Service battery being drained whilst switched off

[Toodle-oo!]

1. NO WAY are you drawing 20A if the batteries are remaining at 12.6V. 12.6V is indicative of a fully charged battery...
2. Buy a voltmeter - you're going to need it in the future anyway. Clamp on ones are really useful to have so that's what I would get...
3. Disconnect all leads from each battery to test each one. (ie: remove the terminals from each battery!) How are you testing? Best (if wet cells) would be a hydrometer - another good investment (pennies).
4. Ask the previous owner if he had battery issues.

 

[Poey50]

Thanks. I imagine it might be sensible to do a factory reset using the buttons on the monitor before doing the calibration...?

As others have suggested you verify the monitor by getting an accurate and independent measure of the various loads, testing one at a time with an ammeter or DC clamp meter. My Victron monitor worked straight out of the box - you don't want to be telling it to ignore current leakage if it is truly happening. (Although, as others have said, 12.6V with a 20 amp load doesn't sound credible.) Once independently verified then you can turn your attention to the monitor if it is showing something rogue.

 

[ste7ve]

As others have suggested you verify the monitor by getting an accurate and independent measure of the various loads, testing one at a time with an ammeter or DC clamp meter. My Victron monitor worked straight out of the box - you don't want to be telling it to ignore current leakage if it is truly happening. (Although, as others have said, 12.6V with a 20 amp load doesn't sound credible.) Once independently verified then you can turn your attention to the monitor if it is showing something rogue.

I've already disconnected each wire, one at a time, from the 20 or so circuit breakers fed from the service battery bank. None of them made a difference to the 'rogue' current.

 

[Poey50]

I've already disconnected each wire, one at a time, from the 20 or so circuit breakers fed from the service battery bank. None of them made a difference to the 'rogue' current.

For the avoidance of doubt - as lawyers say - did you a) measure each load separately with an ammeter or DC clamp meter or b) watch the reading in the monitor to see if the 'rogue' current changed?

 

[ste7ve]

For the avoidance of doubt - as lawyers say - did you a) measure each load separately with an ammeter or DC clamp meter or b) watch the reading in the monitor to see if the 'rogue' current changed?

I only have a simple multimeter and measuring amperage is difficult when CB's are about 4 metres from batteries..!

 

[pvb]

I've already disconnected each wire, one at a time, from the 20 or so circuit breakers fed from the service battery bank. None of them made a difference to the 'rogue' current.

In that case, I'd start by zeroing the monitor's current reading - strictly following the procedure in the monitor manual. You then know that it's zeroed. Then reconnect the shunt and see what the reading is.

 

[HissyFit]

If you know the spec of the shunt, ie its resistance, you'd be able to do this little sanity check with just a basic voltmeter:

Voltage (V) = Current (I) in amps x Resistance (R) in ohms. A current of 20 amps flowing through a 1 ohm shunt would result in a voltage drop across it of 20 volts. Since the voltage of the whole supply is only 12.6v, then there is no way on Earth that this is what is really happening, short of a horrendous faux-pas WRT rewiring the new batteries.

 

[ste7ve]

If you know the spec of the shunt, ie its resistance, you'd be able to do this little sanity check with just a basic voltmeter:

Voltage (V) = Current (I) in amps x Resistance (R) in ohms. A current of 20 amps flowing through a 1 ohm shunt would result in a voltage drop across it of 20 volts. Since the voltage of the whole supply is only 12.6v, then there is no way on Earth that this is what is really happening, short of a horrendous faux-pas WRT rewiring the new batteries.

The shunts are rated as 500A 50mV, so therefore a resistance of 0.0001 Ohm. Therefore voltage drop at 20A would be 2 mV

 

[HissyFit]

The shunts are rated as 500A 50mV, so therefore a resistance of 0.0001 Ohm. Therefore voltage drop at 20A would be 2 mV

That's the trouble with picking figures out of the air: they tend to be way off. I think I failed my own sanity check. At least it still illustrates that a clamp meter is not necessary in this instance.

 

[Poey50]

I only have a simple multimeter and measuring amperage is difficult when CB's are about 4 metres from batteries..!

