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esc or 3 bad battery packs?

Old 08-18-2003, 12:44 PM
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Frag
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Default esc or 3 bad battery packs?

I have a Soarstar in the garage that I haven't flown in a few months because the past couple of times I've tried to fly it, it will barely gain any altitude. Actually it won't gain any and I have to practically land instantaneously. It used to fly great for a e-trainer! It all started when the motor began to pulsate at full speed, going very quickly off/on/off/on. So I figured maybe the brushes were the problem. I did the underwater motor cleaning/run-in and that fixed the pulsating. But, it still didn't want to fly well at all. Just not enough umph! So, I built a new 1600mah nimh pack. Maybe it was just to heavy for the Soarstar....no gaining altitude with that either. So, I have the original 600mah nicad pack, an SR Batteries 1000mah nicad pack , and the 1600 nimh pack I made. All of these fail to get the plane more than four feet off the ground. I replaced the motor with oe . I'm charging with a MKII Hobbico field charger set at >1C for all the packs. Any ideas?
Old 08-18-2003, 01:04 PM
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sierra gold
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Default esc or 3 bad battery packs?

My first impression on reading your post is that the ESC was cutting the battery off due to low voltage. Maybe packs that weren't fully charged?

Of course, a faulty motor might draw too much current and cause a voltage drop that enables BEC for a moment.

It's odd that "cleaning the motor" seemed to fix the problem of it cutting in and out.

If I were in your position, I would buy a new motor and try it. If the problem goes away... it was the motor. If not, you now have a spare motor. I always have one available for "testing" or replacement.

The same logic/procedure could be used for the ESC also. Maybe you could borrow one from someone or purchase one as a spare or for a second plane.

The packs could be tested on a friends plane for good operation/fully charged.

Hope this helps.
Old 08-18-2003, 02:30 PM
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Default esc or 3 bad battery packs?

Thanks SG-

I did replace the motor with a new one to no avail. I'm thinking a couple of things. One, the esc is somehow not 'allowing' max current to pass to the motor. Or two, all three battery packs aren't getting fully charged for some reason. I just find it hard to believe that all thee would develop the same problem at the same time. I've been using the same charger all along and the packs used to do great. Do esc usually fail competely/catastrophically, or can they slowly go bad over time?
Old 08-18-2003, 02:44 PM
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Default esc or 3 bad battery packs?

Does your charger allow you to discharge the packs and then charge them? Does it display digital amount of ma it charged back in?

I had a pack with one bad cell and it manifested itself by not allowing full throttle w/o cutting out, but it would run OK at 3/4 throttle. Not quite the same, but similar.

What ESC are you running?

Sierra Gold
Old 08-18-2003, 02:54 PM
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Default esc or 3 bad battery packs?

No, my charger doesn't display what ma it puts back into the pack. I think what I'm going to do is discharge the packs down and slow charge at 50 ma for 15 hours or so with my Futaba tx/rx charger. What would the typical volts be in a typical 8 cell nicad and 8 cell nimh at full charge?

I can't remember exactly what esc I have, it came with the radio and Soarstar. I tried looking it up on the net in the past but could never locate the maker using the info on the sticker from the esc.
Old 08-18-2003, 03:03 PM
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sierra gold
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Default esc or 3 bad battery packs?

Right off the top of my head... about 11.5 volts. Something close to that, anyway.

AeroMicro has decent prices and very fast service on brushed ESCs:

http://www.aeromicro.com/Catalog/esc...3_products.htm

Good Luck!
Old 08-18-2003, 03:09 PM
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Default esc or 3 bad battery packs?

A 50mah TX charger will work for your 8 cell packs, but 15 hours will only be enough to charge your 600mah pack fully discharged. (actually, you'd want to go about 17 hours at that rate).

The bigger packs would take significantly longer. Use this formula to figure it out. You want to put 140% of the rated capacity in to a completely discharged pack for a slow charge at C/10 rate.

For your 1000mah battery, 140% would be 1400 mah. Divide this by your 50mah charger and you'll get your necessary charge time... 28 HOURS!

If you have a charger that will charge at C/10 (100mah for your 1000mah battery) it will save you some time.
Old 08-18-2003, 03:52 PM
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Default esc or 3 bad battery packs?

How about if I hook the packs to my 'quick' field charger and set the charge rate to .10 amps (its lowest setting). You think that would be slow enough to equal out all the cells?
Old 08-18-2003, 04:04 PM
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Default esc or 3 bad battery packs?

I'm thinking that 0.1 should work.

Are you near Columbus? I did 5 lovely months at Ft. Benning in 1966. Whew, hot and humid and lots of red dirt! Said I could never live anywhere with red dirt and I ended up here in the Sierra foothills with... red dirt.

Sierra Gold
Old 08-18-2003, 05:33 PM
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Default esc or 3 bad battery packs?

Hey SG -
I'm just 30 min. south of Atlanta, but we have plenty of red Gawga clay too!

I'll give the .10 A a try this evening-
Old 08-18-2003, 07:43 PM
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Default esc or 3 bad battery packs?

.1 amps is 100mah. Use the 140% figure to calculate how long to charge a fully discharged pack. Be sure your field charger does not shut off after a certain amount of time. Some chargers have a "timed" charge.
Old 08-19-2003, 10:58 AM
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Default esc or 3 bad battery packs?

How long is the charger charging when you charge at 1C? It should charge the packs for approximately an hour. At the very least, it should go for 30-45 minutes for a partially discharged pack.

Check your charge leads. Things can loosen up over time.
Old 08-21-2003, 11:21 AM
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Default esc or 3 bad battery packs?

Matt, at 1C the charger does operate for about the time you state. It does have a timed cut off according to the description at Tower Hobbies, but have never seen this funtion kick in. It is a peak detection charger, the Hobbico MKII. I haven't tried recharging the packs yet(!) because I've been building a Vector Flight Sukhoi the past couple of evenings. I'll let ya'll know if it works soon.
Thanks-

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