GPak
Active Member
They cannot be charged faster without farther negative impact on performance and reliability, they are already at their limit, and here's why:
In general, for long and reliable operation, the maximum C-rating for an LFP battery under ideal conditions should not exceed 1C. (The "C" rating is the charging current divided by the battery's Ah capacity.)
In reality it is wise to charge an LFP battery well below the max 1C-rate, especially for in-car application with an extreme temperature range and vibrations and when battery state of the charge (SoC) is fully utilized from 0% to 100%.
The most dash cam batteries are LFP with a nominal voltage of 12.8V and a maximum capacity of 96Wh or 7.5Ah (due to air transport restrictions).
For an advertised 0.90h or 54min charging time from 0% to 100%, the average charge rate for the battery is about 96Wh/0.90=107W conservatively assuming 100% charging efficiency.
With an average nominal voltage of 12.8 V, the charging current would be about 107 W/12.8 V = 8.36A, let's conservatively assume 8A as some battery specifications suggest.
Then the charging C-rate is 8A/7.5Ah=1.07C !
As you can see the charge rate already exceeds the limit and this is not in ideal conditions.
So, I think that due to the high 1.07C charge rate combined with full SoC utilization from 0% to 100% and combined with the harsh temperature extremes and vibration in the car, these batteries will never reach the promised LFP potential.
For comparison my 12.8V nominal volt (DIY) LFP battery is rated at 192Wh capacity or 15Ah.
With the same charge speed, I only get 0.53C-rate, and since I have twice the capacity I can sacrifice a small portion of that capacity to limit the SoC between 10-90% (like most power stations), which is important for long and reliable operation.
If needed, a 15 Ah battery can be charged at, say, 12A which is 50% faster than existing batteries, while still maintaining lower 0.8C-rate.
Conclusion:
To charge these LFP batteries faster they need to increase rated Ah and corresponding Wh.
Or better to use LTO battery which can be comfortable charged at 3C-rate.