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Mastervolt MICC amps counting wrong


j04n

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This is one of those 5 year projects where you dabble, fail to rectify the issue, convince yourself it's not important, due to potential cost, leave it a while, come back to it n round we go again n again n again!!

 

now it's back up there since changing my batteries!

 

MICC has never counted amps back in correctly until one day whilst fault finding I disconnected the RJ12 remote cable and the recorded charge amps increased by about 30 amps! This explained the amps I was loosing and all was good once again in paradise. All it meant was that I could not select inverter/ charger manually but I quite liked everything working automatically. Until now, when I've decided there are occasions when it would be useful to manually disconnect the charger and only have alternator charging. I contacted mastervolt and explained the problem but they replied that the RJ12 lead only allows for remote control of the mass combi and should not effect in anyway the amps counted at the shunt. So i thought the cable was maybe defectective so bought a new one. If it wasn't I could always connect it to the additional optional port. 

So, this is what I found;

 

Charge amps recorded on MICC with RJ12 lead disconnected 97 amps.

Charge amps with old RJ12 lead connected 70 amps. 

Charge amps with new RJ12 lead connected 85 amps. 

Charge amps with new RJ12 lead and old RJ12 lead connected to the optional port 85 amps. 

 

The new lead is better but it will still result in the count being way out very quickly. It looks like if I want an accurate count I'm going to have to loose the RJ12 lead and the remote control function but before I do has anybody come across the same issue and found a fix? 

 

Thanks in advance! ?

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6 minutes ago, j04n said:

. Until now, when I've decided there are occasions when it would be useful to manually disconnect the charger and only have alternator charging.

I'm not clear about this point - surely if you are connected to the 'hook-up' you will not be running the engine and the charger will charge the batteries.

Likewise, if you are out cruising and running the engine the charger will not be operational anyway (due to lack of mains supply) so the alternator will charge the batteries.

 

Using mains-supplied electricity is a fraction of the cost ( maybe less than 1/10th) than the cost of generating your own.

 

Am I misunderstanding something ?

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I would say the issue is to do with the negative (0v) wiring of the MICC and or shunt. In other words, the equipment hasn’t been installed correctly.

When you connect the RJ12 lead you are creating an additional connection between the 0v of the MICC and the 0v of the Combi. These of course should be at the same voltage ( 0v) and hence it shouldn’t make any difference. But if the MICC negative supply is connected to the wrong side of the shunt or some such other error, there will be a slight voltage difference between the two negative connections when current flows. I suspect that this slight voltage difference is causing current flow through the additional 0v connection (the RJ12 lead) which is what is causing the problem.
 

I suggest checking the MICC wiring very carefully, for compliance with the MICC manual’s wiring diagram. In particular check that the ONLY thing that is connected to any domestic battery negative terminals (apart from each other) is the  battery side of the shunt, and the single wire that is the shunt battery side sense wire ( to terminal 4 on the MICC). Also be sure that the domestic battery negative terminals are not connected to the engine battery negative. There is definitely a wiring error somewhere!

Edited by nicknorman
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6 minutes ago, j04n said:

When I'm out cruising and moored off grid using travel power which drives the charger as well as using the alternator to charge the batteries. 

Didn't think of that.

 

But, I still dont see why you would not want to use all sources possible to recharge as quickly as possible, when to turn off the battery charger would mean having to run the engine for much longer.

 

Anyway, you answered my question (thank you) and it is your boat to do with as you wish.

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2 minutes ago, Alan de Enfield said:

Didn't think of that.

 

But, I still dont see why you would not want to use all sources possible to recharge as quickly as possible, when to turn off the battery charger would mean having to run the engine for much longer.

 

Anyway, you answered my question (thank you) and it is your boat to do with as you wish.

If you are an actual boater, not just some floating flat dweller who grudging has to move to keep CRT off their backs, then there is no rush to charge the batteries. A nice 8 hour cruise is plenty of time. Charging batteries more quickly shortens their life.

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2 minutes ago, nicknorman said:

If you are an actual boater, not just some floating flat dweller who grudging has to move to keep CRT off their backs, then there is no rush to charge the batteries

 

Was there really any need for that comment ?

 

I have no interest in, or need to, keep C&RT 'off my back' we are 'boaters' and whilst we may not be a 12 month liveaboards, I reckon when we are aboard for 4-6 months we do more miles in a month that the majority of liveaboards do in a year.

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5 minutes ago, Alan de Enfield said:

Didn't think of that.

 

But, I still dont see why you would not want to use all sources possible to recharge as quickly as possible, when to turn off the battery charger would mean having to run the engine for much longer.

 

Anyway, you answered my question (thank you) and it is your boat to do with as you wish.

I've installed lithium cells so if going on a long cruise I won't need both. I can just switch the charger off but then I loose 240v with the way it has been wired. not the end of the world as the inverter would automatically kick in but then risk arriving at my destination with depleted batteries. Not flat as the alternator still charging. I can work around it just I like things working properly. Especially when they cost so much. I didn't buy it, it was already on the boat. 

