Tiberius
10 kW
I'm looking at a special application, that is probably best described as a mini KERS system (Kinetic Energy Recovery System as allegedly used in F1). It has to deliver a short intense burst of power and then spend a slightly longer time recharging.
Assume the voltage is around 100 (that's not actually so important). The outgoing power burst is current I for time T. The recharge time is 4 T.
In this case the minimum useful is I=60 A, but I=120 A would be better.
At first I thought T would need to be 10 secs or more, but that is based on a KERS system being used once per lap. If you think of it being used once per corner then T=1 or 2 sec is useful.
So one configuration could be 60 A out for 2 secs then recharge at 15 A. What cells would you use for this? If the battery could stand 40 C discharge, then 1.5 Ah cells would do. But how many cycles would that last? It needs to be in the many 100's to make it viable.
If I look at a supercap, then I calculate that about 10 F is needed. How practical is that?
There is of course another approach. That is to say that even though T=1 sec is useful, more is always better. Why not take it out to T=10 mins? That then needs 10 Ah cells and a huge cost and weight penalty. But the rate of cycling the cells goes way down, the discharge is only 6 C, and so we'd expect a longer lifetime. What would be the best cells for that option?
Thoughts, comment, advice is invited.
Nick
Assume the voltage is around 100 (that's not actually so important). The outgoing power burst is current I for time T. The recharge time is 4 T.
In this case the minimum useful is I=60 A, but I=120 A would be better.
At first I thought T would need to be 10 secs or more, but that is based on a KERS system being used once per lap. If you think of it being used once per corner then T=1 or 2 sec is useful.
So one configuration could be 60 A out for 2 secs then recharge at 15 A. What cells would you use for this? If the battery could stand 40 C discharge, then 1.5 Ah cells would do. But how many cycles would that last? It needs to be in the many 100's to make it viable.
If I look at a supercap, then I calculate that about 10 F is needed. How practical is that?
There is of course another approach. That is to say that even though T=1 sec is useful, more is always better. Why not take it out to T=10 mins? That then needs 10 Ah cells and a huge cost and weight penalty. But the rate of cycling the cells goes way down, the discharge is only 6 C, and so we'd expect a longer lifetime. What would be the best cells for that option?
Thoughts, comment, advice is invited.
Nick