XLT owner-Problems with NiMH batteries

[jeffmajer]

Has anyone else had this problem. I am pretty new to MDing and reacently bought some NiMH (Nickel Metal Hydride) batteriesfor my XLT, which is pretty well used but seems to work fine with alkaline batteries. While detecting the other day, for the first time with the new NiMH batteries in the machine, it shut down for no good reason. The machine also would not start twice with these batteries powering it. I went out for a couple of hours today. First thing I try to start up with the NiMH batteries and it won't even come on. I switch to some alkalines and I have no problems. Has anyone else had this problem, any ideas?

 

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[Jeff In North Georgia]

These rechargeables should work fine as long as they have a rating of 1800 mah (equal to an alkaline battery) or higher. It is possible you have one or more bad batteries. Check them with a voltmeter or battery tester. Also make sure that you let them charge long enough to get a full charge.

Jeff

 

[jeffmajer]

I'm feeling too lazy to go get my tester, so that will have to wait. The machine did start and if you perform a battery check you get a reading of 10.? (I don't exactly remember) volts. It probobly would have started had I gave it a minute this morning but I just switched to the alkalines rather than deal with that frustration. The batteries were fully charged. I will have to check them though. (When I finally think about it).

 

[Sarge]

Jeff,

You should get a higher reading than 10 volts with freshly charged NiMH batteries. I normally get a tad over 11 volts shortly after a charge then it'll drop to about 10.8 V fairly rapidly & hold at about that voltage for quite some time. This holds true for both my XLT & DFX.

Try cleaning your battery contacts although this doesn't seem to be your problem as the alkalines are working fine. I occasionally clean the contacts on the battery using a pencil eraser & I do the same to the internal contacts in the detector.Very carefully put the pencil inside the battery compartment & softly rub the ends of the contacts.

One of your NiMH batteries might be dead. They should read about 1.4 volts with a full charge after being out of the charger for a time (they're warm right after a charge & may indicate a higher voltage) & unused.

Be double-damn sure that all batteries are in the pack with the right polarity! I was loading my pack today after taking the batteries out of the charger while talking on the phone & upon checking I found one that was reversed.

The same happened last week when I was putting batteries in the charger & almost put one in backwards!

Every month it seems I have more senior moments!!

 

[jeffmajer]

I did get a reading of 11.? when I initially turned on the detector but like you say it quickly drops into the 10.6 (if my memory doesn't fail me) range as these batteries are suppposed to. As far as checking polarity, that was the first thing I checked as well as the contacts inside the battery case itself. Everything was allright. All seated properly with good contacts. Still haven't gotten around to testing the battteries though. I did post this on one of the other boards as well and someone else posted that they had the same problem so they only use alkalines now.
Thanks for the ideas.
Jeff

 

[Sarge]

That's a stumper, Jeff. If your detector doesn't even turn on you can't even read the voltage. That's where a cheap voltmeter will come in handy. The only other possibilty is that you rapid-charged your batteries too long & stressed them to the point where they won't hold a charge. Heat during charging is the worst enemy of any rechargeable battery.I've been recharging NiMH batteries for years in NiCad chargers but they're fairly low current. I have a bunch of chargers for D cell down to AAA & the hottest one is only 100 ma. I prefer using that one as I can charge all 8 batteries at a time. I've collected 3 of those chargers throughout the years & I've got two back-up sets of batteries so in effect I can recharge 24 at a time. I found that a 12 to 15 hour charge is more than sufficient & if I forget & keep them in longer there's no harm done although I don't like to make a habit of it.

One other thought: Are you sure the batteries actually charged? I have to clean the contacts in my chargers every once in a while. I have indicator lights in each 2 battery bank in my chargers & after an hour or so I've checked them only to find one of the banks has no light. I slowly turn the batteries while in the charger putting mild pressure on the contacts by pushing the batteries against them. I have to do the same with my AA packs. The can get dirty while detecting.

At this time I use only NiMH AA batteries for both of my detectors & my handheld 2-way radios & have had no problems whatsoever.

