Hi all,
Well I could show you pictures of the carnage but it's too upsetting :-(
I destroyed my new A-10 this morning in front of a dozen club members.

Jet was flying beautifully till about 5 minutes into the flight the motors stopped dead and with no control at all it nosed in at high speed.
Then we noticed the fire.

My A-10 has the EDF55 300H motors and was running with 3S2P 1200 etecs.
The Etec packs are actually two 3S1P packs that I had parralleled with a "Y" adaptor lead I made myself from deans ultra connectors.

Only one pack was destroyed. It was burnt to a cinder.
The other 3S1P pack wasn't even warm to the touch and is ok as far as I can tell.

Now I didn't worry much about cell balancing (well not at all) except for making sure that both packs were fresh off the charger before parralleling them together.

Is cell or pack imbalance the likely cause of my pack failure?
Because only one pack was destroyed I don't think I could have been overstressing the packs current wise?

Any suggestions appreciated as I would love to build another A-10 as it was flying like a jet should! With authority, but I hate not knowing what caused this failure in the first place.

Thanks for reading
any comments appreciated

Aussieparkflyer

Havent had any response to this query in batteries forum so thought I would re-post in the largest forum here.



Hi all,
Well I could show you pictures of the carnage but it's too upsetting :-(
I destroyed my new A-10 this morning in front of a dozen club members.

Jet was flying beautifully till about 5 minutes into the flight the motors stopped dead and with no control at all it nosed in at high speed.
Then we noticed the fire.

My A-10 has the EDF55 300H motors and was running with 3S2P 1200 etecs.
The Etec packs are actually two 3S1P packs that I had parralleled with a "Y" adaptor lead I made myself from deans ultra connectors.

Only one pack was destroyed. It was burnt to a cinder.
The other 3S1P pack wasn't even warm to the touch and is ok as far as I can tell.

Now I didn't worry much about cell balancing (well not at all) except for making sure that both packs were fresh off the charger before parralleling them together.

Is cell or pack imbalance the likely cause of my pack failure?
Because only one pack was destroyed I don't think I could have been overstressing the packs current wise?

Any suggestions appreciated as I would love to build another A-10 as it was flying like a jet should! With authority, but I hate not knowing what caused this failure in the first place.

Thanks for reading
any comments appreciated

Aussieparkflyer

I wanna see pics!!

Kidding - Seriously though, we need more info:

You say "...no control at all..." which would lead me to believe that you had no battery connection at all (one cell was fine afterward, so rcvr would have had 11.1v for BEC). What ESC were you using? Did it fail? Did you test all equipment afterwards? We first have to rule out that the fire was caused by the impact (Li-Poly's are very sensitive to "crushing").

How many charges did the E-Tec's have? These cells are VERY slow to drift in voltage if handled properly, so if used within specs, they would take many charges to become imbalanced.

I'm also not familiar with the current draw of the EDF55 300H motors.

More info please, I'd love to get to the bottom of this!!

could it be possible that the connector to the unfried battery failed and all the load went to a single pack?

Thanks beafraid for replying..........
give me 10 minutes and I'll post some pics.

I had no control at all even though one pack was still ok.
I personally think from the amount of damage caused that the pack must have been melting while it wqas still in the air......almost certainly not caused by the impact.

I havent yet tested the esc and it could well be a problem. (It was just a generic sp400 esc that I hoped would handle the current........maybe I was wrong.

If you can hang around for a little while I will take some pics of the damage and also test the esc and get back here very shortly.........

I'll grab another brew and hang out for a bit, I'm very curious!!

This site: http://www.allerc.com/edf55.htm
says 7.1 A each for those motors, so you're probably pulling at least 14 A. E-tec's (from my experience) should have been able to pull entire flights at full throttle many, many times before failure with your setup (3s2p). I'm thinking ESC....but I still need to know how many flights the e-tec's had and whether or not they've been abused in any way.....

Ok I think you may be right about the esc.
I hooked it up just now and despite the TX throttle at zero the motors came on full as soon as I connected it . Then the magic smoke came from the esc!

I am only now confused as to why one pack failed so miserably but the other survived unscathed?

I do think this pack was pretty hot even before the crash......

To answer you other questions..........no the packs havent been abused in any way and have been using them for a couple of months now........probably 20 flights on each pack.

As I said the ESC is an unknown brand but was meant for mounting directly to the back of a sp400.
Possibly only 10amp capacity?

There is also damage to my "Y" adaptor lead but I'm assuming that happened in the crash.

ANyway I have just ordered a new slope version a-10 as both the EDF55's seem ok.
Will purchase a 20amp ESC and maybe also upgrade the wiring from the fans to the ESC and the battery.

Thanks for your time beafraid, and have another brew on me.

Also just noticed that GWS chart claims 7.1 amp at 10.8v so with the lipoly's at 11.1v would be maybe even higher.

That's what I was thinking.

You guys could be right as the "Y" harness was broken after the crash.
Its either that or the ESC which I'm pretty sure now was only rated at 10amps.

Anyway Ive ordered a new slope version A10 and will buy at least a 20amp ESC and also upgrade the wiring as a precaution.


here's a few pics..........

another..........

Man, sorry to see those pics!! OUCH!!

From what I've experienced (very little) the rear-mount ESC's aren't designed for more than 12A or so....

One can only guess at this point, but I'd say the ESC failed and shorted the batteries, and at that point it depended on which cell/pack had the best construction and the best handling thus far. Once one cell let go, I'd be willing to bet that there wasn't enough current (for one reason or another) to fry the other pack, and (luckily) one survived. Keep in mind that the aluminum tabs on these cells are very sensitive to heat and are the first to go.

It still may not be a bad idea to peel the shrink-wrap off the other pack and check the individual cell voltage (should be within .1 VDC of one another). This will ensure you don't over or under charge one cell and have this happen again. I've seen a pack survive a crash like this looking flawless, only to find that one cell was shot.

Happy flying!! I'm continuing to abuse these batteries as much as I can afford to see what might happen. I have yet to cause a fire, so you're an inspiration!!