Current meter

[stuart]

Looking at all the various recent posts about battery performance and voltage measurements etc. I'm wondering if its worth while installing a permanent current meter from the battery bank. This would certainly help with energy audits for power usage etc.

 

Anyone recommend a suitable meter? What current range should I be looking to cover?

[John Orentas]

Stuart.

 

What you need is a 'Centre zero' ammeter, the range will depend on what maximum loads you are likely to have, +60 / -60 amps should be ok although the unit will have a considerable overload capability. The meter will show the charge current from the alternator, the current being used by your systems or the ballance between the two.

 

The ammeter will need to be a 'shunt type' to avoid running very heavy cables around the place.

 

Fit a voltmeter as well, very much simpler to fit.

 

When you have instruments to show what is going on, you will begin to get a better feel for the electrical system, of equal importance you will see that a lot of popular pre-conceptions are less than accurate.

 

** A shunt is basically an electrical resistor which when wired in series with a circuit will give a very tiny voltage difference across it, which will be proportional to the current flow. This voltage is measured by the meter which though calibrated in amps, is in fact a voltmeter.

 

John Squeers

[rog guiver]

Mention Mastervolt in you Christmas wish list... excellent products.

[John Orentas]

Stuart.

 

Thought that might happen, you don't need any trendy electronics.

 

Industrial 72mm ammeter £20

Industrial 72mm voltmeter £20

Shunt 50 mv £15

 

John Squeers

[DHutch]

yeah, i woulnt (havnt) botherd with any electronics,

 

we just have a ampmeter the mesures whats going in or out of the boat, and a 3 volt meters one on each battery (2domestics and the bow thurster)

- and a ampmeter on the alternator

 

daniel

[Martin]

Dr Squeers - where do you find meters at that price?

[John Orentas]

Martin.

 

Some electrical wholesalers and of course RS components.

 

I can get them at a good price. My last reply listed prices a year or so old. If anyone want firm prices let me know. I like the industrial square types 72mm need to know the amps range and 12 or 24 volt. I will supply wiring diagrams

 

I hope I havn't broken any rules !

 

John Squeers

[Richard Bustens]

Ar new nane for John O... Dr Squeers Nice one Martin

 

Am i missing something? on a diferent thread we have decided that there is a draw of 200A so what is the use of a 60/60 amp meter.?

[John Orentas]

Richard.

 

I noticed the Dr. bit. I did give myself the title for a year or so, it's a long story but I was acquitted eventually.

 

The +60 0 -60 ammeter was for a normal boat Richard, your floating power station would require something more substantial like a substation with giger counters to monitor your reactor.

 

John Squeers

Edited December 19, 2004 by John Orentas

[DHutch]

yeah, we make use a -30 - 0 - 30 meter, but we dont have an electric cooker!!

[maffi mushkila]

Ah new name for John O... Dr Squeers  Nice one Martin

 

Am I missing something? On a diferent thread we had decided that there is a draw of 200A so what is the use of a 60/60  amp meter?

 

 

Your engine start battery may deliver instantaneous start current of 200 amps dropping to 70 or 80 depending on the size of your engine. I doubt if the other batteries would ever deliver such a current.

 

Except in the case of you Didcot installation.

Edited December 18, 2004 by maffi mushkila

[John Orentas]

Maffi.

 

I think the reference to 200 amps was the consumption of an inverter !

 

John Squeers

[maffi mushkila]

Maffi.

 

I think the reference to 200 amps was the consumption of an inverter !

 

John Squeers

 

 

You could be right John

[Big COL]

John

 

Your living in the past, and I am not being disrespectful, but most modern engines have twin alternators fitted with 45a/90a outputs a 60amp meter is well under rated.

This is why battery management systems have come to the fore, although the meter on these systems is actually measuring volts via a shunt and then recalibrated to amps,it allows far more flexibility than a straight amp meter. I also like to be a purist when possible, but unfortunately technology runs faster than I can keep up with, and I have to admit as much as I try to keep up with it I am slowly loosing the race. I probable like your self like to stick to tried and tested systems, must be an age thing . Having said that you cannot buy EXPERIENCE.

Edited December 19, 2004 by Big COL

[John Orentas]

Hi Colin.

 

Battery Management Systems. Now there is a nice bit of jargon, how do you 'manage a battery', charge controllers seem to work ok if you need to squeeze a bit more charge into your batteries, but remember all alternatores are supplied with a regulator, it's built in. Where does the management come in, could it be a couple of metres in a box with a zero or two tagged onto the price.

 

Anyone who has twin alternator systems and then makes an electrical connection between them is a fool, they have destroyed that vital independence of both systems.

 

Sixty amp reading meter not big enough! I have a 75 amp rated alternator and my ammeter reads +30 / 0 / -30 amps. I have had batteries new and old, flat and fully charged, very rarely has the meter gone off the scale and then only for a few seconds (ammeter shunts have an overload rating of at least 2:1).

 

A couple of simple meters cost very little, thay enable you to see exactly what is going on with your electrical system without relying on percieved wisdom and commercially based often misleading product specifications. I am constantly amazed that in this supposedly cynical age the average person will accept without question some of these 'magic black boxes'.

 

John Squeers

Edited December 19, 2004 by John Orentas

[stuart]

Some electrical wholesalers and of course RS components.

