i_djoel2000
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double post. see previous post
how to predict, or calculate the voltage of the battery after charging using the built in trickle charging circuit?
is my LED implementation correct?
It's in the docs.
No. It will stay on after you unplug the charger, until the batteries die.
To do what you ask, you'd have to put the + end of the LED and current limiting resistor subcircuit between WALL and D1. The other end still runs to V-.
is it still recommended to use 22-33pF in C6 when i set the gain to 6?
bigger capacitance makes the opamp more stable, right?
how could they still run perfectly fine with 4.2V voltage supply?
You're confusing split supply voltages with rail-to-rail voltages. When the datasheet says a buffer works down to 5V, it means the same thing as if it says it works down to +/2.5V.
Where do you get 1.7 V per cell?
Even if you're looking at the still-on-the-charger voltage, it's going to drop quickly from that after you unplug the power supply.
I'd characterize that as "barely enough". It's equivalent in voltage to a 7.2 V type of "9V" NiMH battery. It differs only in being able to provide more current, or run for longer on the same current.
Quote:
Originally Posted by headfone /img/forum/go_quote.gif
I'm experimenting with running two 9.6V 230mAh (ea.) cells in parallel.
Beware that while discharging NiMHs in parallel is mostly safe (best if both batteries are the same age and have the same wear pattern) charging is not. Don't use the PIMETA v2's built-in trickle charger for a parallel pair.
9V = +/-4.5V rails, and this is when the battery is not near depletion. This is too low for AD8620. The recommended minimum supply voltage is +/-5V, and add the fact it is not a rail-to-rail opamp (it clips at 1V below each rail), results in a rather sub-optimal combination.
why can't i use the built in charger for charging paralleled 9v batteries?
Originally Posted by amb /img/forum/go_quote.gif
9V = +/-4.5V rails, and this is when the battery is not near depletion. This is too low for AD8620. The recommended minimum supply voltage is +/-5V, and add the fact it is not a rail-to-rail opamp (it clips at 1V below each rail), results in a rather sub-optimal combination.
It's not so much a "never do this" as a "not a good idea" matter. Batteries are very strange beasts when you start to really look into how they behave; they are far from ideal energy storage devices. When you put two in parallel, they interact, multiplying the number of strange behaviors.
In any case, I don't think you actually want to parallel them. I think you want a series connection and are confusing the terms.
There are 3-position switches of that sort. An on-off-on switch would let you center the switch to turn the amp off entirely, or you could use an on-on-on switch to have the "off" position be one of the two end positions.