Hello,
This is probably going to be a really simple question, but I've been trying to do some research on a solution and I haven't really found anything that's really simple and elegant.
I have a cordless drill that uses 9.6 volt NiCad batteries with only 1.3 Ah of capacity.
What I would like to do is use some high performance lithium cells to replace the NiCad cells.
Three lithium cells gives me 11.2 volts, which should be fine. The batteries I'm looking at are some high amperage RC toy batteries.
Now, what these batteries seem to lack (other than information!) is undervoltage protection. I don't actually know if they do or not, but in product demonstrations of these batteries, they seemed to go down to almost 8 volts before the tests were stopped by the people conducting them.
So for my application, I would like something just as simple as possible for undervoltage protection. I have a fancy charger that will keep it from going over its voltage rating and control charging and all that, so all I need is something to kill the power when it goes below 9 volts, and let the power come back on when there's over 10 volts or so (it doesn't actually matter, so long as the circuit comes back on when the battery is charged).
I already figured I would have to have a separate charge connector, so that's not a concern.
Now, I figured this could be done with a FET of some kind, perhaps a FET that takes more than 9 volts to close the circuit. If there is such a FET, that should work just on its own. Perhaps a FET and a zener diode.
The solutions I've found so far have been ICs that do a whole lot more than undervoltage, or ICs that wouldn't be able to take the amperage or voltage I'm hoping to get (whatever the battery can put out - this is a cordless drill after all).
Anyway, any help is appreciated. I'm hoping this is something simple and I just didn't look hard enough.
This is probably going to be a really simple question, but I've been trying to do some research on a solution and I haven't really found anything that's really simple and elegant.
I have a cordless drill that uses 9.6 volt NiCad batteries with only 1.3 Ah of capacity.
What I would like to do is use some high performance lithium cells to replace the NiCad cells.
Three lithium cells gives me 11.2 volts, which should be fine. The batteries I'm looking at are some high amperage RC toy batteries.
Now, what these batteries seem to lack (other than information!) is undervoltage protection. I don't actually know if they do or not, but in product demonstrations of these batteries, they seemed to go down to almost 8 volts before the tests were stopped by the people conducting them.
So for my application, I would like something just as simple as possible for undervoltage protection. I have a fancy charger that will keep it from going over its voltage rating and control charging and all that, so all I need is something to kill the power when it goes below 9 volts, and let the power come back on when there's over 10 volts or so (it doesn't actually matter, so long as the circuit comes back on when the battery is charged).
I already figured I would have to have a separate charge connector, so that's not a concern.
Now, I figured this could be done with a FET of some kind, perhaps a FET that takes more than 9 volts to close the circuit. If there is such a FET, that should work just on its own. Perhaps a FET and a zener diode.
The solutions I've found so far have been ICs that do a whole lot more than undervoltage, or ICs that wouldn't be able to take the amperage or voltage I'm hoping to get (whatever the battery can put out - this is a cordless drill after all).
Anyway, any help is appreciated. I'm hoping this is something simple and I just didn't look hard enough.