I’ve been writing in regards to the significance of LFP (LiFePO4) batteries for some time now, however I haven’t written about the most effective charging habits for this battery chemistry but.
It’s time to put in writing a small, however necessary article in regards to the topic, particularly as a result of I’ve seen some confusion on on-line boards.
First, let’s evaluate the nominal and most voltages of LFP with different widespread battery chemistries.
- Nominal voltage: 2,3 V
- Max voltage: 2,9 V
- Cycle life: as much as 100.000 cycles
- Nominal voltage: 3,2 V
- Max voltage: 3,65 V
- Cycle life: as much as 12.000 cycles
- Nominal voltage: 3,7 V
- Max voltage: 4,2 V
- Cycle life: as much as 4.000 cycles
Did you discover a sample? The upper the voltage, the decrease the cycle life is.
Frequent liquid electrolytes are chemically extra steady at decrease voltages, that’s partly why LTO (2,3 V) and LFP (3,2 V) battery cells have higher cycle life than most NCM/NCA battery cells that work at larger voltages (3,7 V).
If you cost a battery you’re growing its voltage and at larger voltages the liquid electrolyte begins slowly corroding the present collectors contained in the battery cells.
That is additionally why we nonetheless don’t have high-voltage spinel (5 V) battery cells, which require new electrolytes and higher coating of the electrodes to forestall excessive corrosion from occurring.
Subsequently, it’s apparent that holding the batteries at decrease SoC (State of Cost) is best for his or her cycle life.
Now let’s discuss in regards to the confusion generated by a suggestion from Tesla…
In case your car is provided with an LFP Battery, Tesla recommends that you just hold your cost restrict set to 100%, even for each day use, and that you just additionally absolutely cost to 100% at the least as soon as per week. If Mannequin 3 has been parked for longer than every week, Tesla recommends driving as you usually would and cost to 100% at your earliest comfort.
Does it imply that LFP batteries are proof against additional battery degradation related to frequent full costs? No…
The one motive why Tesla recommends to completely cost the Mannequin 3 automobiles which have LFP batteries is as a result of it helps the BMS (Battery Administration System) to estimate the out there battery capability extra exactly.
In comparison with different battery chemistries, LFP’s cost/discharge voltage curves are extraordinarily flat. Principally, the voltage solely rises when the battery is nearly full and drops when it’s nearly empty. For this reason it’s a lot more durable for a BMS to estimate accurately the SoC of a LFP battery.
Think about wanting on the GoM (Guess-o-Meter) in your dashboard and seeing 20 % battery remaining, however a minute later solely 5 %…
Concerning customer support, for Tesla is extra necessary to have a dependable GoM than to have a battery with a fenomenal cycle life – since one function turns into apparent to the shopper a lot earlier than the opposite.
Nonetheless, even if you happen to all the time absolutely cost a LFP battery, its common voltage will nonetheless stay decrease than it might be in a half charged NCM or NCA battery…
LFP is just not excellent, there aren’t any excellent batteries, batteries are both not ok or ok for a activity. Happily, the LFP battery chemistry is nice sufficient for a lot of duties. I imply, that is fairly apparent since its inventor was John B. Goodenough (this sounded method funnier in my head).
In case you care about holding a lithium-ion battery wholesome, my recommendation is to cycle it between 20 and 70 %, as the information in my hottest article suggests. Then again, if you happen to care extra about having a dependable GoM, that estimates your remaining vary extra precisely, absolutely cost the battery extra usually.
Like many issues in life, possibly the most effective is to compromise and attain a center floor. You’ll be able to often cost your electrical automobile with LFP battery as much as 70 %, however then as soon as every week cost it absolutely – earlier than taking it for a journey (keep away from let it keep on 100 % for a protracted interval).
Anyway, except the GoM is appearing loopy by incessantly displaying sudden drops of estimated vary, you shouldn’t absolutely cost your electrical automobile – even when powered by a LFP battery – fairly often if you happen to care in regards to the cycle life.
I hope that you just discover this text useful and clarifying.