battery thread that was at 3,000 posts a year ago. i've lost the link, but I'm sure some internet searching would find it.
a really nice comparison lead to lithium primer is this blog post from victron ... it even has pictures to help explain the benefits.
http://www.victronenergy.com/blog/2015/03/30/batteries-lithium-ion-vs-agm/
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MtnDon
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# Posted: 24 Oct 2015 06:16pm - Edited by: MtnDon
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Quoting: NorthRick We're weekenders, so our system can easily get the batteries back to full charge and into float while we are gone. I might think differently on battery type if I had to manage power daily.
There is one thing in particular attracts me to LFP as a part time cabin user. That has to do with the extremely low self discharge rate and the ability of LFP to sit at partial state of charge for prolonged periods.
Lightning!
With the FLA left idle for lengths of time it is really imperative to have the PV system, panels and CC, connected and turned on to ensure the FLA have their charge maintained and prevent sulfation. Since having virtually everything except the batteries annihilated by lightning I am very wary of leaving the cabin with the solar up and running. Yet, if I disconnect the PV for more than a few weeks at a time I risk battery damage.
LFP could sit there for most of the year without self discharge damage. Leave the PV cable disconnected with a 10-12 foot gap between it and the CC. Lightning probably wouldn't make that jump.
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Borrego
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# Posted: 24 Oct 2015 08:03pm
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Quoting: MtnDon What are the desert summer temperatures?
They are in the 110d range usually but can easily reach 120d Will that be a problem? I am not there (obviously) except once a month to drive in and check on the place. Although if I could ever get a couple of window units in there, I would love to sit inside and watch the summer desert once in a while.
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MtnDon
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# Posted: 24 Oct 2015 09:04pm
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If you haven't already read the pages by the AZ couple who has had LFP in a converted bus RV, go here.
A relevant excerpt.... According to the specifications for GBS-LFMP100AHX cells published on the Elite Power Solutions website, our battery cells are rated for:
Operating Temperature: -20C to 65C or -4F to 149F.
But while brainstorming potential causes for our diminished capacity recently, Elite let me know that in their experience heat has a huge impact – even within that operating range.
They have observed that a 10C (18F) temperature increase over a baseline room temperature of ~23C (74F) results in the number of lifetime cycles being cut in half.
This means at 33C (91F) usable battery life will be cut in half, and presumably to a quarter at 43C (109F). This is VERY substantial.
I am disappointed that the impact of temperature on GBS cells does not seem to be documented and published online anywhere (though I don't feel it was intentionally hid either) – especially considering 110F is actually a rather common summer temperature in Phoenix Arizona where Elite is located!
There's more in the link above. High desert temperatures are not usually reached by most people in the boat / cruising fraternity. So perhaps all of the marine experiences won't transfer over to life in a desert small cabin. I do know from a friend in the PV business that FLA's don't fare very well, or very long at the elevated temperatures in AZ. This probably needs more research directed at LFP's and elevated temperatures. At least if it is a small system a small bank of GC-2's is cheap enough to replace every few years.
I don't know what I would do if I was contemplating an alternate energy system in those temperatures. Best of luck in whatever direction you take.
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creeky
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# Posted: 25 Oct 2015 10:15am
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the RV post also links to the cruising site's 4000 some posts.
Even with the decrease in capacity he's experienced... under those same conditions he would be on his second or even third FLA pack. FLA decays at double the rate at just 35C. And he's talking about temps that are 42C and above (110F).
And he talks about people using FLA in his situation replacing their packs annually.
What I found interesting is that the comments are more informative than the article itself. Victron chimes in officially with a possible fix for his capacity loss. which is very interesting.
A huge benefit to cabin life is we can protect our batteries from cold and heat. Lithium easier than FLA as there are no corr/expl-osive gases to worry about.
I've thought for a while now that if i was to redo a solar shed I would put the batteries in a basement/cold room below the frost line. Simple solution. Not so good for FLA. But perfect for LFP.
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