having a hard time justifying switch to LiFePo4

[iceledoar]

Well... GCB’s need regular maintenance you know... distilled water, full charge, monitored capacity, keep discharge to 50%max... those cut it and forget it plans go bad rapidly if not maintained.

Adding water every couple months is not that labor intensive. 10 mins max

 

[JAS]

Jeff I’m in a similar position, but on the new end of the spectrum. My place is way out there and not always kept warm in the winter. I decided to go with FLA’s. Having run the place for the last couple years off of a old trolling motor battery and finally upgraded to the Trojan Solar’s 6vdc’s is a huge difference. I know they are slower to charge but usually are full by noon the next day. Im sticking with FLA’s and keeping my money in my pocket. I did add a watering system so I should be able to leave vacant for a month or so during the summer. Avoiding the Arkansas heat and humidity.

It's my understanding that the majority of the water evaporating/misting out happens when charging. Thus, if just sitting for a month or two fully charged and just being maintained won't really use any significant water...

 

[JAS]

Yes only $200.... + $400 in extra solar + $700 generator + $100 for a charger + $150 controller upgrade + 100 in watering and test equipment.

As of now... I haven't purchased any extra solar than I would have one way or another. The generator was/is necessary anyway for power tools, well pump, etc. Don't have an AC charger. (use solar only) Don't understand the controller upgrade? Never bothered with watering/test equipment so that didn't cost me anything additional...

Don't get me wrong, I understand your point and probably most people with very large banks of FLAs do have all those additional costs...

 

[JAS]

Well, more like 300-600 for a pair of quality GC-2's

If you're talking about Trojan or Concord, yes. However, the Costco Energizer GC2's that I have were about $90 each (and still the same price the last I looked). I can't say they're not quality since they've lasted 6 years and still going...

 

[Fred S]

Also remember that if the lithium bms has a low temp disconnect, that will protect the battery. But for a cabin that sits idle, I'd just disconnect the battery before I left. Down side is that you couldn't reconnect the battery when you return, if the battery is at or below freezing.
Or, just take the battery home with you.

Or #2 - I don't think a battery heater needs to be expensive, if you don't mind diy-ing it. You just need to have a reliable low voltage disconnect to keep it from over-discharging the battery.

 

[JAS]

Also remember that if the lithium bms has a low temp disconnect, that will protect the battery. But for a cabin that sits idle, I'd just disconnect the battery before I left. Down side is that you couldn't reconnect the battery when you return, if the battery is at or below freezing.
Or, just take the battery home with you.

Or #2 - I don't think a battery heater needs to be expensive, if you don't mind diy-ing it. You just need to have a reliable low voltage disconnect to keep it from over-discharging the battery.

Yep, if I were to go the Li route, I'd go with Battleborn (currently the only battery with low temp disconnect that I trust)

 

[thenewtbaron]

So to be on the conservative side, an FLA will last 5 years. You're saying the lifepo4 will last 30 - 100 years?!?! That sounds a bit exaggerated... (especially with the risk of charging under freezing temps causing it to be bricked)

I don't think "affordable" lithium batteries have even been an option for DIY people like off-gridders for the last 30 years (let alone 100). How have they been "proven" to last that long?

In fact batterystuff.com claims only 5-7 years. (Yes, I agree that contradicts everything I've been reading as well)

https://www.batterystuff.com/kb/articles/battery-articles/lithium-battery-overview.html

It depends on how you use the batteries and how much you discharge them. That website states else where that AGM can get 300 charge cycles at 60% DOD - that means you'd get like an actual 150 full charge cycles but AGM batteries can be damaged by larger DOD.

LifePO4 can get 1000+ charge cycles at 100% DOD and won't get damaged by the larger DOD. If you ran it to only 60% DOD, you'd probably get like 2000-3000+ charge cycles.

Now, I don't know if this is correct or not but after that 2000+ charge cycles, the lifepo4 will not be useless but should be at 75-80% capacity while the AGM/FLA would be pretty done.

I also don't know the usage case/DOD of that website's estimates are based on. If it was based on daily full cycling, 5 years at 365 days is about 1800 cycles. If you needed the same amount of power of the lifepo4 from FLA, you'd have to have 2.5 batteries, and they would be used up in 300 cycles...or less than a year. You'd have to replace the 2.5 batteries 6 times while still being able to use the LifePo4. so15 FLA batteries vs one lifepo4.

I just googled 12 v 100ah, and the first SLA battery that showed up was 150$/battery or 1800$ of batteries for over that 5 years vs the top of the line battleborn 12v 100ah is around 1000$

 

[JAS]

I just googled 12 v 100ah, and the first SLA battery that showed up was 150$/battery or 1800$ of batteries for over that 5 years vs the top of the line battleborn 12v 100ah is around 1000$

Yep, sounds like a no brainer if cycling batteries daily... In my case, they only get slightly discharged about 2 days every month on average...