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5 minutes ago, Alan de Enfield said:

 

Was there really any need for that comment ?

 

I have no interest in, or need to, keep C&RT 'off my back' we are 'boaters' and whilst we may not be a 12 month liveaboards, I reckon when we are aboard for 4-6 months we do more miles in a month that the majority of liveaboards do in a year.

I didn’t say I was referring to you. It was a general point. But on the other hand, if the cap fits...

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12 minutes ago, nicknorman said:

If you are an actual boater, not just some floating flat dweller who grudging has to move to keep CRT off their backs, then there is no rush to charge the batteries. A nice 8 hour cruise is plenty of time. Charging batteries more quickly shortens their life.

I've completed 450 miles since July and we've been locked down for a month in that time so I take it you weren't talking to me! 

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Just now, j04n said:

I've completed 450 miles since July and we've been locked down for a month in that time so I take it you weren't talking to me! 

No. Wow some people (well two on here) seem quick to take offence. If you actually read what I said then clearly was absolutely not applying to you. The exact opposite in fact. But maybe you enjoy being offended, it seems a popular pastime on here?

 Anyway I have gone to considerable effort to explain to you what the problem with your system is. You don’t seem interested in that issue, only the possibility that you might have been slighted. I’ll leave you to your incorrectly wired system. Enjoy.

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8 minutes ago, nicknorman said:

No. Wow some people (well two on here) seem quick to take offence. If you actually read what I said then clearly was absolutely not applying to you. The exact opposite in fact. But maybe you enjoy being offended, it seems a popular pastime on here?

 Anyway I have gone to considerable effort to explain to you what the problem with your system is. You don’t seem interested in that issue, only the possibility that you might have been slighted. I’ll leave you to your incorrectly wired system. Enjoy.

No offence taken here! I found it funny actually but forgot to put a smiley! ??

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31 minutes ago, nicknorman said:

I would say the issue is to do with the negative (0v) wiring of the MICC and or shunt. In other words, the equipment hasn’t been installed correctly.

When you connect the RJ12 lead you are creating an additional connection between the 0v of the MICC and the 0v of the Combi. These of course should be at the same voltage ( 0v) and hence it shouldn’t make any difference. But if the MICC negative supply is connected to the wrong side of the shunt or some such other error, there will be a slight voltage difference between the two negative connections when current flows. I suspect that this slight voltage difference is causing current flow through the additional 0v connection (the RJ12 lead) which is what is causing the problem.
 

I suggest checking the MICC wiring very carefully, for compliance with the MICC manual’s wiring diagram. In particular check that the ONLY thing that is connected to any domestic battery negative terminals (apart from each other) is the  battery side of the shunt, and the single wire that is the shunt battery side sense wire ( to terminal 4 on the MICC). Also be sure that the domestic battery negative terminals are not connected to the engine battery negative. There is definitely a wiring error somewhere!

I saw your last post first! ? thank you for taking the time to reply. all comments are greatly appreciated. I have checked the wiring several times and all seems good. unless there is a bad connection or split wire. I don't understand why different cables should have a different effect? 

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17 minutes ago, j04n said:

I saw your last post first! ? thank you for taking the time to reply. all comments are greatly appreciated. I have checked the wiring several times and all seems good. unless there is a bad connection or split wire. I don't understand why different cables should have a different effect? 

Well I suspect because of slightly different resistances of the 0v wire of different cables and in particular the connectors thereon. Which gives the clue as to what is wrong.

 

One problem is that you are dealing with a shunt that has a very small resistance. It is designed to drop 50 or 75 millivolts at 500 amps, ie the resistance is 0.0001 ohms. A normal multimeter can’t distinguish between a direct connection and that sort of resistance in a circuit.

 

The problem will lie in one of the various 0v or shunt wires, and there are only 4 of them. I’d depower the MICC and disconnect those wires one at a time to check for continuity, ensure connection surfaces are clean and bright. And connected to the right places as per the diagram! (Yes I know you have checked it, but confirmation bias is a powerful thing!) We are talking about the wires on MICC pins 2,3,4 and 6.

Edited by nicknorman
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2 minutes ago, nicknorman said:

Well I suspect because of slightly different resistances of the 0v wire of different cables and in particular the connectors thereon.

 

One problem is that you are dealing with a shunt that has a very small resistance. It is designed to drop 50 or 75 millivolts at 500 amps, ie the resistance is 0.0001 ohms. A normal multimeter can’t distinguish between a direct connection and that sort of resistance in a circuit.

 

The problem will lie in one of the various 0v or shunt wires, and there are only 4 of them. I’d depower the MICC and disconnect those wires one at a time to check for continuity, ensure connection surfaces are clean and bright. We are talking about the wires on MICC pins 2,3,4 and 6.

Thanks very much nick! sounds logical and worth a try before giving up on it. ?

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