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Old Jul 14, 2012, 06:47 PM
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Help!
Below voltage

I've built a new quadcopter, it's my first, and I'm new to RC completely.

The problem I'm hoping for help with in this thread, there will be others, is my battery.

I've purchased a Swallow AC/DC EQ charger and a Thunder Power RC LiPo 2250mAh 14.8v 4S battery.

When attempting the first charge the charger gave an error of Below Voltage and most of the cells were reporting between 2.5 and 3v.

The voltage would go up very slowly if I left it off the charger but I just left it overnight and there are still two under 3. I've tried changing the charge and V down but still no luck.

I've also tried NiMh but the charger gives an error of wrong battery type.

I've read the sticky but not sure what to do with my setup. It seems this charger is too "smart" to let me do some of the hacks suggested in there.

Any ideas?
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Old Jul 14, 2012, 07:00 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,718 Posts
That was a used Thunderpower battery I guess. New ones come with all cells right around 3.85V. If you can, take that battery back to where you got it and get it replaced. 2.5V is bad!

What's the story on it?

If it's yours forever, set the NiMH for a 9 cell pack and charge at 0.5A till the voltage of each cell is above 3.3v. DO NOT GO AWAY AND LEAVE THE PACK ON THE CHARGER!!!! It must be monitored to prevent overcharging (fire). Personally, I think the pack is a goner......and by the way, watch it all the time, even after it's on the Lipo charger or do it outside just in case. If it starts to warm up or swell, stop the charge, discharge the pack and discard.
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Last edited by hoppy; Jul 14, 2012 at 07:08 PM.
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Old Jul 14, 2012, 07:10 PM
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Hi Hoppy, thanks for the reply.

It is brand new. First use and first charge. Haven't got the quadcopter working properly yet.

When I first received it I tried to put it on the charger and it gave some other error which I can't recall at the moment. A guy at work put his multimeter on it and said it was fully charged. I think it was reading over 14v.
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Old Jul 14, 2012, 07:35 PM
Expo/DualRates = Lack of Skill
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San Diego, CA
Joined Mar 2009
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Did you try to charge it, but don't have the correct adapter for your battery?

A new battery doesn't ship fully charged, they ship at about 3.85V per cell, which is 15.4V for a 4S battery.

You probably measured between 14.8V and 15.4V, and thought the battery was full because it says 14.8V on the battery itself.

Thinking the battery was full, you tried to use it, and ran it dead.

Lithium-polymer cells don't tolerate being below 3.0V very well, especially newer and higher performance cells.

Ideally, you don't want the resting voltage to go below 3.70V per cell.

A fully charged 4S lithium-polymer battery is 16.8V.
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Old Jul 14, 2012, 07:55 PM
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No, I believe I have the right adopter to charge it. My charger came with a number of little adopter boards.

But I didn't leave it to charge so it was most likely half charged.

It seems my charger is too "smart" to do some of these things. E.g. It knows the battery is LiPo and refuses to try and charge in any other mode.
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Old Jul 14, 2012, 08:22 PM
RC Helicopter Pilot
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Joined Mar 2010
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Brand new TP packs come with at about 50% charge (3.85V), never fully charged.
Sounds like you ran the battery right out of the box.
Now you have over discharged it below 3.0V.
The charger doesn't like LiPo that low and will give an error message.

You need to start to charge the pack as a NiMH until the voltage gets up over 3.0V on all cells.
Then switch back to LiPo and it should charge.

You may have damaged the pack.
Always cycle a new pack about 5 times when new.
That would be -
charge at no more than 1C
discharge at no more than 5C to under 4.0V.
Never store the pack fully charged
don't discharge below 3.70V.
Don't drop one on the floor.
Don't store one in a hot place.
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Old Jul 14, 2012, 08:34 PM
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Yep, sounds like that's what I've done.

Now the problem is how try and save it with my charger.

If I set it to NiMH C=0.2A and plug in the battery I still get a "balance voltage is too low error" and constant beeping. Should I just leave it there? Or is the charger doing nothing?
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Old Jul 14, 2012, 08:39 PM
RC Helicopter Pilot
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I don't know anything about your charger.
But it does work with a better charger.
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Old Jul 14, 2012, 09:41 PM
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United States, IL, West Chicago
Joined Feb 2008
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Speed_E

I tried to find a manual on this charger but I can't find one.

Can you select an option to do a direct charge without balancing? If so, you can charge the battery without looking at the balance taps, run it this way for a minute at a low input like .2 or .5 amps, then check to see where the individual cells are. Once you are over 3 volts per cell, turn balance back on and complete the charge at whatever rate you want. Do NOT let any cell go over 4.2 volts!!!

Ernie
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Old Jul 14, 2012, 09:52 PM
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United States, IL, West Chicago
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According to your manual(Found it)
"If the battery charge leads are ONLY connected to the output banana sockets without connecting
the balancing connector on the lithium battery pack at the balancing port on the charger,
the charger should charge or discharge the connected lithium pack without balancing the pack."

This should get your pack recharged, but you need to do it slowly while you monitor the individual cells with a multimeter.

Ernie
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Old Jul 14, 2012, 11:01 PM
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Thanks Ernie b. that's very helpful. I'm trying that now, just holding the leads in thre at the moment.
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Old Jul 14, 2012, 11:26 PM
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Great. That seems to have got the battery charged.

But if I try it with the balance board it doesn't complain about low voltage. Instead it says no battery. Which is what it did when they were both brand new and made me think it was fully charged.

I continued to charge it on the other sockets, not the balance board, until it was 2250mah and about 15.5 v.
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Old Jul 15, 2012, 12:18 AM
RC Helicopter Pilot
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United States, CA, Westminster
Joined Mar 2010
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You put 2250mAh back into it and the voltage was only 15.5V?

That is not good.

A full pack will read 16.80V
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Old Jul 15, 2012, 06:26 AM
3RN13
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United States, IL, West Chicago
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Speed_E

If you have a multimeter, set it to volts and measure the battery.

From the Red to Black lead should be Min 14.8 to max 16.8

Check the cells individually on the balance tap you should read between any two adjacent wires 3.7 to 4.2

If you are within those numbers, hook up your Charge Lead and the balance tap and start the normal balance charge.

Ernie
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Old Jul 15, 2012, 06:40 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
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Once it's over 3 volts per cell. Put it back onto Lipo charge with the balance plugged in, then let it charge in balance mode. It should shut off when it reaches 16.8 as Woodcrafter says. When your using it, use a timer and never let it get below 3.5 volts per cell for maximum longevity. One of those little cell checkers is a handy tool to have to monitor you batts.

Gord.
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