 

[gnubie]

LifePO4 can get 1000+ charge cycles at 100% DOD and won't get damaged by the larger DOD. If you ran it to only 60% DOD, you'd probably get like 2000-3000+ charge cycles.

There's a lot of old figures out there for lifepo4. Things have improved since their initial commercialisation. It's not unusual to see quality battery manufacturers upfront rate their batteries at => 2000 cycles at 80% discharged, but if you look a little deeper and get the spec sheet the expected lifetime is ~2000 cycles at 100% discharge with 80% discharge yielding a lot more cycles. This isn't done by understating the capacity of the battery either, but there is that option of course.

Battleborn state their batteries will do > 3000 cycles at 100% discharged, and then be down to 80% of original AH rating. There's been a lot of debate over BB setting their BMS to cut off before true 100%, ie they over provision their battery which isn't a bad thing, but the ultimate answer to that is to add up the watt hours in all the cells and do a discharge test.

 

[thenewtbaron]

Yep, sounds like a no brainer if cycling batteries daily... In my case, they only get slightly discharged about 2 days every month on average...

Do you leave them trickle charging or just let them set in the cabin? LifePO4 has a pretty low self-discharge rate compared to some other chemistries.

I think you'd be fine. It just becomes a a balance between ease/safety vs cost for you. LifePO4 have a lot less fiddle work, have to charge it up less often because of self-discharge, don't have to worry about acid or fumes, and if you push it to its limits rarely it won't burn out it capacity.

BUT

it does cost a lot.

 

[thenewtbaron]

There's a lot of old figures out there for lifepo4. Things have improved since their initial commercialisation. It's not unusual to see quality battery manufacturers upfront rate their batteries at => 2000 cycles at 80% discharged, but if you look a little deeper and get the spec sheet the expected lifetime is ~2000 cycles at 100% discharge with 80% discharge yielding a lot more cycles. This isn't done by understating the capacity of the battery either, but there is that option of course.

Oh, I agree. I was just using hyper conservative numbers.even with very very low estimations of these batteries make them almost half the cost after 5 years. Less buying of batteries every year.

Then thatlifepo4 battery will still be pumping out 3/4ths of the power, so if you grab another battery.. you are up to 1.75x the power for the same cost of the AGM batteries...so it will get cheaper as you go.

 

[JAS]

Do you leave them trickle charging or just let them set in the cabin?

I leave them connected to the solar panels.

I'm now leaning towards building a 2nd small system inside the cabin. (Be that a battleborn or Lion Energy battery with components or a "solar generator").... Something I can carry back and forth and also use at home during power outages

 

[thenewtbaron]

I leave them connected to the solar panels.

I'm now leaning towards building a 2nd small system inside the cabin. (Be that a battleborn or Lion Energy battery with components or a "solar generator").... Something I can carry back and forth and also use at home during power outages

If you plan to use it for backup power and moving it back and forth, solar generator. Easy to transport and has almost all the stuff together at once.
cost isn't too bad. Will has some good reviews online there.

 

[tmgibs9870]

It sounds like it might be worthwhile to put your lead acid where it's not freezing. Sure they will work, but at diminished capacity. If vans can find room, should be a snap in or next to a building. There are many improvements that you could make to your existing system. Which one will you do first? Unless you set a budget that includes maintenance and repairs nothing else makes sense either.

 

[iceledoar]

I’m going to chime in one last time. I know that all of the high rollers out here buying Li batteries, will help drive the price down. But, considering the times, I decided to keep the extra $2500 or so in my pocket. That buys a lot of grub and fun. As for the, very well documented lives of Li and/or FLA’s, lets take an honest look at life and ask ourselves where we will be in 5-7 year, when the $300 pair of FLA’s Are starting to show some age. In my case I’ll be in my 60’s and, hopefully battery tech will have taken another small step forward, for solar kind, and the price will be somewhat lower. The extra ~$2500 was invested and is now worth $2600, the market was really good, so I celebrated and bought a very nice bottle, read through a solar forum and again determine what to buy.

Crystal ball says keep your money in your pockets

 

[theoldwizard1]

Well no lithium isnt for recreational solar systems. Its for 24/7/365 solar systems. All the disparity in chemistries lay in the issues of charging lead batteries to 100% every day.

Probably the best response !

You can replace FOUR GC2s for less than $400. Space and weight are not an issue, so no lithium benefit. Maintenance is not an issue, so no lithium benefit. Below freezing is not an issue, but it is for lithium !

Spend the money on upgrading your solar and inverter and adding four more GC2s so that you can use the generator less !!