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  #21  
Old 08-10-2006, 04:36 PM
ROF ROF is offline
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Default Re: Battery Clinic follow up & Questions

Originally Posted by Brian Memory effect is an urban myth....you do get voltage depression but its effect of overcharging caused by cheap domestic chargers. If you don't over charge then there's no need to fully discharge which reduces the amount of recharging cycles you can do and risks reversal of the cell.
Not quite a total urban myth. Several years ago we actually conducted a study of this in our environmental chamber for some telecom field equipment. Using the same type batteries, same charger, same environmental conditions. Conclusion: batteries fully discharged prior to recharging actually did perform better by lasting longer in the equipment before needing replaced. We're only talking about the Nickel-Metal-Hydride tye (the most common over-the-counter rechargeable type found).

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  #22  
Old 08-10-2006, 08:38 PM
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Default Re: Battery Clinic follow up & Questions

Now look what i started!!

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  #23  
Old 08-10-2006, 08:42 PM
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Default Re: Battery Clinic follow up & Questions

When I mentioned "memory", I was referring only to Nicads which do develop quite a "short term memory". Nimh cells are nowhere near as prone.

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  #24  
Old 08-10-2006, 08:47 PM
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Default Re: Battery Clinic Chapter Two

FOOTNOTE ON CELL STORAGE:

Nicad cells should be discharged to .6V per cell for storage. They should be fully charged and then discharged again after 6 months.

Nimh cells should be stored at full charge. Top off or fully discharge then fully charge every 6 months. The newest Nimhs that have the 1 year shelf life and 10 % voltage loss made by Sanyo just need an occasional top off.

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  #25  
Old 08-10-2006, 10:52 PM
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Default Re: Battery Clinic follow up & Questions

My memory escapes me - LOL
Second thing to go after the hair of course.

Wish Lithium Ion for my MD were availavble.

Thanks again for the excellent post BTW.

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  #26  
Old 08-11-2006, 04:55 AM
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Default Re: Battery Clinic follow up & Questions

I can see the future with lithiums becomming more popular. Right now, lithium polymer cells pose a substantial risk of fire or explosion unless they are cared for, stored, and charged properly. This is beyond what the average "user" will do, and even with all of the warnings, someone will want to sue if they suffer a loss or injury. Lithium ions are much more stable but have their problems as well. I am also led to believe that they don't have as long a service life as the Nimh's but I don't know for sure, as I haven't used them. I have sealed packs that I have used for racing and flight (Nicad / Nimh) that are 3 years old with at least a couple of hundred charges that are still testing out like when they were new. It just takes proper care. BTW the racing puts a lot of stress on a pack, much more than normal use.

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  #27  
Old 08-11-2006, 05:32 AM
Brian Brian is offline
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Default Re: Battery Clinic follow up & Questions

Hi ROF
When batteries came up on the forum last time I mentioned that one of the U.S. Universities had researched 'memory effect' and basically said it is an urban myth though Ni Cads can suffer voltage depression as a result of poor charging. Nimh's also suffer but to nothing like the same amount. Li-Ion are never supposed to be affected.
This information has finally filtered on to the net (check under memory effect but ignore any post from battery dealers who still say that NiMi's suffer no memory effect).
My original Deepstar NiCad pack is eight years old and still going strong. NiCads are getting a little hard to find in the U.K. now since their price dropped considerable but they still have the advantage that they will hold their charge better than NiMi's whilst sat in equipment.

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  #28  
Old 08-11-2006, 03:19 PM
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Default Re: Battery Clinic follow up & Questions

Since I retired I just do not keep up with everything I used to. All inputs to this thread have been insightful and educational.

My laptop and cell phone have the lithium Ions and they they sure last longer than the old cells of yesterday.

- Rusty

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  #29  
Old 08-12-2006, 08:56 AM
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Default Re: Battery Clinic follow up & Questions

I completely forgot about my laptop. 7 years young and still going strong.

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  #30  
Old 09-05-2006, 03:59 AM
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Default Re: Battery Clinic follow up & Questions

Hi Bill !! !

I know you are an expert on battery science and also have experience with an Ace250 detector, therefore
I come to you with the following question :

First, I'll set up the question with a little background. Lately I've been wondering if a metal detector's
coil-signal strength is reduced as a result of declining battery voltage. So I re-read your Battery Clinic! -
Chapter 1 post of July 30, 2006, in the How to Use Your Metal Detector! ! forum.
In this chapter you say that metal detector circuitry is designed to operate on millivolts ( 1/1000 V).

Question :! Notwithstanding that there are factors involved, such as matrix composition, target conductivity
and amount of exposed surface area available for eddy current production, etc., that will control the effective
signal depth, can I run the Ace250 until the batteries go completely dead, or nearly so, with the assurance that there has been no reduction in coil-signal strength and depth ? If the answer is NO, then at what point should I replace (or recharge) the batteries to maintain full signal strength and depth ?

Thanks much !

Todd!

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  #31  
Old 09-18-2006, 07:01 AM
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Default Re: Battery Clinic follow up & Questions

Todd,
Just returned from vacation so I'm just now catching up.

First off, all makes and models of metal detectors differ in their electrical design and therefor will differ in how they perform when battery voltage declines. Usually there is a cutoff and shutdown when minimum operating voltage is not met. Up to this point, all normal functions are met, and the signal comming from the coil is unchanged. Modern design does not allow for gain or reduction in signal transmission at the coil but straight line performance would be the norm. We are not back in the dark ages of early transistors any more.

