having a hard time justifying switch to LiFePo4

[JAS]

Hey all,

So currently I have (2) 6V Golf Cart Batteries in series, (1) 240W 24v Solar Panel connected to a Renogy MPPT Tracer charge controller, (1) 100W 12v solar panel connected to a Renogy PWM charge controller, and a Xantrex ProWatt 600W pure sine wave inverter. This entire setup is outside in an unheated shed about 50' away from the cabin. I'm in central PA and the winters can occasionally get down to around zero degrees F for several days at a time. Yes, I have to water the batteries. But, only about 3-4 times a year and it's not really a problem...

This system has been running my entire recreational cabin for 6 years now and the batteries are still going strong. (I've only run them below 80% charge maybe twice and those two times not below 70%). My normal routine is to run our Champion 2000W inverter generator when running our freezer/fridge conversion, the vacuum, taking showers that uses our Shurflo water pump, and watching movies or the kids playing xbox. So for the most part, the batteries are only there for nightime lights, and flushing toilets, washing hands, etc. When I'm up by myself, I do use it more mainly because I don't always need the fridge and the batteries can easily handle my quick showers, plus no xbox

So at this point, I don't really "need" any more power. But, I would like longer runtime, such that we could watch a movie without having to worry about draining the batteries too far too fast. So the easiest and least expensive upgrade is to just get (4) GC2's and wire them up in series/parallel and as such double my runtime. This will cost me about $450. (I already have a 2nd 240W 24v panel that I can add to the MPPT as well)

Now, if I switch to LifePO4, I would be looking at (1) roughly 240AH 12v LifePO4 to match the (4) GC2s safe runtime. Looks like I could possibly find one of these in the $600 - $800 range (more if I buy from a more "trusted" source). Now I know the theoretical lifetime of these "should" be much longer than FLA. However, if I go this route, I also need to upgrade my charge controller to one with a low temperature cutoff and also setup some way to heat the batteries in the winter. (This could add another couple hundred.) So let's say to be safe, I'm looking at $1500 to go LifePO4 and let's say I can expect 20 years of use (I know maybe more). But, I'd have to deal with the low temp problem in the winter.

Currently, I have no worries about using and charging my batteries during the winter. If I switch, I imagine I'd have to be careful and pay more attention to making sure they're warm before charging as well as being careful not to drain them too far if I know I can't charge them... For $1500, I can stay with (4) GC2's and replace them 3 times. With my low usage, I expect to get 7-10 years out of the GC2's. So about the same long term costs as the LifePO4's... And that's assuming the GC2 prices stay the same

So am I missing something?

Thanks for any thoughts...

Jeff

 

[jasonhc73]

There is no "theoretical longer lifetime". Lifepo4 batteries are well proven to last 6x to 20x (probably way longer if well monitored) longer than FLA.

Yes, the batteries have considerably higher upfront costs.

In 10 years, nobody knows what battery tech we will have available.
You will have gone through 3 sets of lead batteries, or still have 80% of life left in the LeFePO4s.

 

[justicelee26]

Lifepo4 cells are great but it sounds like for your specific application they may not suit your needs. You can always buy some of the 280 amp hour cells from alibaba and those would be very inexpensive for a lifepo4 battery if you don’t mind some DIY wiring. However, if you can’t be sure the batteries won’t be subjected to extreme temps, even with low temp disconnect, you are probably better of with another chemistry. Hope this helps.

 

[Ped]

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.

 

[Craig]

I think if you have been using what you have for 6 years then it works for you and keeping things simple is the best I would continue adding to what you have instead of re inventing the wheel. Just make sure the batteries you have are not gonna reach end of life any time soon.

 

[svetz]

...[been using lead acid] ... it's not really a problem... am I missing something?

Sounds like what you have has been working out well for you. The big reason to switch is generally economics, frequently lithium wins when you consider cycle count vs. Depth of Discharge (DoD). The question is if the extra cost is worth the cycles?

A lot of times, the answer is "no". There are some examples of the math in the Battery FAQ.

You might also look into Partially Charged Carbon (PCC) batteries; Outback's Northstar, or Trojan's Spre line ($400, 2000 cycles at 50% DoD). They're new types of Lead Acid batteries that get you more bang for the $. At least that's what the datasheet says.

Update: Oops.... the SPRE line is for stationary use...they may or may not have something similar for mobile.

 

[offgriddle]

Hey all,

So currently I have (2) 6V Golf Cart Batteries in series, (1) 240W 24v Solar Panel connected to a Renogy MPPT Tracer charge controller, (1) 100W 12v solar panel connected to a Renogy PWM charge controller, and a Xantrex ProWatt 600W pure sine wave inverter. This entire setup is outside in an unheated shed about 50' away from the cabin. I'm in central PA and the winters can occasionally get down to around zero degrees F for several days at a time. Yes, I have to water the batteries. But, only about 3-4 times a year and it's not really a problem...