John Squeers

<{POST_SNAPBACK}>

 

Hi John. I've an account with Farnell - any chance you could pick a ammeter & voltmeter from there list and recommend one to me please?

 

Thanks & Merry Christmas!

 

Stu.

[John Orentas]

Stuart.

 

I don't have a Farnell book just R S Components. I can give you some codes if you let me know.

 

I would recommend a eltro-mechanical type DIN72 moving coil centre reading +30 / 0 / -30 amp (or 60a if you prefer) with compatible shunt (50 or 60 mV)

 

Similar to above voltmeter 0 / 20 volt Dc

 

 

John Squeers

[dor]

Battery Management Systems.  Now there is a nice bit of jargon, how do you 'manage a battery', charge controllers seem to work ok if you need to squeeze a bit more charge into your batteries, but remember all alternatores are supplied with a regulator, it's built in.  Where does the management come in, could it be a couple of metres in a box with a zero or two tagged onto the price.

 

<{POST_SNAPBACK}>

 

 

So John, are you saying that external regulators and "battery management systems" are a con and a waste of time?

[John Orentas]

Dor.

 

Read it again.

 

John Squeers

[dor]

Yes, read it again.

 

Question stiill stands.

[Richard Bustens]

Although it appeares that John is saying that they are no good im'e sure we are missreading what he is saying DOR.

John please elaborate on your comments

[John Orentas]

Richard / Dor.

 

I am a reasonably literate sort of person so I really can't see any reason why anyone should see a need to paraphrase my reply to Colins contribution, if I believed that the proprietry External Regulators or Battery Management Systems were a "Con. or a waste of time" I would probably have used those words.

 

Colin in his reply was being over critical of himself when he said technology runs faster than he can keep up with, he spoke of "Battery Management Systems". I don't know what that means, I suspect it is another name for a charge controller or regulator, these devices have been around for quite a few years, they seem to quite succsessfully modify an automotive alternator to give the different characteristics required for marine use. For those of us who already have a marine spec. engine I would doubt their effectiveness.

 

You doubt my assertion that a 30 amp meter is of sufficient capacity. That is something of a rotary argument, if more people had even a minimum of instrumentation on their boats we would not have so many people trotting out the 'perceived wisdom' that 75 amp alternators charge batteries at 75 amps, that starter motors draw up to 300 amps and fridges draw some absurdly high current on start up.

 

I tell people, don't ask the man in the shop or your boat builder MEASURE IT ! it's easy.

 

There is now a generation of people, brought up in the computer age that genuinely believe that all good things have a piece of inteligent electronics built into them and anything that doesn't must be old fashioned and generally inferior. These same people would find it hard to believe that the world coped quite well before the invention of the micro-chip.

 

When they were chidren how, do they imagine that a million pop bottles a day would be filled, how did Ford manage to build a million Anglia cars in a year. Automation of manufacturing processes was well establised long before the electronic age.

 

What is new, and has arrived along with the computer age is the concept of added value, extended warranties, phones that take photographs, "battery management". We should be very wary of being drawn into all this.

 

John Squeers

[Guest]

Intereting John that you say don't take anyone's word-measure it. Has anyone ever measured volt drop on cables in the real world? I have found them to be significantly less than the charts say. When I am bored one wet day I intend to measure the volt drops on our boat (on the longest runs/heavy loads) to get a further idea. Bet they are less than the tables say though.

 

Just thinking aloud really.

Stan H

Edited December 20, 2004 by stan hesketh

[stuart]

Stuart.

 

I don't have a Farnell book just R S  Components. I can give you some codes if you let me know.

 

I would recommend a eltro-mechanical type DIN72 moving coil centre reading +30 / 0 / -30 amp  (or 60a if you prefer) with compatible shunt (50 or 60 mV)

 

Similar to above voltmeter 0 / 20 volt Dc 

John Squeers

<{POST_SNAPBACK}>

 

The farnell website is very good...

 

http://uk.farnell.com/jsp/endecaSearch/sea...rerDisplay=true

 

I can see lots of Ammeter stuff but didnt see any with a negative current reading.

[Big COL]

Hi John

 

You sound worse than me and my wife thinks that I am a Luddite.

 

Battery management system probably better described as a battery reference meter, consist of one meter with scroll through functions depending on which system you buy and they are all much the same. It gives the following information.

 

1 voltage charge and discharge

 

2 amperage charge and discharge

 

3 Amp hours used and remaining

 

4 Time left in batteries

 

Number one is straight forward it shows the battery Voltage during charging and discharging

 

Number two is the same as number one only this shows the amperage for charge and discharge

 

Number three shows the Amphours used and Amphours left in the battery bank. When you set the meter up you have to load in the total capacity of your battery bank, the meter then uses this figure as the base for its calculations

 

Number four tells you what time you have left in the battery bank. This is calculated by taking the usage over the previous 15 minutes, the time scale for this is adjustable depending on the individual circumstances so the average can be taken over a longer or shorter period. In this mode, because batteries don't discharge at a linear rate, it uses Peukert exponent to compensate and to give a truer figure.

 

Most of these meters also have the facility to couple in a battery temp sensor.

With all of the information that these meters offer I can not see the point of using any thing else, the difference in cost is minimal and its a lot quicker fitting these than individual meters