Dud cell again - part 2 - any ideas??

[Herri]

I have just got back from (trying) to fly my Jodel.

It nosed over on take off (my fault for not having enough up-elevator) on the second attempt it did the same and then nothing worked. I measured the lipos and see there, one of the packs (2x3s 3600mah) was showing zero.

Exactly the same happened on it’s maiden, some months ago and I had to throw an almost new 35C 3200mah 3 pack away.

I thought it was a one off, but obviously not.

Any ideas?

Could it be that when it noses over the prop stops suddenly and the lipo somehow gets an impulse or some thing ? 

 

Cheers

Herri

Edited By David Ashby - RCME Administrator on 02/10/2010 03:55:52

[Steve W-O]

At £60 they are obviously not cheap Chinese batteries (unless someone is making an obscene profit)

 

Take it apart, they often have a small circuit board onto which the cell straps are soldered, along with the balance cables and main cables out to the ESC. I have found some where the cell straps are not properly soldered. Others that may have a dead cell, keep the good ones, and then make up a 4 cell pack, or one good one out of a couple of faulty ones.

[Erfolg]

Herri

 

Do you protect the Lipo at all?

 

I personally, stick some expanded polystyrene at the front, as a cushion.

 

I have seen many electric models crash, by and large the cells survive. A wide selection of cells are used, non seem better or worse than others for crash resistance.

[Martin Harris - Moderator]

Posted by Steve W-O on 01/10/2010 18:09:17:

At £60 they are obviously not cheap Chinese batteries (unless someone is making an obscene profit)

 

Take it apart, they often have a small circuit board onto which the cell straps are soldered, along with the balance cables and main cables out to the ESC. I have found some where the cell straps are not properly soldered. Others that may have a dead cell, keep the good ones, and then make up a 4 cell pack, or one good one out of a couple of faulty ones.

 

 

I must say that many of the more expensive Li-Pos don't seem to be any more reliable than the cheap Chinese ones as far as I can make out.

 

It does make me wonder who actually produces the cells that go into some of the "branded" packs?

 

I've certainly never known a battery to be damaged from a sudden short motor stall - I would have thought the ESC would have been the weak link.

 

If you follow Steve's advice, do be extraordinarily careful not to short anything out while you're working.

 

Of course, on a more flippant note, you could have bought a nice engine and several gallons of fuel for the price of 2 of your batteries, motor and ESC!

Edited By Martin Harris on 01/10/2010 18:49:41

[Myron Beaumont]

Herri

You havn't done what I did have you & left the gizzmo that gives you voltage for the Rx connected to the battery after flying ??  It drains it slowly. I repeat, guess how I know?

ic  Myron

[Herri]

Posted by Myron Beaumont on 01/10/2010 18:49:54:

Herri

You havn't done what I did have you & left the gizzmo that gives you voltage for the Rx connected to the battery after flying ??  It drains it slowly. I repeat, guess how I know?

ic  Myron

 

 No, I'd only just charged the lipos (this afternoon)

What I find strange is that  this is the second time this has happened.

Same AC/ESC but now new lipo. Both times 2 nose overs - then zilch.

Herri

[Herri]

Sorry Erfolg, missed your post.

The lipos hadnt moved as far as I can see. They are quite a tight fit, so I dont really think this was the cause.

Herri

[Herri]

Just to update.

Today I received a new 3S 3600 pack from the model shop.

He sent my dud one off and whoever there, said I could have a new one.

Its taken a few weeks but at least I have a new one.

Cheers

Herri