The reason he posted was that he was confused about the math and was
asking for help.
For which he received a lot of flak, even though this is seb, where
there are supposed to be no stupid questions.
Battery question
Oct 09, 2007
35 Replies
I don't see where the issue here is. since no AHr was giving originally, I stand by original statement, "BARN YARD" figures.
And it's basic math..
So basic, I'm not going to waste my time explaining it., How ever, I did see J. Fields take the time out in breaking it down for those that needed it.. Keep in mind, not all batteries (cells) types behave the same way nor do you want to drain them down to such a low point. So back to my "BARN YARD" figures.
Getting replacement batteries for emergency lighting teaches you one thing. Not all manufacturers rate their products the same way. Or maybe I should say. They lie a little on the performance where others we have found actually are a little generous on their performance specs.
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
Mark,
You made a mistake and you need to own up to it.
We all do, [make mistakes] once in a while, and while it\'s
humiliating when it happens in public, it\'s part of how we learn.
There\'s nothing wrong with admitting that we\'re not perfect, once we
find out that we aren\'t, but there\'s a lot wrong with pretending
that we are in the face of incontrovertible evidence to the
contrary. :-)
So, since no Ampere Hour figures were given originally, your
barnyard figures were stupid errors?
John,
Did you mean to address me (Mark, a.k.a. redbelly) or Jamie?
Mark
p.s. nice post -- the one that begins "Your load is dissipating: P2 = I2 E2 = 2A * 5V = 10 watts, ... "
My comment was targeted at * JAMIE * who claims to be an engineer but seems happy to make estimates of battery life knowing only its voltage !
Janie is a complete idiot. See his other posts for more examples of utter lunacy.
Graham
stupid
This is the only bit that matters,
" since you're requiring 2 amps, I guess math wise, that would give you more than an hour of running time."
MORON.
Oops, my mistake... Jamie.
happy to
Check the upper left hand corner of page 8 of:
http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_VRLA_Overview.pdf
IOW, you have no clue.
Quit being a rude asshole; this is sci.electronics.basics, where the only dumb question is the one you don't ask.
Thanks, Rich
Jamie's not even up to dealing with 'basic' questions.
Graham
I'm sorry John, I think you have me grossly mistaken .
I really thought you had more common decency than that.
I work in this field all day long, I don't plan on sitting here after hours dumping math for public consumption. If that were the case, I'd live at work.
I do find a few here that seem to pride them self in doing so. It makes me wonder if it's for the good of the general audience or, some one trying to make a mark for them self?
I don't know what you call it where you come from? Here, we call it little man disease
Have a good day.
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
happy to
lunacy.
Hanging around the bath houses again?
I'm not one of your fantasy's
The spelling is "JAMIE" not "Janie"
Get a life.
"I\'m never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
I've read the thread, and unless I missed it, there is something important than hasn't been addressed.
My reaction to your question is that you *should not* attempt to get any runtime from your setup as described, without further investigation. Here's why:
That 11.1 volt figure indicates a (assumed lead acid) battery that is already close to 100% discharged. If it is a lead acid battery, you should be charging it - not taking current from it - as continued discharging once
11.1 volts has been reached is likely to do damage to the battery. The exact voltage figure vs % of discharge depends on a number of factors, but in any case 11.1 volts demands a warning flag that you need to pay close attention to whether or not you want to keep discharging the battery.If you're talking about some other chemistry (e.g. 10 NiCd cells discharged to 1.11 volts per cell), different rules apply.
Ed
11.1 V is common for lithium-ion batteries (3 cells @ 3.7 V).
The op's battery is 20 amp hours.
11.1 may be common for LI batteries, but not at 20 AH. A quick search finds lots of them < 10 AH, and none at 20.Ed
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