rechargeable 9v batteries

[Smooth23]

I'm sure this horse has post-mortally been beaten, but every thread about rechargeables seems to gravitate around AA, which are far cheaper to replace than 9v anyhow. I'm wondering how you guys using rechargeable 9 volts fair? Both the pro-pointer and the Omega 8000 use 9v so I figure why not get some I can re-use? What brand do you guys use and where do you get them? How long do you get on a charge?

[Vethraxx]

Just remember. A rechargable battery does not have the same voltage as it's disposable Alkaline or Lithium counterpart. Even though my detector takse 6 AA (9v), If I put rechargables in I only get 7.2v. (The rechargeables only get 1.2v per battery, not 1.5v) Just about where My detector starts acting strange because the batteries are dead enough not to run the circuits properly.

This does not apply to NiMH or Nicad rechargeable packs as they are designed for a proper 9v or whatever output.

All I can say is try it, and see how far you get on a freshly recharged 9v and compare it to the time you get off a disposable.

[Smooth23]

Originally Posted by Vethraxx

Just remember. A rechargable battery does not have the same voltage as it's disposable Alkaline or Lithium counterpart. Even though my detector takse 6 AA (9v), If I put rechargables in I only get 7.2v. (The rechargeables only get 1.2v per battery, not 1.5v) Just about where My detector starts acting strange because the batteries are dead enough not to run the circuits properly.

This does not apply to NiMH or Nicad rechargeable packs as they are designed for a proper 9v or whatever output.

All I can say is try it, and see how far you get on a freshly recharged 9v and compare it to the time you get off a disposable.

Well obviously NiMH is the only solution for rechargeables nowadays. And you are talking about AA. Just FYI, putting 6 AA in doesn't stack up voltage, it just gives you more mAh of 1.5v

[Bonesquat]

I get excellent results from using 9v rechargeables off ebay.

I can't remember who I bought these from but the one in the middle is the BEST by far, the one at the bottom is also an excellent battery. I've had near the same life with these as alkalines and they're rechargeable. You just can't beat it. I've gotten about 24 hours out of the middle battery and 20 or more on the 300 using the pro pointer. On the old bounty hunter any of these was good enough for a few weeks use. Just remember the best is the BTY battery, the one that's basically as good is the 300 Feeby, the one that works ok but not perfect is the solid green one. They come with a charger though which you'll need. All quality though.

[digdug1968]

What kind of prices do they go for, and How many recharges do they last? Thanks for the info, I only go through a few batteries a year, but they do cut into my clad pile-that I'd rather spend at a coin shop.......

[Monkeywrangler2]

I have used NiMh 9v in my former Cibola, and they worked great. Good lifespan on them too. Better than alkalines. I still use them in the ProPointer. I try to recharge it monthly, which takes care of the self-discharge problem (no one makes low self discharge 9v Nims yet).

I get my batteries at www.batteryjunction.com and have had great service there.

[Smooth23]

Thank you bonesquat, that's EXACTLY the type post I was looking for. I was looking around feebay and the BTY chinese batteries were some of the ones i was looking into.

[FelixtheCat]

I have been using 9V NiMh rechargeables for about 4 years. For me they don't last as long in the detector as alkaline batteries. Another drawback is once the meter on my Discovery detector starts going down to about 50% there's very little time of use left. The ones I have bought have tended to last under 2 years and I have tried about 4 different brands but I haven't tried the BTY. Over the long run, you will still end up saving money over alkalines. One thing that I believe tends to ruin rechargeables is letting them sit for more than one day in the charger. I also only use them in my Discovery. For my CZ-21 I prefer alkaline batteries because I want to minimize the amount of times I open the waterproof battery compartment to change them.

[eetsJakey]

Guys, I'm new here, and well blah blah. here's my two cents on rechargeable 9V's.

First of all, they're not really 9V batteries, if you didn't know this they're actually 8.4v so you're actually short about 6%

the reason they still work, and work good (except for your battery meter, which I'll explain in a second) is that your primary alkaline cell, which contains 6 cells at a nominal voltage of 1.5 a cell slowly drops to about .8V per cell, which is how your battery meter reads the voltage.

NiCd and NiMh batteries on the other hand, maintain a almost constant voltage of 1.2v cell through out the discharge until the battery is nearly dead, it's like the voltage falls off a cliff. dropping to 1V per cell, which is considered dead for the most part. this is why your battery meter may show you have half the battery remaining and within minutes it's dead.
Alkaline discharge curve
NiMh discharge curve you can see how one holds a pretty steady voltage and the other drops.

I am aware that these charts are using different drain rates, but the discharge curve is identical weather you're discharging a .01mA as if you were drawing 1000mA

so a dead alkaline 9V is at about 4.8V where as a dead NiMh or dead NiCd battery is at 7V.

so, the meter on your detector is set to show dead at 4.8V where as when you're using a rechargeable you're actually dead at 7V

Over discharging rechargeable cuts their life in half, with NiCd's it can kill the battery over night. so, after a day of using your detector it's best to charge them, unless your charger is timer controlled, and mine is, then you have to worry about over charging. the charger you want is a "computer controlled smart charger" or any charger that says it uses the ΔV charging method, unfortunately they're hard to find for 9V batteries, for AAA-D cells they're pretty common.

I hope this wasn't too much information and helps at least someone understand what's going on.

I was honestly concerned about using rechargeable NiCd's that I bought from batteryspace in my bounty hunter since i recall the instruction manual saying use alkaline only.

[FelixtheCat]

Originally Posted by eetsJakey

Guys, I'm new here, and well blah blah. here's my two cents on rechargeable 9V's.

Over discharging rechargeable cuts their life in half, with NiCd's it can kill the battery over night. so, after a day of using your detector it's best to charge them, unless your charger is timer controlled, and mine is, then you have to worry about over charging. the charger you want is a "computer controlled smart charger" or any charger that says it uses the ΔV charging method, unfortunately they're hard to find for 9V batteries, for AAA-D cells they're pretty common.

Your two cents are very good! I am going to figure out some way to put a timer on it.

[Banemorth]

I got the Enercell Rechargable 9V from Radio Shack. They seem to work ok.

[RickO]

I prefer Lithium-ion wherever I can use them. I do use the rechargeable packs that come with the detectors (Li for the TDI). RickO

[eetsJakey]

Li-Ion cells are rechargeable. LiFeS2, I'm guessing you're talking about the AA lithium primary cells that energizer makes, those would be LiFeS2 cells. they're nominal voltage is 1.5V per cell, apparently they make these in a 9V battery package as well.

I have a question, do they actually last longer in your detector? From what I understand about that chemistry is that it excels in high drain applications (digital camera's running large motors) and has an extremely long shelf life (like 15-20 years) but the capacity is close to an alkalines. which means in a metal detector it shouldn't last much longer or as long, because most of them don't use a lot of juice. correct me if I'm wrong.