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Discussion Starter · #1 ·
I have fitted an ammeter & a voltmeter on the boat, but the guy wiring them up for me is unable to find anywhere to connect the ammeter to? he has connected the voltmeter directly from the primary battery through the gauge to earth. This morning when I switched on & started the boat the needle was just under the 12v mark then after a few minutes it rose to about 13.5v I assume that indicated that the battery was down from running the automatic bilge pumps, & that once it had topped up the battery it rose to 13.5v? Is this an ok way of monitoring the voltage? Or am I only reading the level of charge in that particular battery?
Regarding the ammeter, he tried to wire it from the back of the ignition switch, but was unable to find an earth, we managed to establish it was working by touching wires to the connections & got either 50A negative or 50Amps positive :eek: where should we connect it to ensure that we are reading the flow of the current & not anything else?
I should say that there is a "split diode" system fitted to keep both primary & auxiliary batteries charged
 

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Volt meters should be wired in parallel, so this should go from the switched side of the battery/ignition to earth, that way it isn't reading permanently. Otherwise it will also draw from the battery. You may have it like this already but it doesn't read like you do....
The Ammeter, depending on type, should either be wired in series or with an inductor around the main load wire. If the series type, and assuming you waant to read charging current? Then it would go in the outpit wire from the alternator. You need this wire through the ignition switch or relay as well.
The charge output wire will invariably be red from the reg/rec unit. If you reg/rec outputs to battery side of a start solenoid, you will need to run 2 cables to your dash, these will need to be heavier cable than what you are joining to to avoid losses and cable overheating. Dont forget to add a fuse to this wire!
An inductive type ammeter is far easier and safer to wire in, as it will only require a 12V feed, an earth, and the inductance part will wrap/clamp to the output wire.

Hope that helps
Steve
 

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Discussion Starter · #3 ·
Volt meters should be wired in parallel, so this should go from the switched side of the battery/ignition to earth, that way it isn't reading permanently. Otherwise it will also draw from the battery. You may have it like this already but it doesn't read like you do....
The Ammeter, depending on type, should either be wired in series or with an inductor around the main load wire. If the series type, and assuming you waant to read charging current? Then it would go in the outpit wire from the alternator. You need this wire through the ignition switch or relay as well.
The charge output wire will invariably be red from the reg/rec unit. If you reg/rec outputs to battery side of a start solenoid, you will need to run 2 cables to your dash, these will need to be heavier cable than what you are joining to to avoid losses and cable overheating. Dont forget to add a fuse to this wire!
An inductive type ammeter is far easier and safer to wire in, as it will only require a 12V feed, an earth, and the inductance part will wrap/clamp to the output wire.

Hope that helps
Steve
Steve
I will print this off & give it to my "man" I am sure he will understand what you are saying, I still look on a "split charge diode" as two cisterns above a toilet, No1 fills up, & the ball valve closes, & No2 ball valve opens to allow that one to fill up as well, from then on the ball valves open as the cisterns empty & call for water. Not very "elecktrickery" but I understand that analogy. :D
How can you tell the difference between a series & inductive ? :eek: Smoke & mirrors again:rolleyes::D
This "inductance part" would that be a metal strap or similar could it be heavier copper wire wrapped around the output cable?
 

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How can you tell the difference between a series & inductive ? :eek: Smoke & mirrors again:rolleyes::D
This "inductance part" would that be a metal strap or similar could it be heavier copper wire wrapped around the output cable?
If you have the inductive type, then you will have a pre wired harness ending in a clamp or some such that goes around the cable, there is also a shunt type that will have a bar that has metal ends with an insulated middle and connectors at each end or the old (series) style where you just have two terminals or two wires that wire inline....

