GetOffYourGas wrote:lorenfb wrote:GetOffYourGas wrote:

So we are talking about two different things. Allow me to elaborate. Your numbers are looking at different C rates for thesamebattery. I was comparing the C rates for twodifferentbatteries. Like, for instance, a 30kWh Nissan battery and a 60kWh Tesla battery.

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 ofcurrent, despite having different C rates, due to the differentcapacities.

P = I^2 * R

Assuming again that both batteries have a 60mOhm internal resistance, theybothhave a power dissipation of 416W.

Consider a 60kWh battery as being two 30kWh batteries in parallel. The result also affects the effective output

impedance of the combined batteries (a 60kWh resulting battery). It's now 1/2 of the single 30kWh battery.

The combined battery can obvious supply 2X the current output of the original 30kWh.

So driving at the same speed for either a single or parallel 30Ahr (60Ahr) battery results in the same power consumption,

as would be expected. Also, the total heating effect of the 60Ahr battery will be less than the single 30Ahr battery,

i.e. the lower output impedance of the 60Ahr battery.

Example - 2 parallel 30kWh

P (for each) = (I/2)^2 x R

P (for combined (60kWh)) = 2 x (I/2)^2 x R) = I^2 /2 x R = I^2 x R/2

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.

Did you overlook this?

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

A 60kWh battery is a 2X a 30kWh battery and would dissipate 1/2 the original power of the single 30kWh

by itself supplying all the power, right?

The equations above also indicate that if you actually did combine (not practical) two 30kWh batteries to

make a 60kWh battery, each would dissipate 1/4 (as noted by Reg & indicated above) each's original power.

Remember, all the 'new' powers need to sum correctlly whether you actually did use two 30kWh batteries

or a single 60kWh battery.