Wattflyer RC Network: RC Universe :: RCU Magazine :: RCU Forums :: RCU Classifieds :: RCU User Reviews :: RCU YouTube
Home Who's Online Calendar Today's Posts RealTime Post Spy Mark Forums Read
Go Back   WattFlyer RC Electric Flight Forums - Discuss radio control eflight > R/C Electric Power - Batteries, Chargers, ESCs and More > Batteries & Chargers
Register Members List Wattflyer Extras Articles Search Today's Posts Mark Forums Read Social Groups

Batteries & Chargers Discuss Li-P, Li-Ion, NiMh, Nicad battery technology and the chargers that juice 'em up!

Thank you for your support (hide ads)
Thread Tools Display Modes
Old 05-12-2007, 12:08 AM   #1
Jon The Buddha
E-Flight Virgin
Join Date: Mar 2007
Location: OKC, OK
Posts: 55
Thanked 1 Time in 1 Post
iTrader: (0)
Friends: (0)
Default NiMh: Charged vs Discharged Voltage

I use a couple of Electrifly 8.4V - 3000mah NiMh batteries to run my Electristar. My questions is about the voltages I am seeing.

The last time I flew, I made sure I ran the plane until the engine cut off. Is this considered to be the point the battery is roughly 'fully' discharged? I measured the voltage out of both batteries and (I am going from memory here) I think they were approximately 8.5 volts. I have also read the voltage on the batteries after what I think is the proper charging time (36 minutes, charging at 5 amps on a basic Hobbico 900 timed charger). I think the reading was around 9.8 volts.

Do these numbers sound feasible? I am concerned about two issues...that I am running the battery down sufficiently enough between charges, and that, when charged, I am not exceeding some max voltage requirement. Until I can get a proper charger, I want to make the best use of the one I have and NOT damage my batteries.

Thanks gang...I am trying to learn this 'magical' battery stuff, but sometimes I get lost in all the info from the many posts and links to battery basics websites!
Jon The Buddha is offline  
  Reply With Quote
Old 05-12-2007, 02:22 AM   #2
Matt Kirsch
Super Contributor
Matt Kirsch's Avatar
Join Date: Jul 2005
Posts: 2,086
Thanked 70 Times in 68 Posts
iTrader: (0)
Friends: (1)

Technically speaking, fully discharged is considered to be .9 to 1.0 Volts per cell on a NiMH. Fully charged is between 1.3 and 1.4 Volts per cell. Unfortunately, you can't tell the state of charge on a NiMH by looking just at its voltage. The no-load voltage will be near full-charge voltage until the battery is almost empty. At 8.5V yours are on the steep slope to becoming completely empty, and do not contain more than a single-digit percentage of their total capacity.

Continue as you are until you can get yourself a nice peak charger, just monitor the battery's temperature. It should not get more than comfortably warm to the touch. Given a sane charge rate (5 Amps is pushing things a little bit, but it's not a totally crazy rate once the batteries have been cycled a few times) once the battery becomes warm, it's charged.
Matt Kirsch is offline  
  Reply With Quote

  WattFlyer RC Electric Flight Forums - Discuss radio control eflight > R/C Electric Power - Batteries, Chargers, ESCs and More > Batteries & Chargers

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
NIMH Rejuvenation - Low voltage cbatters Batteries & Chargers 6 01-13-2008 08:13 PM
LiPo Voltage when fully charged? Lieutenant Loughead Batteries & Chargers 8 11-01-2007 11:02 PM
Wall Charger - Current/Voltage drop when charging NiMH Tom_Pilot Batteries & Chargers 2 10-21-2007 11:02 AM
Which Charger for multiple pack charging (and have voltage monitoring) lipo,nimh mark11233 Batteries & Chargers 11 05-16-2006 03:24 AM
Measured voltages on Fully charged vs Discharged Vendetta Batteries & Chargers 7 02-13-2006 04:15 AM

All times are GMT +1. The time now is 12:01 AM.

Powered by: vBulletin
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2005 WattfFlyer.com
RCU Eflight HQ

Charities we support Select: Yorkie Rescue  ::  Crohn's & Colitis Foundation

Page generated in 0.05907 seconds with 20 queries