Rx battery

[Pilot Ben 28]

Hiya,

 

If I 100% charged a regular 6V rx pack but then didn't fly the plane for some reason, do I need to discharge it that day and then charge it agin next week or can I keep it like a lipo IE at full charge for a few weeks?

 

B  

[Trevor 25]

Ben

No need to discharge nimh packs, I just do a top up charge the day i want to fly.  Every now and then i cycle them (every 3 months or so) as that is supposed to prolong life.  Also depends if they are the low discharge kind

[Pilot Ben 28]

Thanks Trev  

see you later,

 

B

[Bravedan 106]

A NORMAL NIMH battery will steadily start to lose its charge even if not connected anywhere in a few days, unlike a LiPo or LiFe. It is therefore risky not to top up charge before use if several days have elapsed.

The "ENELOOP" and "INSTANT" types were introduced to limit that loss, though TBH I prefer the normal type as a lot of the low discharge NIMH available exhibit other flaws esp the ability to be easily over charged and damaged if repeat charged "to be sure they are OK", as some people used to std NIMH do.

Most chargers are simply sensing the start of a negative dip in cell voltage on charge completion, and some low discharge cells fail to trigger this crude shutdown process fast enough to avoid damage when "topped up" more than once in quick succession.

NIMH batteries of all types do not have the "memory" that afflicted the (now banned from sale) NICAD so cycling is not necc nor is discharge to low or min voltage any particular advantage. (Cadmium is a heavy metal, dangerous in the environment, and must be carefully disposed of)

I tend to use Vapextech products (a local mail purchase firm!)

I charge over 100 normal NIMH packs every week, some of which are over ten years old !!!!

Following on, are you aware of "black wire" syndrome? This particularly but not exclusively affects low current circuits subject to intermittent use like Tx and Rx pack wiring.   It is not a problem exclusive to the black insulated wire (as you will find stated by "experts" on't Internet!) , though can be first evident there through leakage to earth in circuits.

It is blackening and eventually crumbling away of the copper conductor, with increasing resistance and loss of current carrying ability.

Unfortunately it is usually hidden out of sight and mind behind wire insulation/sleeving/casing and has to be looked for. It is usually THIS which limits pack life and has caused over the years lots of crashes!  Its another reason I do not like the Instant type, as with many people they get left for months and are then used with no charge and no inspection!

ANY wiring on RC gear can be affected, cell pack, switch harness, etc. I have had four cell 3700mAh NIMH car packs with shrink wrapped and plastic ends fall apart internally and the wire rot off the out of sight inside the pack battery connection. Simple voltage checks do not find this!

The pack has usually been fine again once the wiring was replaced, BUT if that had been an in use plane pack...................!!!  Hence the general advice to regularly inspect carefully and replace unless frequently used and carefully checked.

[Pilot Ben 28]

Thanks for the info Dave! All my batteries are 6V vapextech items...

 

b  

Edited June 5, 2017 by Pilot Ben

[Trevor 25]

The other advantage of cycling them occasionally is that you can tell if they are giving full or sufficient capacity.  Sometimes they appear to be fully charged but only give a few hundred maH instead of the 1000maH or more they should give, which can catch you out after a few flights

[shanemarsh28 11]

13 hours ago, Trevor said:

The other advantage of cycling them occasionally is that you can tell if they are giving full or sufficient capacity.  Sometimes they appear to be fully charged but only give a few hundred maH instead of the 1000maH or more they should give, which can catch you out after a few flights

I've got a couple of old RX batts that are that I dont fly for that very reason. They look fullly charged and they peak but after only 10 mins or so in the plane, the voltage drops so low that receiver actually powers off! Completely drops dead. They were left in a case for about 4 years fully discharged. I've ordered a proper NIMH/Lipo charger this weel so i'll will try cycling them a few times but my gut says they are fit for the bin  

Edited June 5, 2017 by shanemarsh28

[Bravedan 106]

OK lets treat this as if if were not a wind up...................as some may get confused..........................and putting it in print without clarity is not helping our case for being responsible people fully capable of being safe when taking part in our sport.

 

Cost of Rx battery?     Less than £8

https://www.vapextech.co.uk/batteries/radio-control/receiver-packs/4-8v-battery-pack-48v-2600mah-nimh-flat-vapextech-rx/

https://www.vapextech.co.uk/batteries/radio-control/receiver-packs/4-8v-battery-pack-48v-2500mah-nimh-instance-flat-vapextech-rx/

https://www.vapextech.co.uk/batteries/radio-control/receiver-packs/?p=2

etc, etc...........

Versus:-

Cost of plane, gear, insurance claims, hospital bill, time attending court, loss of flying field, etc, etc, etc?

Good luck convincing a court you were complying with :-

"The person in charge of a small unmanned aircraft may only fly the aircraft if reasonably satisfied that the flight can safely be made."

When they learn you avoided spending £8 to be safe and so avoid someone being injured or worse.

[Trevor 25]

Yes, if a battery is not holding a charge it should be binned.  No amount of cycling will restore it safely.  Cycling a battery can tell you if it holding a charge.  Personally,  i renew my Rx and Tx batteries every 2-3 years regardless

[Pilot Ben 28]

I replace the ones with bigger servos every year! In my hype for example I run big HS645MG servos that draw a ton of power so the batteries are constantly drained and re charged, so I don't risk them longer than a year or two at the most, and if it has been sitting for a year or so I also still bin it or keep it to power something non flight related...

 

B