Wild Dagger cooks my batteries

[martyboy]

I decided to put 2 tamiya super-stock type T motors into my dagger, my local model shop said i would have to change the standard speed controller or it would melt, but decided to give it a go anyway. The speed controller was fine but the battery packs were mega hot and melted the heat-shrink. Then when i ran one pack straight after another it literally blew one of the cells up!! (had used the pack for 5-6 minutes)

Was mister model shop man right about the speed controller is it my cheap speedmind 3000mAh batteries??????

[theshopkeeper]

Nothing to do with your speed controller, at full speed it's a direct connection.

Did you change your plastic bearings in the gearbox for ballraces? If you didn't the extra speed has probably caused them to deform, causing extra strain on the motor, extra current is then drawn and this makes the battery get extra hot.

[martyboy]

Yes i fully ballraced the dagger with the nice teflon blue jobbies so no problem there. any more ideas???

[miramar]

Have you checked if the driveshafts are binding? If not, hold the car so all wheels are in the air, then rotate one wheel by hand. The wheel on the other side should then rotate the other way and there shouldn't be much resistance. If you think the wheels don't rotate easily, compress the suspension (wheels still in the air) until driveshafts are level (in line with wheelaxles and gearbox joints (the outputs)), and rotate again. If resistance is dramatically reduced when compressing the suspension, I would suggest checking if the dampers are the correct length (assembled correctly). Also, if the motor is rotating instead than the "other side wheel" when rotating one wheel, something (probably driveshafts) in the drivetrain is surely binding!

Also, what pinion size are you using? Not the optional 20t pinions, I hope? With the original mechanical speed control and modified motors, you should stay with the original 18t pinions.

[martyboy]

thanks for the replies have checked everything so far but still none the wiser. I always check that everything is rotating fine and regularly clean and grease so cant understand... pinions are standard 18T. friend suggested battery might not be able to discharge as fast as the type T motors are draining it???????

[miramar]

I don't know the Speedmind batteries you are using, but if they are cheap inferior quality batteries (like I believe you indicate yourself), it could in fact be the reason for the trouble you're having. Good quality batteries and a good charger are among the very most important investments and pay off, both financially and technically.

[jozza]

Yep, I would say it's 99% likely to be the batteries. In a heavy discharging state the cheaper cells will get a lot hotter than more expensive ones as they will have a higher internal resistance. The hotter motors will pull a lot more current from batteries and they will get hotter.

I've run Sanyo 2000 and 2400 race packs (niCd) and also Sakura 3000 NimHs in my Wild Dagger and Twin Detonator, both trucks have Magnetic Mayhem motors (23turns) and the cells never get more than lukewarm when running for 20 minutes or so.

Invest in a decent cellpack and it will last years. I'd suggest the Sanyo racepacks, or Modelsport own brand (which use Sakura cells) or the cells which Neil (Time Tunnel Models) sell; I've used all of those and they have all been good.

Also, if you have a good quality peak charger it will keep the batteries in good condition, one with a build in discharger is useful too.