Max voltage of your nimh slimpack ?

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Max voltage of your nimh slimpack ?

Post by hihosilver »

Can anyone who has fully charged up their 9.6v 1600mah nimh slimpack (safari/etrac/explorer) battery, and who has a good quality multimeter, let me know the max voltage your pack charges up to please? :-/

Also if you have ever measured the minimum voltage your pack drops to before it stops working in the E-Trac, I'd be interested to hear this level too.

Thanks folks. ::g


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Re: Max voltage of your nimh slimpack ?

Post by Fusion »

9.6 Volt packs are made up from 8 cells. An individual cell will easily be 1.4 V when freshly charged, probably more like 1.45 V. So your 9.6V pack could definitely read 11.6V fresh from the charger.
I know that some 7-cell NiMH PP3 batteries of mine read 10.4V when freshly charged, which works out at 1.48V per cell.

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Re: Max voltage of your nimh slimpack ?

Post by hihosilver »

I know that about batteries and supposed voltages but cheers Fusion. Do you know what the maximum input voltage is before the E-trac won't function due to the internal circuitry protecting from overvoltage, and it's minimum cut-off voltage at all please?
I don't fancy rooting around trying to find it out if someone has already done so. :))
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Re: Max voltage of your nimh slimpack ?

Post by Fusion »

Sorry, I know nothing at all about the eTrac's power requirements, but I would be surprised if there is any kind of over-voltage protection in it.

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Re: Max voltage of your nimh slimpack ?

Post by Mega B »

Just seen the details in the MDF Auction site regarding the RNB batteries and this is some basic information from the advert.

Our Rechargeable Batt Pack is 12.5 volts. The Minelab Rechargeable is 9.6 volts. “It Does Matter”
Our ML-3100 Weighs Only 10.47oz. The Minelab Slimpack Weighs 14.72oz.

And they are rated at 3100mah LITHIUM-ION BATTERY PACK.

I doubt that this info will be any good but you never can tell.
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Re: Max voltage of your nimh slimpack ?

Post by Koala »

Don't have a E-Trac to test for you

general NIMH


Voltage fresh out of the charger depends on the charger used


Some fast chargers when the batteries are still almost too hot to hold can almost be 1.5V (1.48,1.49V)

most chargers its normally around 1.45V


Both quickly drop to 1.2V




The minimum voltage for you detector to work you need to work out for yourself.

As an example my detector has a 8V regulator that is protected by a diode which has a voltage drop of 1.1V so above 9.1V tested while switched on should work. This is not the case. As the detector makes a beep it draws more current and the voltage drops more. Voltage with out sound needs to be above 10V. If I take the batteries out and leave them awhile the voltage will bounce back slightly and can even be put back in the detector but will not last long.


Headphone used, outside temperature and age/quality of the batteries all affect the results.


Also testing battery voltage with a volt meter at rest does show how much charge is left. You really have to measure them under some sort of load

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Re: Max voltage of your nimh slimpack ?

Post by hihosilver »

Cheers for that folks. Yes don't worry koala I know how to check but it would require opening the case and as it's still under warranty I won't just yet.
Will set it up to use lipo's some time in it's future so that's why I was asking about battery packs. Will be a case of finding the right type as they're all rated diferently for sudden discharge voltage, etc, so putting the feelers out early. ::g Would need to make a circuit for it though to nip any harmful situations in the bud. I don't fancy blowing any circuit protection fuses or other components. =))
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Re: Max voltage of your nimh slimpack ?

Post by BILLS FINDS »

the info was in one of the mags when they tested the RNB battery pack i will try and find it for you
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Re: Max voltage of your nimh slimpack ?

Post by Fusion »

It would've helped a lot if you had told us all along what you were trying to achieve, rather than asking somewhat obtuse questions about NiMH cells, when what you actually wanted was to know about LiPo cells, how to make up packs of them, whether they would be OK in the eTrac etc etc.

A much simpler solution would be to replace the 1600 mAh NiMH's with 2200, 2400 etc NiMH's. You can still use the existing charger, though you'll have to leave it on charge for a lot longer, 24hrs probably.

A lithium replacement would be 3 cells in series. They are normally charged up to 4.2 Volts, ie total = 3 x 4.2 = 12.6V when fresh, falling to maybe 3.5 V per cell flat.
You can also parallel up pairs of cells, making a 6 cell pack, it depends on what size cells you can fit in.

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Re: Max voltage of your nimh slimpack ?

Post by stargazer »

Fusion wrote:Sorry, I know nothing at all about the eTrac's power requirements, but I would be surprised if there is any kind of over-voltage protection in it.

Yes Etracs do have a over voltage protection built in.

I use eneloop re-chargeables and sometimes when fully charged up the Trac posts a message for 'overload' then shuts down.
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Re: Max voltage of your nimh slimpack ?

Post by hihosilver »

BILLS FINDS wrote:the info was in one of the mags when they tested the RNB battery pack i will try and find it for you
Thanks look forward to it. ::g
Fusion wrote:It would've helped a lot if you had told us all along what you were trying to achieve, rather than asking somewhat obtuse questions about NiMH cells, when what you actually wanted was to know about LiPo cells, how to make up packs of them, whether they would be OK in the eTrac etc etc.

