Battery Life Issues

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I have seen many posters comment that they are finding their batteries are becoming unreliable after 30 or 40 flights. This does not seem to make a lot of sense since according to most Li-on manufacturers the batteries should be good for ~200 cycles or so. I found this interesting article on Li-On batteries and maintaining them on this site: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
the article indicates that even after 100 cycles the batteries should have near 85% of their original capacity.
It is definitely worth a read and hopefully someone out there can figure out why these very expensive battery packs don't seem to hold up like they should?
Thanks for any replies!
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
 

N017RW

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I have seen many posters comment that they are finding their batteries are becoming unreliable after 30 or 40 flights. This does not seem to make a lot of sense since according to most Li-on manufacturers the batteries should be good for ~200 cycles or so. I found this interesting article on Li-On batteries and maintaining them on this site: http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
the article indicates that even after 100 cycles the batteries should have near 85% of their original capacity.
It is definitely worth a read and hopefully someone out there can figure out why these very expensive battery packs don't seem to hold up like they should?
Thanks for any replies!
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries



The 'smart' system is supposed to protect them from the know abuse issues such as over-charge, over-discharge, improper balancing, etc. so what then would cause this?...

...low quality and while monitoring voltage during charging, do not appear to be charged correctly by the 'smart' system (i.e.CC/CV).
 
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Because they are low quality and do not appear to be charged correctly by the 'smart' system.
Well they certainly aren't "low priced" - not from DJI anyway. It will be interesting to see if anyone who has bought the LimeFuel batteries reports better luck with battery life!
I wonder if that charger that does 4 batteries at a time properly charges the batteries - if you read the article it indicates that the charging rate DOES affect battery life - the DJI charger seems to charge them fairly fast - wonder if that could be part of the cause??
Thanks for the reply!
 

msinger

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Also, I don't know that most people understand how to properly care for their batteries. It seems many people believe the batteries will care for themselves.

Here's a good article about RC batteries (not DJI specific though):
http://www.rchelicopterfun.com/rc-lipo-batteries.html
 

N017RW

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Well they certainly aren't "low priced" - not from DJI anyway. It will be interesting to see if anyone who has bought the LimeFuel batteries reports better luck with battery life!
I wonder if that charger that does 4 batteries at a time properly charges the batteries - if you read the article it indicates that the charging rate DOES affect battery life - the DJI charger seems to charge them fairly fast - wonder if that could be part of the cause??
Thanks for the reply!


I edited since your quote/post.

LiPos should follow a 'constant current, then 'constant voltage' charging profile, CC/CV.

Charging at 1C should produce an approximate one hour charging cycle.

The first 40 or so minutes the battery is fed constant current equal to it's capacity or C rating. So for a P2 will call that 5.2 amps. Once the battery reaches 12.6 the charger then begins the CV phase by slowly lowering the current to maintain the 12.6volts until it reaches about 1/10 or so of the C rating. This usually takes about 40% of total charge time ending after about 1 hour.

If you monitor the P2 batt. voltage during charging it is a slow ramp-up to 12.6 volts at which time the charger shuts-off. This is not CC/CV.

Because the DJI P2 charger can only deliver 4 amps (probably less due to losses) it take more than an hour to charge a 5.2C, amp, battery.
 
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I edited since your quote/post.

LiPos should follow a 'constant current, then 'constant voltage' charging profile, CC/CV.

Charging at 1C should produce an approximate one hour charging cycle.

The first 40 or so minutes the battery is fed constant current equal to it's capacity or C rating. So for a P2 will call that 5.2 amps. Once the battery reaches 12.6 the charger then begins the CV phase by slowly lowering the current to maintain the 12.6volts until it reaches about 1/10 or so of the C rating. This usually takes about 40% of total charge time ending after about 1 hour.

If you monitor the P2 batt. voltage during charging it is a slow ramp-up to 12.6 volts at which time the charger shuts-off. This is not CC/CV.

Because the DJI P2 charger can only deliver 4 amps (probably less due to losses) it take more than an hour to charge a 5.2C, amp, battery.
Agreed - it takes somewhere around 80-90 minutes to charge a battery that has been depleted to around 10% of capacity. Well if the issue is a dual problem - battery quality/charger quality then I will have to keep looking for better batteries and a better charger obviously - can't afford to replace batteries after 30 or 40 flights - it's already a fairly expensive hobby as it is!
Thanks for the info!
 

msinger

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N017RW, are you suggesting it would be best to use a 3rd party battery charger? If so, can you recommend any?
 

N017RW

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N017RW, are you suggesting it would be best to use a 3rd party battery charger? If so, can you recommend any?


No because you can't 'get past' the smart system. With the possible exception of a higher current supply to reduce time but I don't know how the smart system would handle that.

I'm concerned over the apparent (my observations only) charge cycle not being CC/CV.
 
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I seem to remember reading that one should limit their battery use to 30% to get longer battery life...any truth or logic to that?
 

N017RW

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I seem to remember reading that one should limit their battery use to 30% to get longer battery life...any truth or logic to that?


Just a few years ago when flying CP Helis, the rule of thumb was 80% discharge max and never below 3.3v per cell under load. Doubt much has changed.

Although the P3 is touting a 4S 15.2 when currently most all other 4S packs are rated at 14.8v so there may be a new rule for those types.
 

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