Simple voltmeter

[Colvic Watson]

My Halcyon 23 has a Yanmar 1GM with simple electrics to start & charge and run basic nav/cabin lights. When I took delivery of it this week the 10 year old battery was flat so I replaced it - but this is the question - how do I fit a simple voltmeter to be able to monitor it's charge state? I also thought of fitting one of those basic solar trickle chargers to keep it topped up, but if I plug it into the cig lighter socket that won't reach the battery as the electrics use a key to switch the circuit on/off. Can you connect the solar panel directly to the battery terminals? Where best to get a voltmeter and where should it go in the wiring system?

Thanks for the help!

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[paulrossall]

I am not sure where you will get a volt meter from, perhaps Maplins, maybe Index Marine(but I have found Index to be expensive). My voltmeter is connected to my interior lights circuit just because it happens to run near where I put the meter. I switch the interior lights circuit on, on the main panel and then switch the voltmeter on. I would not bother with the expense of fitting a solar panel. From what I have read they only supply a trickle charge, they get in the way and I think it is easy enough to keep your battery (3 in my case) charged from the engine. I am on a swinging mooring during the season and run an Eberspacher, but I do have a motor sailer. It is important to give your engine some regular use so it might as well be charging your battery. Did you fit a leisure battery? What size? Hope you get as much pleasure from your new boat as I have done these last 4 years from mine. Paul

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[ShipsWoofy]

Here is one, I have a pair of these, work very well.

<A target="_blank" HREF=http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=PM11348&N=401>http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=PM11348&N=401</A>

Just wire between your isolation switch and gnd. Or the positive feed to your power panel and gnd.


hope this helps

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[pete]

Hi
Have a look at this http://uk.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=939948&N=401
I have had one for around 3 years on my boat and would not be without it.

Pete

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[ShipsWoofy]

de de de da da da da de de de deee

eeeireeeeee


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[William_H]

It is probably easier simpler to get one of those cheap digital multimeters. And connect it only when you want to know the voltage. You could put a couple of those little sockets in the panel to push the multimeter probes into or even use small screw heads in an insulated (plastic) panel. If the voltmeter or its connections go straight to the battery don't forget to fit a small in line fuse near the battery. Same goes for solar panel connect straight to the battery via small fuse in positive near the battery. However in UK when you have an engine with alternator forget solar. regards will

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[oldharry]

Volt meters are pretty much a waste of time other than for checking that the charging circuit is functioning. As a means of checking the state of charge they are virtually useless, so do not waste your money fitting one.

Why? Firstly, voltage drops in the wiring and switches leading to the meter will give false low readings as the damp air gets at the contacts.

Secondly, battery voltage at the terminals varies considerably with the load on the battery. The bigger the load the lower the voltage - the extreme example being the starter motor which will drop the battery terminal voltage to around 8 volts while it is cranking the engine. Every electrical item switched on will reduce the voltage in proportion to its consumption, even a small light bulb.

Thirdly : switching the load off before measuring the voltage is still no good, as it takes an appreciable time for the battery to return to its quiescent voltage.

Fourthly, during charging the voltage rises hiding the true state of charge. Again after charging it takes quite a long time for the battery voltage to drop back to give a true reading.

Fifthly, different types of battery give different voltages at a given state of charge: a car battery will give a significant drop in voltage as the charge reduces, while a traction or leisure battery is designed to maintain a fairly constant voltage until it is nearly flat. Voltage then drops off suddenly and sharply.

Your other question re the solar panel: yes you can leave it directly connected to the battery provided there is a blocking diode fitted. Without a diode the battery will discharge across the panel whenever there is insufficient light to cause it to charge. Although it will not damage the panel, it will take out more than the panel puts in.


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[geoffatstanpit]

I wouldn't be without mine!

If it reads 12v+ when I switch on it's OK

If it reads more when the engine's running, the charging plug is in properly.

If it goes below 12v I need to take the battery ashore and put it on the charger.

All useful information

Geoff

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[bedouin]

RS do a very nice little unit - go to rswww.com and check out 365-6252.

