christopher small Posted February 9, 2008 Share Posted February 9, 2008 Went to go flying today with my GWS Slow Stick,but the 7.2 volt Nicad battery pack wouldn`t charge up enough.The charger is a 12 volt Irvine delta peak,I have had this problem before but after a few times it charges properly ,but today it wouldn`t,4 battery packs all brand new,connected to an old car battery at 12.2 volts on the DVM,gave it 5 seconds to recognize the battery pack, then disscharged it ,then it switches itself to charge when ready. But stops charging after only 10 minutes,when it should go on for an hour(400 mah pack charging at 0.4 amps) motor then runs for about 20 seconds.What am I doing wrong.(Not ready for Lipos yet ) Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 9, 2008 Share Posted February 9, 2008 Are you sure all setting s are correct - maybe it is not actually discharging it all, although by the sounds of your flight duration, it is not charging it. have you tried slow charging the pack ? Quote Link to comment Share on other sites More sharing options...
martyn sharp Posted February 10, 2008 Share Posted February 10, 2008 Hi chris i had the same problem and it was my feed battery i got myself a mains feed and all was fine i was geting 12 v olts on the meter but understess not a lot Hope this helps Martyn Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 10, 2008 Share Posted February 10, 2008 Ah, I think Martyn is on to it here...just picked up your comment about you using a car battery supply. If it is only reading 12.2V it is pretty much flat...should be showing around 14V when in good condition. Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 10, 2008 Share Posted February 10, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 10, 2008 Author Share Posted February 10, 2008 Looks like it could be the battery then,that would explain why sometimes its perfectly ok,and other times no good at all.Lovely day for flying but no batteries all 4 wouldn`t charge.I have a large regulated power supply here with 13.8 volts at 30 amps,10 amps and 6 amps,so I shall probably plug into the 10 amp supply and try that.I have also got my 4 channel trainer and OS 25 almost ready,so I shall try that.Many thanks Chris Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 10, 2008 Author Share Posted February 10, 2008 I have now plugged into my 6 amp power supply,disscharged then charged my 7.2 volt 400 mah battery pack at 0.4 amps took 27 minutes which is much better than 10 but should have taken an hour.Or have I made a mistake somewhere. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 10, 2008 Share Posted February 10, 2008 If you use the PSU, the high current output will be fine too...the charger will only take what it needs from it Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted February 11, 2008 Share Posted February 11, 2008 All right, work this one out.I charged up seven packs the other day. I used two chargers, One was my all singing Graupner ultra duo plus, the other was a mains peak detector charger.None of the packs were properly charges, just a little or nothing in each. Tried again with the mains one, it kept cutting off, eventually magaed about 1/3rd charge fater restarting the charge about 4 times.Cycled a pack on the Graupner, Said it had the full amount in the battery. Haven't had a chance to check that out. Quote Link to comment Share on other sites More sharing options...
Doug Ireland Posted February 11, 2008 Share Posted February 11, 2008 What a carry on over a bunch of batteries! Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted February 11, 2008 Share Posted February 11, 2008 I agree, that is why I love i.c. I am not really into this electrickery. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 11, 2008 Share Posted February 11, 2008 Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 11, 2008 Author Share Posted February 11, 2008 Hi PeterSounds like you have had the same problem as me,batteries charging up in 5 minutes not an hour as they should be,something to do with the Delta Peak charge of the battery(how does this work Timbo)whatever it is, is coming on too quick,I charged up my one battery walked up the bank behind our house (t ook 10 minutes ),started up my plane and immidately the motor died right down and stopped.I would like to find out what is happening.I Don`t give up on anything,I have my MDS 40 to sort out in the spring.Chris Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 11, 2008 Share Posted February 11, 2008 Put simply, the delta peak system uses a sensitive bit of circuitry to detect exactly when the cell/s have "peaked" -usually signalled by the charger seeing a very slight falloff of voltage just after reaching their peak value, in the order of a few millivolts. It is worth noting that for this system to work you really need to be charging at a fairly fast rate 1c or .5C.....anything much slower than this and it really wont work well. Quote Link to comment Share on other sites More sharing options...
