Energy What are your thoughts on PB vs LFP ?

I am pondering which way to head re investing in a battery bank.

Lots of Pro's/Con's to consider either way. The crucial part of this is how these fit into YOUR particular circumstances.

LiFePo4

Pro's
- Short charge times - can take a big charge current (so can use most of what charge current you can produce)

- Can stand in a partially discharged state for a good long while without any damage and then charge right back up when you can do so

- Peukert's law does not affect them to any real degree;

- Can discharge a huge amount of energy quickly which directly translates to running bigger loads and if needed, from a smaller battery bank then the PB equivalent.

- Energy density is higher then PB - so more energy in a smaller footprint then PB which could be valuable if room/space is at a premium for whatever reason

- Weight reduced for a given amount of energy storage Vs PB - could be important on a boat or in an RV or on the 5th floor of a building for example

- No off gassing. Vital for indoors deployment.

Con's

- Better know what you are doing if you want to home brew your own LFP setup.

- special charge curves and charger setup - not a problem per se, but be aware of it.

- Make a mistake on Charge/Discharge and you can probably kiss the bank goodbye forever.

- LFP fire is a specialty fire that not many know how to deal with - not a problem if you plan for the worst and get educated.

- not really known at this point what the life expectancy REALLY is. They have not been around long enough for critical mass penetration into the offgrid crowd. Do they really get up to 5000 cycles if the charge/discharge regime is followed?

- More expensive upfront then PB



Lead Acid (PB)

Pro's

- Been around forever, so well understood and lots of equipment made for them

- Generally can take a beating and survive - good for beginners new to battery banks

- Lowest cost out there (Flooded Lead Acid types)

Con's

- Cursed by Mr Peukert and his "law"

- Can only use a max of 50% of the banks capacity - 25% if you really want the longest service life they can give.

- Because of the above point, the bank needs to be much bigger then you may like if you want a useful amount of energy out of a PB bank. Maybe not a problem if you have the room for them on the ground floor and can afford it upfront.

- very heavy - hard to move around to get in/out of place. The initial headache of getting them in not so bad if they are to be there for 10+ years (and hopefully last 20+ years in service...(2v jars)......... )

- Most cost effective battery is Flooded Lead Acid - so constant maintenance required ( water top up / SG readings recorded )

- Voltage sag under heavy load/discharge - can be overcome by a bigger bank installed for a given load condition

- CANNOT tolerate a discharged situation for any length of time - is fatal to the bank if left too long discharged

- takes a long time to finish the absorption stage - depends on your situation but if charging off solar then the solar charge window (4-6Hrs a day) is generally not long enough to do bulk charge then the absorption/taper charge. So this means running the genset to finish the charge cycle off if you want max service life from the bank.

- If no solar and charging is via Genset only....WOW, thats an expensive charge cycle in diesel consumption (depends on size of genset and other opportunistic loads that take advantage of the genset being on)


I am sure there are other points to this and as I say several times it really depends on your situation - a lot of variables could swing it one way or the other for YOUR situation.

But in general, which way do you lean...? PB of LFP and why ?

Hope to get some insight from others on this.

Rgds

 

When I first started with our new computer living in the mountains with untrustworthy grid power, we used gel cell battery inverter and a battery charger , later I added the solar panel to supplement the battery charger and that grew from there.
At the time there was not a lot of information so I turned to the RV industry and spoke to the folks that lived in them, and their choice was 6 volt golf cart deep cycle batteries people converted to in place of the big truck batteries . So that's what I've been on sense .
I used 12 volt deep cycle boat batteries for years as well because they were free and already used pretty heavily.
My system has a switch on every singe component including every single solar panel so that if there is a failure I'm on top of it.
So I have both 6 and 12 volt batteries on line.
IMO though some have invested a lot of math , fact of the matter is the sun and clouds and dust don't care ,nor the curvature of the earth .
Solar panel reception is not on and off , all of them vary with exposure . Batteries are not much different due to manufacture.
Depending on your settings (meter) even new batteries will have variations and age respectively.
The bank will settle (if it allowed to) to the voltage of the lowest one .
Isolate each battery and they will settle to their own value . .
I once had an idea to make a automatic switch that rotated through the bank sampling the lowest and charging that one and moving to the next , another switch selected batteries for the load at hand ,no more than necessary. the idea is noble but the practicality was a waste of investment .
fact , Batteries have an individual life , do the best you can and treat them as individuals.
There have been a lot of new batteries introduced , let every one else be the gini pig and pay for the R&D , after the dust settles then I will consider some new battery .
If I had unlimited resources I could be tempted to get cast iron/lithium (I think)
Very large and heavy but in the end last infinitely longer than any thing else supposedly .
But I would add the to my system , I'm not afraid of mixing it up .
I see my solar as a small stream and my batteries buckets . if there's not much coming I fill what I can , however if there is a greater supply coming and I haven't the buckets to catch it ,it's my loss.

