Sidewayz

I have, so to speak, dusted off the cob webs off my TC3. I have brand new batteries in my Lynx 3channel controller (8x Nimh 2500Mah), my 6X C cell Nimh 3300Mah seem to be charged ok.

I think i'm having troubles with my ESC which is a Duratrax 8T pro. I did a bare test run (only ESC, battery pack hooked up) and within a few secs the motor practically died on me.

Battery connections seem warm to hot, hitting the trigger upon first connection was ok but within a few pulls it lost power.

ESC has acted "funny" the last time i used it ie press the reset/program button but it did nothing, along with a few other issues but mainly loss of power.

So my question is, what's the best way to test the ESC and what would be a good replacement if it's dead? I don't race but would like to have a bit of fun.

Sending to Duratrax for servicing isn't really an option due to high postage ( i live in Australia), can someone please help?

zaphod42

My Feedback: (3)

How long did it sit? Could the motor bearings or such have dried out? If you have another motor try that with the ESC (no need to mount it in the car - just hook it up) before you go for an ESC. You could also have any of the bearings in the drivetrain hanging up - move the motor so the gears don't touch and see if it spins freely. You can also turn the motor (you will feel the cogging but it should turn OK once you overcome the magnetic field for each step). If the battery connectors seemed hot but the ESC didn't get hot it may not be the ESC.

Sidewayz

Yeah i have the car apart, was testing just the ESC and motor. Tried again today and it seems to be working ok with my 27T but my 14T doesn't. Looking back i remember taking apart the 14T because i couldn't get one of the screws out that holds the cam to the motor (allen screw was rounded off), it was working before i opened it. Any tips on how to remove a stubborn rounded off allen screw?

One thing that does worry me a little is the charge time for my 3000Mah.....(it's not 3300Mah) it seems to charge too quickly. I have the charger set on 2Amps which was the same the last time i used it (about a year ago) but i remember it took quite a bit longer to charge. What type of charge time should i expect if the battery pack is in good condition?

I also bought a set of matched 3600 singles that needs to be put together, are solder tabs really necessary to use or can i get away with using wire instead?

Lastly why doesn't the button on the ESC seem to do anything? When i hold it down, the green light stays on. Doesn't appear to do anything if i press or hold the button.

BTW, thanks for the reply and help.

zaphod42

My Feedback: (3)

The charge time for a discharge 3000 mah pack at 2 amps should be 1.5 hours (3000 milliamps = 3 amps / 2 amps = 1.5 hours). What has likely happened is that the cells self-discharged to the point where you need to start with a good base charge again.

Like any battery that has gotten fully discharged or is new off of the shelf you will have to slow charge it the first time or two to re-equalize the cells. If you charge it at about C/10 (where C is battery current capacity - IE: 300 mah for your 3000 mah battery) the cells will all get a chance to get equally charged and then the battery will act better. It takes some patience - it will take 10 hours or more for a full charge but the pack will perform much better for it. I'll explain the reasoning below.

When a battery reaches it's full charge the current going into it only serves to create heat. When you charge at a high rate your charger will read a peak when the first cell gets hot and starts creating a negative delta voltage when the pack isn't equalized (it's a long winded explanation of that - I'll go into it if you want me to).

The cell that reaches full first will build up heat quickly and may get damaged and the rest won't get a chance to get full. When you slow charge then when each cell reaches it's capacity it can dissipate the extra heat without damage and without tripping the peak detection until several of the cells are full so they all get more or less the same charge. Two or even three slow cycles is best if you have the patience - that way all of the cells will be equally full and they will play together better for fast charging later.

This applies both to packs that have been stored for a long time and gone flat and especially for new packs (it is a good idea to start with the cells equalized so none of the cells get too hot). Heat is the main enemy of NIMH cells and the most likely time to damage them or shorten their lives is when charging too fast on unequalized cells. If you run side by side cells (|||||| instead of ===) and can afford a discharge tray that is even better but this will work OK.

Battery bars are better - they will give you structural strength for the pack as well as carrying the current (although you should still glue the cells together with shoe goo or RTV or something).

As far as getting the screw out that depends. If it's a round head try filing off the sides to get flats to hold on to so you can use pliers to get it turning. If it's countersunk or inaccesible try taking an old allen wrench and gluing it into the hole with a metal epoxy (here is the US we have stuff called JB Weld - I'm sure there is something similar there - be careful not to get any on anything you don't want stuck together). It will take probably 4 hours or more to set but once it's stuck it will hold more than enough to remove a set screw (most are rated at 4500 psi or more). You will have to cut the end off of the allen wrench to get it off (or just throw the whole thing away) but that should do it.

Sorry, as for the ESC button I can't help you with that since I'm not familiar with it.

Sidewayz

Thanks for the reply Zaphod,

My charger only allows for 500mA so charging it at 300mA isn't really an option.

Structual strength with the battery pack isn't really a worry, I can use old paddle pop sticks as support along with insulation tape. I don't see how solder tabs vs wire is a concern, do you mean using wire has more resistance? I don't see how this is so.
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With the screw i can't get to the head, otherwise it would be off (had these types of problems working on car engines), using some sort of metal poxy would be a good idea, thanks i'll give it ago.

zaphod42

My Feedback: (3)

One of the advantages of side by side packs is that they dissipate the heat they build up so well because of the majority of each cell's surface is exposed to the air. Using sticks and tape will block all of that possible heat dissipation. Battery bars will definitely also have lower resistance than wire (even if you use 12 gauge wire) - the cross sectional area of the metal in the bars is much higher than the area in wire (think of all the gaps between the strands) and the good quality bars are made of alloy that is a much lower resistance per cubic mm then the standard copper of the wire as well. In top speed you will not notice the difference but given the high current draw of the motors (especially your 14 turn) when they first start accelerating that lower resistance will mean more punch out of the corners. The fall off in performance is probably not enough to be too noticable if you are just bashing but if you decide to go racing modified you will definitely notice the difference.

500 ma will have to do for the initial charge rate - it will really help get your batteries properly set up for future use. As long as you use them regularly after that you can mostly charge at a high rate. (It is a good idea to discharge them to about 0.9 volts per cell once in a while and slow charge them to re-establish the equalization.)