This system has been running my entire recreational cabin for 6 years now and the batteries are still going strong. (I've only run them below 80% charge maybe twice and those two times not below 70%). My normal routine is to run our Champion 2000W inverter generator when running our freezer/fridge conversion, the vacuum, taking showers that uses our Shurflo water pump, and watching movies or the kids playing xbox. So for the most part, the batteries are only there for nightime lights, and flushing toilets, washing hands, etc. When I'm up by myself, I do use it more mainly because I don't always need the fridge and the batteries can easily handle my quick showers, plus no xbox

So at this point, I don't really "need" any more power. But, I would like longer runtime, such that we could watch a movie without having to worry about draining the batteries too far too fast. So the easiest and least expensive upgrade is to just get (4) GC2's and wire them up in series/parallel and as such double my runtime. This will cost me about $450. (I already have a 2nd 240W 24v panel that I can add to the MPPT as well)

Now, if I switch to LifePO4, I would be looking at (1) roughly 240AH 12v LifePO4 to match the (4) GC2s safe runtime. Looks like I could possibly find one of these in the $600 - $800 range (more if I buy from a more "trusted" source). Now I know the theoretical lifetime of these "should" be much longer than FLA. However, if I go this route, I also need to upgrade my charge controller to one with a low temperature cutoff and also setup some way to heat the batteries in the winter. (This could add another couple hundred.) So let's say to be safe, I'm looking at $1500 to go LifePO4 and let's say I can expect 20 years of use (I know maybe more). But, I'd have to deal with the low temp problem in the winter.

Currently, I have no worries about using and charging my batteries during the winter. If I switch, I imagine I'd have to be careful and pay more attention to making sure they're warm before charging as well as being careful not to drain them too far if I know I can't charge them... For $1500, I can stay with (4) GC2's and replace them 3 times. With my low usage, I expect to get 7-10 years out of the GC2's. So about the same long term costs as the LifePO4's... And that's assuming the GC2 prices stay the same

So am I missing something?

Thanks for any thoughts...

Jeff

I started my solar journey with lead acids five years ago. I was always disappointed with how much energy and time it took to charge them, how little amperage they stored, how quickly they ran down and how soon their already lackluster performance declined. I also found the smelly, corrosive, harmful to breathe, mold inducing, explosive sulphuric acid fumes unacceptable.
Last summer I upgraded my small solar system to small lifepo's and the difference has been night and day.
Before discovering lithium batteries, I considered solar power to be an impractical and expensive toy.
Lithium, (batteries), have literally kept me in the game.
Note: because I live in a place that can experience twenty degree's below zero farenheit, I keep my Lifepo's under the cabin in an unheated root cellar below the frost line.

 

[JoeHam]

Well no lithium isnt for recreational solar systems. Its for 24/7/365 solar systems.

Hey, I respectfully disagree. I have found them worth the additional INITIAL cost over the past 5 + years for the reduced weight and maintenance requirements alone. Everything else is a bonus. ?

 

[JAS]

There is no "theoretical longer lifetime". Lifepo4 batteries are well proven to last 6x to 20x (probably way longer if well monitored) longer than FLA.

Yes, the batteries have considerably higher upfront costs.

In 10 years, nobody knows what battery tech we will have available.
You will have gone through 3 sets of lead batteries, or still have 80% of life left in the LeFePO4s.

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

 

[JAS]

I started my solar journey with lead acids five years ago. I was always disappointed with how much energy and time it took to charge them, how little amperage they stored, how quickly they ran down and how soon their already lackluster performance declined. I also found the smelly, corrosive, harmful to breathe, mold inducing, explosive sulphuric acid fumes unacceptable.
Last summer I upgraded my small solar system to small lifepo's and the difference has been night and day.
Before discovering lithium batteries, I considered solar power to be an impractical and expensive toy.
Lithium, (batteries), have literally kept me in the game.
Note: because I live in a place that can experience twenty degree's below zero farenheit, I keep my Lifepo's under the cabin in an unheated root cellar below the frost line.

Yep, you're last Note: is the key If I would have designed the cabin from the start with the thoughts (and understanding of lithium) from the beginning, I'd be in a better place to make the switch. Now, I have too much investment in the infrastructure to make changes (or more accurately want to make changes)

 

[JAS]

Sounds like what you have has been working out well for you. The big reason to switch is generally economics, frequently lithium wins when you consider cycle count vs. Depth of Discharge (DoD). The question is if the extra cost is worth the cycles?

A lot of times, the answer is "no". There are some examples of the math in the Battery FAQ.

