AA batteries in adaptors same as C Cell?

shell820810

I am running an item that takes 4 x C batteries. I have loads of rechargeable AAs (2000-2700 mah). I bought size C adaptors and have tried to different sets of batteries in the items and it doesnt seem to be running at the power it should. I am now not sure if the item is faulty, or whether there isnt enough power in the AAs to run it. Before I go and buy 4 x C batteries, I would like some opinions on how different the power supply will be using the two different battery options.

maninthestreet

The only difference between AA and C cells will be their capacity, not their voltage.
Exactly what is the 'item' ???

shell820810

maninthestreet wrote: »

The only difference between AA and C cells will be their capacity, not their voltage.
Exactly what is the 'item' ???

Its a Fisher Price swinging baby chair.

chunkychocky

We use AA rechargeables in anything that will take them, and that includes using 'C' adapters for my son's keyboard, his ELC CD player and hubby's torch. The only thing that we've found that the adapters won't work in is an ELC toy hoover. Goodness only knows why the adapters don't work in that when they do in everything else, but we've given up and just buy C batteries for that one item.

shell820810

just googled and apparently Alkaline C batteries can hold up to 8,000mah (x 4 compared to the 2500x4 that the rechargeable AAs will give me). I assume this is the issue??

maninthestreet

shell820810 wrote: »

just googled and apparently Alkaline C batteries can hold up to 8,000mah (x 4 compared to the 2500x4 that the rechargeable AAs will give me). I assume this is the issue??

No - capacity is just like the size of a fuel tank in a car, it does not affect the voltage. Though rechargeable batteries have a nominal voltage of 1.2, compared to 1.5 for alkaline batteries (but in my experience, rechargeable batteries, when fully charged, actually produce in the region of 1.4 to 1.45 volts).

espresso

maninthestreet wrote: »

No - capacity is just like the size of a fuel tank in a car, it does not affect the voltage. Though rechargeable batteries have a nominal voltage of 1.2, compared to 1.5 for alkaline batteries (but in my experience, rechargeable batteries, when fully charged, actually produce in the region of 1.4 to 1.45 volts).

The available current is much less though!

The Fisher Price swinging baby chair is fitted with C cells because smaller cells would not supply sufficient current. Rechargeable NiMh C cells are typically rated at 4500 - 6000 mAh compared to 1700 - 2900 mAh for AA's.

Rechargeable C cells are often available cheaply at Aldi and Lidl.

shell820810

So the Cs should make a significant difference? I don't have a charger for C batteries so will probably just try the nonrechargeables first.

espresso

shell820810 wrote: »

So the Cs should make a significant difference? I don't have a charger for C batteries so will probably just try the nonrechargeables first.

Yes alkaline C cells (Duracell types) have a typical capacity of 8000 mAh and are capable of supplying much more current for heavy load applications like you have.

TimothyEBaldwin

espresso wrote: »

The available current is much less though!

The Fisher Price swinging baby chair is fitted with C cells because smaller cells would not supply sufficient current. Rechargeable NiMh C cells are typically rated at 4500 - 6000 mAh compared to 1700 - 2900 mAh for AA's.

mAh is not a unit of current, just like miles are not a unit of speed.

Whilst larger batteries can typically supply more current than smaller batteries of the same chemistry, NiCad and NiMH batteries can supply more current than alkaline batteries of the same size.

This is not simple...

espresso

TimothyEBaldwin wrote: »

mAh is not a unit of current, just like miles are not a unit of speed.

Whilst larger batteries can typically supply more current than smaller batteries of the same chemistry, NiCad and NiMH batteries can supply more current than alkaline batteries of the same size.

This is not simple...

It is very simple!

The maximum recommended current for common alkaline battery sizes is:

AAA - 100mA, AA - 150mA, C - 480mA, D - 650mA

If you tried to use four AAA's in a motorised device designed to use four D's, would you expect it to work correctly, regardless of mAh capacity?

The batteries need to be able to supply the current drawn by the device without the voltage collapsing.