 

LiFePo4 too rich for my blood. Maybe as more are produced, the cost will gradually drop, but you're probably looking at years.

In the meantime, it's flooded lead-acid for me.

If building a new system I'd purchase a charge controller capable of charging both types. That way if a miracle happens and prices drop for LiFePo4 at a time when your old lead-acid battery bank requires replacement, you'll have that option without having to add the cost of a new charge controller at the same time as having to purchase a new battery bank.

 

I agree , I like having back up systems, even if I never have to fall back on them as the original ages the secondary is ready to go.

 

I have installed a number of back up power systems for clients over the years. Dont do it anymore though. I am more interested in getting back to the plot and using my time to get the place moving...so much to do, so little time....

I do have a Victron Quattro 48v 5000VA inverter connected to 8 x 220 Amp/Hr AGM's - (4 x 12 v 220Amp/Hr to make 48v and 2 strings in parallel). This keeps the house going here in town through the night when the grid is down ( a few times a week) - I have about 150W of LED security lights going all night and I usually leave the TV on all night (long story). I have a VSAT modem that stays on 24/7 as well as wireless router, VoIP phone, the refrigerator and a few lights left on around the house all night (so the house is well lit up at night from a distance so the bandits know there is someone here). I am finding that with the fridge unplugged we go all night and into the next day no problem. With the fridge plugged in and working I find about 6 to 8 hours and the inverter is blinking red lights at me - never actually had it shut down though.

Well thats all well and good. But I need to get back to the bush. So I need a complete new system on the plot. My plan is to heavily over panel to carry heavy loads during the day - I want to pump as much water as I can during the day. Trying to figure out how much battery do I actually need. I know all the usual power budget stuff. But thing is, the more battery you have the less you draw it down and that means shallower discharges and therefore longer battery life.

But this is where it gets confusing. I never believe what the sales people say (i find sales people to be insincere snakes!)

What is the life of PB? I used to be dead set keen on the HUP SOLAR ONE battery system. But gee haven't the prices shot up on lead over the last few years!!

If I went PB i would definitely go for 2V cells.

But is PB the way to go on a new from scratch system these days? Is LFP more cost effective over the long haul? Trying to find the the answer to that question is turning out to be hard.

So I am breaking it down to my particular situation. I have plenty of room so thats a non issue. I would build a specialty battery room for them so weight is of no concern at all as it would be on ground level - i'd throw a concrete slab for the job. Venting gases is no problem in a purpose made building to house the batteries.

So it really comes down to how long it takes to fully charge a PB bank and the voltage sag that one gets from a PB bank ( i see this now if I load my present system). Then there is the maintenance issue - its Ok when I am there but when away I dont have anyone competent enough to do this, so that's a problem.

My number one fear with PB is if I lose grid, its January and its raining all day everyday and I get little isolation for the day, and the genset breaks or more likely there is no fuel in town (we get this from time to time) and I cant get enough charge back into the bank. LiFePo4 solves that problem as this battery chemistry doesn't care about sitting depleted for a while.

But the cost. Is it really worth the premium for LiFePo4? I am really stuck on this one. My Heart says go LiFePo4, my head says stick with tried and true PB.

At a loss on which way to jump here.

 

I've seen a lot of discussion about golf cart batteries here but has anyone here ever investigated electric fork truck batteries? They are made to absorb considerable amounts of vibration and other abuse, and the chargers are probably not inexpensive. Keep the cells full of electrolyte, and charge them regularly, service life should be acceptable. I don't know if technology has moved on, I am sure the ones I used were lead/acid. The batteries I am familiar with are made with replaceable cells, so they could be daisey-chained together to make almost any desired voltage. I've seen photos of a pickup converted to use them.

 

I have been using LiFePO4 batteries since 2011. What do you want to know?

I guess all you need to know is for large storage banks I'm sticking with lead acid.

 

This is easy...

Go with LiFePo if you have the money; get flooded lead batteries if you don't.

There is also a third alternative: Absorbed gas mat batteries. They cost more than flooded but less than lithium. No ongoing maintenance issues, no outgassing, no acid to spill or leak. No fire hazard and you can use probably use the charger you already have.

It's a nice compromise between the two.

 

The agm route has worked out well for me, but I don't have a large system. Only a 3060 a/h battery bank. The current bank is two years old and hasn't shown any degradation thus far...fingers crossed for a long life.

 

Thanks for the replies.

A lot of the information I am reading suggests that the calendar life of both 2V PB cells and LFP are thought to be similar. So no real advantage of one over the other there except PB is PROVEN to be so, LFP......just talkin so far.

