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Old Sep 15, 2005, 08:59 PM
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I don't understand how to properly charge the lipo pack after partial discharge...

I only flew about half a charge today. I'm not sure if it's safe to put it back on charger in this state. I have a hobbico mkII charger that auto detects the cell count and I thought I remember someone saying that it may improperly detect the cell count if theres a charge on the battery. Its a 11.1V still showing 11.38V. Isn't that number supposed to drop? Can someone durect me on this?

Just trying to avoid burning down the house!

Thanks in advance!
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Old Sep 15, 2005, 09:31 PM
Southern Pride
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Haralson County GA. USA
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A 3S if between 12.45 and 12.6 when fully charged. It is considered empty when at 11.1 volts. LVC are (should be ) set at 3 volts per cell(9V) under load, when the load is removed the voltage goes back up some. The only time your charger would like overcharge if the voltage wa at more than 12.45 and you tried to charge it.

http://www.rcgroups.com/forums/showp...1&postcount=11


Charles
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Old Sep 15, 2005, 10:56 PM
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I just charged it and it reads 12.1V, is that acceptable?
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Old Sep 15, 2005, 11:04 PM
Southern Pride
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Haralson County GA. USA
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The link I provided shows what that charger should do. I guess 12.1 is OK just not close to a full charge.

12.1 /3=4.03 or 76% charged.
How accurate is your DVM?

From post at link.

4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%




Charles
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Old Sep 15, 2005, 11:22 PM
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Sorry, I didn't see the link at first.

I'm disappointed at 76% usable capacity. At least there won't be any fires I guess.

How does that affect actual flight time? Or does it? I thought mAh=flight time.

Or does voltage only equal the speed of the motor while mAh equals the length of the flight?

I think its an ok DVM, its one of the digital craftsman units. I need a dedicated one made for electric flight though, the leads give you kind of a jumpy reading if your hands aren't steady as I'm using micro deans.
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Old Sep 15, 2005, 11:49 PM
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xray..its your charger,,that specific charger will not fully charge lipos..90% capacity is best youll get,.,,
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Old Sep 16, 2005, 08:02 AM
Southern Pride
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Sucessful electric flight has a great deal to do with math.. I would encourage anyone who is interested in electric flight to bone up on their math.

Fully charged 4.15-4.2 (will vary) per cell *3=12.45-12.6

If you could fly for 10 minutes off of a full charge but you only had a 75% charge then .75*10=7.5 min. flight.


A 3S LiPoly charger to 12.1 is at 76% state of charge(approximately).

Most MK II charge to 12.3 for a 3S. There is a big difference between 4.03 volts per cell and 4.1 volts per cell. A 90% charge is fine for most flyers but a 75% charge is not acceptable for most.


Fully charger 4.2 v =100% available for use
empty 3.7v == 0% available for use
The difference between a single cell being full or empty is only 0.5V

Useage will vary by user.
Charles
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Old Sep 16, 2005, 10:48 AM
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xray..you can do what i did..keep the mk2...because that allows you to charge 2 lipos at the same time..and then buy a apache 2500 lipo charger..you can get em for around $35 if you shop around...and use the lipo charger to fully charge the lipos once the mk2 has gotten them near their capacity..
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Old Sep 16, 2005, 12:56 PM
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heh, welcome to the club... thats my EXACT setup

rumme doesn't lie. Its the most cost effective vs. performance vs. convenient setup around. They are both prominent and respected chargers...

Though both units (MKII and Apache) have small faults... but they are the perfect pair IMO because they cover each others faults. They are like Lincoln Logs that fit together, or like Tetris.
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Old Sep 18, 2005, 01:46 AM
Throttle,,What's that?
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Wrong post
Pat
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Old May 15, 2008, 02:50 PM
Dick Corby
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Enumclaw, Washington
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I've been using the FMA 6S charger and my computer to maintain my batteries for the past year. I think the 6S is no longer available, but there is a 10S charger available.

It has allowed me to monitor every aspect of my batteries, and I'm convinced that it is extending the life of my Li-Po's. I have a couple of 2100 MAH packs that are almost 18 months old, and still within .05 volts of when they were new.

The plus side is that it has allowed me to recover some packs that were way out of balance for some of my buddies. It takes a lot longer to balance a pack that is way out of balance, but does bring it to balance again, and then using the batteries they still stay in balance after repeated use.

Being able to see a visual graph of the battery state before, during and after a charge is priceless. Also makes me aware when I may have mistreated a pack. Well worth the initial investment.
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Old May 15, 2008, 03:04 PM
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Quote:
Originally Posted by xray328
I just charged it and it reads 12.1V, is that acceptable?
I used to have the Mark II charger...I took it back because it only charged up to 12.2 volts...I exchanged it for the same....still 12.2 or sometimes 12.3 The manufacture said that's normal for that charger. I like 12.6 on my batts. BUT you lipos should get more miles on them charging to 12.2 + or -
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Old May 15, 2008, 03:29 PM
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Quote:
Originally Posted by everydayflyer
A 3S if between 12.45 and 12.6 when fully charged. It is considered empty when at 11.1 volts.
In that 12.6 volts is the peak voltage, 11.1 volts is the nominal voltage and 9 volts is the cut off voltage how is it you consider a 3S empty at 11.1 volts. By empty does this imply that this is the acceptable voltage when storing a 3S LiPo for several months? Also, when storing a LiPo for a few months is there any advantage storing it in a refrigerator (zip-lock bag)?
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Old May 15, 2008, 04:28 PM
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Quote:
Originally Posted by microwave
In that 12.6 volts is the peak voltage, 11.1 volts is the nominal voltage and 9 volts is the cut off voltage how is it you consider a 3S empty at 11.1 volts. By empty does this imply that this is the acceptable voltage when storing a 3S LiPo for several months? Also, when storing a LiPo for a few months is there any advantage storing it in a refrigerator (zip-lock bag)?
When storing lipos it normally advised to store at 50% capaity. About 3.8v/cell is what i store mine at, and yes, i think storing in a fridge does help life span. How long do u plan on storing for?
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Old May 15, 2008, 04:51 PM
Southern Pride
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Haralson County GA. USA
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Quote:
Also, when storing a LiPo for a few months is there any advantage storing it in a refrigerator (zip-lock bag)?

http://www.rcgroups.com/forums/showthread.php?t=864576


Charles
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