Dave Rose Posted February 7, 2014 Share Posted February 7, 2014 Hello, I have no experience of Life receiver packs, but I am considering getting a 700mah HK life receiver pack which has a receiver plug and is used without a regulator. I am trying to ascertain how i would check the capacity left after a few flights in the field. If it were a nimh pack i would plug the lead into my checker and get a read out. Can i do the same with the life , seeing as how it has the same type plug? If not, what do I do. ? Obviously i don't want it to die on me in the air. Also, I intend using it in a full house moulded glider, slope soaring. How many minutes flying would be safe ( a rough idea ) before re charging - which i can do in the field.? . TIA Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted February 7, 2014 Share Posted February 7, 2014 I have to admit to never ever using a checker, I use an on board indicator and make sure it's in the green while waggling the sticks before take off. I see how much charge I put back in after a few flights to gauge how many flights I can get out of the pack with a reasonable safety margin Quote Link to comment Share on other sites More sharing options...
chris basson Posted February 7, 2014 Share Posted February 7, 2014 I Seem to remember someone on another thread quoting 100 ma per servo per hour plus 100ma/h for the rx...However I can't recall whether this was for analogue or digital servos so not much use...This will obviously also depend on your flying style.But if you have an hour or so to spare why not power it all up and waggle this sticks a lot then stick it back on charge to see how much you put back into the pack, that should give you a rough idea!!Chris Quote Link to comment Share on other sites More sharing options...
Dave Miller Posted February 7, 2014 Share Posted February 7, 2014 I believe that a LiFe cell will give you the same time as an equivalent mAh rated Nicad pack. They do give a more stable voltage output than other types but the voltage does drop quickly on a fully discharged pack. So the question to ask yourself is how long is your present pack good for and use that as a guide. Bob's advice above is good too. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 7, 2014 Share Posted February 7, 2014 Be a bit careful Dave, you may get significantly less time for the equivalent capacity - as the voltage is higher than a 4 cell pack (and slightly higher than a 5 cell) then the current will be higher - although the servos will be faster. Quote Link to comment Share on other sites More sharing options...
iqon Posted February 7, 2014 Share Posted February 7, 2014 nimh checkers are for 4.8 &6v, life is not either of these you need to buy another checker, better safe than sorry... Quote Link to comment Share on other sites More sharing options...
Phil Green Posted February 7, 2014 Share Posted February 7, 2014 Its difficult to tell the capacity left in a life cell by measuring the voltage, the discharge curve is too flat. Best way is to familiarise yourself with the setup by playing with it as Chris suggested. Starting with short flights followed by a measured top-up charge, then increasing the length of flights and again checking how much goes back in, when you get to a combined flght time that needs say 2/3 of the packs capacity to recharge then you've found a comfortable limit. Life cells drop rapidlly so I wouldnt suggest using the last third or quarter of capacity. I've recently added a 'fuel-guage' type of readout to Wayne Giles' Lipo ESR meter firmware - after much experimentation from experts all over the world, we concluded there is no perfect correlation between voltage and remaining capacity and we settled on a compromise averaged from many discharge plots. At best, fuel-guage style meters are only approximate. The flat discharge of life cells makes a life fuel-guage even more so. Cheers Phil Quote Link to comment Share on other sites More sharing options...
Dave Miller Posted February 7, 2014 Share Posted February 7, 2014 Posted by Martin Harris on 07/02/2014 11:02:02: Be a bit careful Dave, you may get significantly less time for the equivalent capacity - as the voltage is higher than a 4 cell pack (and slightly higher than a 5 cell) then the current will be higher - although the servos will be faster. Will they? I think that mAh rating is provided for the nominal battery voltage so they will provide a higher wattage which is where the extra work comes from. Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted February 7, 2014 Share Posted February 7, 2014 i use my hitec checker switched on to the 6 volt range it give a rough indication of where it is as soon as it get into the yellow i would stop Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 7, 2014 Share Posted February 7, 2014 Posted by Dave Miller on 07/02/2014 12:07:01: Posted by Martin Harris on 07/02/2014 11:02:02: Be a bit careful Dave, you may get significantly less time for the equivalent capacity - as the voltage is higher than a 4 cell pack (and slightly higher than a 5 cell) then the current will be higher - although the servos will be faster. Will they? I think that mAh rating is provided for the nominal battery voltage so they will provide a higher wattage which is where the extra work comes from. I think you might be confusing the capacity with a Watt Hour rating. The capacity of a 1000 mAh battery refers to the amount of current that it will supply for an hour, To illustrate with some round figures: If your pack voltage is 4 Volts and you have a resistance of 4 Ohms in the circuit it's supplying then the current will be 1000 mA - the pack will last for 1 hour. Connect a 6 Volt battery of 1000 mAh capacity to the same circuit and the current will be 1500 mA so the pack will discharge in 40 minutes HTH Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted February 7, 2014 Share Posted February 7, 2014 Posted by Lee Smalley on 07/02/2014 12:13:06: i use my hitec checker switched on to the 6 volt range it give a rough indication of where it is as soon as it get into the yellow i would stop Be very careful Lee...Lifes have a very flat discharge curve in my experience & the voltage collapses very rapidly as they become exhausted. HK offer a LiPo/LiFe on board monitor which is useful....I find my batteries tend to sit at second green for ages...once it moved to 3rd green I'd think about stopping flying.... Quote Link to comment Share on other sites More sharing options...
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