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Given that lithium ion batteries degrade with time and energy throughput, will deliverable power also be affected by state of health (SOH) degradation along with capacity?

Internal resistance increases as the battery degrades which means output current will get limited. Expanding on that, is the power that the battery can deliver to the power converter and ultimately the motor decrease with degradation?

Does that mean that as the battery pack ages, the horsepower of the EV will decrease?
 

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I'm guessing here but I would imagine the pack is nowhere near delivering it's maximum as a design so even with high degradation I would say you should keep at least most of the power.
The bigger problem thern would be a degrading pack which is being asked to work closer to it's maximum to deliver the similar results - most likely making it degrade faster and the spiral then continues until it gets to a point where either the pack levels out at it's low point or the car's range is useless.
 

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Most packs would have considerable reserve in power output over what the motor/heater is capable of consuming - the maximum power drawn from the battery is already electronically limited to significantly lower than what the battery could deliver to give it this headroom.

One reason for this is that internal resistance of the cells does go up dramatically when they're cold. For example cell resistance roughly doubles at a cell temperature of 0C compared to 25C. Yet despite this EV's don't seem to limit the discharge rate significantly until you perhaps get to even lower temperatures.

By the way, the original premise of internal resistance increasing as the battery degrades is not generally true with Lithium Ion cells used in EV's as they are specifically optimised to avoid increases in internal resistance. If it's just "normal" degradation there is usually no significant change even if the SoH is as low as 70%. However a cell with a defect or which has suffered an "event" that has damaged it can have higher than normal internal resistance.

For example in my Ion pack there is one single cell which seems to have significantly higher internal resistance than all the others. This is evident when rapid charging (at an initial rate of 43kW) as the voltage on that one cell immediately pokes up above all the others and hits the maximum 4.1v cell limit quite early during the charge while the others are still at 4.075 or so. This also has the effect of causing premature throttling of the charge rate when rapid charging as the BMS strives to avoid that individual cell going over voltage at the expense of slowing the overall charge rate even though the other 87 cells could handle a faster rate to a higher SoC.

If there is any change in cell resistance of a cell that has fallen to say 70% SoH, then the increase is much smaller than the increase you'd see of a good cell being subject to low temperatures, which does dramatically increases the resistance, and this higher resistance is allowed for in the design or the car.
 

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Does that mean that as the battery pack ages, the horsepower of the EV will decrease?
I would say not in practice, there are ev's with multiple hundreds of thousands of miles on one battery with no power degradation I am have read of, some of which, being taxis, have had the "worse" possible charging regime of fast charge rates (and not much degradation of battery either)
Much more (IMO) worrying is the high repair cost out of warranty, witness in particular the current thread about an iMiev being written off and see also numerous threads about high repair costs on BMWi3's. Not necessarily unexpected with BMW but I think much worse with their sole Ev.
 
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