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Any recommendations on the type of ammeter @Dannyc should get? I've got an old Victron BMV 501 that uses a shunt, wired permanently in to the negative wire to the battery bank. The hand held multimeter I have has a limit of 10A DC current before it blows its internal fuse and would need breaking in to the battery wires before use. What about a DC clamp meter? Can fit over wiring in use. Don't have one myself.

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2 minutes ago, Jen-in-Wellies said:

Any recommendations on the type of ammeter @Dannyc should get? I've got an old Victron BMV 501 that uses a shunt, wired permanently in to the negative wire to the battery bank. The hand held multimeter I have has a limit of 10A DC current before it blows its internal fuse and would need breaking in to the battery wires before use. What about a DC clamp meter? Can fit over wiring in use. Don't have one myself.

I at present use a NASA bm2. It does volts and amps in one large easily read and easily installed package. 

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2 minutes ago, Jen-in-Wellies said:

What about a DC clamp meter? Can fit over wiring in use. Don't have one myself

That's the type to use (unless the charger / alternator is 100+ amps).

 

I find mine useful for all sorts of things - you can measure the current the Inverter takes in standby, the current the fridge takes, check if the alternator is actually out-putting etc etc

 

What it won't do is 'count' Ah to determine total consumption (ie how many Ah does my fridge use per day ?)

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Back to the problem in the first post. As Brian says some people wire the fridge straight to the batteries or the battery side of the master switch (amusing the master switch is in the positive lead). If so then all you need to do is to move the fridge cable to the switched side of the master switch. I theory you should replace the cable between battery and master switch with a thicker one but I lay odds you will not have to.

Back to the problem in the first post.

 

Edited by Tony Brooks
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1 minute ago, Alan de Enfield said:

That's the type to use (unless the charger / alternator is 100+ amps).

 

I find mine useful for all sorts of things - you can measure the current the Inverter takes in standby, the current the fridge takes, check if the alternator is actually out-putting etc etc

 

What it won't do is 'count' Ah to determine total consumption (ie how many Ah does my fridge use per day ?)

So, a shunt based monitor like a NASA BM2, or Victron BMV type for overall consumption and measuring amphours and a clamp on for instantaneous measurements from particular bits of kit.

 

Jen

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6 minutes ago, Jen-in-Wellies said:

Any recommendations on the type of ammeter @Dannyc should get? I've got an old Victron BMV 501 that uses a shunt, wired permanently in to the negative wire to the battery bank. The hand held multimeter I have has a limit of 10A DC current before it blows its internal fuse and would need breaking in to the battery wires before use. What about a DC clamp meter? Can fit over wiring in use. Don't have one myself.

 

One of these, or the NASA is ideal providing you ignore the battery SoC % reading (unless you regulary recalibrate for falling battery capacity and periodically synchronise the reading when the battery is fully charged) and make full use of rested no load voltage to ascertain SoC, amps for instantaneous load and amp hours out for approximate capacity.

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43 minutes ago, DannyC said:

OK thanks for the info.

 

I tested the battery when charging yesterday and it was running at 13.9

 

I am charging at the moment, so I will take a look and see what the situation is.

 

My batteries are fairly new (Dec,18), and I have been careful with them, so hopefully the damage isn't too great.

 

 

The trouble is you don't know if you are being careful because you don't know if you are fully charging them or not. You are running your engine and hoping for the best, You are however looking after them at the other end by not over discharging them. I don't know why as a minimum builders don't fit a volt and ammeter

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It is far from ideal to charge batteries on tick over while tied up if that is what the OP means about tick over. Set the revs to provide the highest current reading and gradually, reduce them as the current falls. If you have no ammeter for now charge at about 1200 rpm dropping to 1000 rpm after half an hour.

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5 hours ago, DannyC said:

Oh I didn't know that - the leaving for one hour thing. 

You can use a voltmeter to measure or the state of charge (see Alan's table), but of course there must be no charge or discharge when you take that reading. In addition, you should either measure the voltage about an hour after charging or switch a light on for a few minutes after charging and then take the voltage. If you take a voltage reading directly after charging you'll be measuring the surface charge on the plates which dissipates after a while, and you'll be getting a 'false' high voltage reading.

