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Question: sovereign GT battery system

JimmyCT

JimmyCT

Well-known member
I have a question regarding the GT battery system. I plan on using 8 AA nimh batteries instead of constantly buying akalines (obviously due to cost) my question is concerning the MaH. Can I use a higher rated (ex 2500 Mah) batteries or should I use the same Mah as the optional NiMh (1000 mah). My concern is that I do not want to harm the electronics with the higher Mah. Websites selling Nimh states that the higher the mah the longer run time of the battery. I just want to double make sure before dropping them in and frying my new machine. Thanks in advance for the help.:help:
 
First thing is that rechargeable are only 1.2 volts a piece while alkaline are 1.5 so with the alkaline you have the 12 volts needed to operate the Sovereign while the rechargeable are only 9.6 volts. Now many say it will work if you use a higher Mha batteries, but it still don't make the 12 volts the 8 alkaline have. The factory rechargeable packs have 10 cells in them to make the 12 volts you need.
For me i only use a factory rechargeable pack and the alkaline pack for backups with the alkaline in them as i know I have the voltage needed Minelab recommends. On the Explorers they will work with no problem as they run a 9.6 volts on the rechargeable pack to with a voltage reg when using 8 alkaline at 12 volts.

Like I say many will use them and say they work, but myself i wont take a change on missing a once in a lifetime find because the voltage was too low. I am sure if Minelab wanted it to run at 9.6 volts they would have made it that way like they did with the Explorer.

Rick
 
RICK-I CAN ALREADY TELL THE GT IS MORE SENSITIVE SENSE I BOUGHT THE RECHARGEABLE BATTERY PACK INSTEAD OF USING THE 8 BY 1.5 BATTERY PACK I HAD BEEN USING SINCE MY ORIGINAL RECHARGE BATTERY PACK WENT SOUTH. I MAY HAVE MISSED SOME COINS. THANKS-MARK
 
Thanks Rick for your explanation. Much appreciated.
 
Better batteries will NOT do a dime's worth of difference to increase the performance of the machine! Metal detectors have a voltage regulator in them. What that means is it doesn't if the input voltage is 12V or 14V, it's still only going to get fed a lower stable voltage by the regulator (like say 9V) in order to keep the machine stable and operate within specs. I have tried to squash this myth for years but once again BETTER BATTERIES DO NOT GIVE BETTER PERFORMANCE! Better batteries will only increase the run time, period, end of story.

Now, yes rechargeables are only rated at 1.2V but that's an average. In reality a good pack will charge to much higher than that. If you want to try rechargeables in your GT's regular holder then buy at least 2500ma or higher nimhs. Charge (or re-peak them) the day you plan to go out as nimhs will discharge some on the shelf. I believe the reason why Minelab used 10 cells in the stock rechargeable is because they are using ancient Sub A 1000ma cells in the GT. That lower of a capacity and that old of a technology won't hold it's charge well on the shelf, and with that low of capacity it will run down real quick. Solution? They upped the voltage by including 2 more cells so if the pack sits around on the shelf it will still have enough voltage to run the machine weeks later. A good 8 AA 2500ma or higher (buy the highest you can) pack should run it just fine so long as it was peaked the day you go out.

Another thing: A 2500ma nimh or higher will out run a regular store shelf battery these days. The store battery may start out at 1.5V but it has less capacity then the nimh, which means the regular battery will soon drop lower in voltage than the nimh. The nimh may start out with a lower voltage but it will maintain that voltage over a longer span of time than the store shelf battery.

The GT's voltage regulator needs about 10.5V to run, so as long as the pack voltage is above that you'll be fine. Some of my nimh packs hold about 11.8V when fully charged, and that was after letting it set for a few hours to insure I wasn't reading an artificial voltage high caused by just being on the charger.
 
I'm with critterhunter on this and have bee using 8x rechargables for years, you do get longer run times now as the AA's now come in greater capacities but the 1.2v is not the maximum capacity of these, when they get to 1.2v they are getting well down, fully charged you are more in the region of 1.35- 1.4v.

I have been getting much better run times on 8 x 2800mah rechargables compared to the factory 10x 1000mah rechargable pack(its new too) getting in the region of a 1/3 more runtime on 2800mah down to the low battery alarm. Untill this alarm warning sounds off the detector runs just the same with no loss of power etc, if better performance was gained by a full 12v or more I and many more would have a car battery hooked up in that case, its just not true.

What i will say is years ago with the first nicad AA rechargables that came out things were different but things have come a long way since then.

Another thing is you also now have the enerloop AA's that keep 80% charge up to a year on the shelf (only downbit is they only come in 2000mah on AA's at the moment but still a good amount compared to stock) which will help the infrequent users but its still better to do a topup charge the night before or while having breakfast on the day your going out.
 
Kered, glad to hear you have been running 8 AA nimhs in the regular holder with out short run times. I never got around to trying it but I knew based on my experience with rechargeables in other devices (like my plane's TX) that they hold the voltage higher than 1.2V when charged and will hold it higher longer than normal store batteries. It was just a matter of math to figure out how long a nimh at a certain capacity would hold it's voltage above the required 10.5V of the Sovereign's regulator, and if that amount of time was as long or longer than the 10 Sub A cells used in the stock rechargeable pack.

I think the reason why Minelab put 10 in the rechargeable pack is because they are using Sub A cells. Talk about ancient technology, and while Sub As are still used here and there in RC just like Sub Cs are, 1000ma is a rather low capacity of back in the late 80's early 90's or so. I'm not sure what the highest capacity of a Sub A is these days but I bet it's somewhere in the 1800 to 3000ma range, and I remember a long time ago with 1500ma cells came out. Interestingly enough, Sub Cs, which I guess some older Sovereigns use, can be found in 3300ma and higher capacities...and I checked that like 5 years ago so I bet they are even higher now.

Anyway, a Sub A 1000ma cell would not hold it's voltage very high for too long of a run time and so I bet Minelab put 10 in to boost the voltage. Not only that, but those old Sub As they used probably don't hold their voltage well on the shelf compared to more modern versions of the Sub A and other nimhs. Meaning, if 8 Sub A 1000ma cells sat on the shelf for say 2 weeks or more they'd probably already be very close to the 10.5V cutoff voltage.

If anybody decides to go to cheapbatterypacks.com and have them install new cells into your GT holder, I'd ask for the highest capacity they have in those. On the other hand, you could have them install 8 Sub A high capacity cells for less weight. Same deal with old Sovereigns using Sub Cs. Those things are even heavier than Sub As, so I'd tell them to install SubAs in the pack or something. IMO Sub C (and even Sub A) cells are way too heavy for a metal detector. Regular AAs would be a much lighter choice and those could also be installed by them into that holder. On the other hand, I'm running a 750ma 3 cell lipo in my GT's regular holder and it weighs next to nothing. You might think I don't get long run times as the stock pack is 1000ma but remember that lipos hold the voltage very high to the very end of discharge, so it doesn't trip the low battery alarm as fast as other batteries would.
 
Since this thread is linked in the battery sticky under the description of the topic of using 8AA nimhs in your regular holder, I wanted to further link this thread to another thread that goes further into this discussion of if you can or can't use 8AA nimhs in the regular holder when the stock rechargeable pack uses 10...

http://www.findmall.com/read.php?21,1756661
 
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