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SCSJeff
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# Posted: 17 Oct 2018 17:32
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ICC,
I didn't want to keep hijacking offgrididaho's thread...
OK, So in my scenario...
I currently have (2) 6 volt 200AH batteries in series: 12 volts at 200AH = 2400 watts. Costs about $180. I'm the same, I try to avoid going lower than 25% down. So 25% of 2400 = 600 watts. I'm already on my 5th year and batteries are still going strong. (Probably because I haven't taxed them very hard over that span)
If I were to get just (1) of those 12v lithium batteries...
12 volts at 100AH = 1200 watts. Costs $900+. Taking it down 80%: 80% of 1200 = 960 watts. So I definitely see the advantage there. However, at 80% down, I'm at my dangerous limit. On the FLAs, I can go another 25% before I'm at the dangerous limit, correct?
Unfortunately, that initial cost is the stumbling block. I'm still at around my 20 year mark for break even over FLAs. Add on the worry/complication of either only charging while warm or keeping them warm in order to charge just doesn't seem to add up to me...
Other than the lack of off-gassing and weight, what are the other advantages of lithium? In my small setup, neither is that much of a concern.
I can see maintenance. However, with just (2) batteries for me to maintain, that is not much of a big deal either.
I understand they can charge faster. Is that true? And how much is faster? I'm currently charging with (1) 100W 12v panel on a PWM charge controller and (1) 280W 24v panel on a mppt charge controller. If I start around 80% charge and a full sunny day I can be back to 100% within 4-5 hours (guessing, never really timed it)
Don't I also need to make sure my charge controllers charge the lithium safely?
Thanks,
Jeff
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ICC
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# Posted: 17 Oct 2018 20:08 - Edited by: ICC
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First let me say that I do understand that it is sometimes difficult for many to make the initial purchase of lithium batteries. Even if they may last longer than several sets of lead-acid batteries the fact remains that the initial purchase may easily blow the budget. So, I do completely understand why many folks stick with lead-acid. I don’t have a real good analogy, but it is sort of like comparing a Porsche to a Miata. They both get you to where you want to go. But if you can afford the Porsche, well it is just nicer.
Quoting: SCSJeff Other than the lack of off-gassing and weight, what are the other advantages of lithium?
Yes, much lighter. Maybe not a big deal for stationary use unless you have to carry them a ways from the delivery point to the installation site.
Off gassing… Not just the off gassing is a negative point, but the off gassing also means the lead acid batteries need water to be added periodically.
LiFePO4 (LFP) can be discharged at a higher rate than lead-acid golf cart batteries. If you run microwaves and other hi wattage appliances that can be important.
Better cold performance. Cold temperatures do not decrease the effective discharge capacity to the same degree as cold affects lead-acid.
LFP do not have longevity affected by a deep discharge compared to lead-acid. LFP can easily be discharged down to 20% left. That is you can readily use 80% of the rating and not shorten life much at all.
LFP do not self discharge to any appreciable degree.
LFP may be partially discharged and then left sitting there for months. Lead-acid will be damaged when left in a partial state of charge for an extended period. The ability to sit for long periods at partial charge is a big feature for part time use cabins, IMO. As well because they can sit for extended periods and not be charged or floated, you can disconnect the CC and panels and remove that source of lightning damage. Where I am lightning strikes are common and being able to disconnect the PV is a nice benefit.
No need to worry about keeping the lead-acid charged when being stored through a freezing winter. That was one of the things my friend wanted.
LFP are also more tolerant of higher temperatures. In a desert climate lead-acid batteries deteriorate faster than when kept at moderate temperatures. I have never had that concern but have a friend in southern AZ who literally cooks his lead-acid golf cart batteries, needing new ones every 2 years.
If you rely on a generator for recharging, LFP have the advantage of not needing an absorb stage. Lead-acid can be brought to about 80% charge fairly quickly, but that last 15 to 20% is slow to build up. Not so with LFP .
LFP are very safe. Possibly even safer than AGM, as AGM can encounter a meltdown. Rare but AGM can suffer a thermal runaway.