Edited by blackrose
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5 hours ago, Tony Brooks said:

Set the revs to provide the highest current reading and gradually, reduce them as the current falls.

I've tried doing this on mine but changing the revs upwards only ever seems to make the current drop by a couple of amps rather than rise. The alternator belt seems to be set correctly and I cant see or hear any evidence of it slipping, so no ideas as of yet why mines a bit backwards. 

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8 hours ago, ditchcrawler said:

Some people wire fridges straight to the batteries via a fuse so as not to suffer volt drop through the distribution system. If your fridge is 230 volt it will only work with the inverter switched on.

 

Another reason is that often the distribution board won't cope with the demand of fridge start up. I would expect it to be wired through the isolator, though, or, if not, to have its own isolation switch. (Ours was always on when the domestic isolator was on, until I fitted a separate switch next to the fridge.)

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14 hours ago, Rumsky said:

I've tried doing this on mine but changing the revs upwards only ever seems to make the current drop by a couple of amps rather than rise. The alternator belt seems to be set correctly and I cant see or hear any evidence of it slipping, so no ideas as of yet why mines a bit backwards. 

What’s the voltage doing when you increase the revs?

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23 hours ago, DannyC said:

Hi all,

 

So the other day I left the boat for almost a week. Before leaving, I turned everything off at the switch box and turned of fthe isolator switches too. The battery was fairly well charged when leaving (well over 50%). However, when I returned we found that the fridge was still on! So somehow, even thought I had cut out all the power, the fridge was still managing to draw from the batteries - everything in the freezer was still frozen! I checked the battery using the volt meter and it had dropped down to 11.4 (eek!).

 

Ever since I have been cruising I have been so so careful not to let the batteries drop below 12.2v. We use a fairly limited amount of power, but I am starting to wonder about the fridge. Something seems to eat all the electricity, and I can't believe it is having one 12v light on of an evening and the pumps + the occasional laptop charge.

 

Do you think my fridge may not be 12v? It is a Lec brand fridge, but there is no model number on it, so i am not sure the best way to check, and how can it be wired so it is not controlled by the fuse box/ isolator switches.

 

What do you guys think? I am well aware that I may be being a moron!

Do Lec make a 12v fridge? If not you may have to look for a dedicated inverter directly wired to your battery bank. Hopefully this will will have an on/off switch allowing to turn the fridge off if leaving the boat. 

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1 hour ago, grahame r said:

Do Lec make a 12v fridge? If not you may have to look for a dedicated inverter directly wired to your battery bank. Hopefully this will will have an on/off switch allowing to turn the fridge off if leaving the boat. 

Shoreline used to convert Lec fridges to 12V so maybe a Lec label got left on the case, but the dedicated inverter for a mains fridge may also be correct. A photo of the works at the back would give the clue.

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5 minutes ago, adrianh said:

You can buy cheapiss dc clamp on meters from CPC.

Part no IN05110 is a typical type

DO NOT BUY THIS CLAMP METER

 

This is the wrong type - it does not measure DC amps.

 

https://cpc.farnell.com/tenma/72-7224/clamp-meter-ac-dc-current-frequency/dp/IN05110

Extract from website :

 

Product Information

DMM Functions:
Current, Voltage, Frequency, Resistance
Current Measure AC Max:
400A
Voltage Measure AC Max:
600V
Voltage Measure DC Max:
600V
Resistance Measure Max:
40Mohm
DMM Response Type:
Average
Range Selection:
Manual
No. of Digits:
3.75
Jaw Opening Max:
28mm
Product Range:
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Sometimes you have to be careful with the cpc website. The operating manuals on the cpc site clearly shows it measures dc current and it does cos I have one. 

 

Even though the psge Alsn linked to doesn’t say it measures dc it doesn’t say it doesn’t either.....

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On 07/05/2019 at 17:47, Mike the Boilerman said:

How are you measuring the state of charge?

 

You stated "well over 50%" in your first post. How do you know this? 

 

Depending on how you are determining state of charge, you could be miles out. In fact with no ammeter, you probably ARE!

 

 

 

 

Maybe he needs a selection of Smartgauges ...

 

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On 08/05/2019 at 15:34, WotEver said:

What’s the voltage doing when you increase the revs?

I'll check the next time and report back, if my memory will let me. 

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