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   SAFETY - Things to watch out for with LIPO batteries

Most of us tend to take our Lipo batteries pretty well for granted, we charge them up, maybe using a Lipo-Safe bag, but most people don't do so, and then we plug them in and pull the Deans connectors apart with very little thought for those little ole wires that come out of the end of our Lipos.

WELL, THAT IS WHERE THE DANGER PART IS.

I have quite a few helicopters of my own, and handle a lot more for other people, especially when going through the FREE Heli-Hospital treatment, and I also have a large number of Lipos of different sizes, different makes, and different C ratings of my own.

The one thing they all have in common (with almost all lipos anyway) is that there are two sets of connecting leads coming out of one end.  One pair connects to the ESC, the other set go into a small white "balancing" plug.

   
Now these wires just appear out from under some form of covering, and we probably never give a thought to how they are connected to the LIPO itself.  Well, quite reasonably, they are soldered to the lipo cells in a specific sequence, especially the thin balancing plug wires, which actually let us check the voltage of each individual lipo cell.  That is how our fancy lipo chargers perform what we call balance charging.

So what you may ask. ?
    

Well, lets consider the case where one or more of these very small, thin wires has come loose from the connection inside the battery it should be connected to. WELL BELIEVE ME, THIS IS NOT AN AS UNCOMMON THING TO HAPPEN AS YOU MIGHT THINK.

You plug the main connector into your lipo charger after a flight, then connect the balancing plug, and away it goes. Correct ?

WELL NO ACTUALLY.

Because in this case one of our balance wires is not connected where it should be, the lipo charger has no way of checking the voltage in that particular cell.  Neither do most chargers warn of this problem. Even worse is if that lead happens to be touching a different connector, providing the lipo charger with the WRONG information.

So we wait till our lipo is apparently fully charged, and off we go and launch our valuable helicopter into the wild blue yonder, confident that we have a least 8 minutes worth of battery power - WRONG AGAIN.

Your valuable heli suddenly starts to lose power rapidly at 60 feet up, and unless you are a well practiced pilot to whom an autorotation is no problem, you may well end up with a damaged helicopter.

What went wrong ?

Easy really, your lipo charger did it's best to charge all 3 cells (11.1v lipo), but it had no idea how well one of the 3 cells was charged, as it had no connection to it directly.  This means that particular cell will almost certainly have NOT BEEN CHARGED sufficiently, because lipo charges have to be very careful to not OVERCHARGE any cell.

The cure for this problem is pretty simple if you are able to use a soldering iron.  If you do not feel TOTALLY confident to do this - DISCARD THE LIPO safely and entirely - THINK SAFETY.

Each of the three individual cells in an 11.1V lipo battery are aligned the same way inside the casing.  That is the + connections are all at on end and the - connections are all at the other end.  there are also soldered connections at the other end linking the cells in series.

BE VERY CAREFULLY when cutting the covering over the cable connection end of your Lipos. 

(DON'T PIERCE THEM IN ANY WAY OR THEY WILL EXPLODE, 
and make sure the knife doesn't short across the solder points)
 

NOW PEEL THE COVERING  BACK SO THAT YOU CAN SEE ALL THE SOLDERED CONNECTIONS...

Check each one, paying very special care to the thin balance plug wires, to ensure they are not breaking at the soldering point, or worse yet, have already broken or have become unsoldered.

If you do find a broken one, make sure you know exactly where it should be connected back to, and then use a 40W or larger soldering iron to carefully remake the joint.  Make sure you get a really good "remelt" of the original solder so that one or both leads that should be fitted there are really well soldered to the cell.

MAKE SURE THE SOLDERING IRON DOES NOT TOUCH ANY OTHER CONNECTION 
OR YOU WILL CREATE A VERY BIG SHORT ACROSS YOUR LIPO

Reseal the end of the battery with some Gaffer tape or similar.

Recharge the cell and make sure all three cells are being charged accurately. One good for use Lipo back in service again.

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