Battery Danger

[terry]

Hey All

Recently one of our flyer's had the misfortune of a battery failure during flight , unfortunately his airplane is toast . The good thing was , no one or anything was hurt or damaged . A CSI investigation was launched and it was discovered he did not check his battery voltage after charging or before his flight . It was checked however after the crash and was found to be around 2.2volts (probable cause is still under investigation , we tried to get CSI MIAMI but they said it was to cold and all we could afford was Joe anyway) .

We all slip up here and there but
POINT
being check your batteries before flight , make it a habit , watch the meter for a few seconds if you see a large voltage drop don't fly , if you don't have a volt meter you should NOT fly .

[jbajkor]

I have tested the battery in question.

Initial condition: all cells equal at 0% charge

Charged the battery: it took 1900mAh (not bad for a 2100mAh pack) All cells measured 1.4V within 0.01V

I have cycled the battery 3 times now. Each time showing capacity between 1800mAh to 1900mAh. This battery did have a habit of dropping out with a false peak! I had to reset the charger a number of times.

Recommendation:
Battery is fine, but set the charger to NiCad peak rather than Nimh, or charge at 200mA overnight.

Sorry you lost a plane over this.
Joe

[terry]

Joe

Would quick charging all the time or a lot of the time present problems

[johnm]

Joe and Terry: On the subject of batteries but not the problem referred to in your last posts. I am from the old school and definitely not up on current battery technology. I use NiCads in my Futaba transmitter (700) mAp and usually 1100 mAp on board my fuel powered planes. My batteries are the slow charge type and accordingly, I charge my transmitter batteries using a 70 mAp charger and my on boards with a 100 mAp one. Both are charged the night before flying, usually for about 10 hours. It is rare that I have more than five flights. A friend has a charger which he purchased recently which apparently contains new techology. It can charge all forms of batteries including the kitchen sink and provides all kinds of read outs. It starts charging at a colossal rate and then backs off as the batteries take on a charge. It charges the batteries very quickly and then backs off to a trickle charge. I keep telling him that he will ruin his batteries because they are not designed to take a quick charge. I tells me that I do not know what I am talking about and he may be correct. My question - can these new type chargers really charge slow charging batteries without ruining them? John Mickle

[chrisp]

Terry define quick charging?.,,, If quick charging is more than 1c (2100mah=2.1amp), quick charging will shorten the battery life.But if kept at the 1c or lower there should bo no problem. Now of course there is always the possibility of faulse peaking,and thats where (like you said "if you dont have a voltmeter you should not fly"). With a voltmeter you can see the charged voltage of the battery and if it isnt what it should be than it either false peaked or the battery may be bad.


John I have myself a decent charger and I tried to charge the new duracell 2300nimh batteries , slow charging @50mah they cyceled a full 2300mah,fast charging @ 1c they barley got 5 or 600mah,so to your question John some batteries are not ment to be charged fast.
but thats just my opinion.

[jbajkor]

Quick charging is fine with any nicad or nihm.....to a limit.

The real enemy is heat. Fast charging with "peak algorithm" will actually overcharge a slight amount. As the battery gets full, heat starts to build up and the voltage will drop a bit. When the charger sees this decrease it stops. So, by nature of this algorithm, a little bit of heat is created. This is ok as long as the batteries don't get too hot.

Overheating problems happen when the charger is looking for too great of a voltage drop (large peak). This will happen to nihms if the charger is set to nicad.

The opposite problem happens if the peak is set too small. The charger could terminate too soon and the battery is not full. This is probably what happened to Jack.

Fast charging this way all the time is ok. It may shorten the battery life from 8 years to 5 years, but some people think it is a worthwhile trade-off. If you fast charge all the time, an ESV is an essential tool.

By far, the safest way to handle nicads and nimhs is the way John does it. Charge at C/10 for 10hr to 14 hrs (overnight). Requires a bit of planning ahead, but you will never have the "false peak" problem.

Finally: don't push it. If you think you're good for 8 flights, stop and recharge after 6 flights and use an ESV.

Joe

[johnm]

Thank you Joe and Chris - I really appreciate your input! It is nice to know that I am charging the safest way possible. Just for your information, I keep good records of my batteries' performance and re-cycle twice a year. Always in the Spring and maybe once during the season. Upon discharge, if a battery shows less than 80% of its capacity, then I discard it. Also, I never use a battery that is more than 5 years old and usually change them after 4 seasons. I have been flying for 25 years, usually more than 200 flights per year and have never had a battery problem. I think I will stay the course. Cheers - John Mickle

[admin]

jbajkor said:

Overheating problems happen when the charger is looking for too great of a voltage drop (large peak). This will happen to nihms if the charger is set to nicad.
Joe

I can attest to this.

This is what happened to a battery pack, Nihm, I was charging on the way to the field. I was using a Hobbico Quick field Charger Mk.II and must have only pushed the button once, Nicad setting.

On the way to the fieldI smelt then saw smoke drift past my head. Iturned to see smoke pouring out of every opening in my H9 33% Edge 540. I pulled oof to the side of the road and got the airplane out of the van. At this point I wasn't sure if I should open the hatch and possibly give oxygen to a smoldering fire but I had 16oz of gasdoline in the tank so I had to do something. Pulled the hatch saw the batterry smoldering inside the faom rubber, cut the wires and took the pack out with the cutters.

Almost lost my plane and my van on that one. .