K01S

I'm new to electrics and just got an E-Flite 15 brushless outrunner for a Super Sportster EP. Got a 2100 Mah Thunder Power LiPo battery pack, an E-Flite 40A ESC, and and an E-Flite Celectra 3 Cell Li-Po DC Charger. After I got it I read the instructions, charged up the batteries and did a bench test with the motor, ESC, and all looked good. Got about a 9 minute run from the batteries.

The way the Celectra charger works is that you hook it up to the battery, press a button and teh batteries charge up. When they are fully charged there are a series of 3 beeps that will keep beeping until you disconnect the battery from the charger. The next tiem I went to charge them they batteries just keep charging and charging and I never get the charger to beep to indicate it's done. Looks like a have a problem but I don't know if it's the charger or the battery pack. Any ideas on how I can find out which it is?

I measured the battery pack voltage and it was about 11+ volts so it would seem like all 3 cells are okay, I think!

I'd appreciate any suggestions you might have.

Regards, - K01S

jdetray

K01S-

A fully charged 3-cell lipo pack should measure around 12.6 volts. If yours is only "11+", there is something wrong.

When you did your bench test, what was the voltage of your lipo pack at the end of the test, before charging?

Did you run the motor until it stopped and would not run any longer? If so, there is a chance that you over-discharged your lipo. Does the pack have a balance connector so you can measure the voltage of each of the three cells in the pack?

As a general rule, bench tests where you run the motor for a long period of time aren't a good idea. Static running is often harder on the power system than flying will be, plus you don't have any airflow to provide cooling. It's easy to overheat something.

- Jeff (NK1F)

K01S

Jeff (NK1F),

It's great to hear froma fellow ham!

Yes, there is a balance connector. Can I measure the voltage right at the pins? Yes, when I did the bench test I did run it until it stopped and then found it would run a little more after it would shut down for a while.

I probably have a bad cell now. Is there any way to bring it back?

Thanks for all your help Jeff (NK1F)

73's - K01S [8D]

jdetray

I'm not familiar with the pin-out of the TP balance connector. But yes, you can measure the individual cell voltage using those pins, if you can determine which pin is common and which ones go to each cell.

You want the cells to measure very close to the same voltage, within 0.1V. If they do not, you can try charging the cells one at a time using the balance connector. If you can get the individual cells back to the same voltage, your pack may be OK.

If the pack was over-discharged, one cell could have been damaged and not be taking a charge. In such a situation, the charger is still trying to charge the pack to full voltage, so it ends up over-charging the good cells.

The first step is to check the individual cell voltages and see where you are.

- Jeff

K01S

Thank you very much for the help Jeff, I really appreciated it.

Regards - K01S [8D]

K01S

I thought I'd close the loop on this topic now that I have some answers. I brought my battery and charger back to the LHS and explained the problem to them. I left it with them and went back today.

It turns out that both the Li-Po battery pack and the charger are working properly. The problem was with the operator (me). It turns out that I mis-calculated how long it would take to recharge the pack. It was a 2100 Mah pack and i figured it would take about 21 minutes to charge at 1 amp. I thought I could charge at 2 amps and have it fully charged in about 10 minutes. Of course I was wrong and the charge time is about 1 hour @ 1 amp and 2 hours @ 2 amps. When I had charged for about an hour at 1 amp I measured 11.1 V and figured it must be charged but in fact teh voltage when fully charged is 12.72.

So everyting is working just fine and I've learned a good lesson. Thanks for your help Jeff. - K01S [8D]

jdetray

I'm glad you found some answers.

One small correction. Charging that pack will take about one hour at 2A and about two hours at 1A.

The maximum charge rate for most lipos is 1C. That's 2.1A for a 2100 mAh pack, 1A for a 1000 mAh pack, 1.5A for 1500 mAh pack, etc.

At the 1C rate, charging ANY SIZE lipo pack will take about one hour.

- Jeff