Posted on Category:Lithium

Why are Lithium (LiFePO4) batteries better than lead-acid batteries?

But let me ask: What do you gain with a 12.8V 7Ah lithium battery? More cycles? Longer life span? Should be +- the same available energy?

Answer: To begin with, an SLA (lead-acid) battery and LiFePO4 battery of the same nominal Ah rating do not have the same usable energy capacity because the SLA will tolerate at best 50% depletion before the damage occurs and capacity reduces.

Lithium (LiFePO4) batteries will tolerate 80%+ depletion, the really good ones (cell phone batteries for example) can go as far as 97% before the built-in BMS shuts it down.

Paper spec-wise, conventional lead-acid batteries are only good for 100-200 max (as per spec) discharge cycles.

Realistically, once you flatten your gate/alarm SLA battery 10 times, its energy capacity drops to maybe 1/2, 1/3 of new.

Vicious circle: The lower the capacity, the more likely you are to flatten it again, more damage it takes.

Lithium has no significant capacity reduction even after 1000s of total depletion (90%+) cycles.

*The above is a slightly modified explanation originally offered by user fdlsys to a question asked by user leonsound on the AV Forum

Summarised

  • Usable capacity vs actual capacity (Realistically Lithium is about 80% to 90% usable vs 30% to 50% for Lead Acid)
  • Lifetime cycles ( Lithium lasts longer than lead-acid )

Charging Time & Loadshedding

Another practical example of why LiFePO4 batteries are better in the context of loadshedding is the charge rate. With the current loadshedding stages there just isn’t enough time between schedules to recharge lead-acid batteries.

Charging a lead-acid battery can take more than 10 hours, whereas lithium-ion batteries can take from 3 hours to as little as a few minutes to charge, depending on the size of the battery. LiFePO4 chemistries can accept a faster rate of current, charging quicker than batteries made with lead acid which makes them uniquely suited for our Eskom problem.

The lifespan of Lithium (LiFePO4) batteries over Lead Acid batteries

Finally, Lithium (LiFePO4) batteries are better able to sustain much deeper discharges than their lead-acid counterparts.

For example, if you discharge your lead acid battery to 50% or so routinely, that battery will likely give you around 100-500 cycles before it needs to get replaced & which is easily reached with Stage 4 loadshedding.

By comparison, a Lithium (LiFePO4) battery can be discharged down to even 20% and is said to deliver around 3000+ cycles. The extended lifespan of the lithium-ion battery, then, is significant making the long-term cost of LiFePO4 much less than lead-acid in the context of Eskom & regular Stage 2 to 6 power outages.