volt vs amp?  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> Electric Aircraft Universe >> Electric Training >> volt vs amp?
Page: [1]

Login
Message << Older Topic   Newer Topic >>
volt vs amp? - 8/25/2003 1:00:32 AM   
ghost rider 425


 

Posts: 44
Joined: 5/8/2003
From: Brossard, QC, CANADA
Status: offline 		When it comes to electric i am so lost,so here is a question that somebody asked and was for a lost of words.

Can a battery for example 9.6 volt 700 mah have a reading of 9.6 volt yet only have 375 mah or do they both work together?

Is it possible to charge an older pack and have the voltmeter show the voltage correct and not the mah?

If you have a brand new pack could you fast charge it or is recommended to slow charge?
       Post #: 1

volt vs amp? - 8/25/2003 7:14:18 AM   
red91sit


 

Posts: 237
Joined: 8/19/2003
From: Red Lake Falls, MN, USA
Status: offline 		First off i'll start with your last question lol it is a good idea to slow charge it for the first time after that u can peak charge it.

Each rechargeable battery usually has 1.2 volts unless it is a 9v battery lol or a lithium. each battery also has a certain mah like 600. then if u connect say 7 of those batteries + to - you get more volts (8.4) and still have 600 mah if u connect them all + to +, - to - you get 5600 mah!!! but only 1.2 volts. volts and mah will change with age when the battery gets worn out and with how full the battery is when it is completely dead it will have o,o full should be what the battery is listed at. or slightly higher.

(in reply to ghost rider 425)
       Post #: 2

volt vs amp? - 8/25/2003 6:34:28 PM   
Matt Kirsch



Posts: 7041
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline 		You can't measure mAh with a simple voltmeter. mAh is a measure of capacity, a current sustained over a length of time. It is completely independent of voltage.

Quite literally, a 700mAh battery should be able to sustain a 700mA or .7A current for one hour before it drops below a certain voltage. It can also run at higher currents: 1400mA for 1/2 hour. 2800mA for 15 minutes (1/4 hour). 4200mA for 10 minutes (1/6 hour). 7000mA for 6 minutes (1/10 hour). That's what mAh means in a nutshell.

Of course, batteries are not 100% efficient. There will be some loss, and the loss will get bigger as the current gets higher. If you're really pushing a 700mAh cell beyond its limits, you may only get 375mAh of useful energy out of it. The rest will turn into heat, that is, the battery will get very HOT!

Another situation where a 700mAh battery may only "contain" 375mAh is if it's only partially charged. Putting the battery on the charger will fix the problem.

A 700mAh battery may only contain 375mAh if it is damaged, as well. In this case, it won't be long before the battery is completely useless, and will need to be recycled.

(in reply to ghost rider 425)
       Post #: 3

volt vs amp? - 8/25/2003 8:53:53 PM   
ghost rider 425


 

Posts: 44
Joined: 5/8/2003
From: Brossard, QC, CANADA
Status: offline 		Thank you,gentlmen

So if i understand correctly you can have 9.6 volt battery but still have mah showing less?But in most cases it is fair to assume that a proper voltage reading will aslo give me the proper mah?

When a battery is fully charged will the mah register higher then rated?

(in reply to ghost rider 425)
       Post #: 4

volt vs amp? - 8/25/2003 9:19:19 PM   
Jim_McIntyre



Posts: 2078
Joined: 4/5/2002
From: Claremont, ON, CANADA
Status: offline 		Volts is a measurement of potential energy

Amps is a measure of current flow (useage of energy)

Milli is a modifier, an amp is a lot of current, the current we use in our application is typically meausured in milli (thousandths of) amps. IOW, 1 ma (milli-amp) = 1/1000 amp.

Hours is a measure of time (I'm sure you knew this one )

mah := milli-amp hours and is derived by multiplying current (in ma) by hours.
Eg.
- 1mah is the ability to sustain 1mill-amp for one hour, or ... 2 milli-amps for 1/2 hour etc.

So your 700 mah battery when fully charged should net you about 1 hour of usage at 700ma... or 1/2 hour at 1400mah (1.4 amps) etc.

The batteries we use are typically rated by their voltage (potential to do work) and their maximum storage capacity when fully charged (in mah). If the battery is not fully charged, it won't be able to deliver current as long. Eg. you may only get 10 minutes at 700ma.

Basically;
current (measured in amps or milli-amps {ma} in our case) is what does the work, voltage is the force that makes the current flow and resistance (measured in ohms) is what limits current.

more voltage := more potential power
more current := more actual work
more resistance := less current (unless more voltage is applied)
more time := more capacity

Think of current as water flow, voltage as water pressure, resistance as a tap.
If you've ever run out of hot water during a shower, or lived in the country during the dry season, you had a direct experience of capacity as well.

Hope this helps

_____________________________

http://scalebuilder.org

(in reply to ghost rider 425)
       Post #: 5

volt vs amp? - 8/25/2003 10:54:52 PM   
ghost rider 425


 

Posts: 44
Joined: 5/8/2003
From: Brossard, QC, CANADA
Status: offline 		Thank you, JIM

That was very helpfull know at lest i can make a some what in formed decision when buying batteries.

daniel

(in reply to ghost rider 425)
       Post #: 6

Page:   [1]
All Forums >> Electric Aircraft Universe >> Electric Training >> volt vs amp?
Page: [1]





Jump to:


Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Member Video Posts | RCU Video Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

© 2001 - 2007 24-7 RC, LLC, all rights reserved.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America

Kaango.com Classifieds

0.766RCU1