Nano-Tech 0,65 4S open circuit

[RSH]

Anyone had problems with the Nan-Tech 650 mAh 4S battery going open circuit?  This particular battery has a detachable balance lead, so has a sub-assembly comprising a mini circuit board that the balance socket and output leads are attached to.

I charged the battery ok, but when connected in the plane showed 0 volts.  Investigation showed a fracture of the main terminal which is a flat metal tab between the cell and the sub-assembly for the battery leads/balance lead socket (see photo; tab is to the right and below the red cable) .  The lead/balance sub-assembly is only secured by the black plastic strip that binds the battery assembly together.  Given that you need to connect/disconnect the balance lead, there is an amount of mechanical load applied and I suspect that this has overloaded/fatigued the cell tab which is quite thin in section.

The problem I have is whether to trust this type of battery.  I count myself lucky as the battery went open circuit with the plane on the ground.  If the tab had been fatigued and partially split, then it seems likely that the joint could have failed completely during a high current launch.

Having now seen the construction of this battery, I feel I should junk all of these batteries.  However, they are light and also small which is what I need.

Has anyone had a similar problem, or can suggest an alternative 4S battery? 

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[PeteMitchell]

I have used these packs for the past 2+years in all of my J planes and never seen a fail like that. 

Even the one that met its end when my Prestige went in from 100mtrs still worked ok with no solder joints broken. It was just the distorted cells that stopped me using it again

They do puff up a bit when abused with 50A+ but hold their voltage ok.

Recently they have always been out of stock so I am now trying GNB 650/4s as a replacement. But they are also hard to find at the moment.