GPX 5000 Battery Faulty

Over the last 3 years I've noticed that my battery has taken longer and longer to charge up to a solid green light with the last year it wouldn't get a solid green light. Today all I could get was an orange flashing light. The user manual says if this happens to contact your dealer. I suspect that means I would walk in with old battery and out with a nice shiny new one and about $400 dollars lighter.
Question is can anyone tell me if I repack the batteries in it will that cure it or is it likely to be a fault in the wiring or circuit board.
Rowdy

Pm mechanic who is on the forum here. He does all that sort of stuff.

Hi Rowdy, have dealt with Mick (mechanic) top bloke, agree see mechanic to get it repacked, regards

Mick the Mechanic's website is here: https://www.detectronicsaustralia.com/

Thanks for the replies.
I did a search on google and I found a thread on the battery pack which said that if you have a flashing orange light it would almost certainly be a dead cell in the battery pack. I pulled the end caps off my battery and slid the aluminum side plate off and my battery has a plug in Siomar pack stuck in with a velcro strip.

I found a utube video of one having the cells replaced but it looks like a tab welding setup would be the best way to replace the cells. Not sure if I would be able to just solder the tabs and still fit it all back together neatly.   I might have the start saving the dregs left over each week out of my pension then get it done properly.
Rowdy

You should replace all the batteries, not just the bad one.  It's quite easy to do, soldering the tabs is easy, you can just buy the tabs to do it that way or you can buy the batteries with tabs like these ones Batteries with tabs

Just do an exact copy of the existing layout.  I'm sure you'd be fine doing it and the tabs are easy to solder.

G'day rowdy

If you going to do it yourself get good quality 18650's with the tabs already fitted to the battery like these, that way you only need to solder the tabs together in the correct order, just follow the pattern from the ones your taking out.

https://www.ebay.com.au/itm/8x-TABBED-Panasonic-NCR-18650GA-3500mAh-tabs-Lithium-Ion-rechargeable-batteries/274592591779?hash=item3feefe6fa3:g:YQkAAOSw~JhfwV~a

davsgold wrote:G'day rowdy

If you going to do it yourself get good quality 18650's with the tabs already fitted to the battery like these, that way you only need to solder the tabs together in the correct order, just follow the pattern from the ones your taking out.

Agree with Dave, very simple operation if you're careful with orientation of batteries. (Take a photo of original then proceed.)
Back when we had the two 45's managed to buy two dead batteries for $50.00, after operation they were still going strong when we sold both machines.
Don't know the cost of a new battery but surmise we saved a few $$'s.

Nightjar, they are $395 for a genuine new Minelab battery for gpx4500/5000 so you would have save a bit I reckon.

cheers dave

Ok you have all talked me into doing it myself, but I won't be in a position to buy the battery cells for a couple of months. Feb/March are expensive months for me but once those bills are paid I'll get to it.
Rowdy

you can't really go wrong, just do an exact copy of what you pull apart, also, you can test you've got it working fine before plugging it into your GPX by checking it's output with a multi meter.

https://youtu.be/ppkdLxxGkp4

https://youtu.be/dYRm_kDnM0U

I also test batteries for these batteries to replace old ones. Just fixed my coil and tested it maybe to build one for myself.

I just pulled the battery pack out of the battery box and removed the end caps off the pack. I measured the voltage across V+ and V- and all I get is 3Mv. If I measure across B+ and B- I get 1.7volts. If I measure from V+ to the plate on the bottom of the pack I get 1.9volts
.
If I am getting this right it would appear I'm loosing voltage through the circuit board in the pack and I'm wondering if the circuit board is faulty. Maybe when the pack is dismantled and I measure each cell I will know if it's a dead cell or the board that faulty. Any input from somebody more knowledgeable than me would be appreciated.
Rowdy

Check each battery, should be between 3.7 to 4.1 volts each. Any one battery lower than this will put the pack out of bms range.

each individual 18650 battery cell should hold a charge of 3.7v and charge up to a bit over 4.0v hence the total way the battery pack operates is in pairs so the detector reads 8.0v+ when full charged and is flat and shuts down at about 7.0v so a technically flat 18650 single battery will be 3.5v or even 3.0v if really flat.

A single dead cell will drain the other cells, but if you disconnect them you may be able to work out the dead one or ones.

it is probably not a great idea just to try and replace a single cell with a brand new one as you don't know how healthy the others really are.

you can try charging up the disconnected cells with a charger that takes Li-ion cells two or more at a time and work out which ones are actually holding a charge that way

cheers dave

Rowdy, one thing to keep in mind here & although might not be rocket science to some, it might as well be to others. Saving a buck by doing your own repair is one thing, knowing how to do that repair competently, is another. By all means have a go at doing it yourself, if you know your comfortable/capable of doing the job, or else, save till you've got the funds & send in to someone who knows what they are doing, for a full battery replacement, before it ends up costing you even more, if something happens to go wrong.
Only my thoughts on this matter Rowdy, no disrespect & nothing personal intended here, for the decision to do or not to do, is all up to you at the end.

Cheers Kon.