Using the toilet analogy, what you are trying to measure goes something like this.....
Charging current- This is the flow rate of the water on the feed pipe before it splits to the 2 cisterns. When both cisterns are full there will be no flow untill one is flushed. Now if one cistern was used supply a continuous flow (fish finder, radio etc) then there will be a continual flow. You would measure this with a paddle wheel inside the supply pipe (series).
An inductive clamp would work something like this- Imagine the water was magnetic. If you had a device clamped against it that had say a ball bearing and a spring, your flowmeter (ammeter) would detect how hard the ball bearing is being pulled against the spring by the magnetism and give you a reading. A shunt would do a similar thing except it would joined in the pipe...
If you wanted to know the pressure difference from the supply pipe from and the toilet bowl, you would connect to the pipe and the bowl (parallel), the direction of the strongest pressure gives your reading. The pipe and the bowl represent the positive and negative of your battery.

As you dont want either to work with the stop **** turned off, you would fit them downstream of the stop ****, the stop **** being your ignition switch ;)
 

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That "running" voltage sounds a bit low, when running/charging you should see 14.5v, try taking the voltmeter leads straight to the battery and see what you get 1. at rest after a while, then 2. with engine running at about 1500 rpm. remember pos to pos and neg to neg.
 

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Discussion Starter · #6 ·
Thank you all for your assistance, I now have a voltmeter, ammeter, & oil pressure gauge fitted & working, unfortunately the temperature gauge that came with the job lot has a longer probe on the end of the cable, than the probe on the existing water temperature sender, ( I was going to cut 3/4" off it but was persuaded no to :eek:)so I will get another M/F fitting & screw that into the water jacket, then screw the new probe into it & it should be fine (far better than a warning light as it approaches boiling point :eek:).
 

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12V shows that your battery is very discharged, don't leave it like that for long otherwise it will die. 13.5V is slightly low for a charging voltage at the battery and will be because split charge diode systems have some voltage drop. Looking at the photo, a clean-up of the diode's terminals would may help.
 

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There's no guarantee that the volt meter is accurate. Compare it with a good multimeter reading, you may find your gauge reads slightly low. No big issue, its just an indicator that your system is working. :)
 

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Discussion Starter · #11 ·
Excellent news Vic, also did you get them crush washer I left with Nigel ??
Yes I got them thank you, the "banjo" actually screwed into a nipple, which was in turn screwed into the block, & it was the nipple that was leaking, new washers right the way through & leak stopped, thank you very much.
 

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Discussion Starter · #12 ·
There's no guarantee that the volt meter is accurate. Compare it with a good multimeter reading, you may find your gauge reads slightly low. No big issue, its just an indicator that your system is working. :)
I know that all gauges are very much "approximations", but it is much more informative to see a stable oil pressure reading, voltage/amperage reading, temperature reading, than looking at a unlit light wondering if it is ever going to come on :eek: At least now I have means of monitoring the workings of the engine & its systems, as opposed to waiting for an alarm to go off & tell me, "We are all doomed Capt Mainwaring" :D
 

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Discussion Starter · #13 ·
12V shows that your battery is very discharged, don't leave it like that for long otherwise it will die. 13.5V is slightly low for a charging voltage at the battery and will be because split charge diode systems have some voltage drop. Looking at the photo, a clean-up of the diode's terminals would may help.
They do look a bit dirty I agree I will clean those up very next job, the voltmeter only shows 12v when I turn on the ignition, as soon as the engine starts it goes up to 13v+ I assume that will be showing the state of both batteries in this 2 battery system? Or not? I have been wondering about that? is the voltmeter showing what is happening to both? If the "auxilliary" battery was to go dud would I see any indication of that on the voltmeter, or does it just show the condition of the "main" battery? Yet more "smoke & mirrors" :eek::D
 

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Discussion Starter · #14 ·
State of ChargeSpecific GravityVoltage12V
100% 1.265 12.7
75% 1.225 12.4
50% 1.190 12.2
25% 1.155 12.0
Discharged 1.120 11.9


- See more at: https://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html#sthash.XnOMjJ2A.dpuf
Jesus there is a lot to know about batteries Ian, I thought they were a plastic case with lead plates inside & some weak acid, I will read that again, there is much to know, & many questions are answered when you have a working knowledge of what is going on "under the skin"
 
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