LiPo deepish discharge question

[Tim Kearsley]

Hi all,

 

On Sunday, I ran four FlightPower 3s, 3300 mAh packs through my new Lander Panther EDF jet.  In each case, I got flights of about 4 minutes, running on full throttle throughout.  In each case also, the power died quite rapidly, presumably because the ESC LV protection kicked in.  I haven't measured the current draw on this model yet, so can't comment on that.

 

Now normally I don't discharge my LiPos so deeply, or cane them so hard.  Yesterday evening, I was flying my Seagull Edge 540 using the same batteries, after recharging of course!.  I was getting noticeably less flight time out of them - normally I would fly this model for about 10 minutes and there would be power in reserve, whereas last night I was losing power again after about 8 minutes.

 

So the question is - do LiPos need a "recovery" time?  They were fully charged before using them last night, but it seems like they have lost some capacity.  The ESC LV protection on the Panther was set to cut in at 3V/cell I believe.

 

Any thoughts?

 

Cheers,

 

Tim.

[Tim Mackey]

The Lander EDF units are high performance fans, but at a cost of course - after all, as they say, you dont get 'owt for nowt. The current draw on these fans is, I believe, around the 50A+ mark and even on a 3300 pack thats quite high - especially if they are not high C rated ( you dont mention the C rate ? ). They are also working this hard all the time, with little or no let-up, so you may have simply just pushed them so hard that they have lost some performance.

1) Did you balance charge them after wards, and check each cell?

2) what capaciy was returned to them during charging, and

3) what was the terminal voltage of each cell?

I am finding more and more these days that the flightpower packs are not as good as they used to be

[Tim Kearsley]

Well the packs are, I believe, rated 25C continuous.  I did balance charge afterwards, but I have to admit that I didn't check the individual cell voltages, nor did I record what charge was put back in (hangs head in shame).  I noted that the packs were quite warm after each flight in the Panther, but I wouldn't have said excessively so.

 

I guess I'll have to see how they go.  I did notice after the more normal flights last night that the first two charged took respectively 2600 and 2800 mAh back in.  Haven't had time to charge the other packs yet as I won't charge LiPos unattended.

 

Tim.

 

[Tom Foreman]

Hi Tim, do you have any way of measuring the internal resistance of the packs? I find this the best indicator to their state of health. My good packs are about 3 -4 milli ohms, my tired packs are about 16 milli ohms. I measure the internal resistance using an FMA cell pro charger.

 

Cheers,

 

Tom

[Bladerunner]

Posted by Timbo - Moderator on 18/08/2009 08:45:16:

The Lander EDF units are high performance fans, but at a cost of course - after all, as they say, you dont get 'owt for nowt. The current draw on these fans is, I believe, around the 50A+ mark and even on a 3300 pack thats quite high - especially if they are not high C rated ( you dont mention the C rate ? ). They are also working this hard all the time, with little or no let-up, so you may have simply just pushed them so hard that they have lost some performance.

1) Did you balance charge them after wards, and check each cell?

2) what capaciy was returned to them during charging, and

3) what was the terminal voltage of each cell?

I am finding more and more these days that the flightpower packs are not as good as they used to be

 I heard the same thing, but apparantly the new eon-x packs are longer lasting. Specs seem good too.