I am having difficulty in figuring out some basic stuff and confused with multiple equations.
I am working on a simulator which simulate a hybrid vehicle journey for some period of time. During journey the vehicle brakes and regenerate energy.
I have already calculated:
- How much energy vehicle is regenerating at each braking event in kWh.
- How long is each braking event in seconds (Time).
Battery specifications are:
Storage = 30.6 kWh or 46 Ah
Max Peak Power = 406 kW for 10 Sec
Voltage = Nominal = 666 V , Min = 486 V , Max = 756 V
Battery Ratting = 6C
Battery max Charge / max Discharge Rate per hour = 6C * 46 Ah = 276 A
Question:
All I want to know is that in one second time, how much energy I can send to battery and discharge from battery?
So in my algorithm I can automate the code to send only the amount of energy which battery can absorb for such given period of time and destroy rest in brake resistors.
I have tried this method but I am not sure if I am doing it correct.
please correct me if I am wrong.
Energy = V x I x T
Energy = 666(V) x 46(Ah) x 1 (hr) = 30636 Wh.
Now, Battery ratting is 6C. So,
Charge/Discharge current = 6 x 46 = 276 A.
Now, with 6C ratting:
Time to charge or Discharge (Run Time) = 46 (Ah) / 276 (A) = 0.17 hr
Run Time in Minutes = 0.17 x 60 = 10.20 Min
From this I can calculate 30636 Wh /10 min = 3063.6 Wh energy can be
charged and discharged from battery each minute. (for 10 minutes
period)Considering this, 3063.6 wh / 60 sec = 51.06 wh energy can be charged
or discharged from battery at each second at 6C rating.Again for Ws = 30636*3600 = 110289600 Ws /10 min = 11028960 Ws energy
can be charged and discharged from battery each minute. (for 10
minutes period)
Please correct me if I am wrong and guide me to perform these calculations properly.
Best Answer
When in difficulty multiply out the units to see if they make sense. We'll see some errors below.
Good. Energy = Power x time = kW x h = kWh. This is correct.
So you have assumed that battery voltage = \$ \frac {P}{I} = \frac {30.6k}{46} = 665\ \text V \$. That's fine.
OK, but let's use 's' for seconds as in the SI standard units.
RMS is supposed to be used to find the equivalent DC voltage or current for a voltage or current waveform. It doesn't make sense in power measurements as the average is what is required.
OK. Add a space between the numbers and the units for clarity. e.g., "6 cars", not "6cars". This is recommended in the SI standard. No spaces before commas.
Here you're a little mixed up again. The ampere already is a rate measurement. It's the amount of charge (coulombs) per second. "Discharge rate per hour" doesn't make sense. Just say "max discharge rate = 276 A".
But now we see a problem. 276 A is the 6C rate which means that it will be all over (charging or discharging) in 1/6 hours = 10 minutes.
The battery can only absorb the amount of energy required to fully charge it from its current state + losses due to heat. I'm not a battery expert but I would expect that the maximum charge rate would be close to the maximum discharge rate.
That seems fair.
Make that "power x time" and that is correct if you sustain it for one hour.
That's 183 kWh but at the start of the question you had calculated the actual capacity at 30.6 kWh. Your 1 hour needs to be divided by 6.
No, if you are converting Wh to Ws then you would multiply by 3600. So energy = 183 kWh = 183k x 3600 = 659 MWs (MJ, megajoules). (But don't forget that 183 kWh is wrong to start with.)
No, kW/s is nonsense.
As @jonk has suggested, hit the edit link under your question, clean it up taking care with your numbers and units and then ask the question at the end.
Update after edit.
I think you're making it more complicated than you need to. Just figure out the charge / discharge power, \$ P = VI = 666 \times 276 = 182484 \ \text W = 180 \ \text {kW} \$ to two significant figures.
Energy transfer rate at this power will be 180 kWs or 180 kJ. (This should make it easy to convert back and forth between electrical and kinetic energy.
To convert from kWs to kWh divide by 3600.
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