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[DPRG] High-power DC-DC converter

Subject: [DPRG] High-power DC-DC converter
From: Chuck McManis cmcmanis at mcmanis.com
Date: Sat Sep 20 15:08:01 CDT 2003

At 11:53 AM 9/20/2003 -0400, Michael Flora wrote:
>Actually the main reason I'm interested in conversion is that I've got a
>couple of 48VDC permanent-magnet motors out of leafblowers, and I'm trying
>to use the cheapest 12V lead-acid batteries I can find.  I suppose I could
>use 4 of them but I'm trying to minimize weight.

Well 12->48V conversion will be on the order of 10 - 15x as expensive as 
batteries so if cost is your issue then more batteries will be a better 
solution. Since you're constrained on weight I'd suggest smaller batteries, 
but if you're building a combat robot then you will find the best 
weight/power ratio that is reasonably affordable to be from Sub-C sized 
NiMh cells. See www.battlepacks.com for a pointer.

>On a slightly related topic, does anyone on this list have any experience
>with ultracapacitors?  They promise at least 10x the energy density of
>batteries at much lower weight, but I have a feeling they'd bust my budget
>(and probably anybody's budget except the Pentagon).

Funny you should mention these, the really cool ones are the ones that are 
made by EPCOS but the last time I checked they were > $1000 each in small 
quantities and the power density was not as high as batteries. Their 
56V/100F model is 1.6 kG (about more 3.5lbs) and you need a 20 of them to 
run your 48 volt motors for the 3 minutes of a match.

--Chuck



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