Lipos - Voltage sag under load??? - WattFlyer RC Electric Flight Forums - Discuss radio control eflight

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

Lipos - Voltage sag under load???

Old 01-03-2009, 03:27 PM
  #1  
Buck Rogers
Member
Thread Starter
 
Join Date: Apr 2007
Location: Bristol, UK
Posts: 511
Default Lipos - Voltage sag under load???

How much should the voltage go down under load with a Lipo battery. I have some Dualsky Lipos that seem to sag a lot under load even though they only have about 20 - 30 flights on them.

They seem to drop about 0.5 V with a 3 amp load and over 2V with a 20 A load. Is this right? My other Loongmax Lipos don't seem to drop nearly as much.
Buck Rogers is offline  
Old 01-03-2009, 04:02 PM
  #2  
Murocflyer
WAA-08 Pilot #1
 
Murocflyer's Avatar
 
Join Date: Mar 2007
Location: Edwards AFB, CA
Posts: 7,044
Default

Well shucks. I thought the .5V drop is normal for batteries under load, but I can't find a chart to prove that.

Frank
Murocflyer is offline  
Old 01-03-2009, 04:35 PM
  #3  
slipstick
Super Contributor
 
Join Date: Oct 2005
Location: N.Staffs, UK
Posts: 2,350
Default

Can't say without knowing what capacity/voltage batteries.

E.g. if they were 4S 1000mAh 15C batteries and they only sagged 2V at 20A you'd be doing really well. OTOH if they are 2S 4000mAh 25C then they're terrible.

Steve
slipstick is offline  
Old 01-03-2009, 05:39 PM
  #4  
Buck Rogers
Member
Thread Starter
 
Join Date: Apr 2007
Location: Bristol, UK
Posts: 511
Default

They are 1800 mah rated at 25C and up to 50C burst (allegedly). The problem is that with such a voltage sag I'm getting dangerously close to the LVC at WOT with over 50% capacity remaining in the battery.

Considering I'm only running these batteries at less than 1/2 their rated capacity I thought the size of this drop seems excessive.
Buck Rogers is offline  
Old 01-03-2009, 05:48 PM
  #5  
Rodneh
Member
 
Join Date: Oct 2005
Location: Florida, USA
Posts: 753
Default

Have you checked your connectors? Make sure that the drop is at the batteries and not due to some thing causing an increase in the external impedance between the load and the battery.
Rodneh is offline  
Old 01-03-2009, 06:51 PM
  #6  
everydayflyer
Southern Pride
 
everydayflyer's Avatar
 
Join Date: Oct 2005
Posts: 717
Default

http://www.wattflyer.com/forums/showthread.php?t=41023

Charles
everydayflyer is offline  
Old 01-03-2009, 06:56 PM
  #7  
jooNorway
Member
 
Join Date: Jul 2006
Posts: 574
Default

All my setups draw appr 10-14C. Then I usually read 3,5 - 3,6 V/Cell at load.
jooNorway is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
diverdon
Batteries & Chargers
20
12-08-2008 04:04 PM
bhatch21
Batteries & Chargers
16
09-06-2008 05:19 PM
onesubdrvr
General Electric Discussions
2
10-17-2007 05:22 PM
Lysander
Power Systems
7
03-02-2007 02:51 PM
Flyboy Dave
Humor
7
08-29-2005 04:15 PM

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


Quick Reply: Lipos - Voltage sag under load???


Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.

Page generated in 0.09336 seconds with 13 queries