Very Computer

Hi,

I have been looking around the Web for info about using NiMH batteries (the
ones used in the Revo).  It seems that they are better than NiCad's because
they do not suffer from the memory effect but what I have not found out is,
is it best to keep the batteries fully charged for most of their life or is
it better to let their charge drop to say 50% before recharging?

Any thoughts/pointers to the answer?

Chris M

As I unsderstand it, NiMH batteries DO suffer from the memory effect,
although not as badly as NiCads. As such, it is best to allow the batteries
to drain before recharging. Now if Psion had splashed out on Lithium Ion
batteries, we wouldn't have this problem...

Adrian

Quote:> Hi,

> I have been looking around the Web for info about using NiMH batteries
(the
> ones used in the Revo).  It seems that they are better than NiCad's
because
> they do not suffer from the memory effect but what I have not found out
is,
> is it best to keep the batteries fully charged for most of their life or
is
> it better to let their charge drop to say 50% before recharging?

> Any thoughts/pointers to the answer?

> Chris M

If what you're saying is true about letting the battery drain first, then it
is strange for Psion to state in the manual that the best way to maintain
the battery is to always keep it topped-up. I've heard of NiMH batteries
used in cellphones are best maintained by draining them first but as I said
it earlier the Revo manual strangely says otherwise.

torc

Quote:> As I unsderstand it, NiMH batteries DO suffer from the memory effect,
> although not as badly as NiCads. As such, it is best to allow the
batteries
> to drain before recharging. Now if Psion had splashed out on Lithium Ion
> batteries, we wouldn't have this problem...

> Adrian

I've read conflicting things about NiMH batteries. Adverts for them tend to
state "Memory Effect Free", but elsewhere I have read that they DO suffer
from memory effect to a MUCH smaller degree than NiCads.

The Manual? Who reads those anyway?    ;-)

Adrian

But according to the manual, Psion recommends constant recharging to keep
the batteries in shape...

In practical use, neither NiMH nor NiCad suffer from memory effect.
There are two ways in which they can be damaged -
a) overcharging cooks the cells,
b) allowing a set to run flat may result in the weaker cell having
current forced through it by the stronger one(s).

Neither of these things is in any way related to the near-mythical
memory effect which you are unlikely to ever see in real life. I've used
both types of cells in my S5/5mx and they work fine.

James
--
James Annan

Once in a while a near full discharge is beneficial. I say near, but this is
har to determine of a Revo accurately.. if you discharge NiMh too far they
might not recover. niMh is much more toelerant of regular top-up charges
than NiCd, which I guess is one of the reasons why Psion chose NiMh. This is
the mode of operation that's used in mobile phones.

Cheers!

--
Nigel Wright, Palmtop Publications.

Quote:> Hi,

> I have been looking around the Web for info about using NiMH batteries
(the
> ones used in the Revo).  It seems that they are better than NiCad's
because
> they do not suffer from the memory effect but what I have not found out
is,
> is it best to keep the batteries fully charged for most of their life or
is
> it better to let their charge drop to say 50% before recharging?

> Any thoughts/pointers to the answer?

> Chris M

On Wed, 7 Jun 2000 17:59:13 +0100, "Nigel Wright"

Is this substantiated by scientific evidence or anecdotal?

Russell.
TO REPLY BY EMAIL:
Change nospam in reply address to iee

New info (April 2000) from Psion re: Revo power, seems to agree with you,
Nigel. Regular top-up without over charging (i.e. keep between 80-100%
charged, then remove PSU charger) is best!

I have yet to get my Revo back from Psion to confirm.

Gary J

Why don't you visit a few websites dealing with this? I spent a great deal
of time doing this for Palmtop and the evidence I gathered was both
scientific and anecdotal. From a personal point of view, I have found it
beneficial to discharge NiMh from time to time because when I didn't I did
seem to get the odd occasion when life was shorter than usual despite no
change in the pattern of use. Quality of the charger is important too - buy
something that uses delta V charging.

--
Nigel Wright, Palmtop Publications.

On Fri, 9 Jun 2000 21:20:22 +0100, "Nigel Wright"

I have and most of the information I have found is from dubious
sources, no proper research results.

Quote:>I spent a great deal
>of time doing this for Palmtop and the evidence I gathered was both
>scientific and anecdotal.

Well how about allowing us to benefit from the knowledge you have
gained?  Can you quote a few good references please?

Quote:>From a personal point of view, I have found it
>beneficial to discharge NiMh from time to time because when I didn't I did
>seem to get the odd occasion when life was shorter than usual despite no
>change in the pattern of use.

You have to run such experiments carefully and be sure to eliminate
effects which may be connected with the charger itself.  The Revo
charge control seems to have problems with monitoring the battery
state sometimes.  When I had this problem I did a hard rest and then
recharged the battery fully before switching back on.  Yes, I know,
this is anecdotal:-)

Quote:>Quality of the charger is important too - buy
>something that uses delta V charging.

Absolutely.  However with the Revo you have no choice the charging
control is built in.

Regards,
        Russell.
TO REPLY BY EMAIL:
Change nospam in reply address to iee