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View Full Version : Are Lithium-Ion Batteries Worth It?


Rob Beckers
18th June 2016, 15:33
We recently started selling Lithium-ion batteries (http://www.solacity.com/product-category/batteries/lithium-ion/), not without some trepidation, as these are expensive and I do not want to sell items that don't live up to the promises. At CAD$7,500 for a 400 Ah 12 Volt battery bank, this is nearly 10x the price of Surrette's flooded lead-acid batteries. Compared to sealed lead-acid (AGM) it would be about 5x the price for Lithium-ion. By the way, that price does include the Battery Management System (BMS), it's build into these batteries.

Even the much-hyped Tesla battery, which incidentally is the cheapest Lithium-ion I've seen so far, is still around 4x the price of lead-acid, and that price does NOT include the absolutely needed BMS.

So, is it worth it?

The claim to fame of LiFePO4 batteries is that they last many more cycles. The supplier we get them from claims 4000 cycles at 80% DOD, and over 6000 cycles at 50% DOD. For most off-grid people that would mean a 20+ year life-span. But does it really last that long?

What is great as well is that there's really no maintenance. These are sealed batteries, you can't do any maintenance, and they are supposed to be insensitive to state-of-charge. Where lead-acid is destroyed if the batteries sit at partial SOC for long periods of time, Li-ion has no problem with that (as far as I know).

There are those that claim a Li-ion battery bank can be sized much smaller than a comparable lead-acid bank. I'm not sure how that is supposed to work. I can see that it can be a little smaller due to the larger SOC swings you can make on a regular basis with Li-ion, but seeing how some installers use Li-ion battery banks that are just a fraction of the size of what a properly sized lead-acid bank would be I don't follow the logic of that.

What I've read about Li-ion batteries is that they do need some baby-ing: Discharge them below 20% SOC and you do permanent damage. Charge them to 100% and let them sit at that does permanent damage. The BMS is supposed to take care of these limits. The BMS also limits charge and discharge currents (as it needs to be able to bypass them).

Li-ion also seems to have a problem with temperatures below 0C; it works, but at much lower charge and discharge currents.

I'd like to hear from others, hopefully those with experience with Li-ion, and find out what's real, what's hype, and ultimately if it's worth the investment. I would like to know how people should properly take care of a Li-ion battery bank; they are expensive enough that I'd hate to see them destroyed due to improper care.

Let's hear it!

-RoB-

Paul Camilli
19th June 2016, 08:34
I think they have there place but until prices come down a bit more FLA's are still the best 'bang for buck' in an 'off grid' home. I've been 'off grid' since 1985, live around others that are and look after a couple of systems for neighbours. Rolls 4000 series and fork lift truck cells are what I've most experience of but I've tried NiCad too and wasn't overly impressed.

That's as far as home life goes but in my 'day job' I look after these babies,

https://lifeattheendoftheroad.files.wordpress.com/2014/12/024_thumb1.jpg?w=716&h=538

216 LiFePO4 modules giving 600kWh of usable energy if taken down to 80% DoD Enough to supply 20% of the daily energy needs for a 500GRT RoRo hybrid ferry. I have to say, that when we took delivery of the vessel three years ago I did have my doubts. However, that's them done over 1000 cycles and they are still as good as new and almost 100% efficient. Seriously, we monitor energy in and energy out via calibrated instruments and they really are over 97% efficient after three years.

As Rob says, and I agree with him, a good BMS system is essential and it is the only part of our system that has caused minor hiccups.

https://lifeattheendoftheroad.wordpress.com/tag/european-battery/

There's plenty of folks over on the EV forums that would disagree, saying that they just need 'bottom balancing' and then charging to a certain voltage. That's certainly not been my experience, on the contrary (though this may be due to the sheer number) I've found that once the voltages of the individual cells start to drift off the norm they kind of runaway until the system is reset.

The other thing I've noticed is that they do prefer regular cycling so are probably more suited to solar than wind or a combination of both. For an RV, caravan or application where space, safety and weight is an issue then most definitely, even at today's prices. For the 'off grid' house where they can be kept outside in an insulated shed then perhaps not just yet. For 'grid tied' and 'self consumption' where the batteries are kept in a broom cupboard then absolutely.

Cheers, Paul

Jaime Gonek
27th June 2016, 18:41
Lithium Ion has a place, in portable systems especially (www.growinggreener.ca/grengine being an example). Long term in a home, however? Perhaps not until the cost comes down significantly.

Chuck Roberts
2nd December 2016, 16:36
What do you base your costs on? Cost per watt hour? Cost per amp hour? Cost per year of life of the battery bank? Those could all turn out to be very different costs.