Voltage to change batteries

[tauzero]

17 hours ago, Togomi said:

I've already got a TRS jack, but it's not possible to measure the voltage.

0V.

 

Imposible in these basses.

 

Which bass?

[Togomi]

2 hours ago, tauzero said:

 

Which bass?

Fender American Deluxe jazz bass and American Elite Precision bass.

[Woodinblack]

4 minutes ago, Togomi said:

Fender American Deluxe jazz bass and American Elite Precision bass.

 

Yep, they have switched sockets, there is no power on that.

[Dood]

A standard multimeter set to read volts applied to the Ring and Sleeve of the output jack on a bass with active electronics won't give an exact reading, because placing the multimeter in the circuit in this way is in series with the preamplifer and battery, which would be correct if trying to take a current reading. A standard multimeter should be placed directly across the + and - terminals of the batteries for the most accurate reading. I.E, in Parallel with.

 

[Stub Mandrel]

6 hours ago, Dood said:

A standard multimeter set to read volts applied to the Ring and Sleeve of the output jack on a bass with active electronics won't give an exact reading, because placing the multimeter in the circuit in this way is in series with the preamplifer and battery, which would be correct if trying to take a current reading. A standard multimeter should be placed directly across the + and - terminals of the batteries for the most accurate reading. I.E, in Parallel with.

 

 

A very high input resistance voltage probe would do the job.

[Woodinblack]

18 minutes ago, Stub Mandrel said:

 

A very high input resistance voltage probe would do the job.

 

Only on a circuit with no reverse voltage protection or anything.

[tauzero]

7 hours ago, Dood said:

A standard multimeter set to read volts applied to the Ring and Sleeve of the output jack on a bass with active electronics won't give an exact reading, because placing the multimeter in the circuit in this way is in series with the preamplifer and battery, which would be correct if trying to take a current reading. A standard multimeter should be placed directly across the + and - terminals of the batteries for the most accurate reading. I.E, in Parallel with.

 

As I said on page 1, a DVM has a very high impedance and so you'll finish up with a potential divider between the preamp and the DVM. The lower the drain current of the preamp, the higher its effective resistance so the lower the DVM will read for the same battery voltage.

 

24 minutes ago, Woodinblack said:

Only on a circuit with no reverse voltage protection or anything.

 

If it has reverse voltage protection, that would just be a diode, so drops 0.6V as it would be forward biased. And that 0.6V would be lost to the preamp anyway IYSWIM.

[Woodinblack]

27 minutes ago, tauzero said:

If it has reverse voltage protection, that would just be a diode, so drops 0.6V as it would be forward biased. And that 0.6V would be lost to the preamp anyway IYSWIM.

 

Of course it would, but not sure why that is relevant to the battery voltage? You aren't trying to establish the voltage the preamp needs, I assumed people are trying to put a lot of effort into measuring a battery

 

[tauzero]

58 minutes ago, Woodinblack said:

 

Of course it would, but not sure why that is relevant to the battery voltage? You aren't trying to establish the voltage the preamp needs, I assumed people are trying to put a lot of effort into measuring a battery

 

 

No, it's just another inaccuracy in the reading. It does mean that if you have two identical preamps, one with a diode protection and the other without, then the one without will continue working while the battery drops a further 0.6V after the one with the diode has died.

[Woodinblack]

8 hours ago, tauzero said:

No, it's just another inaccuracy in the reading. It does mean that if you have two identical preamps, one with a diode protection and the other without, then the one without will continue working while the battery drops a further 0.6V after the one with the diode has died.

 

Indeed, and due to the tollerance of preamp voltage sources, and how batteries maintain their voltage to near the end, thats still the same gig and you should have changed the battery ages ago!

[Jo.gwillim]

I've found the easiest thing is to just weigh the bass from time to time. As the battery charge gets used up it gets lighter. Only a fraction of a gramme but kitchen scales are good enough. 

[Togomi]

I've tried today to check the voltage when previous stop of working.

I took old batteries, the same of last Saturday, and I was been playing.