 

[jeffmajer]

I finally got around to testing those batteries. They are all at 1.26 to 1.28 v. I sure don't get it.
Jeff

 

[sniffer]

I know with my DFX, once the voltage drops to 10.4 - 10.5, it starts to give off a lot of false signals. I tried NiMh in mine and they only work for about 2 hours. Not worth the extra expense

Sniffer

 

[Sarge]

Wow, Sniffer. I've been using the NiMH pack in my DFX for over a week with 2-3 hours minimum a day except for Thurs. & Fri.The voltage dropped to 10.5 fairly rapidly from 10.9 ( those batteries were charged a month before I put them in my detector so they lost the voltage that you get with a freshly charged battery). I detected Mon. thru Wed. & when I finished it was still at 10.5 volts. after using the same pack the week before. I can normally go a good two weeks on the same pack with mild metal detecting. Going 8 hours a day for a week will use them up faster of course.

I've been using NiMH batteries of all brands for years & never had any problems either in the XLT or DFX. HOWEVER- I have noticed that some AA batteries are just a teeny bit shorter than others. Is it possible that they're not making good contact? I also make it a habit to clean the contacts on the batteries fairly often. I usually will twist them while they're in the pack & that seems to clean the ends of the batteries as well as the contacts in the pack. I have a 2-way radio that requires that to be done often. I'll get a low battery reading & I just open the radio & turn the batteries a half a dozen times. The low bat. indicator goes out & stays out for quite a while.

What are the brands of the batteries you guys are using?

I still think you may have a charging problem. The batteries are either getting too much of a charge & are stressed out or not enough of a charge. Have you cleaned the contacts in your charger? I'm starting to grasp at straws as I'm totally stumped as to what the problem is where I've had so much good luck with NiMHs.

 

[jeffmajer]

Sarge,
Thanks for all of your responses. You know one of the first things I did when I got them was check their size with a dial caliper and compared them with some alkalines. I just remeasured them along with a duracell and a rayovac alkaline. All three brands were within a .25mm range from smallest to largest: duracell, Nimh, rayovac. I am using are Ultralast, I bought them at a computer store while looking for something else. They are made in China of course. Contacts are all clean on batteries, Battery pack and inside the machine. I am going detecting today, I will try to remember to grab the things off my desk and give them a spin today.
Jeff

 

[jeffmajer]

I don't know what happened but I tried using the rechargable batteries yesterday, and guess what? No problem. I know better than to complain. I hunted for about 3.5 hours and no problems at all. Machine gave a battery reading of 10.2 v before I shut it off at the end of the day. Sarge, If you are still monitoring this post, do you let your batteries run down or do you keep them topped off, and do you find that it has any effect on the performance of your machines? Let me know.
Thanks,
Jeff

 

[Sarge]

Jeff,

I'm sorry for the delay in responding. I'm normally only on Thursdays & Fridays from the site where I do armed security on those days.

I try to run the batteries down until I get a low battery indication.I have a spare pack & 8 additional AAs in my car at all times so I can afford to run the pack down. With NiMH batteries it's not required like it is with NiCads but it's a habit I got into. At times I top them off, though, with no ill effects. If I do that a few times with a pack then I make sure I run it all the way down eventually. I do the same with my cell phone batteries. I have a spare fully charged with me at all times due to the fact we no longer use two-radios other than short range ones on the job & that's my commo with the PD & the other officers under my supervision at this site. It's our lifeline.

I'm glad the problem ironed itself out. I still think it was a contact problem with at least one of your batteries.

My NiMH pack that I was using last week at 10.5V is still functioning after detecting Sat, Sun, Mon,, & Wed for a few hours each day & it finally went down to 10.4V & flickers to 10.3V so I interpret it to be 10.35V. Now it'll probably start going down faster. I also use a fairly hot program in an area with lots of trash signals so it's working the battery hard.

