jigeye

I have a 5600 mah/ 7.4V Lithium Ion Battery. I have a Hangar 9 Voltmeter which can put either a .5, 1, or 1.5A load. I have a Triton Jr. charger of which I am familiar.
I understand I am not supossed to fly when the voltage reaches 7.4V {to be on the safe side}.
Which load should I put on this battery to check the voltage?
When I check it with no load it's 7.9V. When I put a 1A load on it it's 6.9V. Does this mean I should not fly?

B.L.E.

Sounds to me like it's time to retire those batterys if the internal resistance is so high that you get a 1 volt drop with only a 1 amp load.

KC36330

most 7.4v Li-Ion have a stop flying voltage of 6.9 with a 1amp load.

kc

BarracudaHockey

My Feedback: (11)

Lithium batteries life cycle starts the day they are made, every thing over 2 years or so use is gravy.

Sounds to me like they are shot, mine charge to 8.4 and run around 8.1 to 7.9 with 1amp load on them and will stay that way quite a while.

sawdust

My Feedback: (7)

Are your batteries fully charged when you take your voltage reading? If not charge them up and take another reading. Fully charged for a 2 cell pack is 8.4 volts.

A good battery that is nearly discharged will show a large voltage drop with even a small load.

bob

jigeye

I tried charging it today with the Triton Jr. Since the battery is 5600 mah/ 7.4v I sat the charger for 5000mah/7.4V. It would only charge to 8.04V before cutting off. After this, I put a 1A load on it and it showed only 7.58V. I then tried charging it with less mah {2600}. It went about 5 min and stopped. Same deal 7.58V reading with a 1A load.

I wanted to make sure it was not in the way I was charging, but apparantley this battery is spent.

sawdust

My Feedback: (7)

Do you have the charger safety charge time set correctly. You want to make sure that it is not timing out before the full charge. If you charge at the 5000 7.4 rate that will take just a little longer than 1 hour to charge the battery if it is nearly discharged. If they will not charge to 8.4 volts the batteries are probably no good.

Be very careful charging these batteries. Make certain that they do not get hot or that they are not swelled. Charge outside on concrete.

8.4 volts is the voltage of a fully charged 7.4 lipo pack. Under load the pack will drop below 8 volts in a short time. But they should stay within the 7 volt range for most of the run time. Most ESCs for a 7.4 LIPO are set to shut off the motor at 6.0 volts.

Go to one of the suppliers like FMA Direct and look at a discharge curve on a 7.4 LIPO pack. They have some 4800 mah packs. You will note the initial drop at the beginning and then the discharge will be flatter, and then at the end a big drop. These curves are generated using a substantial load on the battery.

The problem with weak LIPO batteries is that they can go completely bad and cause loss of control. And they are dangerous when charging. So be careful.

What happens when you run the motor on these batteries? If you have the ESC set correctly it will shut down the batteries at the correct voltage.

Is there someone in your local area that can help you analyze your batteries using a different charger?

Be careful.

bob

KC36330

lithium batteries when charging use a set voltage for the turn off point, not a peak detection like NiCd/NiMh, if the Triton Jr is cutting off you've reached the chargers set voltage (could be wrong but likely not). 7.58v w/ a 1amp load is acceptable as a fully charged battery, i would however use the Triton Jr to cycle it to 6v and check the capacity of it after you let it sit for several days at full charge. if it cycles 80% of the rated capacity, use it.

kc

a65l

My Feedback: (17)

I think Bob is right. It dosen't matter if the battery has reached it's peak voltage or not. I don't recall if the Triton sets cutoff time based on battery capacity or not. That might be the pro elite.....

Andy