I am weeping with joy as the Lithium Iron Phosphate battery (LFP or LiFePO4) completely changes off grid energy storage
Recently I stumbled across the Balqon LFP 9kw energy storage battery. It comes complete: battery management system, even a fuse, so it’s plug and play. The benefits look amazing, but how will it fare in comparison to my lead acid battery pack?
What is LFP or LifePO4?
Basically it’s a rechargeable lithium battery with lithium ferrophosphate cathodes. Ya. I don’t know what that means either.
The chemistry behind LFP batteries was originally discovered by researchers at the U of Texas in 1996. By 2004 preliminary cells were being made and by 2006 mass manufacturing began. It is only recently, however, that prices have come down enough to be competitive in the off grid solar world.
For more information see wikipedia.
Why LFP for off grid?
LFP batteries have a number of qualities well suited to off grid solar application. The power storage is virtually immune to temperature change, quite unlike FLA (Flooded Lead Acid). The chemistry is exceptionally stable which means they don’t burn or explode. They have a much higher power density and don’t off gas. This means they take up less space, weigh 1/3 the amount, and can be used in an unventilated space (the broom closet?).
So how does LFP compare to my lead acid battery pack:
(also see the recent post by Simon which compares technical and cost aspects of LFP battery vs lead acid)
|LFP vs Flooded Lead Acid (FLA) battle of the storage solutions||Balqon battery pack (9kw)||My FLA pack (14kw)|
|Lifespan (at 3kw daily discharge*)||20 years (7,000 cycles)||6 years (3,000 cycles)|
(note: both batteries can be left unused to very low temps)
|Should be kept above freezing for charging||Should be kept around 20C/70F for best results. Battery loses significant storage when cold.|
|Storage||Can be left partially charged for months||Must be kept at full charge|
|Charge efficiency||better than 90%||less than 80%|
|Battery pack weight||260 lbs||720 lbs|
|Ease of use||Easy||Moderate|
|Requires ventilated space due to dangerous off gases||No||Yes|
Key considerations for off grid life
The key advantage to LFP is the fact it doesn’t have to be fully charged all the time. One of the worst killers of FLA is sulphation. Sulphation occurs rapidly when the FLA battery is left uncharged for any period of time.
If you go to any off grid solar site you’ll also find that lots of folks kill their FLA packs by forgetting to water them. Well you don’t need to water LFP.
And of course deep discharge is the number one killer of FLA battery packs. Again, LFP batteries handle deep discharge far better.
The only advantage to lead acid is initial cost. I can put together a lead acid battery pack for around $2k (updated price: the batteries I use are now 385×6=2,310, $US plus cables and fuse). The Balqon is listed at $3.35k $US. I would buy it in a heartbeat. Just the maintenance issues of watering and heating make it a better choice. Of course the fact that it will also last several times longer makes it cheaper in the long run.
In fact I could increase my energy use to 4.5 kw or 50% dod on the LFP pack and still get almost double the lifespan (5,000 cycles or 13+ years). So yes, hand me another hankie.
Is there a downside?
The only downside has been that LFP battery management is relatively new. So the cost and building issues for a “diy” guy like myself has been a challenge. Now that companies like Balqon are releasing complete battery packs ready to plug-and-play. This barrier has been removed. And I am seeing LFP battery packs being released all over the world. Germany and Australia seem particularly keen.
If you’re looking to build a full time off grid power system. Forget lead acid battery packs. LFP is the new king.
(Also read the post LFP is King, which highlights the study by Princeton University researchers comparing LFP vs FLA batteries. Most informative.)
Almost no self discharge is ideal for seasonal off grid solar
This is particularly true for those of you living off grid seasonally. Because the LFP pack doesn’t self discharge you can leave it behind for a season and not worry about ruining your battery pack.
Thank you Balqon
And I take my hat off to Balqon for bringing a complete package to the off grid community. Folks, I salute you.
* I chose 3 kw because that's what I try to keep my max dod to here on my off grid farm.