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: <email@example.com> <firstname.lastname@example.org> <email@example.com>
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Date: Mon, 06 Jan 2003 15:19:43 GMT
NNTP-Posting-Date: Mon, 06 Jan 2003 10:19:43 EST
On Mon, 06 Jan 2003 15:25:06 +0100, Roger Johansson
>>If your discharge rates are of such a nature, you are
>>stepping outside the specs for the battery's proper use.
>You have obviously not read the earlier discussion in the same thread.
>John is not trying to stay within specs, on the contrary, he is using
>these batteries like no battery manufacturer ever imagined they would
Which is all but stupid.
>Maybe you could find and read the earlier messages in the thread, I
>think it would make you understand what this is all about.
I do understand. A person is using motors AND batteries in a manner
that is destructive. I am supposed to help?
>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.
>John is probably not counting on getting 100A out of a D cell, but he
>wants to have measuring equipment to try it, to see the difference
>between different cells.
They all act like they are about to explode at those levels, and
real data about what Mfgrs are better is probably not possible. ANY
Mfgr's battery may or may not fail.
>When it comes to your statement that batteries in series does not
>raise the current capacity it seems obvious that you are right, but
>think about a fixed very low load resistance. If we can raise the
>voltage it could actually push more current through that load.
>If the batteies can take it.
Sounds like a kludged way of performing the work. If the motors are
low voltage devices, then the batteries would do better to provide
more current *AT* the working, proper voltage. That would mean more
batteries in parallel, AT the right voltage. The when the demand goes
up, the voltage hangs on, and the motor can PERFORM the task the way
it was meant to. AND BETTER at that.
>That is why he talks about putting batteries in series to raise the
>Please read the earlier massages in the thread, www.groups.google.com.
I don't really need to. I have burn in racks at work that regularly
test at 1kW and at 4 units at a time. We use fans to heat the lab
with the heat that the resistor banks exhibit.
What we do NOT do is ask power supplies OR batteries to do more than
they are designed to do. It is simply like asking for trouble. If he
wants more output torque, he should step down the shaft speed with
gear reduction or chain and sprocket reduction. Motor stalls would
cease, and higher speed peaks would be possible when loaded down.
He could get just as much data in attempting to charge one up at
100A. The data would look very much the same. Heat up until BANG!
It might sound silly, but so does hitting one that hard on the