R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 06-25-2009, 06:37 AM   #1
Tech Apprentice
 
capturefx's Avatar
 
Join Date: Jun 2009
Location: BALTIMORE MD
Posts: 74
Trader Rating: 1 (100%+)
Default PLEASE TEACH ME HOW TO UNDERSTAND BATTERY DISCRIPTION.

im new to electric rc comming from nitro, please help me understand the description of these batteries. i remember they used to be so simple back then just grab a 7.2 1500 mah and up and go.

for example : 2 cell 7.4V 5200mAh 25C Li-Polymer Lipo Battery Pack

2 cell means theres 2 pieces of batteries in it? and a 7 cell would have 7 pieces of batteries in it . please correct me if im wrong im a noob.

i know what 7.4 and 5200mah means but what is the 25C??

capturefx is offline   Reply With Quote
Old 06-25-2009, 06:55 AM   #2
Tech Addict
 
Miller_Time's Avatar
 
Join Date: Jan 2008
Location: Charlotte, NC
Posts: 678
Trader Rating: 11 (92%+)
Default

The "2 cell" generally means how many cells in series. A 2 cell lipo (7.4 volts) may have 2 actual cells or it may have more The full description would be 2s1p for example - 2 cells in series, 1 parallel, the difference is how they are wired. Cells in series add voltage while cells in parallel add their mAh (capacity) but not voltage. It's usually just said as "2 cell lipo" because the voltage is what really matters in terms of equipment compatibility.

You could have several ways to make a 7.4 volt 5000 mAh battery pack. At 2s1p it would be two cells in series, each cell being 3.7 volts and 5000 mAh. Or it could be 2s2p which would be four cells total, each cell being 3.7 volts and 2500 mAh. Two pairs are wired in parallel and then those pairs are wired in series. In actual use there is no difference between those two packs, although the size/shape could be different.

The "C" rating is the discharge rating, 1c equals the total amperage capacity of the battery. So a 20c 5000 mAh pack is rated to discharge 100 amps, while a 40c 5000 mAh battery can deliver up to 200 amps. The thing to remember here is that C ratings are highly subjective. Usually that rating is to indicate the "continious" discharge - meaning the battery should be able to deliver that many amps over a period of 10 seconds or more continiously. However it could also mean the burst rating (up to 3 seconds only), and you also have the confusion that there is no real standard for measuring discharge ratings. Some companies will over rate their batteries while some will under rate them. Confusing yes, but in general you can use the C rating to determine the quality of the cell.

That also means that, assuming the ratings are accurate and using the same method, a 40c 2500 mAh battery can deliver the same amperage as a 20c 5000 mAh battery - 100 amps in both cases. The 5000 mAh battery could do so for longer as it has more overall capacity however.
__________________
www.HobbyStop.com
Miller_Time is offline   Reply With Quote
Old 06-25-2009, 08:07 AM   #3
Tech Apprentice
 
capturefx's Avatar
 
Join Date: Jun 2009
Location: BALTIMORE MD
Posts: 74
Trader Rating: 1 (100%+)
Default

thanks miller time! it makes so much more sense. now i dont have to be all lost when looking for different types of batteries .

i think im gonna go lipo 7.4 30 to 40c 5000mah and up.

thanks again.
capturefx is offline   Reply With Quote
Old 06-25-2009, 09:57 AM   #4
Tech Addict
 
Miller_Time's Avatar
 
Join Date: Jan 2008
Location: Charlotte, NC
Posts: 678
Trader Rating: 11 (92%+)
Default

I've been using the Reedy packs lately and I really love them. The standard pack is a 40c, the saddle pack is 35c, both at 5100 mAh. The thing I like about them is they are reasonably priced, with a hardcase, and you can charge them at 2c (10 amps).
__________________
www.HobbyStop.com
Miller_Time is offline   Reply With Quote
Reply



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

Advanced Search

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
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 09:36 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net