A much simpler solution would be to replace the 1600 mAh NiMH's with 2200, 2400 etc NiMH's. You can still use the existing charger, though you'll have to leave it on charge for a lot longer, 24hrs probably.

A lithium replacement would be 3 cells in series. They are normally charged up to 4.2 Volts, ie total = 3 x 4.2 = 12.6V when fresh, falling to maybe 3.5 V per cell flat.
You can also parallel up pairs of cells, making a 6 cell pack, it depends on what size cells you can fit in.
Wait what?! What I'm interested in is people's pack voltage levels, just like I mentioned in the first post, regardless of what I plan to do with lipos in the future. I'm not wanting info on lipos, or how to make a lipo pack, or to know if lipos would work in an etrac or not. Any DC power source can be used to power anything, regardless of it's chemistry. I already know plenty about lipos.

Yes, it's easy to make a nimh/nicad/etc pack, anyone with hands, a knife and similarly rated batteries could do that in their sleep. A lipo pack has some good benefits such as being lighter weight, charge faster, last longer, etc. Of course there are negatives to using such chemistry too.

And yes it says in the manual that certain batteries shouldn't be used due to the circuitry inside. Almost all electronics will have over-voltage protection circuit/s otherwise they'd be hazardous, or easily damaged.
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Re: Max voltage of your nimh slimpack ?

Post by BILLS FINDS »

just checked my mags and can't find the issue with it in it was the test for the RNB battery they did voltage checks on the minelab battery and the RNB looks like it was in one of the mags the wife chucked out sorry cant help more
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Re: Max voltage of your nimh slimpack ?

Post by hihosilver »

Ok no problem Bill, cheers for looking. ::g
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Re: Max voltage of your nimh slimpack ?

Post by Fusion »

Interesting what Stargazer says about shutdown, you would think that the RNB packs would cause this problem all the time...unless specific precautions were taken, such as intentionally charging them to less than the normal maximum. That would be an interesting one to know, what's the fully charged voltage of those packs? It would be useful to anyone trying a homebrew Li pack.
Also, is there not a battery holder for these machines that lets you run it on 8 x regular alkaline AA's? This would also top out just over 12 Volts with fresh batteries.

Re: the fast charge 'advantage' of the Li packs. This is because they have a seperate charging connection, going more-or-less directly to the cells. The stock NiMH pack has a small trickle-charger circuit built into it, set at 130mA, I recall, so taking 12 hours for the original 1300mAh packs, maybe the 1600 packs have a 160mA charging circuit. If this were bypassed in some safe way, it would be viable to fast-charge a NiMH pack, too.

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Re: Max voltage of your nimh slimpack ?

Post by Tony Hunt »

All technical details on our RNB batteries can be gleaned from Joe himself the guy who makes them, just google RNB. Funny how even Minelab employees use the RNB pack and Joan Allens repair staff admitted to using them to test repairs on detectors because its the only battery available for Minelab machines that lasted enough hours to check repairs out or thats what they told me once.

The RNB 3100 pack costs little more than the replacement Minelab version and lasts 30 - 35 hours from a 2 hour fast charge, Its a no brainer really as most of our happy customers tell us. When I ran normal Minelab battery pack and their charger it used to have to charge for hours to get enough power soaked up to do an 8 hour stint next day before needing a charge again that night.

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Re: Max voltage of your nimh slimpack ?

Post by Koala »

May not be so good in winter ????

I use NIMH in a torch at minus temperatures. They are fine. But the torch is being warmed in my hand and the 5 watt draw is warming the battery plus the heat from the driver board. In a detector the batteries will be not far from the outside temperature. Not such a big deal if you have another pack in your pocket to swap out.

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Re: Max voltage of your nimh slimpack ?

Post by stargazer »

These batteries that Tony says are a 'no brainer' cost about £100. That is a lot of money to some people. Tony Hunt is also biased here,in my opinion, as he sells them.

That is why I and others use eneloops. Much more cost effective. ( I don't sell eneloops.)

If you have lots of money, then please buy them. No doubt they are good pieces of kit.
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Re: Max voltage of your nimh slimpack ?

Post by hihosilver »

I'm going to make up an eneloop pack as I bought 8 of them last week. How long do they last roughly for you please Stargazer? They are claimed to be a minimum of 1900mah but I believe they are nearer 2100mah so would expect at least 9hrs after a few charge cycles using them in good weather, but maybe your real world usage gets more/less.
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Re: Max voltage of your nimh slimpack ?

Post by dig-dog »

I've got two nimh battery packs, one 1500 from my old explorer and one 1600 that came with my e-trac. Just fully charged both and left to rest for a while and tested voltages.
11.59v 1500 nimh
11v exactly 1600 nimh
Hope this helps
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Re: Max voltage of your nimh slimpack ?

Post by hihosilver »

Perfect. Cheers dig-dog. ::g
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