NiMh batteries

[fly boy3]

Hi all, due to Covid, bereavement and other reasons I have not flown for nearly three years. My Rx batteries are charging well nut must be five or six plus years old. I think I need new ones ?  Cheers FB3

[David Davis]

Hi FB3 and welcome back!

 

Having always been brought up to be cautious with money, I fitted an old receiver, switch and battery to my latest model, a 1957 Guidato designed by Brian Sichi which I intend to use as a basic trainer for elderly beginners. On its third flight it suddenly spiralled into the ground and now I have a considerable repair job on my hands.

 

A new battery switch and receiver are going into the model once repairs have been completed.

 

 

[Frank Skilbeck]

If you have a smart charger you could always cycle them and check their capacity and ability to maintain voltage under load.

I do this on a regular basis with my Nimh batteries, if they don't provide 80% of the nameplate capacity then they get relegated to bench use.

[Nigel R]

Exactly as frank says. Battery lifespan is one of those piece of string type problems. If you have a multi charger of some kind they can be tested quite easily.

 

The key point for nimh batteries is avoiding letting them get completely flat, they do not like that. 

[Jon H]

I agree with Frank and i use this routine myself. 

 

Charge to peak using my normal 'going to the field' peak charger that will do 3 batteries at once. I then leave it for 2 days, and do a discharge recharge cycle at .5 amps down and up. Once done i compare what came out to what went in vs the battery capacity and made a judgement on how the battery is doing. 

 

I also keep an eye on my batteries when charging them in normal use as, for example, i fly X model one week and fly it again a 2 weeks later. If it takes about an hour to recharge after flying it and a 2 week sleep, and this is the normal recharge time i see when i generally fly it in this sort of pattern, if it then starts taking an hour and half or two hours for the same amount of use its a red flag something is wrong. I noted last year that my Sea Fury battery was down into the red after winter inactivity but none of the other batteries in models stored in the same environment were. I did the above cycle test, which it just about passed, but being suspicious i left it for another 3 weeks without flying and it was back in the red again. Clearly not right it was removed, a knot tied in the lead to remind me it is non airworthy, and it now floats around the bench and other places for setup work. I may use it in future to power electric retracts or something not mission critical. 

 

In any event, there is no hard a fast test that will guard against all failure modes. The best defence is knowing your gear and how it performs, look for trends, changes in behaviour etc. Basic vigilance really. 

[Don Fry]

As they say.I have one pack still in use, it’s about 12 years old, installed new in its current airframe. Used regularly, tested for ability to deliver power as advertised, not broke, no fix needed.

No a fan of these cells, but I will wait until I have a reason to get shot of the last of that chemistry

Edited March 8, 2023 by Don Fry

[Andy Stephenson]

If in doubt do a discharge test. The best nickel hydride batteries for longevity are the Eneloop type although not recommended for high current applications.

 

[fly boy3]

Hi Frank , how do you put a load on them on the bench ?

     Hi David, very sorry to see the model come to grief. Bet it was a great flier too.  Cheers FB3

[Frank Skilbeck]

FB3, depends what charger you are using, my chargers allow you to discharge the battery and I typically set a discharge current and cut off voltage, so for say a 2,000 mag 4 cell 4.8v battery I'd set the discharge current to say 600 ma and cut off voltage 4v. The charger then reads out the current, mah and voltage, if the battery volts drop very quickly on load in the first minute, say start 5.5v (fully charged) and drop to 4.5v on a 600 mah load it indicates a high internal resistance, which could lead to a receiver brown out if the servos demand too much current in flight.

[fly boy3]

Hi Frank ,apologies for delay in reply.  I have read that to check the capacity  of battery, you should discharge then re charge. As a newly to electrics could you please explain the procedure.  Thank you. FB3

[Denis Watkins]

Wait for the reply Mr Flier, before you do any discharging.

On any battery chemisrtry, discharging to Zero would damage the pack. The discharge referred to here is a % discharge.

[Jon H]

For nimh and nicd i drain them to 1v/cell which looks like the same as Frank. Although these ni cells are more tolerant of a pankcake flat situation than lithium cells its not a great idea to completely drain them. 

 

 

[fly boy3]

Thanks both for your replies. I have an IMAX B6 charger that has discharging facilities. I will wait a little longer for info on its use for this particular application.  ps Has this forum a system where I can send private mail to a moderator ?  Thanks

[john stones 1 - Moderator]

31 minutes ago, OLD FLIER said:

Thanks both for your replies. I have an IMAX B6 charger that has discharging facilities. I will wait a little longer for info on its use for this particular application.  ps Has this forum a system where I can send private mail to a moderator ?  Thanks

click his name/avatar, message option is there.

