Is it time to retire my LiPo

[Terry Plumridge 1]

3S Lipo, 1800mah,35C.

Interal resistance of 10.7  3.9  and 5.3 milli ohms.

No damage or swelling.

Is it time to bin it?

Thanks, Terry.

[Cuban8]

Have you noticed a significant reduction in flight times with the battery since new? Does it tend to get warmer than it used to in same or similar models?

If no to both and you say there's no puffing of the battery I'd say the battery was fine.

I understand internal resistance figures and their meaning, but for normal sport flying go by more practical evidence before chucking out an otherwise perfectly usable unit IMHO.

[leccyflyer]

^^^^^^^What he said^^^^^^^

 

Measuring individual cell IR and monitoring how that changes over a number of charge-discharge cycles in use* can provide useful information on battery degradation. You have to take a holistic view though - the most important thing being how the battery flies the model. If it continues to give good service and powers the model adequately then I'd be inclined to take that information as more important than an arbitary IR value . When I periodically review my batteries the IR figures cover a hige range and there's a reasonable correlation with battery size - wee ones have much higher IR than the larger multi amp hour capacity batteries. I also consider if there is any physical sign of puffiness or damage before deciding to retire a pack. 

 

If the pack still flies the model nicely then just keep using it, would be my way of dealing with it.

 

 

 

*By which I mean flying the model and using the battery to do useful work, not putting it through such cycles on the bench.

[Shaun Walsh]

1 hour ago, Cuban8 said:

Have you noticed a significant reduction in flight times with the battery since new? Does it tend to get warmer than it used to in same or similar models?

If no to both and you say there's no puffing of the battery I'd say the battery was fine.

I understand internal resistance figures and their meaning, but for normal sport flying go by more practical evidence before chucking out an otherwise perfectly usable unit IMHO.

And check the balance plug/leads to make sure that all the connections are good. I checked a battery which appeared to have one cell with much higher IR until I plugged the balance board into the charger properly.

[Allan Bennett]

I'm with the others when it comes to using batteries for as long as their flight performance doesn't deteriorate too much (or they don't overheat or puff).  For what it's worth though, many moons ago I read somewhere (don't remember) that a study had shown that a desirable IR would be something like 12000 divided by the mAh of the pack.  In the case mentioned in the OP that would be 12000/1800 = 6.67.  I have several 6S 2600mAh packs with IRs greater than that recommendation which are still flying my heli for the same duration as originally, and don't overheat or puff.

[Simon Chaddock]

Surely the "usefulness" of a LiPo depends on how you use it. Any fall off in performance will be far more noticeable and potentially serious in a "3 minute" EDF type flight which equates to a 20+C discharge rate than in a gentle 10 minute fight with an average 6C discharge or even a 20minute slow flyer flight.

 

I always check the cell voltages after a flight and note if one cell is significantly lower than the others as part of the storage charge routine. That fact alone suggest the LiPo should be used in a less demanding situation even if it otherwise does not display excessive heat at the end of the flight.

  

  

[Terry Plumridge 1]

Many thanks for all of your replies. My Lipo decided to voluntarily retire this morning. Due to a catastrophic encounter with Terra Firma it is severely damaged and no longer usable, but as usual everytime you post there is always something new to be learned from your answers.

 

Cheers, Terry.