Balance charge cradle for 4 x AA NiCad

[oldcelt]

My LIPO charger will also handle NiCad batteries. Where can I find a balance charge cradle for 4 x AA NiCad batteries which are used in my transmitter? I have a NiCad charger but can never be sure if the 4 batteries have a balanced charge.

[GIXERMAN]

you can't balance nicads that I'm aware

[oldcelt]

you can't balance nicads that I'm aware

Hmmm ............
Technically I see no reason why not if one has a cradle which ensures that each cell is charged to the same level and switches off the charge to each cell as it reaches optimum. I accept that there may not be a suitable cradle on the market, however.

[waveydavey]

You're confusing balancing of LiPo cells in one pack (which is important) and a NiCd single cell of which there is no need to balance.

That would mean you would need a separate charging circuit per cell as you can't be sure how much each cell is taking, so not sure it's possible.

[Mark_T]

This is bringing back a few memories, I actually built such a cradle many years ago which was used for monitoring the individual cell voltages of a welded pack during discharge, but it could have been used the other way around during a charge. For all practical purposes though Dave is right, you really can't do this with a 4 cell NiCad pack (is it really NiCad or actually NiMH?). You need access to the metal skin of each cell to be able to read the individual cell voltages, or you'd have to wire in a set of 'balance' leads... The standard TX trickle chargers do as good a job as you need for this sort of pack to be honest.

[bothma]

I agree with all that's been said however, as a point of interest when I raced 1/10 touring cars we used DPD's, this essentially was a pules discharged that had two functions one being to match the discharge voltage of each cells and two, to break-up crystals that form within the NiMH batts caused by high discharge rates. You should not expeditions crystal buildup in a NiMH TX batt as the discharge rate is very low.

[oldcelt]

You're confusing balancing of LiPo cells in one pack (which is important) and a NiCd single cell of which there is no need to balance.

That would mean you would need a separate charging circuit per cell as you can't be sure how much each cell is taking, so not sure it's possible.

Very often I may wish to charge 4 x NiCad batteries at the same time. It's often the case that at least one of the batteries has been used in a different device to the others resulting in a lower charge level than the other 3. What happens when those 4 batteries are charged in a standard 4-cell NiCad charger? Does the charging stop as soon as one of the batteries reaches optimum or does it carry on until every cell has reached optimum; in which case the first cell to be fully charged is likely to overheat unless I'm mistaken?

If it stops as soon as 1 battery is fully charged then the others have not reached a full charge.

[bothma]

Very often I may wish to charge 4 x NiCad batteries at the same time. It's often the case that at least one of the batteries has been used in a different device to the others resulting in a lower charge level than the other 3. What happens when those 4 batteries are charged in a standard 4-cell NiCad charger? Does the charging stop as soon as one of the batteries reaches optimum or does it carry on until every cell has reached optimum; in which case the first cell to be fully charged is likely to overheat unless I'm mistaken?

As per my previous post if you that worried about it then discharge the cells to the same voltage which your current charger would more than likely be capable of, I think you are overthinking things a little "no offence".

[oldcelt]

The charger I have is simple in the extreme - no discharge facility!

[waveydavey]

Very often I may wish to charge 4 x NiCad batteries at the same time. It's often the case that at least one of the batteries has been used in a different device to the others resulting in a lower charge level than the other 3. What happens when those 4 batteries are charged in a standard 4-cell NiCad charger? Does the charging stop as soon as one of the batteries reaches optimum or does it carry on until every cell has reached optimum; in which case the first cell to be fully charged is likely to overheat unless I'm mistaken?

If it stops as soon as 1 battery is fully charged then the others have not reached a full charge.

It's charging to a voltage so you can't be sue how much each cell has actually taken. I've found with the boys cars as the Nicd packs get old they reach peak voltage very quickly and discharge within a very short time so even though the charger stops charging and considers it's job done in reality there has been nothing gone in. Which is where your balance theory would work if you could do it. With Lipos as the IR increases in the cell the charger will make allowance for this as best it can and top up only the cell it sees lagging behind in capacity and will do it's best to bring to the same capacity as the others. If it can't it will stop as close as it can.

In your post the charger isn't aware of the capacity of each cell and you're right it would in effect keep going until the voltage is right but that could leave a cell down, which you would recognise only as time lost on where you're using the 4 cell pack

[oldcelt]

It's charging to a voltage so you can't be sue how much each cell has actually taken. I've found with the boys cars as the Nicd packs get old they reach peak voltage very quickly and discharge within a very short time so even though the charger stops charging and considers it's job done in reality there has been nothing gone in. Which is where your balance theory would work if you could do it. With Lipos as the IR increases in the cell the charger will make allowance for this as best it can and top up only the cell it sees lagging behind in capacity and will do it's best to bring to the same capacity as the others. If it can't it will stop as close as it can.

In your post the charger isn't aware of the capacity of each cell and you're right it would in effect keep going until the voltage is right but that could leave a cell down, which you would recognise only as time lost on where you're using the 4 cell pack

TVM. You have put it better than I but you understand why I was asking the question. Since a lipo multi-cell battery can be balance charged, each cell must be monitored during the process. Why isn't it possible to design a NiCd cradle capable of the same thing? I'm not, as you'll have deduced, an electronics engineer.

[Mark_T]

Just to be clear here, are you charging individual loose batteries or an assembled welded NiCad (or NiMH) pack?

If you are charging individual loose batteries then there are many chargers out there that will charge them individually, but say 4 at the same time ...

http://www.gearbest.com/chargers-bat...Fc0y0wodcq4N-A

[waveydavey]

TVM. You have put it better than I but you understand why I was asking the question. Since a lipo multi-cell battery can be balance charged, each cell must be monitored during the process. Why isn't it possible to design a NiCd cradle capable of the same thing? I'm not, as you'll have deduced, an electronics engineer.

I'm sure someone with a better understanding of the battery chemistry might be able to explain and in theory I see no reason why it can't be done but it's not a widely used battery any longer so can't see too much research going into this from charging manufacturers.

[Mark_T]

The charger I linked above will take 4 cells at the same time but will charge and monitor each one individually.

If these really are NiCad cells then the biggest issue with them is false peaks which cause a peak detect charger to shut off too early, the more intelligent ones can combine peak detect with temperature and voltage monitoring to help spot the false peaks, but at some point to have to decide how much intelligence it is worth paying for when a replacement battery is cheaper ...

[oldcelt]

Just to be clear here, are you charging individual loose batteries or an assembled welded NiCad (or NiMH) pack?

If you are charging individual loose batteries then there are many chargers out there that will charge them individually, but say 4 at the same time ...

Nitecore D4 Li-ion NiCd NiMh LCD Smart Intelligent Battery Charger with EU Adapter - Black-24.98 and Free Shipping| GearBest.com

I'm looking at individual batteries being charges at the same time. Thanks for the link.