What do we think the expected cycle life would be for a connector doing that?
On Sat, Mar 22, 2025 at 3:55 PM Cor van de Water via EV <ev@lists.evdl.org> wrote: > > Marco, > Re: power loss/heat in cable > Double current for the same resistance cable means 4x power, so 3kW becomes > 12kW heat for the same cable at double Amps. > Cor. > > > On Fri, Mar 21, 2025, 8:31 PM Marco Gaxiola via EV <ev@lists.evdl.org> > wrote: > > > Back to the main topic; the BYD new pct. release and the ultra fast > > charging idea, I have some doubts: > > > > After watching video portions of the new BYD HAN-L electric vehicle being > > capable of charging at a Megawatt level and being able to recover up to 250 > > miles of range in just 5 minutes, I did some brief homework from their > > online demo video and wanted to ask your thoughts are; > > > > > > First following their claims from the video +some minimal math & Ohm's law: > > a peak charging power of 1000 Watts (or 1MW) on a 1000 volts nominal > > voltage battery pack, would mean that the peak charging current would reach > > the 1000 amps. > > > > > > Since I wasn't able to find all the specs from reliable sources I wanted > > first to estimate what type/size of battery pack would be able to stand > > such an amount of current/C-rate, so I used their also claimed 10C max. > > charging rate and determined it should be at least a 100.2 kWh pack. > > > > > > Then I determined that, in order to build such battery pack capable of such > > claimed performance, this would have to used at least 303 LFP cells (BYD > > tech) in series to form a 1000V nominal battery pack and each cell must be > > at least 100Ah each for a total of 100.2kWh of energy. > > > > > > Finally I plotted the charging curve, gathering my data from the EV's > > dashboard shown in the video; Instant charge power, state of charge (SoC), > > elapsed time and recovered range. Here are my doubts: > > > > > > (see link below for charts) > > > > > > - I find the charging curve, instant power Vs SoC lines a little odd. > > The gained SoC should be steeper during the 997-1002 kW stage and then > > slow > > down once power drops to 662kW. If you are reducing power by almost > > half, > > shouldn't the rate of SoC increments also be reduced? > > - Similar to the added range, the yellow curve should be less steeper > > right at the 662kW drop, but instead if continues the same until half of > > that power step before the next lower stage. > > - In order to safely transfer 1000 Amps from A to B without risks of > > melting or fires, in a 'non-liquid' cooled cable system, the cable size > > would have to be huge and require at least one DLO-646 wire for each > > pole > > (positive and negative). In this example the cable is rated for ≈815 > > amps > > with a diameter of 1.45 inches each! Can you imagine the size and > > weight of > > the charging cable? If we would go with liquid cooling approach, a > > typical > > CCS1 liquid cooled EVSE cable running at ≈400-500 amps (despite the > > running > > voltage) dissipates around 2.5-3kW of wasted heat, can we imagine the > > energy losses on a 1000amp 3-4 meter long charging cable? > > > > > > Then to add to all this above; these calculations and assumptions aren't > > including any thermal management and electrical hardware required to keep > > all these cells, high voltage cabling, contractors, etc. properly cooled > > and safe from melting from the very high power even the short current > > burst. Then we would need to account for a fast battery degradation at such > > high 10C rates, right? > > > > > > Link to a shared google sheet with my data and calculations, please check > > it out and comment: > > > > > > https://docs.google.com/spreadsheets/d/1JjZzukWrvFXYlFQbzC1Mfaj8SKSa08CAIBtJtKhGwkc/edit?usp=sharing > > > > > > > > Marco Gaxiola > > > > > > > > On Fri, Mar 21, 2025 at 11:07 AM Lee Hart via EV <ev@lists.evdl.org> > > wrote: > > > > > Lawrence Winiarski wrote: > > > > Maybe for vehicles with close enough voltages, all that's necessary is > > > to connect the packs together to equalize them? > > > > > > In fact, fast charging has been done this way by EV racers and hobbyists. > > > The internal resistance of the batteries themselves handles most of the > > > voltage drop between the packs. It's sometimes called "dump" charging. > > > > > > If the two packs are nominally the same voltage, the initial peak current > > > is huge; but it drops exponentially over time until the two equalize at > > the > > > same voltage and state of charge. It can take a long time to reach this > > > point, so it's only useful to get a relatively small amount of charge in > > > quickly. > > > > > > But if you want the receiving pack to end at a higher state of charge, > > the > > > sending pack needs to have a slightly higher nominal voltage. > > > > > > Dump charging works; but only if everything is right. With no fuses or > > > circuit breakers, things can go very wrong if there is a failure! > > > > > > > Yeah, the pack swap has lots of prob if you aren't swapping your own > > > pack... > > > > > > I agree. The problems aren't with the hardware; they are with people. > > > > > > When the same person or business owns both the EV and its packs, battery > > > swapping works. Thousand-pound lift truck batteries are swapped in just a > > > few minutes every shift. Or your Ebike battery runs down, so you pull it > > > and pop in a fresh one in second. > > > > > > Given human nature, I suspect that battery swapping only works for a > > > rented or leased EV. Then the same entity owns both the vehicle and > > battery. > > > > > > Lee > > > -- > > > Excellence does not require perfection. -- Henry James > > > But it *does* require attention to detail! -- Lee Hart > > > -- > > > Lee A. Hart https://www.sunrise-ev.com > > > > > > > > > _______________________________________________ > > > Address messages to ev@lists.evdl.org > > > No other addresses in TO and CC fields > > > HELP: http://www.evdl.org/help/ > > > > > > > > > > -- > > Marco Gaxiola > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20250321/463feb10/attachment.htm > > > > > _______________________________________________ > > Address messages to ev@lists.evdl.org > > No other addresses in TO and CC fields > > HELP: http://www.evdl.org/help/ > > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20250322/ba7f3858/attachment.htm> > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
