I want to fit a voltmeter in the cabin to keep an eye on the leisure battery state

Murv

Murv

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It's just a cheapy LCD readout display, and I'm going to mount it in the new bulkhead panel once I've cut it.
Is there any reason that I can't just tap it into the lighting circuit, or any convenient wiring close by, rather than running wires through direct to the battery?
 
Hi, There is no real reason why you cant connect it locally, provided that you pick up the pos and neg of the same circuit and can accept that there might be a slight inaccuracy when the circuit is loaded, this due to the volt drop in the wiring, but for indication purposes it should be fine. It may be worth considering fitting a small switch and local inline fuse for the meter.
Many of these small digital meters are designed to snap into a thin (say 2mm) plate and the hole has to cut quite accurately as they often have a very narrow land area inside the bezel.
 
I have used one of the EBay displays, but the two wire one.I use a 1/2/both switch so I can check either battery.The one showing volts to 2 decimal places is good.
I did this on the recommendation of a friend who was a commercial marine electrician.He has 3 of them them on his Westerly Storm monitoring individual battery banks.
They are ideal if you do not want to pay out lots of money on a all singing battery monitor.
 
Murv said:
It's just a cheapy LCD readout display, and I'm going to mount it in the new bulkhead panel once I've cut it.
Is there any reason that I can't just tap it into the lighting circuit, or any convenient wiring close by, rather than running wires through direct to the battery?
Click to expand...
If you calibrate the meter for the remote connection when it's under load. it will read over when the circuit is not loaded. Calibrate it when the circuit's not loaded, and it will read under when the circuit's loaded. Ohm's Law and all that.

The only way to install it properly is to wire it directly to the battery, then depending upon the cable length and thickness, and the meter's current draw, recalibrate it..
 
I've got one that taps into the supply a long way from the batteries - almost a complete waste of time. Under load, it gives a frighteningly low reading, which I just don't want to see when in reality, all is fine.
 
Fantastic, thanks all!
Sorry, I should have said, I already have the meter. And, yes, it was a bugger to cut the hole for it, especially as it was in the brand new bulkhead panel that I carefully spent the day making!
Anyway, it's mounted in the wood now, just need to go down and put the switches etc in.

The plan was to fit two small toggle switches (I have those) with inline fuses so that I can check either battery. What sort of switch could do both? I assumed such a thing wouldn't exist.
I will connect directly to the batteries then, I don't suppose the meter itself is that accurate so seams counter productive to introduce any further possible errors.
 
Murv said:
The plan was to fit two small toggle switches (I have those) with inline fuses so that I can check either battery. What sort of switch could do both? I assumed such a thing wouldn't exist.
I will connect directly to the batteries then, I don't suppose the meter itself is that accurate so seams counter productive to introduce any further possible errors.
Click to expand...
One single pole double throw (SPDT or toggle) switch will allow you to connect the meter to either battery (assuming both battery negatives are permanently connected).

eg http://www.maplin.co.uk/p/sub-miniature-toggle-switch-a-fh00a
 
Thanks for that, I already have the cables, I can't remember the amp rating but it's not heavy stuff. It literally will be just supplying the meter so I'm not concerned about that bit.
What is that sort of switch called? all I'm coming up with are the huge rotary ones for selecting from either bank!
 
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