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Old 06-24-2011, 10:11 AM   #1
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Default Low voltage lipo....need help

Hi,
I was trying to charge my 7.4v 2cell 30c Turnigy 5000mAh lipo on my Imax B6AC charger but the LCD screen indicate low voltage....

The lipo battery is brand new...is there anyway to save the battery...thanks
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Old 06-24-2011, 02:37 PM   #2
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Do you know the voltage of the battery ?

You can do the following to try and recover it

Set the charger for nimh mode
Charge the pack at 0.5 amps
Watch the screen and stop when the voltage reads 6.5v
Stop the charge
Change back to lipo mode
Charge as you normally would

Keep a good eye on the pack as you may have done permament damage


Cheers
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Old 06-24-2011, 05:56 PM   #3
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You got a bad lipo - the voltage should never be so low on a new lipo that your charger won't change it. I would take it back and get a good one if you can.


The above rescue method will should work, but the lipo will not perform as good as it should.
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Old 06-25-2011, 02:23 AM   #4
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Are you sure its the lipo, I got some new lipos the other day, tunigy 5200 7.4 2s, and when I tried to charg at 5.2amps my power pack could only deliver 3amps and the charger was giving me a voltage error. Just a thought?
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Last edited by driftcrazy; 06-25-2011 at 04:44 AM.
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Old 06-25-2011, 04:15 AM   #5
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Default Low voltage lipo....need help

Thanks all...

I will try out the slow charge later tonite...
Not sure if it's a bad lipo..

By the way what is the setting for charging the battery
1. Lipo discharge
2. Lipo storage
3. Lipo fast charge
4. Lipo balance
5. Lipo charge

Regards

Md Natsir
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Old 06-25-2011, 04:40 AM   #6
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LIPO BALLANCE (if you have balancing a plug which is seperate from the power cords) ensures your cells are charged evenly. When you select it it should give you the option of setting the amps. Ideal amps is whatever the mah rating is by 1's, so 2200mah would be 2.2amp or 5000mah is 5.0amps. then check that it is the right volts, 2s is 7.4v, 4s is 14.8v. then confirm and start the charge.
Having said that make sure your power supply can deliver the amps you choose.

LIPO FAST CHARGE is just that, a quick but unbalanced charge.

LIPO STORAGE is for when you know your not going to use the lipo for a while and keeps the cells in a stable state.

these are all you should need to use for now.

from memory on that charger you use the arrow key to select and confirm and the plus and minus keys to set the values.

hope this helps.
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Old 06-25-2011, 05:26 AM   #7
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There is no need to discharge lipo - that's a waste of lipo finite cycle life. If you've got a good charger, lipo storage mode will discharge the lipo if voltage is above storage voltage (~3.85v/cell) and charge it to the storage voltage if its below - this is the only time lipo should be discharged on a charger. Beware that most chargers have a very small discharge watts and discharge current so if you put a fully charged lipo on storage mode , it may literally take days to get it down to storage voltage - discharge it in the RC, its much faster.

You don't use lipo charge since that doesn't include balancing - this mode is for lipos that have no balance wiring (still some made this way...). Lipo balance charge mode will provide the safest method to charge the lipo and is the only way you should be charging them. This charges and balances the individual cell voltages - you hook balance wires and main power wires up at the same time.

Lipo fast charge - this basically is for racers when charging between heats and it doesn't provide a full charge. No real reason to use it if there's time for a full charge.

Lipo charging is set by the C rate recommended by the lipo manufacturer. 1C = capacity(mah)/1000 so for your 5000mah lipo, 1C charge rate = 5000/1000=5amps. If you charger can supply high charging currents, and the lipo manufacturer recommends higher than 1C charge rates, then you can charge at 2C, 3C etc up to the recommended max. I have some 4s 5000Mah Turnigy's that I charge at 3C (15amps).
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Old 06-26-2011, 01:35 AM   #8
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Default Low voltage lipo....need help

Thanks everyone for the great help....I manage to charge the lipo after the low nimh charge to 6.5v...hope it will last...
So how do I prevent this from happening again....thanks
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Old 06-26-2011, 01:49 AM   #9
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Make sure your esc's lipo low voltage cut-off is on and if your not going to use the lipos for a while run a lipo storage mode on your charger.

Glad you got the help you needed.
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Old 06-26-2011, 07:09 AM   #10
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Default Low voltage lipo....need help

Currently I am using the Xerun 80A V1 esc to run my Emax and Summit...the esc low voltage cut off range is between 2.6v to 3.4v...I am not sure which one to choose.
I was thinking of getting the voltage checker to monitor the lipo...thanks
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Old 06-26-2011, 08:32 AM   #11
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I run a Castle MMM and use 3.4v/cell as a cutoff - this is for a Sav Flux, have another in a FLM Ext EMaxx set at the same value and a 3rd in a G2R set at the same lvc.

I run 5000mah 2S lipos x2 and with this cutoff, I typically see 3700-3900mah going back into the lipos on recharge staying comfortabley below the 80% guideline.

These heavier MTs need a higher lvc - that way they don't overdischarge lipos.
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Old 11-25-2011, 05:25 AM   #12
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Default Lipo 11.1 V

I am having the same problem with a 11.1 V 3S battery. The Imax b6ac says "Battery Check: Low Voltage". Do I follow the exact same instructions as the above and stop charging at 6.5 V? Or should I stop at 10.5V?

Thanks for your help in advance.
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Old 11-25-2011, 05:32 AM   #13
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Stop it at about 3.2V/cell, which for you is about 9.6V.

Monitor this closely. Charging a LiPo on NiMH is dangerous. If you walk out and forget it, you can burn your house down.
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Old 11-25-2011, 05:49 AM   #14
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If the lipo is new, I'd take it back and get one that doesn't have a voltage prob. This one will not be as good as one that started life without this prob.


If you have to, following the above should get it chargeable as a lipo when voltage is up over +/-9v. When I rescue lipo like this, I charge to 3.1v/cell before switching over and charging as a lipo.
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Old 11-25-2011, 06:22 AM   #15
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Thanks for the quick reply. Think I'll exchange it for a new one!
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