Ammeter - advice needed

[blackrose]

Don't mean to hijack the thread but rather than starting a new one....

 

I'm on shore power but I've had my charger switched off all day because of the heat and I don't want the cooling fan running all day. Anyway, when I came home the SoC on my smartgauge had dropped to 97% which I thought was a bit odd as I'm sure nothings been running since I switched the charger off this morning and it's a brand new battery bank. However I can't guarantee that the SG is properly calibrated because I don't think I've run the bank down to less than 74% and back up to 100% three times since the new batteries were installed. The battery voltage was 12.8v

 

The other thing is that my shunt meter was showing an +0.3 amp charge without the charger on. I assume what I'm seeing there was the surface charge on the plates? But after being home all evening running water and shower drain pumps lights, etc, it's still showing the same +0.3 amp charge and the voltage is 12.75v. The SG now reads 96%. 

 

Previously the shunt meter has always been spot on with 0 amps shown with no charge or discharge.

Edited July 23, 2019 by blackrose

[Slim]

On 18/07/2019 at 21:54, WotEver said:

I’m much the same. I spent several hours rearranging the plumbing for a new sink yesterday. Soldering copper pipes etc. I used my blowtorch, solder mat, flux and solder for the first time in a few years, but if I didn’t have them then the job couldn’t have been done without waiting days for a plumber and then paying him a few hundred quid. 

 

As for multimeters, last time I counted I have nine, I think. All but two of them work, only one has a D.C. clamp, and only one of them has been recently calibrated. 

They can’t charge their caps if they’re switched off though either. 

-And I  thought I was doing well with 6 (all working ) multimeters

[jonathanA]

50 minutes ago, Slim said:

-And I  thought I was doing well with 6 (all working ) multimeters

Can I count all the ones I’ve lent to the mutants (offspring) and never got back ? 

[nicknorman]

1 hour ago, blackrose said:

Don't mean to hijack the thread but rather than starting a new one....

 

I'm on shore power but I've had my charger switched off all day because of the heat and I don't want the cooling fan running all day. Anyway, when I came home the SoC on my smartgauge had dropped to 97% which I thought was a bit odd as I'm sure nothings been running since I switched the charger off this morning and it's a brand new battery bank. However I can't guarantee that the SG is properly calibrated because I don't think I've run the bank down to less than 74% and back up to 100% three times since the new batteries were installed. The battery voltage was 12.8v

 

The other thing is that my shunt meter was showing an +0.3 amp charge without the charger on. I assume what I'm seeing there was the surface charge on the plates? But after being home all evening running water and shower drain pumps lights, etc, it's still showing the same +0.3 amp charge and the voltage is 12.75v. The SG now reads 96%. 

 

Previously the shunt meter has always been spot on with 0 amps shown with no charge or discharge.

Surface charge doesn’t manifest itself as the batteries taking charge. Probably it is a gauge offset error due to the high ambient temperature.

 

Regarding the Smartgauge reading, did you not have a fridge etc on? Is the 12.8v reading you mention, read from the Smartgauge or something else? If not the Smartgauge, what voltage reading is that giving?

Edited July 23, 2019 by nicknorman

[blackrose]

3 hours ago, nicknorman said:

Surface charge doesn’t manifest itself as the batteries taking charge. Probably it is a gauge offset error due to the high ambient temperature.

 

Regarding the Smartgauge reading, did you not have a fridge etc on? Is the 12.8v reading you mention, read from the Smartgauge or something else? If not the Smartgauge, what voltage reading is that giving?

 

Ah temperature affecting the shunt meter. Could be that. 

 

Regarding the SoC on the smartgauge, no I don't have a 12v fridge (I don't believe in them!) Nothing was running from the batteries, I'm sure of that. No discharge shown on the shunt meter and everything goes through the shunt apart from one bilge pump perhaps? But there's no water in the engine space.

 

The voltages are taken from the smartgauge and the shunt meter. There's an 0.05v difference. The smartgauge goes to 2 decimal places and is 0.05v lower.

 

Edited July 24, 2019 by blackrose

[nicknorman]

The Smartgauge only reads to the nearest 0.05v - ie the last digit is either 0 or 5. It looks as though the Smartgauge is slightly under-reading but I don’t think it’s of any consequence. If it is reading 3% low on SoC then so what!

[MtB]

1 hour ago, nicknorman said:

The Smartgauge only reads to the nearest 0.05v - ie the last digit is either 0 or 5. It looks as though the Smartgauge is slightly under-reading but I don’t think it’s of any consequence. If it is reading 3% low on SoC then so what!

 

So it confirms a Smartgauge cannot be relied upon to tell you when a battery is fully charged. The manual even tells you this, as any fule kno.

 

I'd be more concerned about the 0.2A discharge showing when everything is OFF. Meter error seems unlikely to me. Meters are not generally so unstable as to lose their calibration when the ambient temperature rises 10c.

 

Edit to add:

 

I'm curious about the British Gas smartmeter in the photos. I wonder what the sum of the quiescent currents is of the four meters installed....

