You need new batteries for your cabin or RV. Maybe you’ve been thinking about energy backup for your home. But every time you run a search online, you find thousands of options, and conflicting performance information, and prices at both ends of the spectrum. Or maybe you see someone hawking some amazing new technology that their cousin’s uncle’s former college roommate discovered while hiking in Nepal. And now you’re worried about making the wrong choice.
My goal in this battery article series is to demystify these products to help you make an informed choice.
This first in the series deals with cost. Are Lithium batteries worth the investment?
Higher Up-Front Cost
Yes, Lithium batteries are more expensive than lead-acid, but their energy throughput, cycle life and efficiency means far greater utility over their lifetime. And utility is what batteries are meant to deliver.
It’s All About Energy Throughput
Due to the nature of the chemistry, it is recommended that lead-acid batteries be cycled to no further than 50% of their rated capacity on a regular basis in order to ensure a long service life. By contrast, Lithium’s longevity threshold is typically 80% depth of discharge. Lead-acid battery chemistry is not as efficient in storing and delivering energy (80% efficiency), which means if you put 10kWh into a lead-acid, you will only get 8kWh back out. Whereas with lithium (95%+ efficiency) you can get 9.5kWh back out.
Comparing Lithium To AGM Lead Acid
Here’s a simple comparison between a 10kWh rated LFP battery bank and standard AGM golf cart format (GC2) batteries…
Lithium (Iron Phosphate LiFePO4)
Usable Capacity : 8kWh (4 units @ 80kg total)
Round-Trip Efficiency : 7.6kWh
Cycles* : 6,000
Total Energy Delivered : 45,600 kWh
Typical Cost : <$8,000
$/kWh Delivered : <$0.18
Lead-Acid
Useable Capacity : 5kWh (8 units @ 240kgs total)
Round-Trip Efficiency : 4kWh
Cycles* : 1,500
Total Energy Delivered : 6,000 kWh
Typical Cost : <$3,200
$/kWh Delivered : <$0.53
Read Your Spec Sheets
Some Lithium batteries quote cycle life of up to 10,000 10,000 cycles?, and Lead-Carbon can see as many as 3,000. This would result in approximately $0.14/kWh delivered for Lithium, and $0.30/kWh for Lead Carbon (which are more expensive than standard AGM).
Sometimes large cycle life numbers are pure marketing. It is important to note that they may simply be derived at gentler charge/discharge rates, and shallower depths of discharge. Try to compare numbers derived from the same test conditions.
Avoid Investing In Landfill
Of course, this comparison only works if you make a quality investment. Purchase a cheap, silly-name battery company product off Amazon, AliExpress, or other landfill portal, and all bets are off whether your investment will live beyond 4 years.
As you can see, there is no question that Lithium is the better investment. And, with costs coming down a little more each year, the numbers keep getting better!
Does this mean you should wait until next year to purchase your new Lithium batteries? No… like any investment, like planting a tree, the best time to start is now.
Next Article…
The various ‘flavours’ of Lithium