LiPo out of shape

[Tansley]

I recently bought a Trackpower 4900 LiPo and charger. I've been well pleased with the performance of my B4 with 6.5 Novak Brushless Motor with Speed Pashion ESC, until this weekend.

After racing I checked the car and battery only to discover the battery is no longer flat, but the top & bottom have swollen noticably.

The max charge rate I used is 5amps, so I don't think it was overcharged, any ideas would be appreciated.
:(

[DCM]

don't quote me on this, but it does sound like your trakpower has gone.... take it out of the car and put it out the garden, where it can't burn anything down. Then email or phone trackpower, or PM Mark Christopher on here.

[neiloliver]

Were you charging it at a maximum of 4.20V per cell? Sounds like it was either incorrectly charged or the cells were not correctly formed during manufacture which has caused them to 'pillow'.

N

[jimmy]

This happens from over-discharge - maybe it happens from charging also?? I've no idea. But I did this to a lipo in vickys car last winter - I left it in the car for 2 weeks and the capacitor drained the battery slowly and it expanded. I didn't try to charge it.

Does your ESC have a cut off and is it 'engaged' ?? - I think I'm right in saying you'd not use lipo cutoff if using nimh, so it probably would need switching on.

[evilbert]

the lipos can 'pillow' from over disharge and over charging and they should only every be charged at 1C, so in your case a max charge of 4.9a. so technically charging at 5amps is overcharging. i'm not sure how much over the 1c you have to charge before they will go like that.

either way for it to happen suddenly like that sounds like it is over dishcharging. You should never let the cells drop below 3v per cell so if you can check the voltage give it a try (with a voltmeter not by putting them on charge lol) and see what the voltage is, if its below 6v then you know thats where the problem is and as jimmy says make sure that you have lipo cutoff enabled on your esc and if your esc doesn't have that function invest in an external lipo cutoff, a much cheaper solution than ruining cells every week.

as for your old cells the safest thing to do is to put them in salt water which will completely discharge them and make them safe, i'm not sure on the exact way of doing this (how much salt to use or how long to leave them in there but i'm sure there are numerous guides on tinterweb).

HTH

[peetbee]

coincidentally my trakpower has just done this.
Nothing wrong with the trakpower, it was the cutoff on my GTB not cutting off properly.
The car just slowed down and I pulled off and charged it straight away. The battery looked fine at the time, it was only after I took it out the case yesterday that I discovered it had swollen :(
It's now out in the garden in a metal bin.

[DCM]

Pete, I have images of you behind sand bags, tin helmet on, and warning signs up.... I must leave off the paints I think!!

[peetbee]

Don't panic Mr Mannering, Don't Panic!
They don't like it up em sir

http://www.pistonheads.com/inc/images/boxedin.gif (http://www.pistonheads.com/gassing/smilies.htm#)

[DCM]

thats just made my day haha

[Spoolio]

Seen this on a couple of Trakpower 4900's when they were "new" on the scene last year. I've had mine since Nov 07 and they are always charged on my cheapo Ansmann Deluxe (!) charger with an inline Trakpower V-balancer module. So far no problems at all, don't know if its luck or the V-balancer but I'll just keep doing more of the same.

[Tansley]

Thanks to all you guys for your comments and advice.
I spoke with TrakPower and told them what had happened, that the LiPo cut off is set on my ESC and that the battery has never discharged down below 6.8 volts.
As for charging, maximum its ever been charged at is 5amps.

I've sent the Battery back to Trackpower for examination.

[Tansley]

Just to let you know I heard from FlightPower / TrakPower. They acknowledged the battery was faulty and the new
battery arrived this morning. Thats what I call good customer service.

:D:D:D:thumbsup::D:D:D