Endless-sphere.com

by **jag** » Sat Feb 12, 2011 10:30 pm

liveforphysics wrote: For smallish sized packs, backpack makes a lot of sense. Backpack with a compact, quiet, high current opertunity charger and a few Nano-tech packs able to be charged in 6mins makes boatloads of sense. Even if you only have a couple hundred watt-hours, you can really leverage them well with a setup like that.

Quick "opportunity charge" sounds like a good idea. Problem is, where to find a powerful (around a kW) yet compact and quiet charger. The Meanwells many of us use are 350W/kg. The Flatpack2 I just bought is 800W/kg. However this is nothing compared to the power density of some of the DC-DC converters that are around 2000W/kg. Problem is the DC-DC are typically max 70V in (48V nominal). They are small beacuse Switching frequency is in the 100kHz to MHz range. (Most 110V mains PSUs seem to be 10's to 100kHz range)

So is there some source of compact 110V to 48V PSU/chargers I've not found?

by **magic carpet** » Tue Mar 06, 2012 11:54 am

dirty_d - I didn't make the bike itself, I just did the conversion to an ebike.
That's an understatement! Beautiful job on a beautiful bike!

by **crossbreak** » Sat Mar 17, 2012 9:43 pm

congratulations for your build miles, it is a very harmonious concept, keep making it prefect for your all day use before you buy components for your second build

I did not do so. Now I have some parts lying around worth a hundred bucks which I maybe wont use any time because I learned from experience in between

Quick "opportunity charge" sounds like a good idea. Problem is, where to find a powerful (around a kW) yet compact and quiet charger. The Meanwells many of us use are 350W/kg. The Flatpack2 I just bought is 800W/kg. However this is nothing compared to the power density of some of the DC-DC converters that are around 2000W/kg. Problem is the DC-DC are typically max 70V in (48V nominal). They are small beacuse Switching frequency is in the 100kHz to MHz range. (Most 110V mains PSUs seem to be 10's to 100kHz range)

I was once told that the power supplies for large CPU (the ones on the mainboard which switch down the 12V DC to 1.2V for the CPU, about 100Watts and more) are supplied by step-down converters that use "some khz". But they use 7-10 phases. Does the phase count affect power density? I write power electronics on monday. maybe i should know this

EDIT: ok I got the answer myself: the more phases u switch the smaller the smoothing coil will be. That way it effects power density.

I also use meanwells and they are quite heavy if you try to take them with you. I also use bmsbattery charger 400W, which definitely plays in a different class