Re: Batteries again, sorry you're almost right.

if you plugged a nimh pack into the HB's charge jack, the external
pack would charge the internal batteries.

but it would not power the board significantly.

this is because the HB's charge jack includes a current-limit resistor
(designed to allow the correct current for indefinite trickle-charge).

so you won't get enough current through to run motors or anything,
you'll just trickle-charge the internal pack via the external source.

while we're on the topic, the dangerous thing that you should *not* do
is wire a high-current source (like a nimh pack) to deliver charge
current through the RJ11 jack.  this charge path is not
current-limited internally to the HB (except via the fuse) and bad
things can happen.  the internal nicad pack will deliver and/or accept
large amounts of current, causing big discharges of heat and
potentially bad results (e.g. battery pack explosions).  the fuse
protects against this but why play with fire.

are you having big battery life problems with the internal pack?

fred


In your message you said:
> This should be my last question in terms of batteries. Assuming that I have
> nicads powering the HB, what effect would there be if, when the batteries wer
e
> getting low, I connected a fully charged battery pack (e.g. containing the ni
mh
> cells) into the power jack ?. I imagine that the nimh pack should power the
> board and charge the nicad pack slightly. Am I correct ?. I am now thinking o
f
> using the nimh cells as either a backup power supply or as a supply for the
> comms converter board (which has the overall effect of the above question) so
> that the hb batteries should only be powering the hb when connecting the
> converter to a laptop where there is no access to mains power.
> 
> Can someone confirm if my thoughts are viable ?.
> 
> Thanks
> 
> John Hatton
> johnhatton@email.com

