State of Charge

[zboss]

Just about 3 days ago I installed a balmar smart gauge alongside my mastervolt. So far, I feel like I'm getting much better data from the balmar. It says in the instructions that it takes 4 days to sync properly but what I am seeing from this gauge makes much more sense than what I'm seeing from the mastervolt.

Basically, the mastervolt is showing me being full when I reach float voltage (13.2) rather than absorption target voltage (14.8). So it's saying I'm at 99% full while the smart gauge was showing low 80's. It took almost all day with my solar and wind to get up to 98% charge on the smart gauge.

The mastervolt is also way off on voltage readings. When charging the mastervolt and smart gauge show very close voltages but when drawing down, the mastervolt reads a much lower voltage... About .2 volts. So my volt meter and my smart gauge read the same but my $700 mastervolt shunt is way off.

Incidentally, when I asked my mastervolt dealer about the discrepancy he had nothing to say and the line has suddenly gone dead. Since I'm still within my 1 year warranty I think I'm going to challenge the install on my credit card. I tried to get him to test it many moons ago but he claimed I needed to drive the boat back to Maryland from the Carolina's. I bet I get a referral to a local mastervolt dealer real quick. Mastervolt has only ever responded to one generic email I sent in regards to how they define a charge cycle, so I'm generally displeased with their customer service as well.


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[sailinglegend]

Originally Posted by zboss

Just about 3 days ago I installed a balmar smart gauge alongside my mastervolt. So far, I feel like I'm getting much better data from the balmar. It says in the instructions that it takes 4 days to sync properly.....

The manual says 2-3 charge cycles to sync, not 4 days! The longer you use it and take it from 100-50% SoC the more accurate it will become.

Anyone who has the 10 year old original SmartGauge should download the new Balmar Manual which is much more helpful.

Don't be too hard on Mastervolt as ALL shunt based BMs can become inaccurate as the batteries age. I suspect your 0.2v drop on load compared to fully charged is an installation problem. The voltage sense wires MUST go to the positive stud of the battery and the load side of the shunt. Saving cables and installation time by wiring these positive and negative wires to master switches or to the engine block negative will cause a voltage drop.

[zboss]

I'm pretty sure the installation was done very well, the marine installer engineer did a spectacular job at the wiring. The shunt is connected properly.

The issue is the voltage reading not the amp reading. I can see no reason why the voltage reading would be so far off. Voltage readings should not wander over time... The voltage is the voltage.

What is perplexing is that my wind generator regulator, which has a voltmeter on it also, shows the correct voltage. So, it's only the master volt meter in between that shows the incorrect voltage. This says to me a bad circuit board or bad software.


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[Ex-Calif]

Glad to hear about the SmartGauge. Mine is in transit as we speak...

[Terra Nova]

It's more than likely a bad (ground) connection.

[zboss]

Originally Posted by Terra Nova

It's more than likely a bad (ground) connection.

But there is only two wires in an two wires out. If it was a grounding fault at the master shunt, a) I would get a warning, b) anything after that shunt would show a similar drop in voltage. This is not what happens. A voltmeter placed both before and after the shunt read higher voltages than the shunt.


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[Jim Cate]

ZB, perhaps I am misreading your post, but the shunt itself is not involved in the measurement of the system voltage. Its sole purpose is to measure the current flowing through it. The shunt is nothing but a very low ohm resistor in series with the main buss. You measure the current by measuring the voltage drop across this resistance. If you were to measure the voltage above ground (or below line voltage if the shunt is in the negative lead) on both sides of the shunt, the difference is a few millivolts or so, depending on the current.

I agree that it sounds like the voltmeter in your monitor is out of calibration. A poor connection in that circuit will not make much of a reading difference because the current drawn by the voltmeter is extremely low. Thus the voltage dropped in a poor connection is tiny and will not make a big difference in the reading.

Out of calibration instruments really bug me... I sympathize with your frustration.

Jim

[Ex-Calif]

Originally Posted by zboss

But there is only two wires in an two wires out. If it was a grounding fault at the master shunt, a) I would get a warning, b) anything after that shunt would show a similar drop in voltage. This is not what happens. A voltmeter placed both before and after the shunt read higher voltages than the shunt.


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I have scrolled up and down this thread but can't find the model number of your mastervolt BM.

Care to share?

<edit> what is getting me is your statement about only 4 wires. The BTMIII for example can have up to 7. The shunt (amp measuring) is separate from the voltage sensing - it requires 2 wires. The voltage sensing requires 1 wire per bank (up to 3). Then you need power and ground for the unit (2 wires)

The shunt will have only 4 connections. But that is not where voltage is being measured.

http://images.mastervolt.nl/files/Qu...II061113EN.pdf

[Stu Jackson]

Originally Posted by ontherocks83

Can you elaborate on this a little? I can understand the 14.4v and 1.5% being full but after it hits that it eventually goes to float voltage. Why is float not considered full? I'm sure I'm missing something obvious I just don't know what it is.

Glad you Got It from MS's explanation.

Another way to say it is:

FLOAT IS NOT FULL

The only way to determine a full bank is when the voltage is ___ and the acceptance is less than ________ % of C.

[sailinglegend]

Originally Posted by Stu Jackson

FLOAT IS NOT FULL....

I think it's always easy to explain that unless a charger is actually measuring the current going into the battery AND it knows the size of the bank then it can't know when it's full! Hence chargers are designed to 'charge' your battery and not 'overcharge' it, so almost all if them will switch to Float before the battery is full.

[zboss]

It's a mastershunt 500.

http://www.mastervolt.com/marine/pro...h-system-fuse/


When I'm referring to the shunt I mean the unit as a whole not the shunt component. In this particular design they are one and the same.

The mastervolt "shunt" reads the voltages and current and sends the data to the remote display over master connect.


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