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Old Jan 05, 2012, 12:52 PM
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OMG WHY? Lipo battery sub 2.7v

Hi everyone,

I cant believe that im here. My 3s battery is at about 1.7v per cell. I read and I read about lipos and how to take care of them but I foolishly forgot the battery attached to my quad. I was wondering, why did it get from 3.80v per cell to what it is now in one night, I didnt use the quadcopter and the ESC's were not armed?!?!

Anyways im going to attempt to charge the battery when my charger(which is like 1 week late) will arrive. I read that I must be in a fire-safe area and charge at 0.3A until 3v then try normal charging. Any advice?

BTW I put my battery in the fridge at about 0 celcius to preserve it, is this ok?
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Old Jan 05, 2012, 01:18 PM
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United Kingdom, England, Redcar
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Ive charged my batteries under the Nimh setting at 0.1 amp until 3.0v then swapped the charge setting onto lipo and balance rather than charge , takes ages but so far luckily its worked and ive not noticed any power loss yet..............................................
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Old Jan 05, 2012, 02:33 PM
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Originally Posted by scousethief View Post
Ive charged my batteries under the Nimh setting at 0.1 amp until 3.0v then swapped the charge setting onto lipo and balance rather than charge , takes ages but so far luckily its worked and ive not noticed any power loss yet..............................................
I did the same thing you did and it does work. But hears the catch. You must have a lipo battery cell tester. Plug that into the battery's balance plug the whole time you are charging it on the nimh charger. Watch the charge in all three cells. If the two good cells reach 4.19 volts before your bad cell reaches 3 volts, THEN ITS OVER STOP THE CHARGE. If you dont you will have a fire on your hands. IF the bad cell reaches 3 volts before the other cells reach 4.19 then you are good to go. And please dont turn your back on the charger.
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Last edited by soulreaper; Jan 05, 2012 at 02:38 PM.
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Old Jan 05, 2012, 03:05 PM
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use the above advice at your own risk...to me batteries are cheap enough not to bother with trying to fix a DAMAGED cell...just repalce the batery. If you do "save" the battery I'd think twice before I used it in a multi rotor...when flying a plane or heli dead stick or autos are an option if the battery dies in flight...with a multi... you just crash

The reason the battery discharged even though you weren't "using" the quad... BEC's draw/use power the second the ESC is pluged in

I have stored my batteries at storge voltage in my Gun room/hobby room fridge(beer and battery fridge) for years now... its set to about 40 degrees F.
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Old Jan 05, 2012, 06:45 PM
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You shouldn't store that deep discharged lipo in the house at all. I'd put it a week into a bin of saltwater (outdoors) to discharge it fully and then into the recycling with it. That lipo is done. Isn't it puffed up when you touch it?
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Old Jan 06, 2012, 03:57 PM
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Well im charging my battery now and so far so good.Its ar 7.5v.Actually something weird happened,at 7v it said batterie full.I changed the charge rate from 0.1 to 0.2 and its continuing fine.Btw my battery isnt puffy at all and the salt water discharge is true or just a joke(in the case I cant charge it)
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Old Jan 06, 2012, 04:00 PM
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Also(this can be because of my b6 clone) voltage is varying between 7.3 and 7.6.
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Old Jan 07, 2012, 02:12 PM
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Originally Posted by soulreaper View Post
I did the same thing you did and it does work. But hears the catch. You must have a lipo battery cell tester. Plug that into the battery's balance plug the whole time you are charging it on the nimh charger. Watch the charge in all three cells. If the two good cells reach 4.19 volts before your bad cell reaches 3 volts, THEN ITS OVER STOP THE CHARGE. If you dont you will have a fire on your hands. IF the bad cell reaches 3 volts before the other cells reach 4.19 then you are good to go. And please dont turn your back on the charger.
If you are worried about overcharging some cells while trying to charge one particular cell, you could just charge one cell at a time by adding wiring to charge an individual cell through the battery balance connector.
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Old Jan 07, 2012, 02:19 PM
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Originally Posted by Theelectronicguy View Post
...the salt water discharge is true or just a joke(in the case I cant charge it)
I have read this in a number of places. The electrically conductive salt water is supposed to slowly leak the charge in the battery until it is out of charge.

I have heard that sometimes quite a bit of charge can be still left after dunking in salt water, so I would still treat a dunked battery with care. Where I live, lipo batteries are dealt with as hazardous waste.
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Old Jan 07, 2012, 02:47 PM
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please elaborate on how to do this, I have just bought 2 x hobbyking 4S 5000 and BOTH are 3.70 V for 3 cells and 1.50 V for one cell. I wish hobbyking had a local shop i'd be in there screaming at them.. oh well cheap and nasty and takes your chances eh?

still please elaborate on how to do this...

cheers

Quote:
Originally Posted by flying-llama View Post
If you are worried about overcharging some cells while trying to charge one particular cell, you could just charge one cell at a time by adding wiring to charge an individual cell through the battery balance connector.
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Old Jan 07, 2012, 11:03 PM
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Originally Posted by jetbootz View Post
please elaborate on how to do this, I have just bought 2 x hobbyking 4S 5000 and BOTH are 3.70 V for 3 cells and 1.50 V for one cell. I wish hobbyking had a local shop i'd be in there screaming at them.. oh well cheap and nasty and takes your chances eh?

still please elaborate on how to do this...

cheers
1. Get a balance connector that mates to the one on your battery.

2. Each cell in the battery has its + side connected to one balance connector pin and its - side connected to another balance connector pin.
Find the pins that connect to the cell that you want to charge
(in your example, the 2 pins that have 1.5V difference between them).

3. Connect your charger to those 2 pins and charge at a rate described earlier in this thread.

For step 1, one inexpensive source of mating balance connectors are various balance plug convertors and extension cables available at HobbyKing and elsewhere, such as

JST-XH 4S Wire Extension 20cm (10pcs/bag)
http://www.hobbyking.com/hobbyking/s...idProduct=9737

Female JST-XH <-> Male Kokam 4S 10cm (5pcs/bag)
http://www.hobbyking.com/hobbyking/s...idProduct=9925

Buy some that have a balance connector that mates to the balance connector on your battery. Then cut the wires to separate the 2 connectors in the extension or convertor cable and connect the charger to the 2 wires leading to the pins that you want.

Hope this helps.
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Old Jan 07, 2012, 11:08 PM
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thats very helpful . Thank you very much.
ill be sure to report back if i survive recharging these 2 lipos. ill be doing it outside for sure !!!!

cheers !
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Old Jan 08, 2012, 04:46 AM
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I think the reason why it ate your battery overnight is the ESCs - if they have linear BECs, they will still draw some amps even when not powering the motors...
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Old Jan 08, 2012, 04:47 AM
let's brm together!
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oh, and the electronics also can take something like 500mA, so 8 hours of sleep is 4Ah...
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Old Jan 08, 2012, 09:09 AM
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Well, unfortunately I have not been as lucky as others.One of my cells is dead but the other two are fine! I going to try to make a 2s pack out of this and im going to ask the seller why the Esc's did not cut power!!!(maybe it thought it was a 2s battery?the total voltage at the beginning was 11.5v so dont think so). 4 amps? That much, then I dont get it. A 3s 5000A battery that's at 11.5v should of gone down to... nvm that's right I even have been lucky because it should of been 3v for the pack and I had 3.5v.
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Last edited by Theelectronicguy; Jan 08, 2012 at 09:19 AM.
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