 

As the batteries recover, they work at first, even though they sound bad. After a while, the bass stopped playing when active. I removed the batteries and they showed about 8 V (together, like 4V each one), but the voltage gradually increases.

With the batteries connected, it showed 0 V.

 

19 hours ago, Woodinblack said:

 

Yep, they have switched sockets, there is no power on that.

What a sh..., I wanted to test them without opening the tap.

[Woodinblack]

1 minute ago, Togomi said:

What a sh..., I wanted to test them without opening the tap.

 

I can see the convenience but as you have an actual battery compartment on those, its hardly that much of an issue, it takes less than a minute and it only has to be done every few months.

[nekomatic]

12 hours ago, Jo.gwillim said:

I've found the easiest thing is to just weigh the bass from time to time. As the battery charge gets used up it gets lighter. 

This is literally true though! The change in mass is given by the m in E = mc², where E is the electrical energy. 
 

You must have some amazing kitchen scales, however. 

[Jo.gwillim]

11 hours ago, nekomatic said:

This is literally true though! The change in mass is given by the m in E = mc², where E is the electrical energy. 
 

You must have some amazing kitchen scales, however. 

Yep being a nerd i did actually work this out at 0.2pico grammes.

[Jo.gwillim]

Just now, Jo.gwillim said:

Yep being a nerd i did actually work this out at 0.2pico grammes.

Sorry 0.2nano grammes

[Hellzero]

1 minute ago, Jo.gwillim said:

Yep being a nerd i did actually work this out at 0.2pico grammes.

Are you working for the ESA?

[Jo.gwillim]

2 minutes ago, Hellzero said:

Are you working for the ESA?

Alas no. Just a bass player with a broken collar bone feeling sorry for himself missing out on gigs with too much time on his hands. 

[mcnach]

On 23/06/2025 at 09:22, Stub Mandrel said:

Thinking about it, a sensible compromise would be to use older batteries for practice/rehearsal and keep fresher ones for gigs. You could keep track of which batteries are freshest by measuring their voltage.

 

 

 

The battery on any of my active basses tends to lasts many months, usually well over a year. Once you figure roughly how long you can go I find it simpler to just replace batteries regularly. Having part-used batteries and fully charge ones to alternate with seems like faff that can only lead to mistakes. I change my battery once a year, done.

 

 

 

[tauzero]

On 24/06/2025 at 00:46, tauzero said:

You can get a reading from a multimeter between ring and sleeve which will be proportionate to the battery voltage but not equal to it.

 

I replace batteries when they're somewhat under 9V, if I spot they're below 8V I'll replace them otherwise I'll replace them when they die.

 

KMI Batt-O-Meter incoming, I'll report on it when it's here.

 

 

TL;DR - it works but needs some extra bits to work with certain basses with recessed sockets, eg Ibanez SR series.

[JoeEvans]

I still like the idea of a bass with a rechargeable battery and a USB C socket on the back to charge it.

Or just an XLR out and phantom power.

Both totally OTT as solutions but for some reason I'm drawn to an easy external power source.

[Hellzero]

25 minutes ago, JoeEvans said:

I still like the idea of a bass with a rechargeable battery and a USB C socket on the back to charge it.

Or just an XLR out and phantom power.

Both totally OTT as solutions but for some reason I'm drawn to an easy external power source.

Check Warwick...

[tauzero]

18 hours ago, JoeEvans said:

I still like the idea of a bass with a rechargeable battery and a USB C socket on the back to charge it.

Or just an XLR out and phantom power.

Both totally OTT as solutions but for some reason I'm drawn to an easy external power source.

 

You'd spend more time plugging and unplugging the USB lead than replacing a battery once a year.

[JoeEvans]

7 hours ago, tauzero said:

 

You'd spend more time plugging and unplugging the USB lead than replacing a battery once a year.

Yes - as I say, it's a totally OTT solution...

[Jo.gwillim]

Well going totally ott why not have wireless charging like my phone with a charging station built into your guitar stand.