camasleaf wrote:SageBrush wrote:Reference ?BrockWI wrote: Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.
Heat is proportional to the square root of the current. Twice the current means four times the heat.
GetOffYourGas wrote:camasleaf wrote:SageBrush wrote:Reference ?
Heat is proportional to the square root of the current. Twice the current means four times the heat.
And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?
That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.
GetOffYourGas wrote:camasleaf wrote:SageBrush wrote:Reference ?
Heat is proportional to the square root of the current. Twice the current means four times the heat.
And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?
That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.
Yes, but keep in mind that the battery is arranged as 96s so you start at a very low current and work your way to chargingcamasleaf wrote:SageBrush wrote:Reference ?BrockWI wrote: Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.
Heat is proportional to the square root of the current. Twice the current means four times the heat.
It also is defined at discharging the full capacity in one hourcamasleaf wrote:GetOffYourGas wrote:camasleaf wrote:
Heat is proportional to the square root of the current. Twice the current means four times the heat.
And current is related to Voltage as V = I * R. It is not related to capacity in any way. Assuming the same pack voltage, the current is the same. So why again is 1C discharge going to produce 4x the heat of C/2 discharge?
That's not to say that 1C discharge isn't tougher on the battery than C/2. Maybe it is, or maybe it's gentler. I don't know. But I don't see how it relates to heat.
Google battery 1c meaning
"Charge and discharge rates of abattery are governed by C-rates. The capacity of a battery is commonly rated at 1C, meaning that a fully charged battery rated at 1Ah should provide 1A for one hour. The samebattery discharging at 0.5C should provide 500mA for two hours, and at 2C it delivers 2A for 30 minutes."
camasleaf wrote:Heat is proportional to the square root of the current. Twice the current means four times the heat.
lorenfb wrote:
Using the relationships from the previous posts (1C & C/2):
Power = I^2 x R, where I is the motor current and R is the impedance of the battery (typically 60mohms @ 70 deg F)
Then at 1C I equals about 60 amps and battery Power = 216 watts.
Then at C/2 I equals about 30 amps and battery Power = 54 watts
The rise in battery temperature is a function of the thermal resistance from the battery to the chassis.
The actual battery temperature over time is a function of the chassis temperature which is a function of
ambient.
camasleaf wrote:Google battery 1c meaning
"Charge and discharge rates of abattery are governed by C-rates. The capacity of a battery is commonly rated at 1C, meaning that a fully charged battery rated at 1Ah should provide 1A for one hour. The samebattery discharging at 0.5C should provide 500mA for two hours, and at 2C it delivers 2A for 30 minutes."
GetOffYourGas wrote:Let's assume both are 360V.
1C of a 30kWh battery (360V * 83.3Ah) = 83.3A
C/2 of a 60kWh battery (360V * 166.6Ah) = 83.3A
Both batteries output the same amount of current, despite having different C rates, due to the different capacities.
BrockWI wrote:GetOffYourGas wrote:Let's assume both are 360V.
1C of a 30kWh battery (360V * 83.3Ah) = 83.3A
C/2 of a 60kWh battery (360V * 166.6Ah) = 83.3A
Both batteries output the same amount of current, despite having different C rates, due to the different capacities.
Trying to wrap my head around this but if I understand this correctly the 60kWh pack is supplying twice the power of the 30 kWh pack in the quote above correct? What I was suggesting is the same load for both packs at the same Ah draw given the same operating voltage, then larger pack would have less internal resistance and thus less heating. Also the larger pack would have more mass (for better or worse) to absorb the internal heat.