So with PB that means - over sizing the bank to deal with voltage sag - which is a very real problem with PB. Next PB issue is to get the very LONG life (number of cycles) means DOD no more then 25% (or maintain 75% SOC). So that generally means a bigger bank overall which costs $$$ (I can remember when batteries were cheap and panels expensive)

The flip side of the battery coin...LFP.

No voltage sag of any real consequence at a reasonable size bank (there is SOME voltage drop but its not anything near PB levels)

Since an LFP bank really wants to stay between 80% SOC and 20% SOC to get a decent amount of cycles (or to get as many cycles as you can out of the LFP bank, between 80% SOC and 40% SOC) you can buy less AMP/Hrs upfront. This does help to level up the cost a ....little

So all of those trade offs are understood. I have never used LFP for a battery bank so I have to go by what I read online, but there are far too many individuals reporting the same observations so I am going to consider the information as reliable.

So with all that understood, what then separates the 2 types of battery?

I like that PB is a well known/used/understood tech. Its slightly uncomfortable that LFP just doesn't have the runs on the board yet, so it may not turn out as well as we might hope down the road and that would be an expensive lesson.

But buy the same token, its hard to turn away from the advantages of LFP. Short charge times are incredibly attractive if it all goes to hell and I am reduced to genset for an extended time for recharging. No maintenance is another BIG one where I am. I've mentioned that when I am home on the plot all is well. But when I am not.......ahh lets not even go there. Another biggie is...... if for some reason the bank took a big energy hit and got depleted to the point that a BMS disconnected the loads to the bank at say 15% SOC, there is no damage done. ON PB that is fatal if I am far away and not coming back for a while (in the situation where its all gone to hell and the only way to recharge is via genset - no one I could trust to do it)

So I am just repeating myself i guess. I am split down the middle 50/50 on this.

Loads on battery would be for myself in my small house, and say enough capacity for another 2 to 3 small houses (planning a small lodge for the future). The big thing is needing to run a centrifigal airpump non stop. About 2HP. So that really means genset, but the cost of running the genset can be offset by running the genset for 2 hours to the load and to charge batteries, then turn the genset off and run the airpump on battery for an hour, then 2 hours on Genset, then 1 hour on battery etc through the night. Its not so much the cost of fuel but rather the availability of fuel at times. The need to run the air pump is mission critical.

During daylight hours, I plan to have enough solar panel to run everything. Its really only the night hours that are the concern. There are some days in January that could be a problem during the day as well due to heavy rainfall.

 

Hi Sloth,

Yes I can put in a 200amp 11Kv to 380V 3 phse transformer if needed and I mostly have the power to run a big charger because of that. Grid does go down at least once a week and sometimes power is diverted away from us to other parts of the country so we get load shedding now and then. But in general there is a lot of grid power available to us these days.

I do have a mission critical application where i need to keep a 2HP air pump (blower, not compressor) running 24/7. Genset is the obvious backup and that is part of my plan overall. However we also get fuel shortages from time to time meaning sometimes there is no fuel to be found for 500 klms+ anywhere around us. Fuel storage is a MAJOR issue because of theft. Store much more then a few hundred liters of fuel and then I need a guard on it around the clock. Nothing easy here.

The other plan is to put a pretty big solar array in to pump water with and to charge batteries with (the attraction to LFP is here). But thats a ways off yet as it depends on other projects being completed first. Grid is always cheapest of course but the dependability issue has to be weighed up and factored in as well. I am planning on keeping a fish breeding/hatchery running and cant afford to lose the fish stock because they come out of a National Park Area so permission hard to get to collect breeding stock. Other fish stocks come out of Congo and that is a whole other set of issues getting in and out of there. Better to get in, get whats needed and not go back in there too often if possible. So keeping water supply up and air to tanks via air blower is mission critical.

 

Just direct drive an air blower off a liquid fuel engine instead of running a generator to run a motor.

 

what is a liquid fuel engine ? Sounds interesting and could be a great way forward for me, but I am not really sure what a liquid fuel engine is

 

Again, thanks for input. So evenly split down the middle on which way to go. If the costs were the same I think the LFP would be a no-brainer. Alas, they are expensive little critters. So it comes down to this ; each individual has to decide if the cost is justified in his/her situation.

Think I will just keep reading for a while and see what experiences others are having out there. I do want to get it done but I dont have to order anything tomorrow.

Thanks for your input.

 

If you are interested in batteries this is about the best I have come across - its long so you will have to really interested, but its as through as any of the most detailed out there......

 

If you only ever read one article on LFP , this is the one.

LiFePO4 Batteries On Boats

 

We have been using LifePO4 batteries to power our off-grid home for 2 years now with no complaints. We run a refrigerator, air conditioner, lights, water heater, TV, laptops, etc. with 300AH worth of batteries at 24v and a 2500w solar array. Our generator is out of service more than not so we give them a good workout.