WARNING: Messing with ANY battery type, rechargeable or not, always carries risk. Charging, storage, car, destroying your detector, personal injury, losing an eye, burning down your house, and so on...Any of which can cause a fire or worse, so don't mess with this stuff if you don't know what you are doing. Lipos got a bad rap early on due to them not featuring balance ports and balance chargers to monitor each cell as it charged. As a result many fires were caused when one cell was overcharged in the pack. Virtually all lipos these days and lipo chargers feature balance ports for charging, so the fire thing is pretty much history. Sure, a lipo can still catch fire or explode if you short it, cut it open, dent it badly, or so on, but so can any other battery type on the market. Just like handling gasoline isn't "safe" when you pump gas, neither is ANY battery out there. But, with minor common sense precautions and a little education to know what you are doing, it's no more of a risk than anything else. Just like you don't smoke while pumping gas, you don't do a few simple things to a lipo and the risks are minimized to where there is no need to fear. Respect? Yes, but don't fear...
OK, why lipos? For starters, dirt cheap these days if you know where to look.Lighter than pretty much any other battery type for great weight savings. Even lighter than 8AAs. Smaller and yet with huge increases in capacity for longer run times. 1 hour charge times without pushing the pack. Hardly measurable self-discharge on the shelf so a year after charging it's still pretty much at full capacity. Holds it's voltage very high to the end of discharge, much better at holding it high than non-rechargeables, nimhs, or nicads. Small and compact so a spare battery is easy to carry in your pocket compared to 8AAs.
What you see in the Pics below are a 750ma 3 cell series lipo. Cost me about $5 or $7 so I bought two. One as a backup in the field. See how small it is in my hand compared to 8AAs? This size pack should probably easily fit into the Excalibur Alkaline POD too I would figure? And I can guarantee you it's light as a feather compared to 8AA non-rechargeables, and of course much lighter still than the rechargeable stock pack that uses 10 sub A nimhs. The stock pack is 1000ma capacity, yet I seem to get more run time with my 750ma lipo. How so? Because lipos hold their voltage high to the end of discharge. They don't drop the voltage nearly as steady while draining as non-rechargeable AAs, nimhs, or nicads.
You could of course buy a bigger capacity pack than the stock one and still drop a bunch of weight, like say a 1450ma 3 cell series lipo for around $14 or so. I was just shooting for maximum weight savings in the light weight custom shaft and some other mods I did to my land shaft for my GT (such as using a Whites lower carbon tall man rod and a Whites arm cup). Dropped about a pound and a half without even touching the control box.
Before going further, if you have any detector that uses 8AAs in series it *should* be fine to run a 3 cell series lipo in it. 8AAs in series is 12V. A 3 cell series lipo is 12.6 volts at full charge. Hardly even worth mentioning, as voltage regulators (which I think all detectors use for the most part to keep them stable with a static output voltage to the circuit board that doesn't change as the battery drains) often have a rather large window of input voltage. Say around a 9V to perhaps 13 to 14.5V input range or so to output for example a static 8V to the circuit board. Regardless of what the voltage input is to the regulator, it's still only going to put out the static voltage the circuit board wants to stay stable. But, as with all things in life, there are no guarantees, so if you fry your detector don't come crying to me. I don't know what the high end window of voltage tolerance all regulators for all detectors have. I guess there could be some out there that will thermal overload on .6V, but I doubt it due to the variances in even non-rechargeable store bought batteries as to their starting voltage. Some are higher than others. Either way, it's your own risk.
Also before going further, you need to be aware that a lipo can be ruined if you drain it past 3V per cell (which is 9V total for a 3 cell series pack). The Sovereign and Excalibur low battery alarm kicks in around 9.8 to 10.2V. For that reason, no need to fear draining your lipo to far down. If you hear the low battery alarm time to charge the pack. If you own another detector, you are going to need to figure out your low battery alarm as to if it kicks in above 9V. If it doesn't, then you've got a few options...
A) If you know the current draw of your detector, time your hunts by dividing the current draw into the capacity of the pack. I'd undershoot the hours projected by say 5 hours to be safe. See "C" for more on that.
B) If your detector features a voltage display then monitor your pack voltage often while hunting and when it gets down to say about 9.5V or so stop using the pack to be safe in case your voltage display is a hair off. Then figure out how many hours you hunted on that pack and now you know how long you can hunt with it without needing to watch your voltage display here and there. Just set an alarm on your watch before starting a hunt with how many hours you have left and there you go. See "C" though about undershooting that time to be safe to account for higher amp draw at trashier sites.
