Holy Sheet - Page 2

Siress · #16 12-21-2002, 02:54 PM

I always leave room for doubt but it was something he said that convinced me and I can't rember exactly what it was. I will get back to you all.

binaryterror · #17 12-22-2002, 10:14 AM

Listen, no one wants to fight over a well known fact about mah.

I don't care what this guy says/said, he is wrong. Maybe you should consider him less than a genius.

rmyc · #18 01-11-2003, 03:02 AM

yall i'm backing up Siress ..but i kinda agree with the the other

Mah dosn't make the car go fast.. well kinda ..
lets put it like this.........

batteries with larger compacity usualy have a higher discharge rate.
thus., the motor would be able to suck more juice , and the car would go faster..
kinda like how nicad make the car go faster then nimh

but then again ,the larger the battey the more the weight which again slows the car..

i'll say they both are the same

fastboy · #19 01-12-2003, 06:15 PM

bigger mah DOES NOT mean a higher discharge rate.
it means it has more capacity and will deliver a set current discharge for alonger period.

a 700mah cell will not be quicker than a 300mah cell and vice versa.
what makes a cell turn a motor quick is having a low internal resistance and a high discharge voltage under load.
also having good quality connectors.
if you charge 2 identical packs but charge 1 at 100mah and 2nd at 500mah the 2nd pack will have more punch and will also be hotter at the end of a charge..not a good thing.
how do i know these things??...18yrs of electric r/c racing,trust me.

rmyc · #20 01-12-2003, 06:46 PM

yah i know that but large batteries have a larger discharge rate.
trust me. that's why you have to charge small batteries at a lower mah.

fastboy · #21 01-13-2003, 03:47 AM

sorry but you are wrong about large batteries having better discharge rates.

ask stock racers which are the punchier batteries 2000mah or 2400mah..guess which they use,yep 2000mah.

if you compared say a watch batterie to a nicad then yes you are correct,but when it comes to aaa and aa then you will not notice a difference,the reason why aa may be quicker than aaa in your car is because you charge aa at a higher current which ultimately gives the batteries a higher discharge rate,the current at which a batterie is charged can make a tremendous difference trust me.

ag04 · #22 01-16-2003, 06:36 AM

my vote goes with fastboy... with my limited knowledge, fastboy has it all covered

ag04

Hicountry · #23 01-16-2003, 03:45 PM

fastboy

I have 16 years as a Navy Aircraft Electrician. 4 of those running a battery shop. Lead-acid and NiCD. You are right!!!

Everyone else read what he said and take it as gosphel. I could burry the sight in proof but that would take all the fun away. When you get payed to teach kids these things then argue with me, until then keep up the good work fastboy.

Hicountry out!

bigbamboo · #24 01-16-2003, 04:34 PM

Quote:

Originally posted by fastboy
a higher current which ultimately gives the batteries a higher discharge rate,the current at which a batterie is charged can make a tremendous difference trust me.

SO does that mean a battery charged with a rapid charger (higher charge rate) will have a high discharge rate and improved performance? If so it'd be an atvantage to buy the quick charge vs a 12 hour charger.

I'm not science based. :-)

Bigbamboo

fastboy · #25 01-16-2003, 06:31 PM

yes it would be better to buy a fast charger rather than a 12hr trickle charger,altho you will experiance a shorter user life of the nicad,ie you may only get 100 good charges at a higher charge rate.
remember to buy a charger that is suitable for the cells you are charging,meaning dont buy a 4amp charger for charging 300mah AAA...THEY WONT LAST VERY LONG!!
ideally you want a charger that you can alter the charge rate right down to say 200mah.

for charging 250mah 2/3 AA use linear charge of 300mah.nomore.even then the cells do get warm quickly but not overwarm.

for700mah aaa i use 500mah charge rate,you could maybe use a little more but 500mah is plenty.

if you can get a small fan to keep the cells cool while charging then do so,it will help.

Hicountry · #26 01-16-2003, 06:53 PM

The pamphlet that came with my charger "in general" said to charge batteries at twice their capacity.

I dug up some manuals from work. It seems that the higher capacity the battery has the higher your charge rate can be in relation. ie 250mah probably 350mah is good, but a larger 2400mah pack can be charged at 5amps.

You must be careful because if a battery gets too hot it will go into thermal runaway and explode. Yes even these little cells.

We used to "overcharge" batteries at work if we had to get a jet out. It requires constant supervision because things can go bad quikly.

A good rule of thumb would be to charge batteries under 1ah at 150%.....1ah to 2ah at 175%.......2ah to 3.3ah at 200%

Remeber that a better quality matched pack can handle more.

Hicountry · #27 01-16-2003, 06:57 PM

Remember, no matter what general rule you follow, if the cells feel hot (not warm) then you are overcharging them. Back it down a little.

bigbamboo · #28 01-16-2003, 08:08 PM

My wife uses 7.2volt stick batteries to charge her strobe on the camera. These batteries will provide for thousands of flashes and rather than recharge when they are already half charged, she rigged a car headlight to slowly drain the charge. I guess its to prevent memory from ruining the batteries. It seems to work for her.

FYI

Bigbamboo

fastboy · #29 01-17-2003, 04:56 AM

just remeber that with a car headlight bulb it will not stop when the batteries are flat and if all the cells are not a very good match some of the cells will be discharged before others sending some into cell reversal,in short a bulb is ok if you are there to take it off when the bulb starts dimming but can do more damage than good.