Battery Cycling

[Steve Hargreaves - Moderator]

Ever mindful of the dreaded black wire corrosion I try & keep my batteries (e-flight power packs & Rx/Tx batteries) charged when not in use however to rejuvenate my batteries for the "New Season" I reckon a good "cycling" is the answer & here I finally get to the point......What sort of voltages/currents should I use? Should the discharge cycle cut off at 1v per cell..? 1.1v...? 0.9v.......??? & what would be a suitable discharge current relative to the battery current?? 1C...? 0.1C??? & finally how close to the nominated capacity should a battery get to be considered good??

I reckon poor battery maintenance is the main reason for many crashes & the last thing I want to see is a much loved model hit the dirt 'cos some numpty (ie me!!!) didn't look after his cells properly!!!!

All thoughts greatfully received.....

[bushwhackerbob]

Having had a brand new battery pack (nicad) die on me during a 1st flight I always give my battery packs 3 cycles at the beginning of each season.
My charger is a propeak mercury with a limited discharge current.
I always stick to 1c charge and discharge rates according to the manufacturers rating when cycling cells.
The capacity is indicated on the charger display and I have always achieved a higher capacity reading than stated.
E.g. after cycling a 600mah pack in excess of 650mah.
Discharge voltages vary according to the types of cell used (1.1v/cell for nicads).
Good manufacturers usually quote capacities below achievable levels.
it is best not to charge or cycle at high rates and always give the 1/10th capacity charge initially unless otherwise instructed by the manufacturer.
Always follow the recommendations for the battery type. If not sure be safe and get advice from an electric flight specialist supplier. There are several in the uk.
I have also had problems with switches. Make sure that the switch contacts are man enough for the currents being used. This is especially important with e-flight systems where currents used are particular high. Use higher voltages for lower currents ( ohms law).

[Steve Hargreaves - Moderator]

Thanks for that Colin.....I have a Hyperion EOS5i that I can just set & leave....at 0.1C cycling 3 times is gonna take some time!!!!!!!

[bushwhackerbob]

Hi Steve

Hope the advice was useful. You did not say which type of pack you are using but although I have not used lithium cells much I believe that they should not be cycled. Also NIMH do not develop memory as do nicads so I'm not sure about these although my charger will cycle them whereas it refuses to cycle lithiums.
perhaps some of the e-flight guys could share some of their experiences.
At the moment I am on infernal combustion.

A good charger is a wise investment. Also consider a Whatt meter which is useful for measuring voltage, current and watts consumed.

Cheers Colin

[Steve Hargreaves - Moderator]

Yeah...I'm more of an ic man myself although I do dabble in sparky flying. The cycling issue is more for my Rx packs than anything. LiPos tend not to have a memory or self discharge much so I'm not concerned about them...nor my e-flight batteries to be honest.....if they get a bit tired then you get shorter flights but with still enough power to operate the servos after the power cutoff activates & you can land the thing...a dodgy Rx battery can really spoil an afternoon though if it curls its toes up part way through an enthusiastic bit of aerobatting

[Paul C]

NiCad's developing a memory is a bit of an urban myth. Modern NiCd's don't have this problem, this story dates back to old satellites that had very specific patterns of charge and discharge to do with their orbit..
That said, modern NiCd's and NiMh's DO suffer from "Sleepyness", when they are new or when they haven't been used for a while they do need a kick or 3 to get them up to full capacity, esp the ones used for high current applications. How many people have seen the flight time on a new pack almost double after a few charges ?

I always do a couple of cycles on any new battery, firstly to test it (as someone mentioned above, battery packs are not immune to manufacturing errors) and secondly to wake them up..

As for LiPo, I haven't seen a memory or sleepyness on my packs, they appear to be a lot better out of the box. Any agree / disagree ?

Paul

[Bladerunner]

Good point w.r.t the Nicd's and NimH cells. They can be "sleepy" if unused for a month or more.
Lithium Ion and Lithium Polymer cells do not suffer from the aforementioned characteristics. The only thing to watch out for with Lipo's is the operating temperature. Recommended range for discharge is -10degC to +55degC (+5degC to +45degC for charge). You will notice they become "sleepy" once temperatures drop below zero. By the time you get to -20degC they are almost useless.
This low temperature effect is alleviated by discharging the pack, which does of course raise it's temperature - following charge and discharge cycles are then more efficient.

[Peter Wood]

I would appreciate some definitive advice on charge / discharge rates for Rx batteries, both NiCd and NiMh.
My SM Services cycler discharges at 300mA so I use that on both my Prodigy and new ProPeak Sigma chargers irrespective of cell capacity.
But when it comes to charge rates I really do not know what is correct. I normally charge my flight packs at 1C ie 0.8 amp for a 800 mAh pack,using peak voltage cutoff. Some of my Overlander packs suggest this is OK on the label. However some guys at our club suggest that this is not a good idea as Rx packs are not designed for higher charge rates and it will shorten their life. On the other hand it seems to me that this can lead to over charging. Eight hours at 0.1C is 50% of capacity when the pack might have been almost full after the previous session.
I have noticed that a number of my packs only have 75% capacity after a couple or three months without charge. Is this because of the previous higher charge rates?

[Bladerunner]

You can decide what charge rates you're comfortable with, as long as you operate within the maximum boundries for charge acceptance. Currently, for the chemistries we use the following maximum charge rates are safe:

1.) Lipo = 1C (compulsory, do not exceed)
2.) NiMh = 1C (TX, RX cells)
3.) NiCd = 1C (TX, RX cells)
3.) NiMh = 2C (motor drive cells)
5.) NiCd = 4C (motor drive cells)

If your battery packs can't handle this max rate of charge, bin them and get some new ones. Charging at these rates from time to time not only exercises the cells, but shows they are in good condition(the exception to this is Lipo's).

Trust that helps.