Am I killing my batteries?

[Richlizard]

I have done my best to research battery voltages, timings and alarms etc., and thought I had it all sussed. I am well aware of the 80% rule and because I only have voltage checkers, I have listened to other people';s suggestions and set my lowest voltage warning for 14.5v and have not had any problems running for ten mins, rarely even getting the first red light or timer on my controller.

I carried out lots of tests, listened to others'; comments and set my alarms accordingly. But now i have concerns...

On my F550, I use 4s lipos, 5200 mah, 14.8v

Fully charged, they are at 16.8 or 16.9

It is only recently I read that checking how many milliamps are added to the battery that is the important thing. My charger has this facility, but I am hoping that someone might tell me this is not an accurate way to do it. This is why...

I finish a ten minute flight and more often than not my battery is around the 14.9v mark. I don';t think this is hammering it at all. So I put it on the charger at a very slow rate as anything over 3A I get an input vol error on my iMax charger. So it charges up to its usual 16.9v, nicely balanced, and I check how much ma it put back...

This is normally around 4,900!!!

Unless I am miscalculating, that means I regularly run the batteries down by almost 95%!!!

Surely this cannot be right? Or perhaps is this expected when on a slow charge instead of the full 1C charge?

Any help appreciated.

[flybywire]

Rich, i';m sure you';re over thinking this one, sounds like your lipo';s are tip top.  I charge my 5000';s at 5 amps, but in truth my rip max charger ramps down to about 3 amps after 10 mins or so.  I let it do it';s thing, it takes 2 hours to cram one full, and it does it very slowly, virtually no current for the last half hour!

Ps my lipo';s are getting a bit tired now, they';re a couple of years old or more, so they drop to 14 v or a little less with no real disasters.

[Hands0n]

I was going to say similar - appliance of too much science, bends the brain cells a bit.

Balance charge, let it do its thing and fully charge. That';ll do the trick nicely. Unless your charger is a bit off.

[dirtyharry]

it takes a bit more to fill em than actually goes in.

If I take my 5000 mah batteries down till the lipo alarm goes off it takes 5400mah to fill it. If I do a discharge test after charging,   it comes back with around 5000mah in the pack.

I take my new batteries and fly them till the lipo alarm just goes off ( about 20 minutes) , I then set the timer on the radio to a few minutes less ( 16 minutes) and its job done.

[Cloudbuster]

Rich !!! All is well with ur batts !!! That sounds like they are being used very efficiantly and you have a spot on charging regime !! The only thing i always do before i go out is give them all a last little tickle with the charger to make sure they are tip top. I have found that some of the older lipo,s will drop off a bit overnight after charging and that little poke means they are at peak power when i am out. Lipo';s are very good for predicting flight times as they are very consistent in there power delivery, just dont bash one they burn really well ....

Regards rob 

[Richlizard]

Ok thanks for putting my mind at rest everyone.

It kind of does beg the question though. How is it possible to know you haven';t used more than 80%?

I worry too much :)

[andythilo]

Get one of these:

http://www.align-trex.co.uk/batteries/batt-accessories/nimh-and-lipo-voltage-cell-and-capacity-battery-checker-over2333.html

Run your 550 for 5 mins, check what';s left. Then 6, 7, 8 etc.. until when you land you see just over 20% showing. Then set a timer on you';re transmitter for that time.

It';s not 100% accurate, but it';s better than over-discharging them.

[flybywire]

Ok thanks for putting my mind at rest everyone.

It kind of does beg the question though. How is it possible to know you haven';t used more than 80%?

I worry too much :)

Do you mean in the air?  An osd with mah consumed will tell u, obviously your charger will tell u when you get back home!

[Richlizard]

Do you mean in the air?  An osd with mah consumed will tell u, obviously your charger will tell u when you get back home!

I have just fitted and am highly impressed with the DJI Mini iosd. But this only gives voltage information (I say only, but it is very impressive).

My charger doesn';t tell me what the current mah is, only the voltage. It only tells me how much I am putting in, which from what I am understanding here is actually not a good way to tell how much the battery has been wallopped.