New AA battery recharger - have I goofed?

[Lobster]

Just bought myself a Uniross Sprint 90 AA battery charger, primarily on the basis of it having an intelligent charging system.

However, it only takes 90 mins to charge two AAs, or 3 hrs to charge 4.

AIUI it's important to charge slowly to avoid frying the batteries... why is it that every damned charger you see advertised crows about how quickly it recharges batteries! Why can't I find one which will happily trickle charge overnight?

Or am I worrying too much?

I'm assuming that it will be better if I charge my batteries 4 at a time, not 2: is that right?

Thanks David

[Andy Burns]

It has deltaV charging, which means it monitors charging progress and will fast charge until the battery is almost fully charged, then switch to trickle charging.

Although I notice it has to charge in pairs, so perhaps it doesn't monitor each cell individually, which better chargers do (and which I thought was the /point/ of deltaV)

[Merryterry]

I have a Uniross Sprint 15 which charges 4 AAs NmiH in about 15 -20 mins. It has got a fan onboard. They get pretty hot but have had no probs with them on about 50 cycles so far.

[Mike Clarke]

At a guess it probably charges the first pair in about 90 minutes then switches over to charge the next pair for the next 90 minutes. So it makes no difference to the charge rate seen by the cells. That's what mine does, though it's not a Uniross.

[John Rumm]

Yup. It is ok to fast charge cells, but not to fast overcharge them. So long as it has logic to detect when the cells are charged you will be fine.

Not going to make much difference.

[Dave]

As a side note, I have a uniross something or other. It says it takes 19 hours to recharge a pair of 2200 mah batteries

after 19 hours they are pretty hot

is that bad ?

[John Rumm]

Depends a bit on where the heat is coming from. If it is a result of overcharging the cells, then it is not good for them. If however it is just that the charger itself gets hot and that in turn heats the cells then there is less to worry about. It sounds like it is not charging at a very fast rate anyway (i.e. under 150mA). This is still quick enough to damage cells on an overcharge, but not quite as quickly as some of the very fast chargers that only take an hour or two.