Use one of those cheap wall timer outlets for turning it off after so many hours. If the pack is dead, look on the wall transformer for it's current output. If it says 100ma and say the pack is 800ma, then that would be 8 hrs, but overshoot it by an hour or two, both due to the charging process not being very efficient and also due to a healthy pack often holding 200 or 300 more milli amps that the label says.
If you want to monitor the pack for full charge, while it's on the charger read the voltage with a meter. Write that down. Come back in an hour and read it again. Write that down. Continue to do this until the voltage is either right around the same or has dropped, but once you see that give it another hour, because during the normal charging process the voltage with dip a bit here and there and then rise up again. This is normal, but once a larger dip happens than that and it sits right around that voltage, that's when it's peaked, and that's how a charger tells this.
It's called a milli vote threshold setting or m/v. Typically chargers that let you set this will only ask for the "per cell" setting. In other words, for me I normally set nimhs to about 5 to 7m/v per cell, or for nicads about 12 to 14m/v per cell. Reason being nicads dip and rise more than nimhs, and will have a bigger final dip when done. That's why it's very risky to charge a nimh in a nicad charger, because good chance the charger will never see enough of a drop to know the pack is done charging.
For excercising the pack. At least 2 or 3 times a year I like to drain a pack completely dead via using a car tail light bulb or something. If you do this put the bulb on cement as it gets very hot. After about 10 to 20 minutes or so the bulb will go out. Let it sit another 20 minutes to 30 minutes to insure all cells are at equal state of discharge. Some believe you should never drain a pack completely dead, but truth is the voltage will start perking back up again some soon as you remove the load of the bulb.
So long as a pack doesn't sit dead for long periods of time (days or weeks or months) I've never had a cell reverse polarity on me, which is the risk if a cell is dead completely. I like to do this drain/charge/drain/charge thing about 3 to 5 times in a row until my charger starts showing no gains in capacity after about two in a row after that or so. Lacking a charger that shows capacity put back in, just cycle it 3 to 5 times and it should be at its highest capacity possible and back into great shape again.
If you are wondering how to care for the pack, no need to drain a nimh or nicad all the way down, nor to charge it after each use on the machine. Just use it and don't recharge unless you think it won't last the next hunt and don't have a backup pack for the field to throw in. But if the pack has sat for say 2 weeks or more I'd re-charge it before heading out, as nimhs or nicads (nimhs more so) will self drain sitting on the shelf, some faster than others, in only a few days even. There are now low self discharge nimhs on the market that will hold 80% of their charge a year later, but read up on those as some don't live up to their claims.
From memory I think the Sovereign draws somewhere around 50 to 70ma depending on if it's sounding off to a target or not. So here's how to figure out how much capacity has been taken out of it that you need to replace- Add up the # of hours hunted in say 60ma per hour or so and then subtract that from the capacity the label the pack has. Now, look on your wall transformer. How much current output does it have? I'm guessing either 100 or 150ma?
So divide that into the capacity you drained in the field and now you know how many hours to charge the pack from it's current state of charge to full again. Overshoot it about an hour or so more than the math says because of the efficiency of the charging process and also the pack self discharging while it sits. If the math says 5 hours shoot for 6 and it should be full by then, but far easier to use a good charger that auto shuts off and also it's very nice to see capacity put back in.
Just don't use a charger that chargers at say 1C (capacity of pack) or higher in current it outputs. I like to shoot for about 1/3rd to maybe 1/2C when in a rush. So if it's a 1000ma pack say 300ma for about a 3 to 4 hour charge for a completely dead pack, or say around 500ma for a two hour charge. Only if I'm in a huge rush will I charge at 1C or higher (in this case 1 amp), but make sure the pack isn't getting hot. Heat destroys batteries.
