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Old Jan 03, 2013, 09:05 PM
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Cell Pro 10S "Fuel" Accuracy

Hello, I was hoping someone could shed some light on the apparent inaccuracy of my Cell Pro 10S display when I first plug in my battery for charge.

The charger will display a message something like Battery #1 Fuel = 61%
But when I compare these numbers to what I actually put back in the pack the numbers are way off.

Here's an example
Batt #1 Fuel =47% (this is supposed to refer to what's remaining)
Actual charge that the battery took 1725 mah
Battery capacity 4900 mah
4900-1725=3175 actually remained
3175 divided by 4900 = 65% actually remained instead of the 47% that it initially displayed

What am I missing?
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Old Jan 03, 2013, 09:32 PM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
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There are several fuel tables based on LiPoly C rates. Using one that most closely matches the LiPolys true C rate should prove to be more accurate however as LiPolys C ratings are rarely very accurate it is really little more than a shot in the dark.

FYI I spent many days helping to develop the fuel tables for the CP10XP but never rely on fuel tables myself.

There is a thread on this charger here

http://www.rcgroups.com/forums/showt...highlight=10xp


Charles
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Old Jan 03, 2013, 10:04 PM
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Originally Posted by everydayflyer View Post
There are several fuel tables based on LiPoly C rates. Using one that most closely matches the LiPolys true C rate should prove to be more accurate Charles
Charles thanks for your reply, I'm a little confused though. Where do I find a fuel table? Is this something that can be selected in the 10S? If not should I just ignore the chargers display relative to the fuel level and just rely on my real time data?
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Old Jan 03, 2013, 10:32 PM
DOLLA DOLLA BILL YALL
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United States, FL, Orlando
Joined Oct 2012
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you either have really good lipo packs or really bad lipo packs. the quick reading in the beginning is just an estimate based off the cell voltage.

poor quality lipo packs have a lower cell voltage per % discharge than good quality packs. So a good pack at 50% discharge could have 3.9v per cell, while a Turnigy battery would show 3.8v per cell.

The charger doesn't know what you have plugged in, so they just have an average value to give an estimate. the charger charges until the battery is actually full by adjusting the charge rate down till the cell holds 4.2v on its own without any charge current
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Old Jan 03, 2013, 10:34 PM
DOLLA DOLLA BILL YALL
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also you don't want to drain more than 80% of what it's rated for or you will wear down/degrade the lipos over time... so did your calculation include that? Is that 65% of the total rating or is it 65% of the available 80%?

i would argue that there was 53% charge remaining, and both you and the charger were wrong
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Old Jan 03, 2013, 11:37 PM
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My batteries are Rhino 4S 4900 packs. Fairly inexpensive as I recall

My calculations tell me that I still had 65% total capacity left in the battery before I charged it based on the milliamps I replenished. With the 80% rule I still had another 45% to go before I hit the 20% mark.

Looking at it your way comes up to the same thing
4900 x 80%= 3920 milliamps that I have available for use
I used 1725. 1725 divided by 3920 = 44+% that I used or roughly 65% remaining

Are you sure you weren't figuring 80% of the 80%?
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Old Jan 04, 2013, 12:35 AM
DOLLA DOLLA BILL YALL
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United States, FL, Orlando
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4900 * .8 = 3920

3920 - 1725 = 2195 left

2195/3920 = 56% left in the battery using .8 rule

you had the 44% used correct

44 + 65 is 109% lol
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Old Jan 04, 2013, 01:45 AM
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When the Cellpro10s was released the fuel tables for packs were fairly consistent from pack to pack, manufacture to manufacture. By the time packs started hitting 25c and higher, the fuel maps started changing. The Cellpro10s has a single fuel map that cannot be changed. As a result the fuel map for some packs will no longer be 100% accurate.

More recent Revolectrix chargers now have multiple fuel maps and you can create custom fuel maps for all of your packs if you desire.
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Old Jan 04, 2013, 04:25 AM
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Quote:
Originally Posted by quad007 View Post
44 + 65 is 109%
<Hangs head in shame> Would it matter if I told you I had the flu for the past eight days?

Quote:
Originally Posted by Gregor99 View Post
When the Cellpro10s was released the fuel tables for packs were fairly consistent from pack to pack, manufacture to manufacture. By the time packs started hitting 25c and higher, the fuel maps started changing. The Cellpro10s has a single fuel map that cannot be changed. As a result the fuel map for some packs will no longer be 100% accurate.

More recent Revolectrix chargers now have multiple fuel maps and you can create custom fuel maps for all of your packs if you desire.
Thank you for that information. Now that quad007 discovered a problem with my math the values are closer but still off. I will rely on my actual findings.

Reminds me of calculating fuel burn when flying full scale. There was nothing more accurate than measuring how much fuel you can pump back in your tanks after the flight.
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