Balance charge cradle for 4 x AA NiCad

[waveydavey]

My logic is this: all equipment using (say) 4 x AA batteries will have an instruction in the user manual to refrain from mixing older batteries with new. That suggests to me that it is important to have 4 cells with the same level of charge to make the best use of the equipment (and probably the batteries). If, therefore, rechargeable AA cells are used, the same logic must surely apply and balancing the charge must be equally beneficial.

I'd have thought that wiring a balance charge plug to a 4 x AA battery holder must be reasonably straightforward in order to use one's universal charger. The batteries get wired in series with the power plug connected across the extreme ends and the balance plug gets a wire from the extreme ends and another wire from each cell junction. That's how lipo packs are wired - see attached image for a 3-cell pack.

Your logic seems correct and I know how LiPos's are wired, we are agreeing but the fact that charger manufacturers don't and haven't introduced a modern (for want of a better word) charger for this speaks volumes in that it's not required or they see no value in it. Search for balancing NiCd packs on Google and see how many hits you get, my Google Fu ain't bad and I can't find any as I would say many others that have been curious with this thread.

You can wire a NiCd cell as in your example but there aren't any chargers for doing this with this chemistry, or at least none that I can find. You could use your DEV charger I suppose and wire it up as above and it might work, but then again it might not, they haven't seen the point or had the justification to provide this functionality or chargers would be provided with this.

[oldcelt]

Not sure your logic is sound. All the best ideas and creative developments in technology (and other spheres, I suppose) have been because someone spotted a gap in the market and set out to fill it!

[Grumpy]

Not sure your logic is sound. All the best ideas and creative developments in technology (and other spheres, I suppose) have been because someone spotted a gap in the market and set out to fill it!

I tend to concur with waveydavey. NiMh/MiCad batteries have been around for far longer than LiPos and have for decades been charged perfectly well (and stay acceptably balanced) without the extra complexity of dedicated balance connections. Adding balance connectors would appear to be a solution to a problem that doesn't exist and just adds unnecessary complexity and cost to both the battery itself and to the charger.

What would be the perceived advantage?

[oldcelt]

I tend to concur with waveydavey. NiMh/MiCad batteries have been around for far longer than LiPos and have for decades been charged perfectly well (and stay acceptably balanced) without the extra complexity of dedicated balance connections. Adding balance connectors would appear to be a solution to a problem that doesn't exist and just adds unnecessary complexity and cost to both the battery itself and to the charger.

What would be the perceived advantage?

I think I've already outlined my reasoning throughout this thread. I suspect it needs a NiCd/NiMh battery expert to expand on what's already been said. Perhaps a design engineer from a battery manufacturer - anybody listening?

[Mark_T]

As Dave suggests, it just isn't necessary to balance these packs.

In the vast majority of case where you have a NiCad/NiMH pack, they are only ever slow charged so they self-balance.

We can fast charge single cells easy enough, but I'm struggling to think of any 'normal' applications where we fast charge a welded pack... Even our transmitters are all designed for slow charging...

Given the lack of need to do it, it is not surprising that nobody builds the packs that way in the first place and hence no chargers. Also don't forget my earlier point, it is a lot harder to manage the balancing process on NiMH than it is on a Lipo due to the different way you charge them.

[oldcelt]

Slightly got out of sync: I'm only referring to individual AA batteries - nothing welded together in a single pack. I have a plastic battery holder which will carry 4 x AA batteries. If I soldered a balance charge plug to it using the method of wiring similar to a LIPO pack I could, in theory, balance the charge on each individual battery using my universal charger - couldn't I?

[Grumpy]

With loose separate cells there is no requirement to balance charge because you would charge them connected in parallel. Parallel charging automatically balances between cells (with any type of battery, even LiPo).. It's only where the cells are welded/soldered together in series that you have to charge in series.