You might also look into Partially Charged Carbon (PCC) batteries; Outback's Northstar, or Trojan's Spre line ($400, 2000 cycles at 50% DoD). They're new types of Lead Acid batteries that get you more bang for the $. At least that's what the datasheet says.

Update: Oops.... the SPRE line is for stationary use...they may or may not have something similar for mobile.

Thanks for the tips on those batteries! I'll check them out

 

[JAS]

Hey everyone,

Thanks for all the input! It's been great!

I do understand it would be nice to be able to discharge and charge quicker with lithium. However, only once in 6 years have I had to run the generator because the batteries were down to 70%. We are normally only there for long weekends and the batteries have plenty of time to get back to 100% before we are up again. I don't even have a charger (only rely on solar), though I've thought about adding one just to charge while the generator is running anyway.

btw: How big of a charger can I get away with using a 2000W generator (and still have power left for other things)

 

[offgriddle]

Yep, you're last Note: is the key If I would have designed the cabin from the start with the thoughts (and understanding of lithium) from the beginning, I'd be in a better place to make the switch. Now, I have too much investment in the infrastructure to make changes (or more accurately want to make changes)

It's never too late! Use up what you got and carefully upgrade with compatible, improved technology. ~ How do you keep your water system from freezing in winter,?

 

[JAS]

It's never too late! Use up what you got and carefully upgrade with compatible, improved technology. ~ How do you keep your water system from freezing in winter,?

I don't I drain it down every time I leave.

I had thought about insulating the shed and running a propane heater in there to keep batteries warm. But, that just adds to the complexity of the whole thing...(not to mention fire danger of an unattended propane heater) I can only imagine letting someone else use the cabin or even just start it up without me...

 

[offgriddle]

Hey everyone,

Thanks for all the input! It's been great!

I do understand it would be nice to be able to discharge and charge quicker with lithium. However, only once in 6 years have I had to run the generator because the batteries were down to 70%. We are normally only there for long weekends and the batteries have plenty of time to get back to 100% before we are up again. I don't even have a charger (only rely on solar), though I've thought about adding one just to charge while the generator is running anyway.

btw: How big of a charger can I get away with using a 2000W generator (and still have power left for other things)

Figure what you will have leftover for amperage, (watts), to run your charger, then purchase a charger that does not exceed your remaining power output.

 

[offgriddle]

[AQUOTE="JAS, post: 57863, member: 4680"]
I don't I drain it down every time I leave.

I had thought about insulating the shed and running a propane heater in there to keep batteries warm. But, that just adds to the complexity of the whole thing...(not to mention fire danger of an unattended propane heater) I can only imagine letting someone else use the cabin or even just start it up without me...
[/QUOTE]
A big 6'x6'x6' insulated hole in the ground with an insulated bulkhead over it might work for you. There must be no air movement in the hole in winter.

 

[JAS]

Figure what you will have leftover for amperage, (watts), to run your charger, then purchase a charger that does not exceed your remaining power output.

So is it as simple as a 300W charger pulls 300W from the generator at 120v? Or is the 300W what the charger is putting into the batteries at 12v?

 

[jasonhc73]

So is it as simple as a 300W charger pulls 300W from the generator at 120v? Or is the 300W what the charger is putting into the batteries at 12v?

There is a Voltage potential difference.
You limit the current at the charger by how many AMPS you allow it to send to the battery.

I can't think of any charger made that will send the full amount of amps when the Voltage potential gets equalized. The current(AMPS) will get less and less the closer and closer the Voltage gets to the Voltage you set it to.

 

[Supervstech]

So is it as simple as a 300W charger pulls 300W from the generator at 120v? Or is the 300W what the charger is putting into the batteries at 12v?

It is almost that simple...

There are losses. Most basic battery chargers (12V) are, trickle, slow charge, fast charge (6-20A), and full on chargers that hit 50 to 250A...
that is the battery voltage amps, so 10A is 120w... 100A is 1200W. Then you figure losses, 20% is max, most are like 5%... but you will need to figure it.
A2000W generator won’t have trouble unless you are trying the START charging of a full on charger.

 

[Supervstech]

Ok... reading your use of the bank at the cabin... do you need lithium?

ABSOLUTELY!

You run the generator when you want the freezer, etc...
Because lights and the Xbox tax the bank and inverter...

So, you need a 2000W inverter, and another 600watt of solar... and a bank that will sustain this overnight...

If you are worried about winter... PA gets cold... can you put in a cellar? Or, could you add heat to a VERY WELL INSULATED battery storage with low temp cutout protection?

 

[boondox]

As others have said, seems like what you have is working. I have a similar profile of usage to you in that I don't let them get down anywhere near 50%SOC. I got 10 years out of my last set of FLA's. I paid $2500 for them so that breaks down to $250 a year, I think that is pretty good. It isn't quite a true cost because there is the fuel for the genny on rainy days, upfront cost of the genny and maintenance. I just had to replace them last year and after much consideration went with FLA again.

