Can someone with battery charging knowledge please shed some advice on this conundrum

[Oscarpop]

In a nutshell, I am questioning the accuracy of the readout on my victron energy bmv 600 battery monitor. I have read the manual, and there are a million user definable parameters. I so far have only changed the size of the battery bank, as it says the rest should normally be left alone.

So my setup:

300ah of domestic battery 100ah of engine battery. The bmv monitor only monitors domestic .

Mastervolt masscombi 1200 inverter charger.

The user definable parameters I am questioning are the

Charged voltage which is set to 13.1v

And the tail current which is set at 4%

I will attach a screenshot of what the manual says these things do.

Can anyone suggest whether I should change
These parameters, and if so to what?

The reason I am Questioning this is that we have an analogue gauge on the boat that is on the control panel. No visible shunt , however it always reads way below the bmv monitor which does have a shunt. I always figured the analogue gauge was rubbish.

Anyway This morning after three days with no shore power , the battery monitor showed our capacity was down to 80%

However a couple of blips of the bow thruster coming off our mooring and all the nav equipment turned itself off. More revs. Bought it back to life. So low voltage ., which was in line with the analogue reading .

I figure that 80% charge should not allow a couple of seconds of bow thruster without depleting thhe batteries. So I question whether I have the monitor set up correct.y.

All help gratefully received. Similarly please ask if you want more info .

 

[NormanS]

I'm no expert, but it doesn't surprise me that brief bursts of power to the bow-thruster results in brief low voltage. Maybe better if bow-thruster is supplied from a dedicated battery.

 

[ex-Gladys]

Are they flooded lead acid batteries or AGM/Gel? How old?

 

[Oscarpop]

Are they flooded lead acid batteries or AGM/Gel? How old?

They are numax sealed lead acid. 3 years old.
Never fully discharged, and the little battery indicators on the battery are still green.

I've also attached another screenshot which show the voltages that the battery charger sets for bulk and float. This is taken from the mastervolt battery monitor.

Can someone please tell me if I have my voltages set correctly! By comparing the 2 values : tail voltage and charge voltage from my first screenshot which is what I need to define on my battery monitor, with the values from this screenshot.

 

[halcyon]

What does it take 13.1v , on charge voltage, or a off charge no load state ? if it's a charge voltage level, then at 13.1v it will be assuming a near flat battery is 100% charged and all readings will be high.

Brian

 

[seaangler23]

Can you get a multi meter onto the batteries once the charger is at 100% that will give you somewhere to start

 

[Oscarpop]

What does it take 13.1v , on charge voltage, or a off charge no load state ? if it's a charge voltage level, then at 13.1v it will be assuming a near flat battery is 100% charged and all readings will be high.

?

Brian

Sorry to sound dumb, but can you explain that sentence? How do I work out what the charge voltage parameter should be?
charge the batteries completely with shore power, remove all the load and see what the voltage is? Then use that as the charge voltage parameter?

 

[pvb]

Sorry to sound dumb, but can you explain that sentence? How do I work out what the charge voltage parameter should be?
charge the batteries completely with shore power, remove all the load and see what the voltage is? Then use that as the charge voltage parameter?

Your battery monitor requires 2 conditions to be satisfied simultaneously before it will consider the battery bank to be fully charged and reset its capacity reading to 100%. Firstly, the voltage has to be above a certain level for at least 3 minutes, and secondly, the charge current has to below a certain level for at least 3 minutes. The default voltage setting is 13.2v; the default current setting is 4% of the battery bank capacity (ie 4% of 300 = 12A).

It would seem that the monitor was incorrect in showing 80% capacity. The capacity reading can become incorrect if the battery bank is never recharged so that it meets the conditions for automatic reset to 100%. The solution is to charge the battery bank until the reset conditions are met.

However, the image you posted of your battery charger's output is indistinct. If your battery charger has a float voltage below the "charged voltage" setting, the monitor will never reset automatically. Can you tell us which model your charger is? The BMV600 manual tells you to set the "charged voltage" parameter to 0.2-0.3v below the float voltage.

