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Model Forum / Radio Controlled / Land Models / April 2007power loss every time
I received an old RC10T from a close friend, for free. It needed some work (new battery, axles, rewiring, cleaning, body mount, etc.). I replaced the old NiCad battery with a new NiCad battery (Tower hobbies 1500 Ultra Sport), calibrated the speed control, and put new batteries in the radio. I charge up the battery, put it in the car, and after about 30-40 seconds of ok performance, the motor has hardly any power- it only spins the wheels if I lift the car off of the groud. I immediately check the battery voltage and it's always good (7.1+V). I cleaned the brushes on the motor. The motor runs fine when I hook it up to my batteries in my radio (as an alternate power supply). I can't figure out why it dies? I don't want to replace the motor unless I know it's the problem. The charger is older too, but seems to work fine. What shoudl I do? > I received an old RC10T from a close friend, for free. It needed some > work (new battery, axles, rewiring, cleaning, body mount, etc.). I [quoted text clipped - 9 lines] > unless I know it's the problem. The charger is older too, but seems > to work fine. What shoudl I do? Could it be that the ESC is getting hot? Do you have another battery pack to try? I would do just as you have done, and when it loses power, let it sit and cool (maybe help it a little if the ESC has a heatsink, cool it with some canned air, try the motor also) and see if it gets it's mojo back. Check the voltage coming out of the ESC when it loses power also. Replace the motor?..... The motor has no load when hooked to other batteries for testing. Or possibly ,cycle the battery a few more times making sure that a single cell in the pack is hotter than another. > I received an old RC10T from a close friend, for free. It needed some > work (new battery, axles, rewiring, cleaning, body mount, etc.). I [quoted text clipped - 9 lines] > unless I know it's the problem. The charger is older too, but seems > to work fine. What shoudl I do? errr...should read *NOT* hotter (meaning shorted cell) > Replace the motor?..... > The motor has no load when hooked to other batteries for testing. > Or possibly ,cycle the battery a few more times making sure that a single > cell in the pack is *NOT* hotter than another. On Apr 9, 4:17 pm, atr...@verizon.net wrote: Thanks guys. Here's the latest: None of the battery cells seem hotter than the others. I haven't checked the esc for heat, but thought it may be the problem. I did notice the car runs fine again (for 30-40 seconds) if the car sits, w/o charging the battery again. I'll check it again, but closely. I'll also hook the battery directly to the motor, with it in the car and see what it does with a load. I checked the voltage at the motor and it seems fine, but that was w/o a load (motor not hooked up). I don't have another battery to try, but I may bight the bullet and purchase a new or used ESC. I'll be looking for a Futaba MC230-CB. > On Apr 9, 4:17 pm, atr...@verizon.net wrote: > Thanks guys. Here's the latest: [quoted text clipped - 9 lines] > I don't have another battery to try, but I may bight the bullet and > purchase a new or used ESC. I'll be looking for a Futaba MC230-CB. What connectors are you using between the battery and the ESC? Tamiya type connectors are notorious for voltage loss/drop. ( http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXGG99&P=ML ) Try some Deans Ultra type connectors if your not using them already. ( http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXKX39&P=ML ) What sort of motor are you using with what brand/model of ESC? Running a hotter/faster motor than the ESC is permitted will cause the slowing down problem or will eventually blow up your ESC. Poor solder joints can also be the cause a power loss. With the new brushes in the motor, did you run the brushes in? Some times with new brushes they need to be run in without a load for a few minutes on low power (2-4 volts) before they seat into the commutator properly. If the motor can be rebuilt you can also try pulling the motor down and clean the commutator. I use a pencil eraser and sometimes some very fine wet & dry sand paper to clean the commutator. If its a stock type motor try putting some oil on the bushings at either end of the motor. You can also try Integy Power Drops or Duratrax Power Shot Motor Cleaner which helps clean the commutator and gets rid of most road grime in the motor but you should oil the bearings/bushings after using either of these. Good Luck! Thanks for the great info. I am using Tamiya type connectors. The performance is good for 30-40 seconds...would the connectors cause the voltage to gradually lower like that? The motor is nothing hot. It's a "econo-stock". Nothing fancy and I believe it came with the car. The brushes aren't new. I just cleaned them- with contact cleaner. It's seems to run fine on the battery. I've got some more testing to do. I get the feeling it is the ESC. Thanks again. Still sounds like motor to me is just worn out... I have a motor (Rush 10T) that is in the parts bin which had almost the same exact symptoms. Motor would scream for a minute then go flat... Why not just plop down $20 for a cheap motor.. > Thanks for the great info. I am using Tamiya type connectors. The > performance is good for 30-40 seconds...would the connectors cause the [quoted text clipped - 9 lines] > > Thanks again. http://www2.towerhobbies.com/cgi-bin/wti0877p?