My rule of thumb is that I take a spare pack (fully charged) with me always. When I am done I put the spare pack in the machine for its next use and top off the used pack (only with Nimh's). If I have a few short hunts I switch packs at about half capacity. The 250 does not have the drain of the Explorer II, and only uses 4 cells as opposed to 8. Thus far my wife has not used it long enough to really test its longevity in the field, so I just top off the used cells and swap the spares in the same fashion. She usually gets tired after only a couple of hours. By alternating the packs, I am giving "even useage", and not stressing the cells at all by just topping off. With my computerized charger I can actually increase the capacity by percentage. To stay within a "safe zone" I do not exceed a 130 % charge in milliamps when I am anticipating a "long hunt". There is simply no reason to push the cells when I have now two spare packs that will provide at least another 30 hours of time on top of the approximate 15 hours I am starting out with (Explorer II). The charger that I use can also be run off of vehicle current or portable battery pack if I would be out in the bush for a few days, so the battery concerns are almost a non issue. I have a rechargeable gel cell pack that is used for jumping vehicles and has a 12 V outlet and work light. (Pep Boys $ 40.00) This thing powers my telescope, laptop, TV, DVD player, etc when in the field. It is also great around the house when there are power failures. I just picked up a 15 million candlepower "flashlight" at Sam's Club, also with rechargeable gel cells and 12 V work outlet. This thing is so amazingly bright that I went back and bought 4 more to be given as Xmas gifts ( reduced from $ 32..00 each to $23.00 each.) Has high and low beams as well as smaller LED light & fully equipped for 120 V or 12 V recharging with overcharge protection built in. This can also be used as a 12 V source in the field. Just thought I'd throw this in for you early shoppers !!!!

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  #32  
Old 09-21-2006, 12:54 AM
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Default Re: Battery Clinic follow up & Questions

Many thanks for all the info. in your reply Bill !!

Hope the vacation recharged your batteries! LOL! !

Todd

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  #33  
Old 09-22-2006, 05:41 AM
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Default Re: Battery Clinic follow up & Questions

In reality, this years vacation coulda been a whole lot better. Maybe next year!!!!

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  #34  
Old 12-24-2006, 10:43 AM
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Default Re: Battery Clinic follow up & Questions

i found this article and did a copy /paste.
Madison-based Rayovac, the nation's third-biggest battery maker, is broadly launching its revamped rechargeables in a few weeks. The batteries, which are fully powered out of the box, are now only available at Wal-Mart Stores Inc. (WMT) locations with a suggested retail price of $8.99 for a four pack of AA or AAA batteries. Chargers cost $9.99 to $19.99.

The time spent recharging is a major complaint, said Sean Martin, a division vice president at Rayovac, a unit of Atlanta-based Spectrum Brands Inc.

"It's the inconvenience of 'I have to charge them before I can use them and then every time I go back to use them they discharge their power,'" Martin said.

The new Rayovac batteries, called Hybrids, not only ship fully charged but also can hold that power for about nine months when they're not used.

They're made of the same elements as standard nickel-metal hydride rechargeables, but the nickel-metal alloy is treated with a chemical process that allows the batteries to hold their juice longer, the company said.

Hybrids will completely replace Rayovac's other rechargeables after the first of the year.

Electronics company Sanyo has a similar nickel-metal hydride rechargeable called the Eneloop on sale at Circuit City, Ritz Camera and other chains, said David Isola, a Sanyo senior product manager.

He said the company has sold 10 million worldwide in the 10 months they've been on sale. The batteries, which also are fully charged out of the box, can hold their power for up to two years when they're not being used, Sanyo said.

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  #35  
Old 12-28-2006, 06:36 AM
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Default Re: Battery Clinic follow up & Questions

From experience with my R/C batteries. Sanyo absolutely makes the best cells that you can buy, and always seems to be on the leading edge of technology.

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  #36  
Old 01-08-2007, 02:20 PM
cpa49707 cpa49707 is offline
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Default Re: Battery Clinic follow up & Questions

Thanks Bill for a lot of very informative information. Now bring it down to something a Simple accountant can undeerstand. I Have the Ace 250 like your wife and what is the best charger for that model and what are the best rechargable batteries for it. Remember i am an idiot when it comes to this stuff, i just wan't it simple. Thanks,

Terry

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  #37  
Old 01-17-2007, 09:15 AM
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Default Re: Battery Clinic follow up & Questions

The simplest setup would be a "wall wart" type charger like the Radio Shack model shown in my pics. Get one that shuts itself off automatically by sensing voltage peak or a timing circuit. The one (R.S.) shown holds 4 AA's or 4 AAA's. Get the Eveready 2500 Mah AA cells ( Sam's Club / Walmart) pkg of 8. You will then have 2 sets to cycle. Sorry about the late comeback, but my time has been limited in the last week.

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Time in swing 2009: 0.0 hrs.
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I WORK TOO MUCH & SLEEP TOO LITTLE !!!!

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  #38  
Old 01-30-2007, 08:04 PM
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Default Re: Battery Clinic follow up & Questions

Hi Bill Check youy PM. I didnot know there was a follow up on your post on Battery Clinic

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  #39  
Old 02-02-2007, 08:39 AM
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Default Re: Battery Clinic follow up & Questions

Thanks again gor the great article. It has helped me understand things that have been driving me nuts for years!!!!!!
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  #40  
Old 02-19-2007, 11:53 AM
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Default Re: Battery Clinic follow up & Questions

our DFX came with a sealed, rechargeable battery pack and a second pack that holds a good number of AA's ... the info in the owner's manual clearly states that for the sealed battery memory is not an issue but overcharging can be .. the charger that came with the sealed battery has fast and overnight settings ... the manual states that in overnight mode overcharging is not a concern but in fast one must be careful to not leave it plugged in too long ... I haven't figured out just how long the sealed battery will last, so I carry the pack if AA's as a spare ... I appreciate the info in this thread, it has been most helpful

Jim

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