Many customers ask us about new developments: Lithium Ferro Phosphate, Nano technology, Solid state, 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 either Circadian® or ProDurance systems, 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 fits seamlessly into the current 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 here and sold for three main reasons. Better safety, faster charging, and longer cycle life. We would like to address all 3 points in comparison to the DCPower4C 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, since 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 with some recent (2022) Hospital fires in the UK; 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 considered key in certain applications. If you have a block battery under the cart, which needs on shift charging, then a faster charge is important to reduce downtime, disruption, and the hazards of plugging in. However fast charging damages cells irreversibly– the so-called Popcorning effect. If there is pressure to avoid downtime a hot swap solution 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 completely different due to string balancing problems. But more significantly the standard test design masks the real-life issue of parasitic reactivity on the Solid Electrolyte Interface. LIFE cells are especially vulnerable to high voltage degradation and high temperature. The Hospital cart usage pattern has the effect that the cart is plugged in most of the shift and between usage. Since Life batteries have comparatively low capacity the voltage range is maxed out. The result is that the battery spends most of its life at High voltage – right in the degradation zone. So, they decline at a massively accelerated rate versus cell tests!
Then life expectancy is much lower than expected! LIFE manufacturers tend to cover this with long cycle warranties on functionality but read the small print and nearly all LIFE batteries warranty capacity retention for less than one year citing “natural wear and tear”. The wonderful sounding warranty is in fact useless!
- Disadvantages: LI-Iron batteries have a significantly lower voltage, so have less power and much higher volume for the power delivered, thus, they aremuch 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 very difficult and inaccurate forcing users to swap or charge earlier.
The much-touted advantages of LIFE batteries are over-exaggerated, and the disadvantages outweigh in the mobile cart application.
For this reason, DCPower4C relies on high quality premium Lithium-Ion cells, and the market leading 3-year warranty to 80% underlines our total confidence in them. If the customer insists, we can now deliver a LIFE version, but the capacity is less than 50% for the same size battery!