DCFC of a 72V ebike?

[silverramp]

I was wondering if some of you knowledgeable folks could share your initial opinion of a project I'm dreaming about: Specifically, could I use NACS to DCFC a 72V ebike/emoto?

I thinking about building a battery that would be 1S4P @ 72v when riding, but switch to 4s1p @ 288v when using DCFC. Something similar to dewalt's 20v/60v battery packs. I suppose another option is a DC-DC converter, but I get the impression that could perhaps be bulky/expensive at ~5-15kw.

Do you all think this would be very difficult/do you think it would work at many stations in the USA (I wouldn't have a VIN)? To be totally transparent I'm an ebike enthusiast and not an engineer, so my skills would be lacking to pull off doing something like designing a bespoke BMS or other electronics.

I know I can access lvl2 AC charging with 72v off the shelf chargers. DCFC would be a nifty additional charging option, especially for longer trips. The small NACS form factor would be nice on the bike.

Thanks in advance for entertaining my post.

[tom91]

Do you all think this would be very difficult/

Yes

And useless really as you would be pulling almost the same amount of power as charging off AC

[silverramp]

Thanks for your thoughts!

The utility argument would be the greater ubiquity of DCFC vs lvl2 sites. And maybe I could charge at a higher rate, say 2C. But yea, the utility probably wouldn't be enough to warrant the effort!

[szczur333]

I wanted to do it but for cheap and this was possible using chademo - without switching to 288V
BUT:
1. yes, chademo starts from 45 or 50V but only on older chargers, newer chargers has new modules which starts from 150-200VDC so it will not work
2. device with contactors and controller will have similar weight and size that small rectifier charger
3. you can buy small 20A charger which weight only 1kg and takes about 1,1L volume - with 3 of these I will charge my 35Ah battery in 20min (10-90%)