Quoting: SCSJeff I understand they can charge faster.
I'd say 20 to 25% faster using the same PV system. That's an off the cuff estimate as my old lead acid system had a different use pattern, different panel setup, different in many ways.
Quoting: SCSJeff Don't I also need to make sure my charge controllers charge the lithium safely?
That may not be an issue depending on the CC. LFP charge well at 14.4 to 14.6 volts (on a 12 volt battery) and that is adjustable on the good to better CC units out there.
I think that pretty much has most of the advantages of LFP .
I like them a lot. For the home, it is nice not to have to worry about water and sitting at a partial charge. In fact, I have the home battery bank system set to only charge up to 90% full to extend battery life. I have an LFP in the Super Cub for weight saving. I have an LFP set in the RV for the house batteries for the ability to discharge deeply and not worry about needing to recharge soon.
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ICC
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# Posted: 17 Oct 2018 20:25
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LFP have more advantages than disadvantages, I'd say. Even if the life expectancy was equal I'd probably pay 20% more just to avoid watering, avoid terminal corrosion (forgot to mention terminal corrosion above), and have the ability to leave at partial charge without damage.
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SCSJeff
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# Posted: 17 Oct 2018 20:55
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Awesome!
Thanks for the lesson 
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SCSJeff
Member
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# Posted: 17 Oct 2018 21:56
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OK, I just looked up that battery on Amazon.
Now I'm drooling 
Great Reviews and even more advantages given. The BMS on that battery seems fantastic. Eliminates the worry about freezing in my mind. If necessary, I could fire up a big buddy heater in the shed if I need to get a quick charge into the battery. In reality, most of the time when I'm there during hunting season, it only drops below the 25 degree F at night. Not charging then anyway... Although, I did spend one weekend last February when it was 0F for about a 3 days straight
Not sure I would trust my cheap PWM charge controller on it though...
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redwolfguild
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# Posted: 18 Oct 2018 20:06
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What is the min temp that i can charge a LFP battery at?
I currently use a 100 AMP AGM 12 volt and leave it year round hooked up inside the cabin. The coldest recorded temp inside was -2 F one year. Most of the time it stays around 10F indoors when we are not around. My battery is 5 years old and is not holding a charge like it use to, so I want to upgrade. I want to go 24 volt this time, but a LFP would get me by at 12v
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Wilbour
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# Posted: 19 Oct 2018 00:29
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Quoting: redwolfguild I want to go 24
I am using a former Chevy Volt battery that's 24v. It is a 1kw unit. Great guy I know can purchase the complete battery pack and break it down into a couple of 24v packs and the rest are 48v
He also built the "Power Drawer" that Lakeside speaks of. Not as expensive as one may think.
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ICC
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# Posted: 19 Oct 2018 09:56
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Quoting: redwolfguild What is the min temp that i can charge a LFP battery at?
Most of the info states 0 C, 32 F, though those BattleBorn say 25 F, -4 C. Be wary of spec sheets that just give a single operating range of something like -20 to 65 C, -4 to 149 F. That would be the discharge range. My GBS specs clearly state---
Operating temperature ranges -20C to 65C for discharging, and 0C to 65C for charging
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paulz
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# Posted: 19 Oct 2018 10:00
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Quoting: Wilbour I am using a former Chevy Volt battery
Lots of used e car batteries showing up in the classifieds around here, still pricey though. Maybe they will come down eventually. Can you get 12v out of one?
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redwolfguild
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# Posted: 19 Oct 2018 15:34
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Quoting: ICC Most of the info states 0 C, 32 F, though those BattleBorn say 25 F, -4 C.
I guess that would mean I would have to disconnect it when I left the cabin in the winter - which is less than ideal.
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ICC
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# Posted: 19 Oct 2018 18:59
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Not connected over winter is not a problem if you leave it with 50 to 70% charge. It will keep fine. Of course if you need to run things while away that is a problem. Then when you return the battery may need to be warmed when it needs a charge.
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