Condor

I had my 4*40 plugged into my Cirrus Charger all week in preparation for flying on Sunday. When I picked it up, the display on the Cirrus read 5.5V, which looked fine for a 4.8V 600mAh pack. When I got to the field, the radio didn't operate, so I assumed I had accidentally bumped the switch on and drained the battery on the way--funny thing, the switch still appeared to be off...

I made sure the switch was indeed off by switching on and off a couple of times, and plugged a charging cord into my power panel's starter jacks and my receiver's charge lead. About 3 or 4 minutes later, I heard a funny "crack, sizzle and pop" sound, and didn't realize what was going on until I saw some smoke coming out of the fuse! Of course, the 4* is the only plane where the battery is not accessible because I put it all the way in the tail to balance it, and didn't make a hatch for it, so it's surgery time.

I am still at a loss for what I did to ruin the battery. Maybe it WAS charged but somehow went bad, so when I started charging at the field I overcharged it? If so, why did it read OK on the charger/cycler but failed to power the receiver?

Or maybe charging directly from the power panel 12V battery was a dumb move?

Of course, lessons are learned the hard way... I will get and start using a voltmeter, and get in the habit of taking a field charger to the field, rather than leaving them plugged in at the shop. But I would still like to understand where I actually screwed up in managing the battery.

Thanks for your input,

Juan M. Villaveces

Red Scholefield

My Feedback: (9)

You plugged the 12 volt starter battery outlet DIRECTLY into your 4 cell Ni-Cd pack?

"and plugged a charging cord into my power panel's starter jacks and my receiver's charge lead. About 3 or 4 minutes later, I heard a funny "crack, sizzle and pop" "

That "crack, sizzle and pop" you heard was the result of cells venting from hitting them with all the amps your field box battery could apply. They were what we term, in thermal runaway - melt down mode as they got hot from the excessive charge current and the current ramped up as the voltage dropped - separator melted, massive internal shorting - energy dump!

Bad scene!

Ross Kean

Might have been OK for a top-off charge if the field box/starter was 6V. 12 volts would give you a pretty good barbeque!! A lead-acid battery can put out a lot of amps - especially with 12 V going into a 4.8 V pack.

Ross

golf_lake

Your first mistake was leaving on charge all week, which would have overcharged your battery. The normal TRICKLE CHARGE IS 10% of MA rating for 14 to 16 hours from flat. IE 600MA pack requires 60MA for 14-16 hrs.

If you want to leave batteries on constant charge that would need to be dropped to around 20MA.

And stuffing 12v into a 4.8v pack is totally out of the question.

MHawker

My Feedback: (16)

Yup, I think some of those gels are 7amps!

Steve Lewin

They are actually 7 Amp hours capacity and you can dump all of that capacity in not many seconds. Lots and lots of amps !

Steve