Many customers ask us about Lithium Ferro Phosphate, Nano technology, lithium air, lithium sulphur etc. What’s best, what are we doing?
There is so much to say and speculate about this, that we just want to focus on the key points.
By investing in the Circadian® system, your infrastructure is completely future compatible. All the charging algorithms and intelligence are in the battery, so the battery tells the charger exactly what to do, thus a new cell chemistry, size, cell type represents no problem for the Circadian® system.
The new trumpeted technologies are going to be fantastic, but at the moment they are not proven, not cost efficient, and we will not use them until they are. Much of the noise, reports, breakthroughs etc. are to get funding, or academic recognition.
The Li-Iron batteries, or Lithium Ferro Phosphate are currently popular for three main reasons. Better safety, faster charging, and longer cycle life. We would like to address all 3 points in comparison to the Circadian® cell technology.
- Better Safety. LI-Iron technology is considered safer because the Flash point where thermal runaway, or fire/explosion kicks in is higher. ≈325°C instead of the ≈185°C of traditional Lithium ion. The higher flash point is irrelevant if you use a cheap or poorly manufactured cell. These are much more likely to trigger a thermal runaway and once the process is kick started, a high flash point simply represents a delay, this is not really a benefit. Safety is all about the cell manufacturer. It is simply a fact that all incidents come from cells manufactured in certain Far Eastern countries, and currently nearly all medical cell packs are manufactured there. There have been significant fires with LiFeP04 batteries, they remain dangerous goods. Indeed the largest fine for a fire and failure to ensure safe practice is for a LI-Iron battery supplier, we believe, using the very same cells found in so many Hospitals. Safety is not dictated by Cell Chemistry, the competence and attitude of both the cell and the cell-pack manufacturer is what counts! Secondly, as the FDA warns, charger failures or incorrect tolerances most often set of the thermal event. Most of these LI-Iron batteries use a charger made by a 3rd party, so there is no tight control or inter calibration.
- Charging faster, is key in certain applications. If you have a block battery under the cart, which needs on shift charging, then a faster charge is essential, because the charging downtime, disruption, and hazard of plugging in is reduced. But a hot swap with no charger downtime is simply much better. Also it should be noted that a poorly calibrated charger, with low manufacturing tolerances can quickly sink a LI=Iron battery. The question: How good is the charger seems to be ignored.
- Cycle life. The long curves showing 1000s of cycles are totally misleading. These are based on the performance of a cell, not a multi-cell pack which is something completely different. But more significantly the standard test design masks the real life issue of parasitic reactivity on the Solid Electrolyte Interface. This impact is responsible for cell decline or Coulombic inefficiency. The electrolyte additives counter this effect over time. The rapid cycle tests hide this, giving a completely false picture where magically poor cells look just as good as the quality cells! As with Safety, it is not the Cell Chemistry that gives long life, it is the Cell design, the R&D and manufacturing. Nonetheless a Cycle based warranty has little value. It does not say how a cycle is really clocked and if there is a promise of say 5000 cycles in 2 years, no one is going to do that anyway. The only relevant warranty is Years of use above a certain capacity percentage. It is strange that some of the top selling Li-Iron blocks have a 5 year mechanical warranty, but read the small print - they often consider capacity loss as "wear & tear" there is no warranty!
- Disadvantages: LI-Iron batteries have a significantly lower voltage, so less power and much higher volume for the power delivered, so they are much bigger, heavier batteries, therefore less suited for mobile applications or indeed Hot Swapping. The weight to Wh ratio is circa 35-50% lower than other Lithium Ion cell technologies. Their flat discharge characteristics make Run-time predictions difficult and innacurate.
If you still have doubts, ask yourself why Car manufacturers or Laptop suppliers rarely use LI-iron technology? Surely they want better safety, faster charging and longer life? The reason is simply that these advantages are over-exaggerated and the disadvantages outweigh. In our opinion, it is only in the medical cart world where the comparison is with SLA and NiMH batteries that LI-Iron technology has gained a temporary status.
For this reason we have opted for the high quality premium Lithium Ion cells, and the market leading Circadian® 3 year warranty to 80% underlines our total confidence in them.