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Subject: Hardware charging mod
From: Nuno Romao (nunoromao_at_comcast.net)
Date: 2003-09-16


Hi, all. I'm thinking about making a HW mod to my JBR to stop the batteries
from being used while it's connected to the charger. I want to do this
because it seems that the way the charging works right now, the JBR runs off
of the batteries any time it is turned on, except when it's charging. This
means that if you leave the charger connected most of the time, the
batteries are constantly being discharged and re-charged. This seems
wasteful to me: when something is connected to AC power you expect it not to
use the batteries except to charge them. So here is what I want to do: I
would insert a very low value resistor in series with the negative battery
terminal. I would then add a circuit that monitors the voltage across this
current sense resistor and activates the charger in such a way that it
reduces the battery current to zero. This would not interfere with the
normal charging method because this mod would not affect the charging
circuit when the batteries are being charged. I looked for a way to do this
in firmware, but I couldn't see away to do it without sensing the battery
current. Does anyone have any comments or ideas?

Nuno



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