Nicd batteries  - Page 1
Forum section: electronics / beginners

author: Zalos
author_rank: Newbie
timestamp: September 17, 2019, 09:22:06 pm
content: I have 1000 nicd sub c 1.2 v never use them but are 6 years on the shelfIs any way to bring them back on life again?

author: Stray Electron
author_rank: Super Contributor
timestamp: September 18, 2019, 01:32:43 am
content: Just charge them at no more than a 1/10 C rate and they should be fine. I used the same set of Sanyo CadNica's for over 20 years.

author: MosherIV
author_rank: Super Contributor
timestamp: September 18, 2019, 06:45:22 am
content: As suggested, try charging them. See how much charge they hold.Some will be bad, if you are lucky some may be ok.They have been stored without a top up charge, will havd self discharged and long term storage discharged will damage them.The electrolyte may have dried out with long periods like that.

author: Brumby
author_rank: Unknown
timestamp: September 18, 2019, 07:45:58 am
content: I would also suggest a gentle charging.I picked up 8 cordless drill NiCd battery packs many years ago and tried charging one up to see how it went. To my surprise, it held up pretty well.You never know your luck.

author: mzzj
author_rank: Super Contributor
timestamp: September 18, 2019, 08:19:22 am
content: If they still measure above 0.5 volt they are probably good.Only works for high quality cells like Sanyo Cadnica, anything lesser tends to self-discharge to zero volts over many years.

author: Gyro
author_rank: Super Contributor
timestamp: September 18, 2019, 12:19:09 pm
content: Large NiCd cells for aircraft use used to be supplied with shorting springs across their terminals.As long as there is no obvious sign of leakage or corrosion, you have a good chance of recovering them. Constant current at C/10 for 14 hours should do it.P.S. I remember a consumer manufacturer establishing that NiCds could be charged indefinitely as long as the charge currentis less thanC/30. The sort of continuous trickle charge employed in handheld vacuum cleaners etc.

author: ledtester
author_rank: Super Contributor
timestamp: September 18, 2019, 02:45:38 pm
content: There are reports on the web that freezing NiCads can help restore their capacity. If your batteries are old and worn out it might be worth testing that theory out.

author: capt bullshot
author_rank: Super Contributor
timestamp: September 18, 2019, 03:01:24 pm
content: NiCd cells are quite robust. Best way to store them is in fully discharged (or even shorted) state.As the others said, try charging them.In case there's a cell that won't take the slow charge (voltage stays near zero), apply a high current (5A ... 10A) for a few seconds and see if the voltage rises and stays above zero after you removed the current, maybe repeat this a few times. Afterwards charge as supposed.This is an old method to recover cells that have some kind of "internal short" due to overdischarge, usually worked quite well.

author: Zalos
author_rank: Newbie
timestamp: September 18, 2019, 04:12:45 pm
content: Thanks all of you for the advices you gave me

author: Benta
author_rank: Super Contributor
timestamp: September 18, 2019, 05:21:08 pm
content: First of all, you'll need to charge the cells individually. There's no way you can balance them, neither in series, nor in parallel.Second, I recommend a controlled fast charge with preformation, 1...2 C fast charge and final top-off charge. This is the gentlest and optimum way to bring cells back. And they won't even get warm (a warm cell is a sign of bad charge management).The U240xB series of ICs from Telefunken/Temic were designed spcifically for this, but are obsolete. But replicating the charging algorithm in a microcontroller is no problem.https://pe2bz.philpem.me.uk/pdf%20on%20typenumber/A-C/BATTERY.pdfSee page 19.

author: amspire
author_rank: Super Contributor
timestamp: September 18, 2019, 10:18:20 pm
content: Quote from: Benta on September 18, 2019, 05:21:08 pmThere is nothing wrong with charging individually, but one of the big benefits of NiCd batteries is they can withstand prolonged overcharging without a problem, as long as the charge rate is below the 0.1C rate. This is why some of the old chargers are basically just a resistor, along with instructions such as "Charge for 24 hours". This ability to be overcharged allows them to be self balancing when charged in series. You keep charging until every battery is fully charged. It is better not to overcharge, but they handle it much better then Lead Acid, NiMh and Lithium batteries. They also tend to have a long life and can be stored uncharged, so I doubt that Zalos will have a problem - 6 year old NiCd batteries are usually fine. They could easily last 30 years if they are reasonable quality.NiCd do have a memory effect and so they will probably need a few full charge-discharge cycles to get full power.

author: Gyro
author_rank: Super Contributor
timestamp: September 19, 2019, 10:46:54 am
content: Quote from: Benta on September 18, 2019, 05:21:08 pmSorry but I have to disagree on that one....Firstly, there is no indication that the OP's cells are fast charge capable, certainly by the lime you get into the realms of 1C or 2C!AnyNiCd will support C/10 charging. A 14 hour charge will ensure that all cells reach full charge, with an allowance for charging efficiency.Secondly, There's no harm in charging a bunch of cells in series. With a constant current charge they will obviously all receive the same C/10 charge. Given that the OP has a 1000 of them, he's not going to want to charge them all individually. It would be a relatively cheap and simple job to arrange some series strings with LM317s as current sources (with appropriate attention to dissipation/heatsinking and voltage limit (starting from a discharged stack).Note: I'm not suggesting that the cells wouldn't need matching for substantial discharge current in a series battery pack, simply that there's nothing wrong with charging in series strings at C/10 for the appropriate time. As amspire indicated, NiCds are highly resistant to overcharge at a C/10 rate. There would be no harm in extending a test charge to 24 hours.