C) If you don't know how to measure current by you do voltage, then you could simply check the voltage of the pack every 4 hours or so with a cheap $5 volt meter. Once you see it around 9.5V or so time to switch packs, and now you know your rough run time, but again I'd undershoot it by about 2 or 3 hours from what you times so as to account for high times of extra amp draw due to say a trashy park where the machine is sounding off all the time.
D) You could buy like a $3 lipo low voltage alarm from where you can find cheap packs. It will plug into the lipo while it's plugged into the detector and it will sound an alarm once the voltage is approaching the 9V minimum. Just don't forget to unplug it after a hunt, because if you lock your machine in a storage locker or something it might after weeks or months drain the pack down below 9V and nobody will be around to hear it.
A little on lipo care...Most packs can only be charged at a max rate of 1C (meaning if the pack is 1400MA then the max charge rate is 1.4 amps). This equates to a 1 hour charge time. This isn't pushing lipos, but be sure to find out if your lipo is rated at 1C. There might still be some that are not. Some are even rated at 2C or higher charge rates these days, but I prefer 1C. Easy to do the math in my head to figure out the charge rate, and who is in such a hurry that they can't wait an hour? Besides, 1C is fine for most lipos without pushing them. I wonder what kind of life 2C or higher ones will have?
Don't confuse the charging rate with what kind of capacity (run time) is put into the pack. It's fine to charge lipos lower than 1C. Say 1/2C for a 800ma pack would mean a charging amp rate of 400ma (point 4 amps in other words). Charging slower than the max charge C rating just means the lipo will take longer to charge, NOT that you are putting less capacity back into the pack. In this example, the pack is still going to charge to 800MA, it's just that it will take twice as long to charge.
Also, don't confuse the charging C rating with the C rating of the pack that is meant to rate it's amp DELIVERING ability. My little Rhino lipo in the picture below, for example, is rated 1C for charging (maybe it's 2C but I only charge at 1C). Since it's a 750ma pack, that means my max charge rate is .750 amps, or 750ma. BUT, I think you can see on the pack in the pic it says something like 20C discharge rate. That means the pack can supply up to 15 amps (750ma x 20).
Also, if your lipo charger (a cheap one is about $5) has a capacity display as it charges, often you'll note the pack will hold more capacity than the label says. That's a sign the pack is a quality one. But, by the same token, if the pack isn't drained much, you might only put say 200ma into the pack before it's done. It's like filling up a gas tank that already is half full. That doesn't tell you how much gas the tank holds. Same with batteries.
Now, all the above covered, a few more safety tips before moving on...I still put all my batteries, lipo or not, inside a metal box that I've painted the inside of with non-metalic paint to insure no possible way to short the packs. I then divided the packs in the metal box with dry wall (it's non-flammable), and then I drill small but numerous holes in the top of the box so should a battery catch fire or explode the box won't blow it's lid off and can vent the gas through the holes. Diving the batteries into their own chambers lowers the risk of losing them all should one go bad.
The box I stick inside my refrigerator because it's good for the life of rechargeables when put into long term storage. Lacking that, put the box in a cool fire proof place. You don't want your batteries baking or that will shorten their life. A good lipo charger (about $20) will often feature a storage charge. You plug in the lipo, press storage charge, and it will drain or charge the pack to the ideal voltage for storage for months or years so the pack retains it's capacity well while in storage. Storing a pack for long periods that is drained near 9V or charged to full capacity isn't the best thing for maintaining capacity over the life of the pack. Just the same, even not putting your lipos to sleep you'll still get years out of them.
OK, so onto the mod pics for the Sovereign GT/Elite 8AA alkaline holder...Slide the door all the way open, then grab the edge of the lid and pull out. It should pop off the holder easily. Note the raised ridges in the holder to align the 8AAs. Not really needed even if you go back to 8AAs, so take a drimel and grind those down flat and make sure there are no sharp edges, and the reason for grinding those ribs down is so they aren't poking your lipo. Lipos should NEVER be punctured, so let's be safe here.
