Hi all,
I have a Trex 600 and four UH 4100 mAH 6 cell packs (purchased brand new for me by a friend that has a UH account)

Here is how my wake-up call came to me.

I have been extremely happy with my UH batteries to date. (I also have six 3 cell 2200 mAH packs and they are great performers.)

So, I flew my Trex 600 four times yesterday, each flight timed to end at five minutes, as I have been doing for the past three months without any problems.

Each pack was warm to the touch upon removal from my heli.

Called it a day and went home about 3 in the afternoon. Unpacked the car and placed my four now very cool battery packs on a piece of 6mm glass adjacent to my battery charger. The batteries were simply left alone. Not charging, not discharging. Just idle.

Went about some other messing about and went to bed about 10pm. 4 battery packs still laying on a piece of glass. Totally idle.

Wake this morning, "beautiful day, might go put some batteries on charge for a fly later". Go into workshop to find one pack had overheated and been smouldering all night. Fortunately the glass prevented any damage but I dread to think had the pack rolled off the glass! The possibilities are FRIGHTENING!

I have always been careful when charging my packs, I use a UH firebag. Always stay closeby etc but I have never heard of a LiPo just melting down 7 hours after use. I did not consider my batteries at risk because they were cool and idle.

Anyway, lessons for us all;

1. Always treat these batteries as dangerous , not just when they are chargng or discharging.

2. Install a smoke detector with remote caution. ie. so you can hear it from all parts of the house.

I'm feeling very humble and sheepish now. I feel dreadful for endangering our home and each other. All my Lipos are away from the house now!

This can happen to you so please, do be very thoughtful.

Take care all.
kind regards

Ohh, Thank god, that could have been alot worse.

I use a steel box (special made by blacksmith friend, huge, since I have so many batteries) and a smoke detector inside that box in the lid, also smoke detector in the room, centrally connected to the alarm.

Good ventilation from the box, I dont want a bomb.

Its lockable to prevent kids from opening it.

Makes me feel at least safe for me and my family.

Years ago a flying friend of mine had an idle LiPoly go thermal while setting on a flight bench at the field. When I posted about it everyone explained that something had to cause it as LiPolys not being charged / discharged etc. could not do that.
Sometime later someone post about a brand new(never charged) LiPoly becoming burned/scorched (?) in a desk drawer at work.


My biggest concern with idel LiPolys has always been the balancing leads.
Many / most of these are very fragile and not well secured or insulated.If one breaks and shorts a cell or cells. I have always secured the balancing leads to the side of the pack under a rubber band to prevent it from being flexed at the cell terminals .


Charles

how is the HV esc for 6S cooled ?

if not done right the esc will overheat and the output FETs will short thru the BL motor leads and take out the LIPO pack quickly

So, DON'T BLAME IT ON THE LIPO, IT'S DOING ITS JOB TO GIVE U ALL THE POWER U WANT BUT IT WON'T TAKE A FAULT ON THE esc

Hall Woo,
The battery pack was NOT CONNECTED TO ANYTHING FOR OVER 7 HOURS.