 

[jeffmajer]

On this last charge I let the NiMH batteries run all the way down just to see how performance is affected. The actual performance did not seem to be affected immediately, until the display shut down. For about half an hour though it was obvious that the machine wasn't quite right even though it was still finding targets. Every target was reading as an overload. The total run time on that charge was in the 16-20 hour range and after the day was over I checked the charge on the battery anv voltage read 7.8 v. Voltage does drop rapidly in the machine pretty much how the manual describes the battery charge of the White's rechargables. I did check the voltage several times during the day, and up til about an hour before I called it quits, the voltage was reading in the 9.- range. Just thought I would Let you all know.

Good Hunting!

 

[Sarge]

Jeff,

That's usually an indication that you have at least one bad cell or a contact that's offering a large resistance.. The trouble with taking voltage readings on individual AA batteries is that they're not under a load & there's no way of testing them while in the detector while it's on. I've had batteries of all types that read normal voltage until I actually was using them. While under load they dropped way down & as soon as the devise was turned off the voltage was close to normal.

What is the ma rating of your charger? Ideally it should be, off the top of my head, about 100 ma or even lower. Those batteries don't like heat.

There's another thing that happened to me. I had a 10 cell charger, 5 banks of 2 cells. I went through a few brand new batteries when I discovered one bank that went absolutely crazy. It was WAY over voltage. That ate those two batteries right up & the two I tried after that.

I loaned a neighbor my XLT this week & we went detecting as he's on vacation. I put a freshly charged pack in it & it read 11.2 V & dropped to 10.9 after a few hours. Those voltages are perfectly normal.

A 16-20 hour running time is in my opinion about normal especially if you're running a fairly hot program with lots of targets & pinpointing. If you get that much out of them I wouldn't worry too much. At least you don't have to toss them as you would non-rechargeables. It's my contention & borne out by experience that batteries run continuously for a long stretch will lose voltage faster than a battery used for short periods of time. Batteries have a tendency to recharge themselves (surface charge) when idle, thereby extending their operating life a little.

 

[Keppy]

Never use rechargable batteries always use AA alkalines and i never have any problems.........I just never did like rechargeable batteries.....Sell mine on Ebay as soon as they come with the detector....==Jim==

 

[Sarge]

I love them. More expensive but they pay for themselves in the long run. I have some that are over 5 years old & they still accept a charge & last a fairly long time. Now if you're talking NiCads then I can agree. They could develop a memory & they didn't have the staying power. But the newest NiMH batteries with a high mah rating will last a long time while detecting & I don't have to throw them away when they're depleted. They can be topped off before a hunt with no ill effects & won't develop a memory. The down side is a charger is needed, an added expense but I've got about 6 of them, only 2 were bought new. The rest were bought at rummage sales for about a buck apiece.

I've got a couple of two-way radios, actually more than a couple & those NiMHs do a fantastic job. Of course they don't last as long as alkalines but then again they're rechargeable.

To hedge my bets I keep a spare set of alkalines in my trunk. Never needed them. I usually wind up using them in my Mini Mag flashlight on the job.

 

[Keppy]

I love them. More expensive but they pay for themselves in the long run. I have some that are over 5 years old & they still accept a charge & last a fairly long time. Now if you're talking NiCads then I can agree. They could develop a memory & they didn't have the staying power. But the newest NiMH batteries with a high mah rating will last a long time while detecting & I don't have to throw them away when they're depleted. They can be topped off before a hunt with no ill effects & won't develop a memory. The down side is a charger is needed, an added expense but I've got about 6 of them, only 2 were bought new. The rest were bought at rummage sales for about a buck apiece.

I've got a couple of two-way radios, actually more than a couple & those NiMHs do a fantastic job. Of course they don't last as long as alkalines but then again they're rechargeable.

To hedge my bets I keep a spare set of alkalines in my trunk. Never needed them. I usually wind up using them in my Mini Mag flashlight on the job.

Your right i am talking NiCads never liked them.............Never tried the NiMHs .....I might give them a try.............==Jim==

 

[sniffer]

I use the new disposable lithium batteries as my backup batteries and I've had to use them once, still using them, after 20+ hours still holding at 11.2 volts

Sniffer

 

[Sarge]

Now if they only made a rechargeable lithium...