Next, not the small empty chamber to the side of the 8AA compartment. That's where a charging circuit goes in the stock rechargeable pack but isn't used for the alkaline holder. Perfect place to stick your lipo plug out of the way should you want to use 8AAs again, but why the heck would you want to do that? :shrug: Either way, even if your detector is not a GT/Elite and it doesn't feature a small hide away compartment like this, the JST female plug you install is so tiny that I bet it will rest between the two upper halves of two AAs where that little "gap" is between them as they curve upward and away from each other, so I doubt a tiny JST plug will be an issue if you need to throw 8AAs back in one day. And, if you ever resell the detector, just snip the two wires for the plug you installed and no worries because now it's gone.
The black male plug you see in my pics is NOT meant for JSTs, so it's much bigger than a regular male JST. It was just all I had on hand that would mate with a female JST on the battery.
Anyway, for the GT/Elite, onto soldering in the plug. Note the red and black wires in the holder in the empty chamber area. Lift them out with a small screwdriver or something. No need to cut them. Just use a exacto knife to scrape a little insulation off both. Space this two spots far apart from each other so no dangers of a short. Now just solder your male JST leads to them and you're all set!
Because we didn't cut the wires there is no easy way to cover them with heat shrink. You can use a little liquid electrical tape (radio shack or home improvement stores) to paint over the bar wires/soldering if you are worried about it, but that's why I spaced mine apart like I did where I made the two connections. Those wires can't move enough to get their exposed wiring close to each other so I don't worry about it myself. I think I only slid some heat shrink onto one wire, but as said since the wire we soldered the plug to wasn't cut there is no easy way to slide heat shrink over both.
Also, I'm sure the red/black wires in the holder have the right polarity (red +, black -), but that's from memory so you might want to double check with a volt meter that will show "-" if the leads are reversed. Sometimes companies do strange things with wire coloring, so don't take my word for it.
Now, you've got two options to get the plug into the 8AA holder area. You can either just run it's wires over the "wall" that separates the two chambers, or you can do what I did and just heat up a knife and melt out a doorway for the plug from one room to the other. :biggrin: I was worried about the lid of the battery holder pinching the wire over time as the door is slid or pushed on, so I just melted out a pathway.
There you go! All done! Shoot for a 1450ma pack and that should give you about 40 hours or so of run time. The stock pack is about 20 hours (if you're lucky). If around 10 to 20 hours (never timed it) is good for you, or roughly about two or three hunts for your average hunter, then just get the 750ma pack. When pack shopping might want to measure your machine's battery holder to make sure the lipo isn't too thick. Some brands are a bit thicker than others due to spacers between the three lipo cells. And of course measure the length/width of the pack too.
The specs when battery shopping will list dimensions for you to compare. On the GT/Elite the battery door lid has some give to it, so you could probably squeeze a bit fatter pack in there than you measure for if you want. I didn't grind down the ribs in my alkaline holder all the way yet so my lipo pushed on the lid a bit and flexes it out a hair. Doesn't bother me, but I should grind those ribs the rest of the way down to insure I don't one day cut into the lipo.
Lipos are weird in pack size. A bigger pack doesn't mean it has to be thicker, so don't be thinking a 1450ma pack won't fit in your GT/Elite. Kered is running one in both his XS2 and his GT or Elite. You can search the modifications forum for his name and find some pics of his lipo install too. Also, check the battery sticky in the Sovereign forum as there are thread links to more threads on using lipos and educating yourself that we've discussed in the past.
Always charge in a fire proof place like in the middle of a cement floor if you can't keep a constant eye on a battery. I tend to do that anyway, and that's for ANY battery, nimh, nicads, etc.
Make sure if you buy a simple plug-n-charge type charger that you can't change the amp rate on, that it's not a fixed rate above the max charge rate of the lipo (usually 1C is the limit for most lipos). If its slower than that, meaning 1/2 or say 1/3rd the amp rate of the capacity of the pack it's fine, it's just that it will take 2 hours (1/2C) or 3 hours (1/3rd C) to charge the pack. If you don't want to buy a charger that lets you program the amp rate then at least get one with a sliding amp rate switch where you can set the charging amp rate as close to 1C as possible (if the lipo allows 1C...ALWAYS check on your own, as there might be some that don't allow even 1C out there in charge rates.)
And again, I'm not responsible. Don't follow my advice or it's your risk. Research and educate yourself and confirm and verify. Never mess with batteries of any type unless you know what you are doing!