&L=MOTR.html > http://www2.towerhobbies.com/cgi-bin/wti0877p?&L=MOTR.html I may replace the motor, even if it's not bad, but I'd like to definately find the exact problem. The motor doesn't make any noise and will run for much longer than 30-40 seconds when hooked directly to the battery. When your motor died out, would it run again after sitting for a while? It's all a mystery... Thanks again! Yes. After cooling for a bit the motor would then again scream (like it should) for about 1 minute then go flat (run real slow). > > http://www2.towerhobbies.com/cgi-bin/wti0877p?&L=MOTR.html > [quoted text clipped - 5 lines] > > Thanks again! Also, a motor will be alot cheaper than a new ESC if you want to find out the exact problem. Try a cheap Team Orion or Peak Performance or similar motor.. (less than $20) Find out what ESC is installed and it's motor handling capacity, so you don't get too hot of a motor for it. > Yes. After cooling for a bit the motor would then again scream (like it > should) for about 1 minute then go flat (run real slow). [quoted text clipped - 8 lines] > > > > Thanks again! Well others brought up the motor, I too think thats what it is. Its sounds like the brushes are worn. You say its a "cheap" stock motor so most likely cant change the brushes, Correct? Next time it happens pull the throttle and give the truck a good kick in`the rear (seriously) and see if it takes off. Doing this will cause the brushes to move just a bit to make better contact. If it does take off you just figured it out. It's a cheap motor, but I can remove the brushes. Getting replacement brushes may be another story. The ESC is an old Futaba MC210CB. What M78Ultra described (1 minute then flat/slow) is exactly what I'm experiencing. Does anyone have any suggestions for a mid priced motor? I'm not racing it, but would like to have fun with it and have it last. Thanks again! According to the info I find online...It appears the ESC you have has a minimum or can support down to an 18T motor. Like I said before..just order a cheaper motor to test it out... now you know that the "hottest" motor you can get with that ESC is an 18T.. I would simply try your choice of a 19T double wind on it.... such as... http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJBX7&P=7 http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXJHH5&P=7 It's all just my opinion though.... =) http://manuals.hobbico.com/fut/futm0921-manual.pdf MC210CB (esc) NON PROPO REV (brake/rev) 1/92-7/00 (prod. dates) 1.79x1.63x1.02 (unit size) 18 (minimum # of turns) 2.55 (weight) 7.2-8.4V (capacity voltage) 142A (cont.) 568A (surge) 0.0062 (drain) BUILT IN FUSE (misc) > It's a cheap motor, but I can remove the brushes. Getting replacement > brushes may be another story. The ESC is an old Futaba MC210CB. What [quoted text clipped - 4 lines] > > Thanks again! That was a close one! There are seller out there claiming the esc will handle 14 turns, but you and others have confirmed it is 18. http://tamiyaclub.com/CS/forums/thread/210248.aspx I almost ordered a motor last night, but wanted to respond to this post first. I ran the motor for one minute, until it slowed to a crawl, then IMMEDIATELY hooked it directly to the battery....and it still crawled. I'm 99% sure it is the motor that is the problem, and the esc is fine. I have my eyes on the mid priced 18-21T motors. What effect does the number of turns have? I'll be ordering a motor this week and I'll post the results here. Thanks! have you connected it to the same battery or other battery? it could also be some problem in your battery or not? > That was a close one! There are seller out there claiming the esc > will handle 14 turns, but you and others have confirmed it is 18. [quoted text clipped - 11 lines] > > Thanks! Unfortunately, I only have one battery, but it's a brand new battery and the voltage checks out fine after I run the motor down after 1 minute. Thanks. > Unfortunately, I only have one battery, but it's a brand new battery > and the voltage checks out fine after I run the motor down after 1 > minute. > > Thanks. It could still be the battery. Have you checked the voltage while the battery is connected to either the esc or directly to the motor. Nicad batteries are