 

 

 

 

Edited July 24, 2019 by Mike the Boilerman

[WotEver]

57 minutes ago, Mike the Boilerman said:

I'd be more concerned about the 0.2A discharge showing when everything is OFF. Meter error seems unlikely to me. Meters are not generally so unstable as to lose their calibration when the ambient temperature rises 10c.

Easily confirmed by shorting the two sense wires together. If it still reads 0.2A then it’s meter drift, if it reads 0.0 then there’s a 0.2A drain somewhere. Car radio on standby? Phone charger plugged in but not charging anything?

[blackrose]

8 hours ago, Mike the Boilerman said:

 

 

 

I'm curious about the British Gas smartmeter in the photos. I wonder what the sum of the quiescent currents is of the four meters installed....

 

It's only the 2 battery monitors that would consume any current, although the amounts must be tiny. I think it's something like 200mA for the BEP 12v meter. I've no idea about the smartgauge?  The other two meters run on internal batteries.

7 hours ago, WotEver said:

Easily confirmed by shorting the two sense wires together. If it still reads 0.2A then it’s meter drift, if it reads 0.0 then there’s a 0.2A drain somewhere. Car radio on standby? Phone charger plugged in but not charging anything?

 

Thanks, I'll check that. So I take the two wires from either side of the shunt and short them, in effect just bypassing the shunt? Will that work? Sorry it's so long since I fitted it I've forgotten how it's wired up.

Edited July 24, 2019 by blackrose

[Chewbacka]

2 hours ago, blackrose said:

 

It's only the 2 battery monitors that would consume any current, although the amounts must be tiny. I think it's something like 200mA for the BEP 12v meter. I've no idea about the smartgauge?  The other two meters run on internal batteries.

 

Thanks, I'll check that. So I take the two wires from either side of the shunt and short them, in effect just bypassing the shunt? Will that work? Sorry it's so long since I fitted it I've forgotten how it's wired up.

Just an observation but you have reported a current drain of 0.2A (which is 200mA) and also said above that your BEP takes about 200mA.  Is the mystery solved??

[WotEver]

24 minutes ago, Chewbacka said:

Just an observation but you have reported a current drain of 0.2A (which is 200mA) and also said above that your BEP takes about 200mA.  Is the mystery solved??

Beaten me to it. I was just about to make the same observation. 

2 hours ago, blackrose said:

So I take the two wires from either side of the shunt and short them, in effect just bypassing the shunt? Will that work?

Yes and yes. All the meter does is to measure the voltage across the shunt. If there’s no current flow then there’s no voltage and it should read zero. Shorting the wires together ensures there’s no voltage across them. If the meter reads 0 when the wires are shorted together then it’s accurate and the reading of 0.2 is the 200mA taken by the meter or whatever. This is where a clamp meter can help to find out where it’s going. 

Edited July 24, 2019 by WotEver
Added the bit about the clamp meter.

[nicknorman]

16 minutes ago, Chewbacka said:

Just an observation but you have reported a current drain of 0.2A (which is 200mA) and also said above that your BEP takes about 200mA.  Is the mystery solved??

Possibly. But 200mA seems a very large current for a meter. Maybe there is a backlight, in which case it would be a good idea to turn it off. Ditto the Smartgauge LED displays use a fair bit of current which is why most people have them set to go off a short while after the last button press.

[blackrose]

1 hour ago, Chewbacka said:

Just an observation but you have reported a current drain of 0.2A (which is 200mA) and also said above that your BEP takes about 200mA.  Is the mystery solved??

No I don't think so. The BEP meter used to show zero drain with everything off

49 minutes ago, WotEver said:

 

Yes and yes. All the meter does is to measure the voltage across the shunt. If there’s no current flow then there’s no voltage and it should read zero. Shorting the wires together ensures there’s no voltage across them. If the meter reads 0 when the wires are shorted together then it’s accurate and the reading of 0.2 is the 200mA taken by the meter or whatever. This is where a clamp meter can help to find out where it’s going. 

 

Thanks I'll try this when I get a chance and report back. I have a clamp meter so if the battery monitor is accurate then I'll try to find where the drain is coming from.

Edited July 24, 2019 by blackrose

[blackrose]

54 minutes ago, nicknorman said:

Possibly. But 200mA seems a very large current for a meter. Maybe there is a backlight, in which case it would be a good idea to turn it off. Ditto the Smartgauge LED displays use a fair bit of current which is why most people have them set to go off a short while after the last button press.

 

Yes you're right. The BEP manual says "Meter current consumption is approximately 50mA when the back-lighting is switched off. When the back-lighting is switched on current consumption increases to approximately 70mA"

[MtB]

1 hour ago, WotEver said:

If the meter reads 0 when the wires are shorted together then it’s accurate and the reading of 0.2 is the 200mA taken by the meter or whatever. This is where a clamp meter can help to find out where it’s going. 

 

My six clamp meters each seem to have a resolution of about half an amp....

 

 

[WotEver]

22 minutes ago, Mike the Boilerman said:

 

My six clamp meters each seem to have a resolution of about half an amp....

As long as he can get a reading the accuracy is irrelevant. Obviously if he can’t get a reading with 0.2A flowing then the clamp meter won’t help him. 

