Myron Beaumont Posted November 8, 2008 Share Posted November 8, 2008 I use a car bulb normally to discharge nicads . I now am looking for a 16 ohm "something or other" to discharge my 1345 mAh 2s Rx lipo at 1C if my calculations are correct .Can anyone think of any normal bit or bob of a house hold nature think of a lightly candidate fit for the purpose .I've tried several bulbs but nothing seems to come close (unless of course I start wiring them up in series/parallel -A lot of bother & cumbersome !) All suggestions welcome to save a days travelling to buy a resistor ! Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Bruce Richards Posted November 8, 2008 Share Posted November 8, 2008 Been hunting around the garage with my meter and 30M of plastic covered garden wire (type used for training plants) is about 10 ohms so 50m would be about right. Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted November 8, 2008 Share Posted November 8, 2008 MyronGot a Maplin store nearby? 40p Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted November 8, 2008 Author Share Posted November 8, 2008 Phil ! You are so right Thank you .Dont know what happened to my brain cell ? I agree it is of course 5.5 ohms for 7.4 V & 6.1 ohms for the 8.24 V its at at the moment I got a bit mixed up trying to work out what 12V rated bulb I could use -Somehow or other I got waylayed by the wrong facts (even 'er indoors agreed it was 16 ohms - then again shes only a Phd Doctor etc Thanks to you Bruce for your efforts & no we dont have any wire that long in the shed but I found some rope -( No suggestions please .)Will now try & find a 6 ohm bulb (tried 'er indoors's iron but got weird meter readings(no use ---the iron that is !) Probably got a chip in there similar to the one on my shoulder . Gone are the days of a simple rheostat or so it seems --Same goes for my solarfilm iron .Well I have at least broadened my knowledge I think ---until the next problem -tomorrow Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted November 8, 2008 Author Share Posted November 8, 2008 Rob Yep -Theres a Maplins store not far away & I am now the proud owner of a free bus pass (65) Trouble is I know I wont just buy one resistor -I'm sure you know what I mean .Not only that but 'er indoors's favourite shop it is !!! Quote Link to comment Share on other sites More sharing options...
260 Flyer Posted November 8, 2008 Share Posted November 8, 2008 Myron Beaumont wrote (see)Trouble is I know I wont just buy one resistor -I'm sure you know what I mean .Just take 40p with you then! Quote Link to comment Share on other sites More sharing options...
Guest Posted November 8, 2008 Share Posted November 8, 2008 make sure you check resister values when you get them at maplins - I bought 2 recently along with other stuff and didn't bother to check until I went to use them and they were both wrong values. I had assumed they knew there stuff. Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted November 8, 2008 Author Share Posted November 8, 2008 Does the old fashioned colour coding still apply or do I have to learn Chinese.Sorry -lettering got bigger ?? Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Andy Gates Posted November 8, 2008 Share Posted November 8, 2008 How about upgrading your charger with a combined charge / discharger? Saves all this hassle and will stop you over discharging your lipo. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 8, 2008 Share Posted November 8, 2008 Ah but that would apply if the person concerned was going to stick with elektrickery Incidentally Myron do not worry about the discharge rate being exactly 1C - that was only a suggestion, and anything up to around 3 or 4 A with no worries. Discharfging them at even lower rates would also be OK....but might take a long timne ! The only really important thing in this project of yours is to ensure that A) The discharge rate is not higher than the cells are rated atB) The voltage at which you MUST stop the discharge is 6V ( when off load ) If you end up discharging at say 3A then you would need a resistor of around 2 to 3 Ohm ( at least 25 Watts ) and at this sort of current the battery can drop to around 2.85V per cell .....so around 5.7V. When you get this low ( as monitored by a simple DVM across the pack during the process ) disconnect the load, and then check the off load voltage...it should read around 6V or so fairly quickly. It is important to "drain" this pack quite deeply, in order that you can accurately measure how much goes back in when you re-charge. Dont expect full capacity in this "born again" pack, but a few cycles and she may be back to a very useable level. Cant remeber if you had a balancer, but if not, then best to hook a seperate DVM across each cell as it is discgharging to ensure one cell hasnt suffered more than the other....ditto on the recharge. Quote Link to comment Share on other sites More sharing options...
andy watson Posted November 8, 2008 Share Posted November 8, 2008 You guys want to try something called glow fuel............no messing around- just turn up and fly! Now where's my tin hat? Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted November 8, 2008 Author Share Posted November 8, 2008 Thanks Timbo Am at this very moment discharging it with 5 servos connected to the regulator/Rx til I find a 6 ohm resistor (not 16 as I miscalculated!) .Only a small discharge rate I know and am checking battery voltage & voltage going to the Rx every half hour .After 3 1/2 hours so far the battery has dropped from 8.22V to 7.80V & the voltage to the rx has been 5.0 V until half an hour ago when it dropped to 4.99V So far so good & will repeat procedure when battery drops to about 7.00 V ( is that -"deep enough" ? ) Yes I do have a balance charger & Black to no1 red is3.98 V & Back to no 2 red is 7.82V .Not too much imbalance I would assume ? Fingers crossed.Could be a long night for 'er indoors Andy ---- I havn't given up yet --Only when my wallet says to me ----Go & buy some proper fuel while you can & tin hats are for H&S devotees only & by the way I'll swap about 7 chargers for one discharging device !! Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 8, 2008 Share Posted November 8, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 8, 2008 Share Posted November 8, 2008 AmenMyron...get the pack down to at least 6V before trying to refill. Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted November 9, 2008 Author Share Posted November 9, 2008 Will do -now - having re charged last night after falling to 7V - one cell taking 8 mins longer than another to charge - .but a slight increase up to 8.29V (90 % charge ).Wondering whether the 6 servos I have connected will speed up the discharge fractionally ?. Sorry to ramble on about this little problem but the experience may well help others who make "novices" mistakes Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 9, 2008 Share Posted November 9, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 9, 2008 Share Posted November 9, 2008 Myron - how do you know that one cell took longer to charge than the other? Are you charging each cell seperately? if so, why bother - just connect the pack to your balance/charger and let it do the work normally. Quote Link to comment Share on other sites More sharing options...
Former Member Posted November 9, 2008 Share Posted November 9, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted November 9, 2008 Share Posted November 9, 2008 Quote Link to comment Share on other sites More sharing options...
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