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electric flight frrustration


ericrw
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As an avid electric flyer, I do have one frustration! Mainly due to the weather forecasts which predict bad weather for the following day. On hearing this I don`t bother charging my flight batteries and the transmitter. Only to find next day to be an ideal day for flying !!! Eric.

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If the delay is only for a few days, I would just leave the Lipo charged.

If I became worried I would just, put onto a storage charge.

I must say though, I am reluctant to go to storage charge, as i have come to believe that it is the number of cycles that is important, as well as not storing for prolonged periods at full.

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I cannot speak for the rest of the country, the forecast for the NW is nearly always pessimistic. The weather often being better than predicted.

In one area in particularly they are pessimistic and that is with respect to rain. Although I do remember as a youth, the weather here would be grey, just 13 miles away, where my wife (then girlfriend) lived, it would be raining, sometimes quite heavily. In winter it would be cold at home, and snow would be around the Bury/Rochdale area.

I have no complaints in general with respect to forecasting.

I do not know about the rest of you, i have on the desk top both the Met Office and a Microsoft weather utility, which I refer to the day before and often on the same day.

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Like some of the others, I leave my LIPO's at about 4.0 to 4.1v at all times and they're ready to go and I don't care about the odd 0.2v and it's associated reduction in capacity - I've got 3S cells 3 years old and haven't noticed any significant drop off in performance and they've been stored at over 4v at all times.

I never tend to fly until the batteries are flat and swap batteries a lot - I have a lot of LiPo's

Does anybody have firm evidence that keeping them at 90%+ harms them or is it like the old wives tales about NiCads and 'Memory' which I never experienced in over 15 years of flying and car racing?.

I've read about 40% capacity loss after storage at 60DegC for a whole year but come on, this is the UK..... (nearer the 4% loss at 0-10DegC)

I store my LiPo's in an unheated model room and I cycle the use of my batteries by labelling them when bought so I quess they're all used at least once a month during the summer and less during winter when the temperature in the room is maybe below 10DegC for extended periods but it does have an antifrost heater set a 4DegC.

If someone has more than anecdotal evidence of harm then I'll just postpone re-charging the batteries as I re-cycle the numbers.

Thanks for any feedback.

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I have suspected that some of the issue with respect to Lipos and full storage revolve around the relationship of charge voltage and temperature.

I have the impression that charging a Lipo to 4.2V, when cold say 0 degree, will have the effect of the cells voltage going beyond 4.2v when in a higher temperature, say 20 degrees. As the chemistry of the Lipo does not allow this, the result is some damage to the cells chemical structure.

I do not know this is fact, just a conjecture I have reached, from reading some articles.

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I recently bought a Power tech Xdrive 6 charger, so together with my Bantam BC6, can charge 5 batteries in about 40 mins. I've then got a seven minute walk from the house to the field. So, if good weather comes along, or the wind drops late afternoon, I can get a session in at short notice. Sorry to sound smug!

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Posted by Biggles' Elder Brother - Moderator on 16/12/2012 16:40:09:

I fly quite a lot so I usually just keep them charged. It doesn't seem to have had any ill effects.

BEB

Ditto, especially as these days, they are comparitively cheap to replace if hey do start to lose capacity quicker than one likes. I suspect this however is due to either

1) Discharging ( in use ) too low ( guilty occasionally at the indoor flying)

2) Thrashing the life out of 'em with v high current demand ( guilty on several counts m'lord ) blush

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Another query?? Should one leave a Transmitter connected to the Wall Charger, at all times when not in use ?? I normally charge the transmitter overnight, using the Wall Charge (or wall wart as Tim calls it!),if the forecast is good weather for flying next day. But then I get caught out if the forecast is wrong! Eric.

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I normally plug mine in before i go to bed, on average thats 7pm, im then up at 6 for my morning flight and its charged nicely, i dont trust chargers to be left on all the time, i fly almost everyday come rain or shine, though i do remember leaving my old futaba skysport 6 plugged into the wall most of the time

Scott

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Posted by Erfolg on 16/12/2012 16:11:14:

I have suspected that some of the issue with respect to Lipos and full storage revolve around the relationship of charge voltage and temperature.

I have the impression that charging a Lipo to 4.2V, when cold say 0 degree, will have the effect of the cells voltage going beyond 4.2v when in a higher temperature, say 20 degrees. As the chemistry of the Lipo does not allow this, the result is some damage to the cells chemical structure.

I do not know this is fact, just a conjecture I have reached, from reading some articles.

 

Store my Lipos in a very cold (but dry) garage never noticed the alleged voltage change or any deterioration.  Aways bring the packs up to room temp if they've been soaking at near 0C though. Also worth keeping them warm in freezing temps over the field - I put a couple of the click type hand warmers in their box - keeps their performance up to scratch.

 

Edited By kevin goodwin on 16/12/2012 19:25:21

Edited By kevin goodwin on 16/12/2012 19:26:33

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