Davsgold, I do intend to replace all the cells but I was a bit confused that I was only getting 3 millivolts across the V+ and V- and 1.7 volts across the B+ and B- terminals.
When I do get around to taking it apart I'll measure each cell individually as if any cells are ok I have another job for them on my fishfinder on the kayak just as long as I can get enough of them to achieve 12v in series/parallel.

Kon. If I didn't feel comfortable in unsoldering and resoldering the cells I wouldn't even consider doing it myself as I have had experience in soldering circuits together but that was back when they were still using valves, not these new fangled printed circuits with all those tiny whatsacallits.
Rowdy

Once done just check it with a multi meter using the pin outs on this thread before plugging it into your detector

Pinout diagrams

I have bought replacement cells [batteries ] from Jaycar . AA ones , good price and no problems . They do stock plenty of others .

Hi rowdy,
i had the same thing happen to my battery about 3 years ago.
I sent it to mechanic for repair and it is still going strong.

Minermike wrote:I have bought replacement  cells  [batteries ]      from Jaycar .     AA  ones ,   good price and no problems .  They do stock plenty of others .  

the gpx4500/5000 battery pack has Li-ion 18650 batteries, 8 of them in the aluminium housing, not AA alkaline ones

As I said they do stock plenty of others . Samsung 2500 mah rechargeable $21.95 each Unbranded 2600 mah with lugs $19.95 same with out lugs $16.95 . They are all Li- ion 18650 .

The ones I was buying were for my Minelab Explorer , rechargeable nickle metal hydride , now sold . Updated to a Nox 800 , a lot better machine .

Minermike wrote:As I said they do stock plenty of others .   Samsung  2500 mah  rechargeable   $21.95 each   Unbranded 2600 mah  with lugs    $19.95      same with out lugs   $16.95  .   They are all  Li- ion  18650 .

The ones I was buying were for my Minelab  Explorer  ,  rechargeable   nickle metal hydride ,    now sold  .   Updated  to a Nox  800  ,  a lot better machine .  

Ok i see what your saying now, but 8 of these would be about $160 and less mAh (2600) than the 8 of these from ebay, which we have used and found to be very good and rated at 3500 mAh and the 8 pack is delivered for $79.95

https://www.ebay.com.au/itm/8x-TABBED-Panasonic-NCR-18650GA-3500mAh-tabs-Lithium-Ion-rechargeable-batteries/274592591779?hash=item3feefe6fa3:g:YQkAAOSw~JhfwV~a

cheers dave

No worries !

The E-bay ones are at Allambie Hts. not very far from me , about 5 kms .

Minermike wrote:No worries !

The E-bay  ones are at Allambie Hts.     not very far from me  ,  about 5 kms .  

Hi Guys,

Just some observations.

Don't solder directly to the ends of Li-ion cells. The heat can damage the internal connection to the nipple. While it may work, it is really bad practice and I sure as heck would not recommend anyone do it this way. You are much better off getting cells with "solder tabs" and then solder them a little bit out from the top of the cell.

The other thing is battery types and capacity. Although some batteries may have much higher capacity than the original cells, you need to look at and understand the discharge curve. You can have all the capacity in the world, but in a gpx you will only use half of it or less due to the 7.2v cut off voltage. With the original sanyo cells, they have actually fully discharged by 7.2v, well there is a little left at this voltage, but if you continue to discharge after you have reached 7.2v, the voltage will drop very quickly, whereas with the panasonic cells, when they get to 7.2v they are only about half discharged.

With old li-ion cells, if they have discharged below 3.2v each, they are permanently damaged. Especially if they have been below this voltage for some time. Attempting to charge them could result in fire. Proceed with caution.

And another thing, you need to make sure the cells are all balanced before you go installing them into a pack, otherwise one half of the pack will be fully charged before the other half and same when discharging.

Now I'm not discouraging people from doing their own re-builds, but it pays to be very informed before you jump in head first thinking it's going to be a walk in the park. Also, sometimes there are other reasons why batteries don't appear to last very long that sometimes need to be fixed.

Cheers Mick

I agree with everything you say Mick, and I always recommend you as first port of call for the battery job, you do a great work, but like you say some will want to do it themselves, so all we can do is try and point them in the direction that will not get them hurt.

Like you have said I would not solder direct onto the top or bottom of a Li-ion battery and always say to get the ones with the tabs on already.

cheers dave

You still have to be careful when messing with Lithium ion batts.
Some handy info here:
https://batteryuniversity.com/learn/article/safety_concerns_with_li_ion

Even after years of development these batteries still burn. best advice when buying these for your detector is to stick to well known brands and steer clear of Ebay cheapies from China. I changed my Sov over to Lithium Iron battery pack that came from China and was an unknown brand and cost just 70 bucks. It lasted about 3 recharges before it started expanding and getting hot. Even my mbl phone battery started getting hot a few days ago.Well known make) Ditched it for a new one. I now stay with NiMh and alkaline for my detectors.
Have never had a carbon zinc, Alkaline, NiCad, or NiMh, Lead acid gell short, burn or get hot.

Use a proper charger designed for the job and use good brand Li-Ion batteries like panasonic