[TheBiscuits]

2 hours ago, Mike the Boilerman said:

My six clamp meters each seem to have a resolution of about half an amp....

Bet you a pint night in the pub they vary depending on the angle you hold them to the cable, and vary every time you use them on the same actual load!

[MtB]

8 hours ago, TheBiscuits said:

Bet you a pint night in the pub they vary depending on the angle you hold them to the cable, and vary every time you use them on the same actual load!

 

They do, which is why I think they are useless for chasing down a current of 0.2A.

 

 

[jradley]

Is that photo of the British Gas smartmeter taken when everything is supposedly switched off and isolated ? It is showing a consumption of 145w - I'm assuming the transmitter for it is clipped over the live output from the inverter, is that right ?

The confusing thing about this is that for the inverter to be chucking out 145w I would expect it to be pulling at least 12A from the batteries, not 0.2.

 

That aside, does the isolator switch in the battery bay disconnect the battery bank from the engine alternator ? (I couldn't quite tell from the photo). If so switch everything off on the boat and and switch off the switch and see if you still have a voltage drop across the meter shunt. It is entirely possible the diode(s) in the alternator is failing and allowing the battery to drain through the alternator.

 

John

[blackrose]

6 hours ago, jradley said:

Is that photo of the British Gas smartmeter taken when everything is supposedly switched off and isolated ? It is showing a consumption of 145w - I'm assuming the transmitter for it is clipped over the live output from the inverter, is that right ?

The confusing thing about this is that for the inverter to be chucking out 145w I would expect it to be pulling at least 12A from the batteries, not 0.2.

 

We're talking about 12v DC here. Everything was off on the DC side of things including the inverter. The British Gas meter is an AC meter and I'm on shore power so we can ignore that for the sake of this discussion.

Edited July 25, 2019 by blackrose

[blackrose]

7 hours ago, jradley said:

That aside, does the isolator switch in the battery bay disconnect the battery bank from the engine alternator ? (I couldn't quite tell from the photo). If so switch everything off on the boat and and switch off the switch and see if you still have a voltage drop across the meter shunt. It is entirely possible the diode(s) in the alternator is failing and allowing the battery to drain through the alternator.

 

John

 

I don't think my isolater switches disconnect the alternators? I'm not sure. But I came back to the boat just now after 24 hours away. It's 37C in the boat (bloody hell) so I've opened all the doors and hatches.

 

Anyway, I haven't had time to short the shunt yet and check the meter but the smartgauge is still showing 100% & 12.8v and the BEP meter is showing this with battery charger off for a whole day. So to me it looks like it must be meter error due to the heat? A drain I could track but where's a charge coming from?

 

 

 

Edited July 25, 2019 by blackrose

[jradley]

5 minutes ago, blackrose said:

 

We're talking about 12v DC here. Everything was off on the DC side of things including the inverter. The British Gas meter is an AC meter and I'm on shore power so we can ignore that for the sake of this discussion.

Fine - it wasn't clear if the mains AC was being powered by the inverter or not. Is there a wiring diagram showing where the ammeter shunt is in circuit ?  Only by seeing that would it be possible to tell if it would register a drain caused by the alternator, but assuming the big rotary switch is on the feed from the alternator it's a very easy thing to try to rule out.

 

John

3 minutes ago, blackrose said:

 

I don't think my isolater switches disconnect the alternators? I'm not sure.

 

One wire goes to the battery bank - just trace the other wire to see where it heads off to.

[blackrose]

Just now, jradley said:

Fine - it wasn't clear if the mains AC was being powered by the inverter or not. Is there a wiring diagram showing where the ammeter shunt is in circuit ?  Only by seeing that would it be possible to tell if it would register a drain caused by the alternator, but assuming the big rotary switch is on the feed from the alternator it's a very easy thing to try to rule out.

 

John

No wiring diagram. I fitted the shunt myself. It's just connected to all the battery negatives + a few other negatives that go through it. Every 12 negative on the boat runs through the shunt, apart from maybe a bilge pump?

3 minutes ago, jradley said:

Only by seeing that would it be possible to tell if it would register a drain caused by the alternator

But there is no drain now, instead it's a phantom 0.4amp charge

[jradley]

14 hours ago, blackrose said:

Every 12 negative on the boat runs through the shunt, apart from maybe a bilge pump?

But there is no drain now, instead it's a phantom 0.4amp charge

I'm assuming you have a separate battery for engine starting, is that right ? The question then becomes how is the charging of the starter battery and the domestic bank managed ? If you have a an automatic split charging system wired between the two, which side of the shunt is it - battery side or domestic side ? Depending on how it is wired it is entirely possible that an automatic split charging system allows charge to flow from the starter battery to the domestic bank and vice versa - it shouldn't, but that doesn't mean it's impossible. A wiring diagram would be really, really useful to have.

[WotEver]

58 minutes ago, jradley said:

split charging system

My thoughts wandered along the same lines. Either the meter is telling porkies or there is a variable charge flowing. Between battery banks would seem the most likely. The quickest way to know is to short out the sense wires. If the meter shows 0.0 with them shorted then it would suggest that two battery banks are somehow linked. Bow thruster bank?