[Paul De Tourtoulon]

Ok the old cadmium nickel battery's especially the SCR ones needed decharging to get the maximum from them, look at the old 7.2cv 6+ cell ones, but the Nihm will be ruined if you decharge them, they don't ( if I remember right) have the same 'memory' problem that the cadmium nickel battery's had.

[john stones 1 - Moderator]

6 hours ago, OLD FLIER said:

Thanks both for your replies. I have an IMAX B6 charger that has discharging facilities. I will wait a little longer for info on its use for this particular application.  ps Has this forum a system where I can send private mail to a moderator ?  Thanks

 

Sent you a message OF, click envelope top right at side of your name.

[Christopher Wolfe]

I still have my lovely ACE PCR (Positive Current Reversal)  NiCad battery charger that I purchased over 20 years ago.

 

The pulse charger actually measures the battery voltage, spikes it with a negative high current pulse (to remove dendrites) and then gently charges the pack.

 

I have had a 4.8V Sanyo NiCad on charge since 2001 and it still has 98% capacity according to my RCM Jim Oddino ESV load tester.

 

NiCads are still available here in my part of Australia, Panasonic from a dedicated battery store are great.

 

Showing my age.

 

Chris

Edited March 21, 2023 by Christopher Wolfe
20 years out of date with my original post - please put it down to old age

[Engine Doctor]

Re old batteries an slightly off topic . I was given an old model last year with Futaba  M 35meg radio and original Futaba battery pack in biege plastic case. All was in excellent clean condition and no evidence of black wire corrosion and had been hanging in a garage for over 30 years ! ( the garage was not tun of the mill but very large with a firs5 floor, well insulated and dry )The battery showed no life on a voltmeter but not surprising. I thought I'd try a charge just to see if the cells would revive. After a 24 hrs trickle charge they came back to life reading just under 5v and a month later still showed 4.8  .

I wouldn't dream use the battery but it does show how resilient the older cells could be. 

 

I still have the  complete Futaba M series flight pack Rx, four servos , two red and two black, switch harness and battery if any collectors out there are interested? A small donation for the Air Ambulance plus postage will secure it . If interested please pm. 

[fly boy3]

Nice story ED. Nimh batts. are quite cheap compared to Lipos so I will purchase what I need of new ones. I am still mystified by the info on Lipos being new to electrics. Right, I charge my Lipos, check capacity and go flying. Pack up, but don’t know when I will fly again. What is the correct procedure at this moment ?  Thank you.

[Paul De Tourtoulon]

1 hour ago, Engine Doctor said:

 

 

I still have the  complete Futaba M series flight pack Rx, four servos , two red and two black, switch harness and battery if any collectors out there are interested? A small donation for the Air Ambulance

Et la boucle est bouclée,,,

In English, and the circle is complete,

And a blood donor would help when the old Futaba 'uncontrolled' plane plows into the crowd.

 if you get what I mean,,,🤪

[Engine Doctor]

1 hour ago, OLD FLIER said:

Nice story ED. Nimh batts. are quite cheap compared to Lipos so I will purchase what I need of new ones. I am still mystified by the info on Lipos being new to electrics. Right, I charge my Lipos, check capacity and go flying. Pack up, but don’t know when I will fly again. What is the correct procedure at this moment ?  Thank you.

If your not going flying for a couple of weeks then recharge your liposuction when you get home and they will be fine when you next go . If its winter time and your not likely to fly for a few months then discharge to storage voltage a d liposuction should be fine.

1 hour ago, Paul De Tourtoulon said:

Et la boucle est bouclée,,,

In English, and the circle is complete,

And a blood donor would help when the old Futaba 'uncontrolled' plane plows into the crowd.

 if you get what I mean,,,🤪

Actually the old M series was very reliable radio but it is suggested for the collectors amongst us and not for general use. Having said that a couple of members still use 35 Meg at our club and report that since 2.4 became the norm radio they never get glitches as they did back in the day ? They still get ribbed about being tight wads.

[fly boy3]

Cheers ED, I got it at last.  Also I still use my Futaba 35mhs radio for a vintage Super Scorpian  model built in the seventies.  Thanks again for the info.

[Paul De Tourtoulon]

Only Pulling your leg Engine doc,,,I bought my Futaba "M" six channel set in 1975  (27mhz) and never a glitch, I still fly my Futaba FX-30 on 41 mhz, including my Wren jubilee Rafale and all my helicopters, .61 and .50 powered, and there also no worrying knee trembling glitches,,,

[J D 8]

Also still have a working Mseries TX,the workmanship inside is just lovely to look at.

[Nigel R]

On 20/03/2023 at 15:23, OLD FLIER said:

I have an IMAX B6 charger that has discharging facilities

 

That'll do nicely.