marcot
Well-Known Member
The analog voltmeter - Vdo - displays 30v when charging from shore the 24v battery bank while the digital - mastervolt reads 28,8v. Never done before. Could it be a problem?
Digital and analog voltmeter
- Thread starter marcot
- Start date
Rigger Mortice
N/A
Are you asking about the difference between the two readings or the relatively high voltage of both of them?
The answer is yes, to both questions.
VicS
Well-Known Member
?????? ......... 24 volt battery! ..... RTFQ ( F=full)
Marcot, check what the reading really is with a known good meter. Or perhaps more to the point check the two readings .
We don't know the circuit so dont know how they are wired relative to each and therefore don't know if a little resistance could be causing the difference
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kolster
Well-Known Member
If the 28.8V was measured across the terminals when the battery was being charged I would have thought that was correct, normal charging voltage for a 12V battery would be around 14.4 so the latter figure doubled would be 28.8
Rigger Mortice
N/A
Correct, perhaps I wasn't being clear.
As I read it one, or both, of the readings has gone up unexpectedly and, without knowing what the usual readings are I was saying in answer to the question that either could be a problem. As you say, more reliable readings are needed.
lw395
Well-Known Member
It is possible that your charger is not sending out pure DC, the two meters respond differently to the ripple voltage?
Or they are wired in different points of the circuit and you have a voltage drop that has increased?
If you are charging at say 20A, that one volt drop is 20W, which is enough to cause damage if it's at a point like a connector.
So I would borrow another multimeter and investigate.
Maybe worth setting a multimeter to AC Volts, to get an indication of the ripple voltage. If this is a lot more than it used to be, it's a sign the batteries are getting old as their impedance is rising.
Or your charger s more ripply as an output filter is failing.....
lukedh
Well-Known Member
The internal resistance of the analogue metre is much lower (10x lower) than the resistance of a digital metre typically 20MΩ. The metre resistances is in parallel with the circuit, the high resistance of the digital metre will take less current from the circuit being measured, the two metres will give different readings. The digital one will be more accurate.
Which doesn’t tell you if there is a problem with the charging, though it looks like kolster may be right. You could ask Mastervolt they should know.
Which doesn’t tell you if there is a problem with the charging, though it looks like kolster may be right. You could ask Mastervolt they should know.
VicS
Well-Known Member
But if both are connected at the same time to the same point in the circuit they should read the same.
halcyon
Well-Known Member
Most charge sources ( except solar ) are a pulse.
The digital meter will normally follow the pulses closer so you see a mean voltage, the analog meter will not be quick enough to follow the pulse so shows near to peak voltage.
Brian
Rigger Mortice
N/A
TBH, until OP clarifies just what it is that his setup has "never done before" we are pi$$ing in the wind .