engnrng
Well-Known Member
- First Name
- Bruce
- Joined
- Feb 8, 2020
- Threads
- 9
- Messages
- 553
- Reaction score
- 795
- Location
- SoCal
- Vehicles
- 2022 GTPE, Kona EV, 2023 BMW iX
- Occupation
- Engineer
Since most DCFC are used on longer trips, it is more likely that the battery is warmer when first plugged in, which starts the charge rate slower than max until cooling system and charge rate balance the heat generation and rejection in the system. Yes, I would expect automotive charge curves to be based on pack size, battery temp, SOC (and the related pack voltage). That is how the BMS works on our off-highway BEV system (forklift with 100 kWh battery). Other factors that can affect charge rate include brand of charger (there are standards for safety, but not for performance). We did our initial testing on ChargePoint chargers rated at 62.5 kW, but never saw a rate higher than 54 kW due to software limits on their side even though our packs could accept up to 84 kW. They "assumed" 400 V battery systems, where ours is 600 V nominal. Notice the Audi curve is the highest one, certainly due to nearly 800V nominal. Most automotive batteries are hanging around the 400 V area. Obviously, the higher the pack voltage, the more kW can be accepted for the same current. There are a couple of excellent books on BMS that are theoretical, but the manufacturers tend to keep their BMS protocols very proprietary so that Marketing can say things like, "up to 150 kW" even if that is rarely seen in the real world.Interesting. So does that mean charging curves are dynamic rather than static, based on something like battery temperature? Such that the BMS will deliver more power when the battery is cooler (like when you first plug it in) and then reduce the power as the battery heats up?
I just assumed it was a fixed curve based on SOC%, but I don't really know.
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