Peak Power NOT amps was:Hawker voltage sag

[badfishracing@att.net]

Hello Thomas and all,

I have came to the realization that amps don't mean near 
as much as power!  I can pull 50KW for about the first 
second, but that quickly drops to 30KW, and 20KW by the 
end of the 1/8th mile.  A better senario would be a 
constant 30-40KW.  OK.  I'm learning.  Watch out 
Thunderstruck......


Darin Gilbert
Bad Fish Racing


Thomas Cook Wrote:
Hi Darin,

I don't think I have ever talked to you, but I have 
heard some about you as I played a big part in the 
building and racing of the Thunderstruck Pocket Bike. 
>From what I understand, you are probably pushing your 
batteries too hard. Remember you want peak power, not 
peak amps. If they are sagging below 6v, I highly doubt 
it is worth it to get the amps. Have a look at the 
graphs on the Manzanitamicro.com website. Rich hasn't 
done any testing on your specific batteries, but an old 
optima is up there, the small svr batteries that we use, 
an old hawker 38? and a nicad battery. We are about to 
put larger SVR batteries in an electric car that is 
going racing in woodburn, so we have some experimenting 
to do too... I think in your case, if you need that much 
current, you need to get a larger battery. Then again, 
you could probably just pull a bit less current and have 
a little bit more power to play with. After that it is 
all about weight transfer, traction, efficiency, 
gearing, etc. Reading your message again, it sounds like 
you are concerned that your batteries are bad. I don't 
think they are, just being over worked. 40 volts at 
300amps isn't too bad at all. Heck, try putting one of 
those cheap loadtesters that only does 50-75 amps on a 
new, fully charged and cycled hawker, and you might be 
surprised at how low it goes with only the tester 
attached. 

You ask what we see with our batteries. Um, I have been 
pushing for some data gathering stuff, but we don't have 
anything that we can put on a vehicle right now. We are 
running a controller in the bike that probably ramps up 
to 650 amps maybe 50 feet off of the line, and then 
falls steadily from there. We are almost at top speed 
coming out of the 8th.

Have Fun!

-Thomas Cook



>From: badfishracing@att.net 
>Reply-To: ev@listproc.sjsu.edu 
>To: ev@listproc.sjsu.edu 
>Subject: Hawker voltage sag 
>Date: Thu, 29 Aug 2002 01:43:41 +0000 
> 
>Hi all, 
> 
>I recently got a fluke scopemeter and have an abundance 
>of voltage/amperage data to analyze. I'm surprised at 
>my voltage sag on my 48V 16ah hawker genesis pack. 
> 
>900 amp draw > 33.2 volts 
>after about 1 second 
>812 amp draw > 22.8 volts 
>after amp draw falls to about 300, volts come up to 
>about 40. 
> 
>Um, that's less than 6V per battery? What do you guys 
>see, or what do you guys with SVR batteries see? 
> 
> 
>thanks in advance, 
> 
>Darin Gilbert 
>