Doug Ireland Posted February 11, 2008 Share Posted February 11, 2008 Just finished charging my ignition pack.7.2v 1500ma. Took 97 minutes at 0.5A with a final voltage of 8.66v and 769ma put in. Think its cooked! Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 11, 2008 Author Share Posted February 11, 2008 Thanks Timbo much appreciated,I should have this old charger working soon,What should the voltage of the battery be when the cells have peaked?And can i use this voltage measurement to tell if the battery is fully charged?I have noticed in the past when the batteries haven`t been charging up properly ,and I have turned up the charging current it has worked much better.So I shall go for a faster charge rate,So should I go from 1C which I am using now to 3C 1.2 amps charge for a 7.2 volt 400 mAh battery. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 11, 2008 Share Posted February 11, 2008 I wouldnt advise going more than 2C for a battery which does not specifically specify it is safe to do so. Also, IF the charger is not detecting the peak very well, ( and some just dont ) and you are on 3C rate, the battery could easily overheat and be damaged / vent / explode.Most nickel cells are peaked at around 1.4 - 1.5V per cell, and the charger then detects a slight fall off in volts ( accompanied by a temperature rise ) and this is when it should cut offor drop to trickle rate.If the cell is measuring around 1.4 or so after charging then it is "good". Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 25, 2008 Author Share Posted February 25, 2008 I have now got a Ripmax plug in the wall charger,250 mAh output which I have left on charge with my 400 mAh nicad pack for 2 hours when i switched it off the battery was rather hot and the plastic was smelling a bit.How do I work out how long to charge a flat nicad pack up to full charge?and should it get hot? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 25, 2008 Share Posted February 25, 2008 Hot no, warm...probably. It should take around an hour and 15 mins approx to charge from empty, if charged at 1CYou pumped in 500 m/a to a 400 m/a pack which may not have been empty anyway...so it cooked it.Leaving a nickel cell ( or any for that matter ) on a fairly high rate charge for longer than an hour or so will overcook it. Nicads ususally tolerate a very low trickle rate ( say .01C ) for long periods...but mh less so. Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 25, 2008 Share Posted February 25, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 26, 2008 Share Posted February 26, 2008 Not heard of that one . Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 26, 2008 Author Share Posted February 26, 2008 On the battery pack it says standard charge 14 hours at 40 mA.The charger puts out 250 mA,so obviously I need to reduce the current,what is the best way to do this. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 26, 2008 Share Posted February 26, 2008 Well if you dont actually have a battery charger that you can set to the rerquired cell /cell count / current / cycle / etc etc you really ought to buy one. They are NOT expensive these days, and if you get something like the propeak prodigy it does LiPos as well when you get to using them...and you will do one day Meanwhile, easiest thing to do is insert a resistor in the positive line from charger to battery.Assuming you're charger puts out say 6V....at 250 m/a and you want 40 m/a then Ohms law says you need to add in around 30 ohms to drop 210m/a ( .21 of an Amp ) The law says R = V / I so......if Volts are 6And the current drop required is .21 of an Amp Then 6 /.21 = 28 Therefore you need a resistor of around 28 -30 Ohms. The power flowing through the circuit will only be around 0.24 of a watt...so use a resistor of at least 1/4 watt or bigger. Of course all this assumes certain things including the charger supplies constant 250 m/a which it may well NOT do, also the current flowing will change ( drop off ) as the battery charges. For these reasons....please insert a ammeter ( use a standard multimeter on current range setting ) in the positive line to monitor the current actually flowing. Experiment with different value resistors to obtain the result you need. The above image is what's known as the magic triangle - it is used to calculate all formulations of Ohm's Law. Use a finger to hide the value to be calculated. The other two values then show how to do the calculation.HTH Quote Link to comment Share on other sites More sharing options...
christopher small Posted February 27, 2008 Author Share Posted February 27, 2008 Thanks Timbo,Brill just what I needed to know,I have had enough of fancy chargers,only more to go wrong.I tried some calculations last night with Ohms law,couldn`t get it right,never was much good with electronics,even though I am a radio ham.I have loads of electronic components so I shall start looking right away,might put a simple meter in line as well.If I had the money I probably would get a decent charger,this one cost £5-99Regards Chris. Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 27, 2008 Share Posted February 27, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
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