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Subject: Re: Reducing contact resistance for low volt use?
Summary: What do you think of these ping times eh?
Reply-To: You can't see me, and I pass right through planets...
References: <firstname.lastname@example.org> <email@example.com> <firstname.lastname@example.org>
X-Newsreader: Forte Agent 1.91/32.564
Date: Tue, 07 Jan 2003 05:17:39 GMT
NNTP-Posting-Date: Tue, 07 Jan 2003 00:17:39 EST
On Tue, 07 Jan 2003 02:22:35 +0100, Roger Johansson
>> I do understand. A person is using motors AND batteries in a manner
>>that is destructive. I am supposed to help?
>I just wanted to inform you that there are facts you don't know about
>here. It is not as nutty as it sounds to begin with.
>But close to :-)
You may be right, I may be crazy, but others appear worse off than
>>>These battle-robot builders regularly take out 30 A for 6 minutes from
>>>3000mAh cells, and 50A for short durations, and they are trying to
>>>push performance even further.
>> All they need to do is put more batteries in parallel with those
>>already in place. More current per pack, not more voltage.
>I have a feeling they have tried different possibilities.
I am not so sure.
>They obviously have a weight limitation, and thus a limitation on the
>number of batteries, and the question is how to get a maximum of
>performance out of these batteries during a very short time.
>Under conditions very close to shortcircuiting them.
>I guess they have already tried reconnecting these battery packs so
>they become two series chains connected in parallell, instead of one
>series chain of batteries.
>I just thought about the idea to put a battery in a bath of mercury
>which somebody mentioned earlier.
Not a good choice, unless it is in a gastight container. Hot
mercury gives off deadly gases. Particularly if it boils.
>It would actually be possible to measure the voltage during the
>discharge process by holding the battery with probes connected to a
>voltmeter, isolated probe wires, only the contact points un-isolated.
I suppose. No different than measuring "across the load". This one
is a liquid load. Neat. But deadly.
>The energy dissipated could be measured by monitoring the temperature
>of the mercury bath. A reasonably small amount of mercury in a
>container not much bigger than the battery. From the energy
>dissipation and the voltage curve we could calculate the current.
Calculate the resistance of the mercury bath with a fixed contact
plate size, then place a known value copper resistance across the
battery as well. Read the voltage on THAT resistor (the copper), and
calculate the other, using the wire for correction factors for the
bath later on.
>If there was an Association for Prevention of Cruelty to Batteries we
>would be in serious trouble :-)
I guess. Hell, he'd be better off with a capacitor bank on standby
in the circuit, with a switch that gets thrown if the device ever
falls below a certain voltage. Surge caps can produce some amazing
instantaneous currents without damage for hundreds of pulses.
There has to be a way to deliver energy to this guys load (the motor
not the fixture) without dropping the batteries to a nil voltage.
DC to DC converter between batteries and motor.
Hey! I know! Lets just put a big coil of wire in the car, and
excite it inductively! Hahahaha.... Like a door pass key.
Yeah... we could send a whole 500 femtowatts to the car! :-]
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