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Curious to your thoughts on the LiPo batteries contained within the Nokta machines. They (Lithium Polymer batteries) are a wild breed in many formats and within the RC community tales of exploding fire batteries are not uncommon. They have special regulations regarding transport/shipment (especially within aircraft) and I've read they can be extremely fickle in regards to charging/storage. I'm only looking for input on the batteries themselves. The product line is amazing and what you get for the price is impressive (SIMPLEX!) and not in question.

Hope everyone is well!

-Bryan

 

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I think due to such low draw on the small lipo batteries contained within detectors, you don't get the same heat issues as those contained on high output RC motors, nor the same issues with charging RC battery packs (overcharging or wrong charger settings for specific battery packs).  Can't say I have heard of any detectors exploding due to heat or fires due to piercing of the battery packs, the electronics contained in detectors and chargers these days also make it near on impossible to over-charge or run them totally flat.

Considering the XP Deus uses three separate LiPo batteries to operate and that it has been around for 9 years now, pretty much proves how safe and convenient their use is, not to mention good longevity considering my Deus is now 5 years old still with the original batteries.  

I have never had an issue with long term storage, so long as there is around half charge on the detector (or wireless coils)

Since XP implemented the use of miniature LiPo batteries on the Deus, most manufacturers have now followed suit including Minelab, Nokta Makro, and more recently Garrett, both for detectors and pinpointers, so that should say something.  We should also thank the use of LiPo batteries for the advent of physically smaller detectors and the inherent lack of weight, and making it much easier to produce sealed waterproof detectors.  
 

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This may answer your question. In a nutshell Lithium Ion is older and uses a liquid barrier between the layers which can be easily damanged and the Li-po use a dry barrier so they can be thinner, smaller and flexible.

When the barrier is broken they basically short out which causes the overheat.

https://www.androidauthority.com/lithium-ion-vs-lithium-polymer-whats-the-difference-27608/

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5 hours ago, Goldpick said:

"I think due to such low draw on the small lipo batteries contained within detectors, you don't get the same heat issues as those contained on high output RC motors, nor the same issues with charging RC battery packs (overcharging or wrong charger settings for specific battery packs).  Can't say I have heard of any detectors exploding due to heat or fires due to piercing of the battery packs, the electronics contained in detectors and chargers these days also make it near on impossible to over-charge or run them totally flat.

Considering the XP Deus uses three separate LiPo batteries to operate and that it has been around for 9 years now, pretty much proves how safe and convenient their use is, not to mention good longevity considering my Deus is now 5 years old still with the original batteries.  

I have never had an issue with long term storage, so long as there is around half charge on the detector (or wireless coils)

Since XP implemented the use of miniature LiPo batteries on the Deus, most manufacturers have now followed suit including Minelab, Nokta Makro, and more recently Garrett, both for detectors and pinpointers, so that should say something.  We should also thank the use of LiPo batteries for the advent of physically smaller detectors and the inherent lack of weight, and making it much easier to produce sealed waterproof detectors."  

Thanks Goldpick! Appreciate you taking the time to write such a thoughtful response. Appreciate ya!

-Bryan

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Ultimately I think Lithium Batteries in a device are nothing to be concerned about, they are a good power source, with good properties... They just need to be handled "correctly" (usually in the case of a "built-in" battery, this means handled by the manufacturer of the device correctly, with some exceptions outlined below). So I think nothing to worry about with detectors using lithium batteries, I even think it's a good idea 🙂

Now to dive into the details of why I say that:

As I think has already been mentioned the major reasons a Lithium based battery becomes dangerous are:

  1. Electrical Short
  2. Over-Current (drawing too much current from the battery at once, sometimes caused by #1)
  3. Incorrect Charging Process
  4. Physical Damage (resulting in #1)
  5. Physical Damage, resulting in distortion of internal geometry without shorting out, but this can cause small areas of the battery to become "bottlenecks" and alter the resistance, charging characteristics, etc... End result is that within that small area over-current, or incorrect charging can happen even if the battery as a whole is treated correctly following the damage.
  6. Too much heat (caused by one of the above directly)
  7. Too much heat (in extreme environments)
  8. Too much heat (combination of a hot environment with a factor above, both to a lesser degree, but in combination, enough to be a problem)

All of the electrical (short, overcurrent, charging, etc) can be managed by an internal lithium battery controller, sometimes called a BMS, or Battery Protection circuit. These are either built into the battery packs, or built into any device using a bare lithium cell. Provided this was done correctly, many of the above issues can be mitigated. In the case of all our commercial metal detectors, this will have been done correctly in order to get industry certification

In super-high performance scenarios, sometimes even with a BMS, you can see for example consistant high current draw, close to the line, which ultimately results in overheating, etc... But in the case of a metal detector, the current draw is very low, so no real "stress" being put on the battery. (RC vehicles are commonly known for this, because you want the lightest possible battery that gives you the most power, and you go all out for like 10-15 minutes killing the battery entirely in that time. This is usually compounded by the fact that RC batteries are usually bare cells, and there are minimal or no battery protection circuits in the RC vehicles, which is why you read of so many RC batteries exploding).

Finally, the physical damage scenarios, again our metal detectors aren't usually exposed to any situation at high risk of damaging the battery.