resilient for coming back up to their said voltage after being disconnected from the car. My racing packs go straight on a discharger when I've finished a race and if the packs dump during a race the voltage will always show 7.1 - 7.4 volts, but when I press the button on the discharger they will quickly drop down to 5.4 or below volts. What brand/model charger are you using to charge battery pack? Your charger could be the problem if the battery pack isn't getting full charge to start with. New battery packs sometimes need a few charges before they come to life. Something else you could try to make sure its not the battery or charger at fault is to do a little load test of the battery pack. Get a old head light globe from a car (I use a 100 watt Halogen globe) and with the volt meter connected to the fully charged battery pack, connect the headlight globe. Depending on the watts of headlight globe you should be giving the battery a discharge of similar values as the car would be when running. Check the time it takes to discharge the battery (when the light dims and the voltage drops). If its similar or equal to the run time of the car then its most likely the charger or the battery pack at fault. Also once the light dims disconnect the globe and watch the volt meter, you should see the volts jump back up. Sorry to be so long winded but I would rather you rule out all other possibilities before you definitely say its the motor. The battery is a brand new Tower Hobbies 1500. I have an older charger (I don't have it in front of me now- at work). I will definately try the test with the 100 watt halogen globe. Thanks! Well, I couldn't find my headlamp, so I propped up the a.s end of the car and ran it down to a crawl, checked the voltage at the motor and it was 5.2V! It sprung back to 7+V afterwords. It's a brand new battery, so.... should I run the battery down with a light bulb then recharge it? I'm getting a new charger too, even though the oooold one seems to be working fine. It's probably tired too. I think I've got it!!!! Richard and Ultra were right (but all answers are appreciated)! I ran the battery down by hooking it to a light bulb, then charged it up. The truck now runs like a bat out of hell, blowing donuts on my basement floor, and without slowing down after several minutes. The new battery came to me somwhat charged and I through it on the charger before running it. The cycling was the fix. Thanks to everybody! Now I'm going to install the CV axles and will probably go ahead and upgrade the motor. Except from RCCarTips.com "Big "Comm" versus Small "Comm" In general, big commutators provide more torque while the regular size commutator provide more rpms. Big comms - High load, high current applications. Off-road racing. Small comms - High rpms, lower current applications. On-road racing. ---------------------------------------------------------------------------- ---- Number of Turns Refers to how many times the copper wire is wound around each pole of the armature. Basic guide: More Turns (e.g. 19T) = Higher torque, less rpm, longer battery life. Slower but easier to drive. Less Turns (e.g. 12T) = Less torque, more rpm, shorter battery life. Faster but more difficult to drive. ---------------------------------------------------------------------------- ---- Number of Winds Besides the number of turns, the number of winds refer to the number of wires wound around the armature. Basic guide: Single Wind = Most bottom end power. Power is achieved at lower rpms. For short racing tracks with a lot of turns. Double / Triple / Quad = Less bottom end power. Power is achieved at higher rpms. For long racing tracks with long straights. ---------------------------------------------------------------------------- ---- Comm Drops Usually designed to increase power in stock motors, and usually increases rpms. But using commutator drops would require frequent motor rebuilding. Use only a few drops before each run, and clean the motor with a high quality motor spray after each run. ---------------------------------------------------------------------------- ---- Hand versus Machine Wound The method of wrapping wires around the armature is either done by a machine or a human being. Hand wound - More precise, more power, more expensive. Machine wound - Less precise, less power, less expensive." > That was a close one! There are seller out there claiming the esc > will handle 14 turns, but you and others have confirmed it is 18. [quoted text clipped - 11 lines] > > Thanks! Wow! Thanks for taking the time to post all of that great info. No I know what to look for. THANKS!!! at last. apart from the results i still don't understand turns and winds. ho hum : Except from RCCarTips.com : [quoted text clipped - 51 lines] : : Machine wound - Less precise, less power, less expensive." |
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