Earlier suggestions were to physically disconnect at the bank positive battery terminal and check for amperage there with your multimeter.

The suggestion of measuring voltage aicross the shunt looks like another way of independently testing whether the problem is real or apparent if you have that accuracy.

 

[HissyFit]

The suggestion of measuring across the shunt looks like another way of independently testing whether the problem is real or apparent.

Isn't that what shunts are for?: Turning current flow into a representative voltage drop, so that it can be read by a voltmeter without having to break into the circuit.

 

[JumbleDuck]

Isn't that what shunts are for?: Turning current flow into a representative voltage drop, so that it can be read by a voltmeter without having to break into the circuit.

Nowadays yes, since digital meters measure voltage. Mechanical meters measure current and for them the job of the shun is to provide an easy path for most of the curent, leaving a know small amount to flow through the meter.

 

[179580]

Is this yours:

View attachment 94620

Seeing posts like this, as a new browser, I am not sure if I wish to continue with my involvement. On the whole you do come over as being somewhat bombastic.

 

[pvb]

Seeing posts like this, as a new browser, I am not sure if I wish to continue with my involvement. On the whole you do come over as being somewhat bombastic.

If you decide to continue with the forums, you'll eventually discover that there are basically two types of poster - those who know what they're talking about, and those who don't have the first idea but feel compelled to offer their "advice". Boater Sam is in the latter category; Paul Rainbow is in the former category. If you know what you're talking about, it can be frustrating to see the garbage posted on here by those who don't. Saying that Boater Sam wasn't being helpful was truthful, and I don't think that's "bombastic".

 

[Poey50]

Isn't that what shunts are for?: Turning current flow into a representative voltage drop, so that it can be read by a voltmeter without having to break into the circuit.

Yes, I was writing in support of independent testing to first check if the problem is real or apparent and this is one of two methods mentioned to achieve it.

 

[Poey50]

If you decide to continue with the forums, you'll eventually discover that there are basically two types of poster - those who know what they're talking about, and those who don't have the first idea but feel compelled to offer their "advice". Boater Sam is in the latter category; Paul Rainbow is in the former category. If you know what you're talking about, it can be frustrating to see the garbage posted on here by those who don't. Saying that Boater Sam wasn't being helpful was truthful, and I don't think that's "bombastic".

And anyone hanging around long enough will discover that Paul, as with others (but he is usually paid for what he does), is generous with his time sometimes including detailed schematics for individual problems. Even the arguments actually contain some important contrasting viewpoints forcing us to think.

 

[Boater Sam]

If you decide to continue with the forums, you'll eventually discover that there are basically two types of poster - those who know what they're talking about, and those who don't have the first idea but feel compelled to offer their "advice". Boater Sam is in the latter category; Paul Rainbow is in the former category. If you know what you're talking about, it can be frustrating to see the garbage posted on here by those who don't. Saying that Boater Sam wasn't being helpful was truthful, and I don't think that's "bombastic".

Very sad that you feel it clever to post like this.
As far as me knowing what is what, 56 years in the electronics industry after an apprenticeship building missiles would seem to make a mockery of your view.
You are not worthy to assess my qualifications.

 

[179580]

Very sad that you feel it clever to post like this.
As far as me knowing what is what, 56 years in the electronics industry after an apprenticeship building missiles would seem to make a mockery of your view.
You are not worthy to assess my qualifications.

This is exactly why I question my involvement here. Having don a historical search on persons relevant I find a trail of rudeness and what I would term as bullying.

 

[Poey50]

In that case, I'd start by zeroing the monitor's current reading - strictly following the procedure in the monitor manual. You then know that it's zeroed. Then reconnect the shunt and see what the reading is.

Actually, I've looked again and pvb is correct - if you read the whole of the paragraph I referenced in the manual, simply disconnecting the load from the shunt and then zero it gives a simple check on whether the monitor is accurate. Apologies for misleading - this is the simplest of the three methods of checking.

 

[Boater Sam]

Unfortunately this is prevalent in most forums.
There are some that I will no longer post on. But I enjoy trying to help people so I persevere. I ignore most of the rubbish but occasionally I just have to spit back a bit. Sorry to affect you, its only jousting.
Very late for me here so bed calls, night all,