Archive for the ‘RC Stuff’ Category

Why you shouldn’t buy batteries from Ebay…

Monday, February 16th, 2009

So i bought the drifter and i bought a couple of 7.2v packs from the LHS for about $40 each – they were 3600mah batteries.  Good but expensive (for a cheap drifter anyway).  So, i spotted an ebay store based in Hong Kong that was selling 2 X 3800mah Ni-Mh packs at about AU$40 for the two posted.  It seemed like a pretty good deal so i thought what the hell.  I mean, it’s not as if i need special ‘super power’ racing packs anyway as the car is not raced as such.

I buy items from HK all the time so i had no hesitation.  My Heli’s, parts and most of my Maxx parts all come from HK and i have never had any problems with the service.  Infact, i’ve had more problems with local sellers on ebay than i have with international ones…

Anyway, 7 odd days later I got the two packs in the mail.  Generally the first charge should be for 10+ hrs at 1/10C or 380ma in this case.  I done that, the packs got warm as they should and nothing more.  So, i popped one in the car and went for a drift.  It seemed ok but didn’t last very long – about 5 mins which is pitiful.  The other pack was the same.  So, i slow charged them both again and gave it another shot the next day – Same result.  I have never experienced this type of problem with battery packs so i messaged the seller with a general question of ‘How many cycles should these batteries need to achieve full capacity’.  They replied with a generic text along the lines of ‘make sure you charge for 10hrs before use’.  I was not overly happy with the reply but i thought i’d just stick with them for a bit and see what happens.  After about 10 cycles and now using my smart charger at 1c rate (3.8A charge), the batteries would still only take about 1200mah.

I went to message the seller again but it seems that they are ‘no longer a registered user’.  Odd since they had been a member since 2004.  At about the same time I happened to notice that the 3800’s seemed to be much lighter than my 3600’s.  I was starting to suspect that perhaps they were not 3800 cells.  So, with the seller no longer active, beyond 60 days for buyer protection and the cost of a return likely to be at least half the cost of a new battery i decided to crack the heatshrink on the pack to inspect the cells.

When i finally cut through the two layers of shrink wrap i expected to see something dodgey but nothing prepared me for this!

battery_assembled1
battery_opened

That’s right, NO WHERE NEAR 3800mah at 1300mah and not only that they are Ni-CD cells, not Ni-Mh!!!  Buyer beware!  This could have caused huge problems.  I was charging this battery at 1C (3.8A) when it is not really supposed to be charged at any more than 1.3A.  If this had caused a fire or explosion I could have been in serious trouble.  Not only that, it’s complete fraud. I’m not really sure how you could avoid getting these dodgey packs other than staying away from these generic ones completeley.  My guess is that most of the cheapies on ebay are probably all from the same factory and just labelled differently.  Either that or get a 100% money back guaruntee that the packs you are buying are definately of the specified capacity and chemistry.  

If the seller resumes business then i will supply thier ID to anyone who wants it, otherwise just be very careful.

Another toy

Thursday, February 12th, 2009

Over the xmas break i decided to invest in another RC toy.  I love my t-maxx truck but it’s noisy, messy and generally costs a lot to keep it running.  So, i thought i might have a go at an electric car and one step more – a drifter.  I managed to pick up a brand new Tamiya TT-01 chassis off ebay for about $100.  Throw in an ESC, steering servo, RX and a battery and you have a running car.  After that just bolt on some drift wheels and you’re up and drifting.

The advantage i saw with drifing is it’s low speed.  Low speed = less damage when you hit something = cheaper to run.  The other advantage is that you can drift with a real stock crapper, there is no need to do untold amount of upgrades to get it to drift well.  The stock Mabuchi 540 motor does the job fine and there is not a lot of advantage in going for more speed.  Drifting needs torque and not speed – I’ts more about driver skill than how many $$ the person has spent on the car. There are some minor upgrades that come in handy however, notably the shock absorbers.  On the stock TT-01 they are just friction types.  I swapped these for some oil filled dampeners and this has made a significant improvement to drifting.  You also really need to lock both front and rear diffs (nothing a bit of knead-it can’t handle)

Unfortunately the drift scene seems to have almost depleted totally from what it used to be at Hobby Habit here in South Australia.  I remember going to a ‘drift night’ there a couple of years back and there was probably about 30 cars.  It was awesome.  Now, unfortunately there are only about 5 compeditors in the drifing and the drift meet is now only part of thier friday night Hyper10 Racing as a time based event wich is somewhat pointless for a drifing comp.  It’s still great to go there in practice time for some fun though.

Tim and I went there a few times and it was soon apparent to Tim that he needed one too so he bought one not long after i did.  It’s very challenging but even more fun….

If anyone in the southern adelaide suburbs is interested in getting into drifting and/or would like to meet up for some drifting, post a comment here