Nicads and Storage ... - RC Groups
May 19, 2011, 02:46 AM
Registered User
Help!

Hi,

Took my nicads out the other day (for my nitro planes' receivers) and I charged them on the trickle charge overnight.

They are 4 cell nicads and they charged to about 5.32v total.

I read somewhere a fully charged nicad should charge to around 6v??

So are my nicads ok to use?

Also how do you charge your nicads/nimhs to reach their full potential and maximum longevity?

Thanks.
 May 19, 2011, 05:14 AM Zero Expo Trickle charging is used to maintain fully charged cells at full charge. It isn't to charge a drained cell. Your battery should be charged at a rate of C/10 for about 16 hours. For example, if your cells are 800mAh: Code: 800 ÷ 10 = 80 That would mean that the charge rate should be 80mA.
 May 19, 2011, 06:38 AM Registered User Yes, NiCads can be in excess of 1.5v per cell when fully charged, so you should be seeing something higher than 5.32v. As typeRA has suggested, your charge was maybe not enough mA and duration to get the pack fully charged. How long were the packs in "storage", and do you know what voltage they were before you started the charge? Personally, I would cycle them a couple of times and see if the same mAh goes in each time. I don't know what the definitive answer is about ensuring a long life, but I believe that slow charge rate (1/10C) helps. I then judge whether a pack needs binning by seeing how many mAh it takes after it's been used the previous week and then sat on the shelf for a week. No hard numbers, but simply a comparison with what it "normally" takes -- if it suddenly takes more than "normal", it's binned. Operating that way, my receiver and transmitter packs last several years.
 May 19, 2011, 01:50 PM Registered User Trickle charge, by definition, is just enough to overcome the self discharge rate of the battery so will never charge a discharged cell. What you may mean, if you were using a wall wart that usually comes with a system, is you were slow charging. This is typically at 0.1C and to fully charge (an insure balanced cells) is to charge at 0.1C for 15 to 16 hours, longer won't hurt. Your fully charged 4 cell unit could read as high as 6 volts, at least 5.8 volts fresh off a 16 hour slow charge.
 May 19, 2011, 02:14 PM Registered User A fully charged NiCd will only reach 1.35 volts per cell. If you want to bring a NiCd pack back to life you will have to discharge then recharge (cycle) the pack 3-4 times. Discharge down to .9 volts per cell, then recharge the pack at 1 amp using a peak Delta type charger like the Triton, iCharger, etc. NiCd and NIMh packs have to be worked vigorously to get the best performance out of them. Cycling a pack using the above parameters once every 6 months will keep the pack in top condition.
 May 19, 2011, 03:00 PM Intensely Calm Good advice here. As a side note I've found this special treatment is not often required on the newer low self-discharge (LSD) NiMh cells and I'm slowly phasing out all my older ones for this much more predictable type. They seem to have less memory effect (behave more like lipos) and still have near full capacity after a month on the shelf. - David
May 19, 2011, 03:34 PM
Registered User
Quote:
 Originally Posted by Mugwa A fully charged NiCd will only reach 1.35 volts per cell. ...
I don't have any NiCd transmitter or receiver packs any more (all NiMh now), but the two larger NiCd packs I have (7-cell 2000mAh) both normally peak at around 11.6 - 11.7 volts, which is 1.66 - 1.67v per cell.
May 19, 2011, 04:23 PM
Registered User
Quote:
 Originally Posted by abenn I don't have any NiCd transmitter or receiver packs any more (all NiMh now), but the two larger NiCd packs I have (7-cell 2000mAh) both normally peak at around 11.6 - 11.7 volts, which is 1.66 - 1.67v per cell.
The reason for the difference is that the 1.35V/cell is the fully charged settled voltage ie the voltage the fully charged cell will settle at some time after charging so that 1.55V/cell is the fully charged voltage on charge 1.66V/cell sounds a bit high - could well be a diode in series with the pack accounting for the extra.
Nicads will always benefit from cycling if they have been left unused, but generally they are not damaged by discharged storage. Really good ones will last years. I have a Sanyo Rx pack which I had not touched for 14 years and it still had significant energy left in it. A few cycles brought it back to practical use.
BTW it is (or was) and industry standard to assume that a nicad cell was at the end of its life when its capacity has fallen to 80% of rated value.

Wayne
May 19, 2011, 04:40 PM
Registered User
Quote:
 Originally Posted by Mugwa A fully charged NiCd will only reach 1.35 volts per cell. If you want to bring a NiCd pack back to life you will have to discharge then recharge (cycle) the pack 3-4 times. Discharge down to .9 volts per cell, then recharge the pack at 1 amp using a peak Delta type charger like the Triton, iCharger, etc. NiCd and NIMh packs have to be worked vigorously to get the best performance out of them. Cycling a pack using the above parameters once every 6 months will keep the pack in top condition.
How would I go about getting the Nicad down to .9 volts per cell? By flying the plane? And doing this 3-4 times? confused.

What I meant by trickle charge is the wall wart charger, yes.
May 19, 2011, 05:09 PM
Registered User
Quote:
 Originally Posted by hcsk8ter How would I go about getting the Nicad down to .9 volts per cell? By flying the plane? And doing this 3-4 times? confused.
NOO!! You never want to fly a pack that is 4.8volts or lower (for 4 cell packs). You need a charger that can cycle packs (ie, any modern 'smart charger').
May 19, 2011, 08:48 PM
Registered User
Quote:
 Originally Posted by RedStarArmy NOO!! You never want to fly a pack that is 4.8volts or lower (for 4 cell packs). You need a charger that can cycle packs (ie, any modern 'smart charger').
I have a few parkzone nimh chargers, cellpro 4s revolution (believe it's just for lipos), imax b5 (not sure it can cycle but it can charge micads) and that's about it.

There isnt any way I can cycle without a charger?

If not what's the most cost effective charger for the money for nicad/nimh cycling and lipos? thanks!
 May 20, 2011, 04:47 PM Registered User You'll have to study up on how to cycle battery packs, or get together with someone in your area who knows how. I mentioned the Triton & iCharger because I use them and they have the ability to cycle NiCd/Mh packs. For example when you cycle any Nickel pack on the Triton it automatically sets the cutoff voltage per cell for both NiCd/Mh batteries at 0.9 volts/cell, so you don't have to manually set it. When you cycle Nickel packs on the iCharger it also automatically sets the cutoff voltage per cell, it uses slightly different values for NiCd/Mh packs. Pretty much all of the new inexpensive chargers by Turnigy, Hobby King, etc have functions to cycle Nickel packs.
 May 21, 2011, 11:03 AM Registered User You do not need a special charger to discharge your packs but it sure makes the job easier. You can put any reasonable load on your battery by just connecting is between the terminals and then monitor the cell voltages with a VOM (volt-ohm-meter) and, when the voltage across the cells fall to the desired value, disconnect the load. If you are comparing it to factory specifications, the load is generally sized to draw a current of 1/3C and you discharge down to 0.9 volts/cell. When using your Nixx batteries, it is perfectly safe to use them down to 1.1 volt/cell or 4.4 volts for a 4 cell battery. If you stop at 4.8 volts, you probably have at least 40% of the usable energy still available. You can prove this to yourself by putting a reasonable load on the battery and then measuring the time it takes for the battery voltage to fall from 4.8 volts to 4.4 volts. You will find this is quite a high percentage of the total time it takes to fall from a full charge down to 4.4 volts.