GPX 5000 battery voltage.

[redned22]

After fully charging the Lithium battery as the instructions say, it measures only 7.8 volts. A fully charged Lithium battery should measure 8.4 volts.
Does Minelab set the voltage low on purpose, or is my charger faulty?

 

[mbasko]

Mine used to show 8.2v whenever I checked it after charging. I just assumed the 0.2v was lost under load once connected to the detector & it was on?
The chart in the GPX5000 manual appears to show about 8.2v as full charge though.

How old is the battery?
Li-ion batteries can suffer from capacity fade with the repetitive charge/discharge cycle.
It can also be made worse by storing them for long periods in a state of low charge.

As far as I know the Minelab li-ion batteries should be charging very close to the upper safe limit of 8.4v. The charging circuit that protects the Minelab batteries is built into the battery pack.
There is a built in alarm for low voltage at 7.3v & the detector will shutdown at 7.1v (over discharge causes capacity fade with li-ion too & can shorten their lifespan so low voltage shutdown is important).

 

[AuMan]

When you say it measures 7.8v, is this using the battery check function in the gpx menu , or using a multimeter in the battery plug?
If using a miltimeter you need to check pins 1 and 4. Pin 5 is the charge input and will show a lower voltage than what is in the battery.
The battery should reach between 8.2 and 8.4v when fully charged.
If the strip behind the rear panel of the gpx has been damaged due to the power plug wearing out, this can cause the detector to read lower voltage than is actually in the battery and for the low battery alarm to come on before it should.

Can you test your battery on another machine or you borrow a known working battery?
How long is your battery lasting from fully charged till the low battery alarm sounds?

Cheers Mick

 

[redned22]

Mine used to show 8.2v whenever I checked it after charging. I just assumed the 0.2v was lost under load once connected to the detector & it was on?
The chart in the GPX5000 manual appears to show about 8.2v as full charge though.

How old is the battery?
Li-ion batteries can suffer from capacity fade with the repetitive charge/discharge cycle.
It can also be made worse by storing them for long periods in a state of low charge.

As far as I know the Minelab li-ion batteries should be charging very close to the upper safe limit of 8.4v. The charging circuit that protects the Minelab batteries is built into the battery pack.
There is a built in alarm for low voltage at 7.3v & the detector will shutdown at 7.1v (over discharge causes capacity fade with li-ion too & can shorten their lifespan so low voltage shutdown is important).

OK. I was checking the wrong pins. I now read 8.3 volts between pins 1-4. I was looking at 1-5. This is new battery pack I built, (admit now), using 10 Panasonic cells so this battery has twice the capacity a new Minelab battery has.
Thank you.

 

[redned22]

When you say it measures 7.8v, is this using the battery check function in the gpx menu , or using a multimeter in the battery plug?
If using a miltimeter you need to check pins 1 and 4. Pin 5 is the charge input and will show a lower voltage than what is in the battery.
The battery should reach between 8.2 and 8.4v when fully charged.
If the strip behind the rear panel of the gpx has been damaged due to the power plug wearing out, this can cause the detector to read lower voltage than is actually in the battery and for the low battery alarm to come on before it should.

Can you test your battery on another machine or you borrow a known working battery?
How long is your battery lasting from fully charged till the low battery alarm sounds?

Cheers Mick

After fully charging the Lithium battery as the instructions say, it measures only 7.8 volts. A fully charged Lithium battery should measure 8.4 volts.
Does Minelab set the voltage low on purpose, or is my charger faulty?

A bit of explanation.
I bought the GPX 5000 sensond hand, a month or two back.
I am a bit of a modder.
I decided to give it a new battery with a larger capacity, so bought ten Panasonic cells that are 3.6A/h.
Charger these batteries in my Li-ion charger before building my new battery pack with them, so they were charged to 8.4 volts.
Fitting ten cells into the space that previously held only 8 cells meant a challenge, but there was space for the extra cells under the circuit board. So there it is.
I didn't connect the battery to the my machine after the first recharge, but put my Fluke meter on it as I thought the charge time was a bit short. The Fluke pins are fatter than the Minelabs socket connectors so getting a good contact was flakey. But all is good.
Heading to Whipstick this miserable morning, hoping Bendigo's weather is not as bad as here were I live.
Ned.

 

[AuMan]

Excellent, that makes sense.

Regarding the Panasonic cells, you need to check the discharge curves for the cells you select. The low battery voltage of the detector is 7.2v, which is 3.6v/per cell. You will find that at 3.6v the Panasonic cells and a bulk majority of other cells on the market probably still have a lot of capacity left in them.
So the thing you are really looking for is how much capacity is used @ 100ma by the time it reaches 3.6v.
That being said, your pack will work fine, especially with the extra pair of cells added.

Cheers Mick