Voltmeter for monitoring shore power - advice please

oldmanofthehills said:
Low voltage wont damage the charger, anymore than running out of fuel would damage an engine. How could it?

It simply wont work below a certain threshold and modern switching one have lower threshold than older types. I thought that had already be addressed
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Now then, thats the thing, how could it.

Back in the good old (bad old) days of transformers and shunt regulators, then no, it couldnt. However electronics, particularly power supplies of the 21st century are a different beast all together.
Enter the switched mode power supply. The hint is in the word "power". They will do their damnedest to supply the required power regardless of input voltage. We can skip all the mark-space ratio calculations and go straight to P = IV. Since P is (attempted constant) then if V drops, I increases. So, as the supply effectively browns out the current drawn will increase. IF (big if) there is insufficient input protection damage will occur.
 
Lon nan Gruagach said:
Now then, thats the thing, how could it.

Back in the good old (bad old) days of transformers and shunt regulators, then no, it couldnt. However electronics, particularly power supplies of the 21st century are a different beast all together.
Enter the switched mode power supply. The hint is in the word "power". They will do their damnedest to supply the required power regardless of input voltage. We can skip all the mark-space ratio calculations and go straight to P = IV. Since P is (attempted constant) then if V drops, I increases. So, as the supply effectively browns out the current drawn will increase. IF (big if) there is insufficient input protection damage will occur.
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I may stand corrected. But the 230v input can only give about 15A or its circuit protector shoreside will pop. And I would expect up to about 13A charging current at 12v. So is this damage a realistic scenario for a properly designed charger and if it was how is the OP meant to protect his/her charger without continual monitoring of input voltage. Auto-monitoring and alarms (local and via phone), which we specify in large power installations, will cost more than a new charger
 
oldmanofthehills said:
I may stand corrected. But the 230v input can only give about 15A or its circuit protector shoreside will pop. And I would expect up to about 13A charging current at 12v. So is this damage a realistic scenario for a properly designed charger and if it was how is the OP meant to protect his/her charger without continual monitoring of input voltage. Auto-monitoring and alarms (local and via phone), which we specify in large power installations, will cost more than a new charger
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What ?
 
My NASA BM1 tells me the voltage and amps that are going into the battery.

Usually starts at about 15 volts and 14 amps then drops down to 13.8v and 4 amps then 13.8v and 0.5 amp.
 
oldmanofthehills said:
My old style charger has 20A blade fuse and I think said 13A max output on old label. Doesn't draw more than 3 or 5A normally. Were you expecting more or less than that?

I haven't got spec to hand for newer charger in the LM
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Wouldn't expect a 13a current draw from the typical boat charger, mine is a max of 4.5a.If it was 13a i wouldn't be able to boil a the kettle without tripping the MCB. :ambivalence:
 
The confusion here seems to be the current flowing in the output side and that coming into the charger. Yep, 13A on the output at 12V is realistic enough but on the mains input side (circa 230V) this will translate to less than an amp. Apart from slight circuit losses in the power supply the power will be similar. In the good old days of transformer chargers it was simply down to the turns ratio of the windings, the same principle applies with switched mode.
 
Rich T said:
The confusion here seems to be the current flowing in the output side and that coming into the charger. Yep, 13A on the output at 12V is realistic enough but on the mains input side (circa 230V) this will translate to less than an amp. Apart from slight circuit losses in the power supply the power will be similar. In the good old days of transformer chargers it was simply down to the turns ratio of the windings, the same principle applies with switched mode.
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Only if the batteries are fully charged and there's next to no DC output. A 30a charger at full power will use anything up to 4/5a
 
pvb said:
I think oldman is confusing AC current and DC current.
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No confusion, but I may not express myself well when idly posting in tea breaks (doughnut break today as recent Bday). I stated 13A max output from charger, thus 12V DC. I expect its max 230V AC input to be 1/20th of that plus an allowance for inefficiency, phase shift etc.

Incidentally switched mode power supplies are handy in our electronics and cope with a wide range of input votages. And we don't seem to destroy them on our sometimes dodgy 1950era feeders which do sometimes brown out under load
 
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Lon nan Gruagach said:
900 Watts in for 450 Watts out? Only on The Ark!
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Does look high, but that's what Sterling quote for my charger. But that's a max figure and no doubt makes allowances for the charger running flat out and the fans flat out keeping it cool. I know some other manufacturers quote lower figures.
 
I finally had a reply from Mastervolt which says:

If the input voltage drops below 230 - 10% (207VAC) the Charger will not be capable to deliver his Full charge current.
Under 180VAC the charger will give no output current. The Charger will not be damaged.


So although other versions of my yacht do have a voltmeter, maybe I am worrying unduly that I do not have one

Thanks

TudorSailor
 
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