LiPo capacity - RCCanada - Canada Radio Controlled Hobby Forum
RCCanada - Canada's Radio Control Hobby Forum
General RC Heli Discussion Discuss general topics on rotary wing aircraft, including construction, Servo's, Gryo's and Stabilizer discussions. Heli Pro Shop

Thread Tools Display Modes
Old 12-03-2015, 09:25 PM   #1
Dark Helmet
RCC Apprentice
I am: Klaus B
Join Date: Mar 2015
Location: Lunenburg, ON
# of RCs: 6

Feedback: 1 / 100%
Posts: 36
Total Props: 0
LiPo capacity

       Remove this ad - become a site supporter!
What exactly does the advertised LiPo capacity refer to? Is it the usable capacity from 4.2 V/cell down to the storage voltage (3.8 V/cell) or to the nominal voltage (3.7 V/cell)? Or is it the capacity I'm getting if I fully discharge the battery?

I'm asking because I have a brandnew 2S 5000 mAh LiPo and I can hardly get 2600 mAh into it when I start charging at 7.6 V. Also I have noticed that when I charge at 5 A (or 1 C), the voltage immediately goes up quite a bit (about 8 V) which in my understanding means that the internal resistance must be relatively high. If I look at the battery as an ideal battery with a resistor in series, the resistance would be R=U/I=(8 V - 7.6 V)/5 A=80 mΩ or 40 mΩ per cell which seems to be quite high.

Any thoughts on this?
Dark Helmet is offline   Quick reply to this message.

Sponsored Links - Subscribe to remove this ad.
Old 12-03-2015, 11:53 PM   #2
RCC Expert Contributor
Keyrigger's Avatar
I am: Don I.
Join Date: Jul 2012
Location: Mississauga, Ont
Radio of choice:
Spektrum DX18

Feedback: 1 / 100%
Posts: 884
Total Props: 6
Re: LiPo capacity

The marked capacity is the total for the battery. When you discharge the battery, you will bring it down to around 3.75v per cell and if you are patient and add a bit of time per use, you will find out where you will discharge it to 20% of capacity. You would end up putting back in around 4000mAH. I would stop somewhere around 30% so you would be putting back in 3500mAH from its discharged state. I don't do electronics well so my suggestion would be to purchase a good battery checker (not the 5.00 kind) that will give you percentage of charge remaining, individual cell voltages, and internal resistance. My understanding of that measurement is that is done under load, not just a simple check with an ohm meter of the individual cell. Take care.

Keyrigger is offline   Quick reply to this message.
Old 12-04-2015, 02:17 AM   #3
RCC Apprentice
I am: Phil T
Join Date: Jan 2014
Location: BC
Radio of choice:
Taranis DX6I
# of RCs: 9

Feedback: 0 / 0%
Posts: 39
Total Props: 0
Re: LiPo capacity

This is a very good article on batteries
Philtea is offline   Quick reply to this message.
Old 12-04-2015, 06:06 AM   #4
Level 3 Supporter
★ Site Supporter ★
davidmc36's Avatar
I am: David C
Join Date: Jul 2010
Location: Morewood, ON
Radio of choice:
MC-20 MX-20 X9D+ X12S
# of RCs: 25

Feedback: 72 / 100%
Posts: 3,080
Total Props: 44
Re: LiPo capacity

Phil's link is good, clear explanation of all things LiPo.

But specific to a couple points:

It would be pretty normal to see voltage rise to 8V very quickly when charging at 5A, then slowly rise to 8.4 as current is kept constant. Then when voltage hits 8.4, it is held there as current is dialed back until full charge is done.

When you use a battery checker to see how much charge is left in a battery, you want to do it at rest, no load.

It is important to never draw down below 3.0V per cell under load, a bit higher is better. If you have a setting or alarm to protect against overdischarge and it is set to something like 3.3V/cell (under load) they should bounce back to around 3.7 or so after a short rest.
No Bounce-No Play The one who dies with the most toys wins!
MC-20 MX-20 Taranis X9DPlus HORUS
Friends don't let friends fly Spektrum!
Electric flying is pretty much seeing how close to a dead short you can run without setting it on fire.

davidmc36 is offline   Quick reply to this message.
Old 12-04-2015, 06:35 PM   #5
Dark Helmet
RCC Apprentice
I am: Klaus B
Join Date: Mar 2015
Location: Lunenburg, ON
# of RCs: 6

Feedback: 1 / 100%
Posts: 36
Total Props: 0
Re: LiPo capacity

Thanks all, that's helpful
Dark Helmet is offline   Quick reply to this message.

Quick Reply

Register Now

In order to be able to post messages on the RCCanada - Canada Radio Controlled Hobby Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Member names may only be composed of alpha-numeric characters. (A-Z and 0-9)

!!ATTENTION ADVERTISERS!! If you intend on advertising anything on this forum, whatsoever, you are required to first contact us here . Additionally, we do NOT allow BUSINESS NAMES unless you are an Authorized Vendor. If you own a business, and want to do sales on this site via posting or private message, you will need to follow the rules. Shops, Stores, Distributors, Group Buys without being authorized will see your account terminated.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Your Name
Your first name and last initial is required if you plan on using the forum.
Which city & province you live in. This is mandatory for classified listings.
Radio of choice?
Which radio is your current favorite to use?
Number of RC Vehicles?
How many boats, cars, planes do you own?


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

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

Thread Tools
Display Modes

Forum Jump

All times are GMT -5. The time now is 02:47 PM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.