Question about battery recharger

[Big Daddy]

I bought a used battery recharger at a yard sale from a guy who says
it worked fine. I got it home and tried it on four batteries, but
they didn't charge correctly. The batteries are each 2200 mAh. The
recharger says on it:

output: 2x (2.9V -- 800 mA) 4.64 VA

I calculated that if the recharger is outputting 800 mA, that it would
take about three hours to fully recharge a 2200 mAh battery. The
recharger has slots for four batteries, so I put four in for just over
3 hours, and they didn't really seemed charged at all when I was
finished. So I was wondering if maybe the recharger is actually only
ouputting 200 mA per slot (800 divided by four) or 400 mA per slot if
there are four batteries at a time.

Any ideas? Thanks in advance,
John

 

[Mike S.]

I bought a used battery recharger at a yard sale from a guy who says
it worked fine. I got it home and tried it on four batteries, but
they didn't charge correctly.

By what criterion?

How does the charger determine and tell you when the cells are charged?

What state of charge were the cells in when you started charging?
Were they all the same? Is it possible that any of the cells is damaged,
old, or otherwise defective?

The batteries are each 2200 mAh. The recharger says on it:

output: 2x (2.9V -- 800 mA) 4.64 VA

I interpret this as two independent charging circuits, each of which
charges two cells in series at a rate of 800 mA.

I calculated that if the recharger is outputting 800 mA, that it would
take about three hours to fully recharge a 2200 mAh battery.

NiMH charging is not 100% efficient. At moderate charge rates some
estimate you need to put in ~1.4 times the actual capacity. At low charge
rates, efficiency drops further.

The recharger has slots for four batteries, so I put four in for just over
3 hours, and they didn't really seemed charged at all when I was finished.

When _you_ were finished? What did the charger have to say about whether
it was finished? Does it have LED indicators? How many?

So I was wondering if maybe the recharger is actually only
ouputting 200 mA per slot (800 divided by four) or 400 mA per slot if
there are four batteries at a time.

Certainly possible, but that's not how I'd read the markings.