The only scenario I can think of that a Lithium battery in a metal detector might be at risk of becoming dangerous is:

  1. Charging while in a car, sitting in the hot sun... Generally this still shouldn't be a problem as the charge rate isn't extreme usually, but at least this is possibly a way to get a "perfect storm" of conditions that causes too much internal heat in the battery cells
  2. Detector who's chassis is either not waterproof, or compromised dropped into salt water. Causing an internal short.

So I'd advise don't ever do #1, and chances are #2 will result in destroying the detector as well, so send it off for warranty service. If you have a detector you suspect has suffered a short internally due to water infiltration, don't use it until you get confirmation the battery isn't compromised.

It should also be noted that most lithium battery failures aren't as spectacular as the youtube videos and news stories. Many just fizzle, and smoke a lot, or have a small burst of flames. The batteries usually scorch, and puff up. But don't explode dangerously. In cell phones it's a tight space, sealed, and if those go while in a pocket, that might cause a burn for example (the whole samsung battery fiasco), but ultimately in a detector I think risk is minimal.

Additionally, one word of caution: Lithium batteries tend to "Puff" or swell up when they are on the verge of failure. If you ever see a lithium battery in this state, DO NOT use it. Dispose of it. (or in the case of a detector suffering this, have the battery replaced, or seek support from a service center). Not that you'd usually know as the battery is sealed away internally, but depending on the chassis design, it can be noticeable because it can cause the chassis of the device to swell to accommodate the increased battery size.

Finally, some advice on proper "care/maintenance" of lithium batteries:

Lithium batteries degrade due to a number of factors:

  • Exposure to high temperature
  • High Charging Current (usually, the higher, the more degredation)
  • High Discharge Current (again, usually, the higher, the more degredation)
  • Naturally decay over time when holding a charge (higher decay, the higher the percentage of charge)

Lastly, Lithium batteries can fail completely if they fall below a critical charge level (essentially they fall below 0%)

Lithium batteries have a very good power retention capability, they don't "leak" power as fast as other battery types (such as NiMH) but they do still leak power. Sometimes this is sped up slightly by the protection circuitry or "power standby" circuitry in the device. This usually means a percentage or two drop per week/month depending on the specific battery chemistry.

Lithium batteries are designed to have a certain number of recharge cycles before their capacity drops significantly. This is usually a median in a bell curve. Meaning that if very carefully taken care of, you can get more cycles. And if they are treated poorly, they may get much less.

What can we learn from all of the above? 

In order to keep our batteries healthy we should:

  • Not expose them to high temperatures
  • Charge them at a median rate (in this case not usually in your control, up to the design of the charging circuit)
  • Not discharge them too fast (again up to the devices power draw, but in the case of a detector, this just means avoid shorting it out)
  • Don't leave it sitting at 100% charge for weeks/months on end
    • This means if you're going to store the detector for some period of time (weeks/months), then run the battery down to about 50% and store it like that, then charge it up before you want to use it
    • OR just don't top it up to 100% every time you use it
    • if your lithium battery gets 20h of usage from a full charge, then waiting until you've drained it down to 25% and then charging it back up, means your minimizing the amount of time it's "hanging around" at 100%.
    • Big mistake people make with lithium battery powered devices is constantly running them down to 80%-90% then topping them up to 100% all the time, so it always floats near 100%, this will cause the battery to have an abnormally low battery life (why do you think so many cell phones have batteries that won't hold a charge after 1-2 years)
  • Don't leave it sitting at empty for weeks/months on end
    • Again if you're going to store it for some time, just make sure it's topped up at least to 25% (or 50% if you're going to leave it for a LONG time like 6-12 months).

Anyway, that's enough of my ramblings. Hope it helped 🙂

 

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That was a great post. Minelabs manual for the Equinox has very little on  battery maintenance - just saying if the metal detector is not used for 3-4 months the battery performance can degrade so top it up to 100% - which is different to what you are recommending for storage. Doesn't really affect me as i use my Equinox a few times every week so i will now not be so worried about ensuring its constantly topped up.

 

 

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19 hours ago, Glasswalker said:
  •  
  • Don't leave it sitting at 100% charge for weeks/months on end
    • This means if you're going to store the detector for some period of time (weeks/months), then run the battery down to about 50% and store it like that, then charge it up before you want to use it
    • OR just don't top it up to 100% every time you use it
    • if your lithium battery gets 20h of usage from a full charge, then waiting until you've drained it down to 25% and then charging it back up, means your minimizing the amount of time it's "hanging around" at 100%.
    • Big mistake people make with lithium battery powered devices is constantly running them down to 80%-90% then topping them up to 100% all the time, so it always floats near 100%, this will cause the battery to have an abnormally low battery life (why do you think so many cell phones have batteries that won't hold a charge after 1-2 years)
  • Don't leave it sitting at empty for weeks/months on end
    • Again if you're going to store it for some time, just make sure it's topped up at least to 25% (or 50% if you're going to leave it for a LONG time like 6-12 months).

 

That is great to know as it applies to many of us with detectors that use these batteries.  Thanks for all you wrote, not just stating but especially also also explaining.

I guess a question I'm left with is "how do you know the charge level?"  My understanding (may be faulty) is that battery charge indicators on devices that have them are not particularly accurate.  Maybe that is caused by them having to measure different types of batteries (different kinds of disposables and different kinds of rechargeables) with one simple circuit.

 

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Simplex battery. Has a small Thermistor attached.

A thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors. The word is a combination of thermal and resistor. Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements

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