I don't have the same cold climate that you do and that is a consideration for lithium for sure. I do like lithium and with my van went lithium. In that case, not having to keep and eye on them when storing (as much), being able to slowly run them down over a few days and wanting to learn and get some experience were the deciding factors. Along with the fact that if they go dead I simply pack up and drive home, my chest freezer isn't thawing out.

One thing about LA batteries is that they are a known quantity. The have been in use a long time and if you use them in the manner intended they are quite reliable. I sure hope to replace my current set of FLAs with something else when they wear out. I wanted to this time, there is no doubt of the well known shortcomings of FLAs. I'm not bashing lithium, if I was richer and could afford to simply replace my batteries if something goes wrong I would have likely gone lithium. But I can't afford to do so and I know the FLA's will keep the freezer cold and the lights on as long as I take care of them.

 

[Bogart Engineering]

Hey all,

So currently I have (2) 6V Golf Cart Batteries in series, (1) 240W 24v Solar Panel connected to a Renogy MPPT Tracer charge controller, (1) 100W 12v solar panel connected to a Renogy PWM charge controller, and a Xantrex ProWatt 600W pure sine wave inverter. This entire setup is outside in an unheated shed about 50' away from the cabin. I'm in central PA and the winters can occasionally get down to around zero degrees F for several days at a time. Yes, I have to water the batteries. But, only about 3-4 times a year and it's not really a problem...

This system has been running my entire recreational cabin for 6 years now and the batteries are still going strong. (I've only run them below 80% charge maybe twice and those two times not below 70%). My normal routine is to run our Champion 2000W inverter generator when running our freezer/fridge conversion, the vacuum, taking showers that uses our Shurflo water pump, and watching movies or the kids playing xbox. So for the most part, the batteries are only there for nightime lights, and flushing toilets, washing hands, etc. When I'm up by myself, I do use it more mainly because I don't always need the fridge and the batteries can easily handle my quick showers, plus no xbox

So at this point, I don't really "need" any more power. But, I would like longer runtime, such that we could watch a movie without having to worry about draining the batteries too far too fast. So the easiest and least expensive upgrade is to just get (4) GC2's and wire them up in series/parallel and as such double my runtime. This will cost me about $450. (I already have a 2nd 240W 24v panel that I can add to the MPPT as well)

Now, if I switch to LifePO4, I would be looking at (1) roughly 240AH 12v LifePO4 to match the (4) GC2s safe runtime. Looks like I could possibly find one of these in the $600 - $800 range (more if I buy from a more "trusted" source). Now I know the theoretical lifetime of these "should" be much longer than FLA. However, if I go this route, I also need to upgrade my charge controller to one with a low temperature cutoff and also setup some way to heat the batteries in the winter. (This could add another couple hundred.) So let's say to be safe, I'm looking at $1500 to go LifePO4 and let's say I can expect 20 years of use (I know maybe more). But, I'd have to deal with the low temp problem in the winter.

Currently, I have no worries about using and charging my batteries during the winter. If I switch, I imagine I'd have to be careful and pay more attention to making sure they're warm before charging as well as being careful not to drain them too far if I know I can't charge them... For $1500, I can stay with (4) GC2's and replace them 3 times. With my low usage, I expect to get 7-10 years out of the GC2's. So about the same long term costs as the LifePO4's... And that's assuming the GC2 prices stay the same

So am I missing something?

Thanks for any thoughts...

Jeff

You can easily get 2x runtime with your setup, since you have the capacity to recharge the batteries after each night using your generator & solar power. No need to live by the "don't discharge more than 50%" rule. What kills lead acid batteries is not the depth of discharge, but how long they stay discharged.
What the battery manufacturer guarantees is the lifetime amp-hrs. Whether you take this in 2000 shallow cycles or 500 deep cycles has a small effect on the overall lifetime amp-hrs, with shallow cycles giving you slightly more lifetime amp-hrs. You can easily counter this by promptly & fully charging them as per the recommendations after each discharge event. If you can run a shortended version of the equalization stage, run it after each charge cycle. It will reverse the trace levels of sulfation that happens at each discharge & stir up the electrolyte to prevent stratification. With this approach, you can easily extend the cycle life by 20-25%.

 

[Deleted-User]

Upgrade to Lithium, leverage FLA to heat the Lithium pack in times of low temp? (I'm thinking a heat pad/blanket set to say 45F trigger, for example.)

 

[orangeminnie]

Anybody switch to LiFePO4 and regret it?
<Silence>
<Mic drop>

 

[Ped]

Anybody switch to LiFePO4 and regret it?
<Silence>
<Mic drop>

Literally the best purchase I ever made