This is a 2 wire signal powered voltmeter, which means it is very simple to install and does not require a 9V battery to power the meter itself.

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[oldharry]

There is a much more uselful widget than a voltmeter for this purpose, from Maplins and many car shops: An Alternator tester with 4 to 6 LEDS - which do very much the same thing as a Voltmeter, but avoids unnecessary panics when the voltage drops a bit. Left permanently in circuit wired with a push to check button, it gives an instant warning of a low battery and indicates that the charger is working. Being solid state electronics it is less prone to damp problems than a moving coil meter, and is usually around half the price.

Much easier to read than a voltmeter, as it leaves you in no doubt: green - you're OK, amber - you have a problem, red - you're not going sailing today!!


<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by oldharry on 17/12/2004 10:43 (server time).</FONT></P>

 

[cliff]

Maplins do a nice plug in one - it plugs into a cigarette socket and gives battery state

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[dickh]

Also look on ebay - usually lots in the motoring section.
See http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=9903&item=7940648422&rd=1

or just type in voltmeter and lots come up - usually cheaper if you settle for a simple gauge without the red/green/red marking,
See http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=9903&item=7940650262&rd=1


<hr width=100% size=1>dickh
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[Ruffles]

The meter sense wires should be connected to the batteries direct by thin wire. BUT don't forget an in-line fuse near the battery end. My Moody didn't have one - any short and you'd have an instant fire.

Rob.

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[bedouin]

You are being a little pessimistic. Provided that you know how to interpret the readings the voltmeter is a very useful device - I certainly wouldn't be without them. For example

(i) The first thing I tend to do each trip to the boat is to check the voltage of both banks

(ii) During e.g. a night sail I can monitor the voltage of the domestic bank to determine when I need to recharge the batteries.

(iii) Giving an indication of charge state post charge (this is the least reliable reading)

(iv) Monitoring voltage during the charging gives some indication of the state of charge (particularly watching for when the charging voltage reaches the limit).

(v) Useful for checking the output from the Solar Panel when connected.

The key to successful use is to make sure you are comparing like with like. Over time you learn the characteristics of your particular installation.

I really can't imagine any other way of monitoring your battery charge (other than by a very expensive battery monitor system).

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[Trevethan]

I have a faria type voltmeter (round about 2 inches across) that came off my old panel. Workks fine.

Free if you can collect from somewhere in London (based at Limehouse) and a small donation to RNLI.

You'd probably want to put a small push button switch in the circuit to prevent it running the batteries down.

Give me a bell

07900 244 185



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[duncan]

also some electronics have a voltage data window that you can have showing - all Lowrance sounders for example.

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[oldharry]

Yes, but you are used to your boat and its installation. And you will have observed, and be used to all the varying voltage conditions. I have had them on boats, and only one was of any practical use gauging battery condition. That was a large meter which only operated in the range 11 - 15 volts. Even that could be pretty misleading at times. The 5 LED testing widget that I suggested is a far better bet and is what I use very succesfully nowadays.

As I said, Green - its OK, amber - there are problems , red -your in trouble. What could be easier?

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[Joe_Cole]

I think you'll find that the Alternator tester is no more than a voltmeter which is using LED's to display the readings rather than a dial.

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[oldharry]

I wondered when somebody would spot that one...

Just that they are a darn site easier to use - even SWMBO notices if mine goes amber....

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[pappaecho]

I would not use a cigar lighter to connect a solar panel as they tend to be high resistance. I would have a dedicated marine ( and idiot proof plug - so the solar panel is always connected to the battery the right way round). Via a 1amp fuse, and assume that the panel has a blocking diose built in to prevent reverse discharge.
I have a 15 watt solar panel which charges 3 x 110 amp batteries, quite successfully. My digital voltmeter often records quite dramatic difference between the domestic and engine battery, specially when the beer cooler ( fridge) is on .. very important because when the voltage drops below 9 volts the gas alarm goes off and we run round looking for gas leaks which dont exist.
I removed all batteries last week, and was perplexed that my meter was reading 4.41 volts, when I realised that the solar panel was connected, as it was getting dark!

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