My last boat had a Xantrex battery monitor which worked in a similar way, and Xantrex recommended using 2% as the "tail current" parameter, rather than the 4% default setting of the BMV600. If you have continuing problems, it could be worth resetting your monitor to use 2% as the tail current.

 

[pvb]

I now see from an earlier post of yours that you have a Mastervolt Mass Combi charger which has a float voltage of 13.25 - so I'd suggest you set the BMV600's "charged voltage" parameter to 13.0v.

 

[Oscarpop]

I now see from an earlier post of yours that you have a Mastervolt Mass Combi charger which has a float voltage of 13.25 - so I'd suggest you set the BMV600's "charged voltage" parameter to 13.0v.

Thanks Peter .
Will try that. Virtual beer on its way :very_drunk::very_drunk:

 

[Richard10002]

I now see from an earlier post of yours that you have a Mastervolt Mass Combi charger which has a float voltage of 13.25 - so I'd suggest you set the BMV600's "charged voltage" parameter to 13.0v.

And the tail current to 2%.

Chances are the banks capacity is nowhere near its original capacity. I would probably set capacity at 200Ah, and see how things look.

 

[pvb]

Just another thought - isn't the Mass Combi a 230v only device? Do you have an alternative charger which will run on 110v?

 

[Oscarpop]

Just another thought - isn't the Mass Combi a 230v only device? Do you have an alternative charger which will run on 110v?

No, just the mass combo. Although there is no wind today, so we're motoring down the coast of feurteventura. That should charge the batteries

 

[Oscarpop]

And the tail current to 2%.

Chances are the banks capacity is nowhere near its original capacity. I would probably set capacity at 200Ah, and see how things look.

Would I really lose 33% of my capacity in 3 years?
The batteries have never been fully discharged , always topped up with wind, solar and shore power.

 

[pvb]

No, just the mass combo. Although there is no wind today, so we're motoring down the coast of feurteventura. That should charge the batteries

I was thinking of shore power voltage when you reach the colonies!

 

[Oscarpop]

I was thinking of shore power voltage when you reach the colonies!

Oh I see.
No we don't have a 110v unit. Was going to procure one of those step up transformer units that you see in yellow or blue cases . Don't have the space or the pockets for a dedicated marine unit.
Plus I figure that until we get to the states, we will be mostly at anchor.

 

[FullCircle]

You would be astounded how much loading on the batteries the windlass is. Ours is around 80a - which will seriously lower the voltage instantly if you havent got the engine running. I have a switch for emergency use only to use the windlass if I CANT start the engine, but it is one use only.
The battery voltage would recover after use, but it is no surprise if your plotter/autopilot shut down.

 

[Oscarpop]

So I have now changed the parameters to 2% and 13v.

The battery monitor is saying the batteries are charged.
However the shore power is still putting charge into the batteries.

Again , I feel as if unit still is t set up properly.

How's this for a solution: wait until the shore power stops charging. Unplug it. Cut all he power in the boat, so that there is no draw and see what charge the battery holds, then reduce it by 0.2v . Or have I got this arse ended ( again)

 

[pvb]

So I have now changed the parameters to 2% and 13v.

The battery monitor is saying the batteries are charged.
However the shore power is still putting charge into the batteries.

Again , I feel as if unit still is t set up properly.

How's this for a solution: wait until the shore power stops charging. Unplug it. Cut all he power in the boat, so that there is no draw and see what charge the battery holds, then reduce it by 0.2v . Or have I got this arse ended ( again)

How much current is still going into the batteries? If it's only a few amps, you could manually reset the state-of-charge, then turn off the charger and see whether the state-of-charge reading drops in line with your expectations as you use battery power.

The monitor's historical menu could be useful, too. Perhaps you should note the number of times it's automatically synced, together with the number of days since last full charge. Seeing if these change in the days ahead will help you to check what's happening.

Your proposed solution won't work.

 

[Plevier]

They are numax sealed lead acid. 3 years old.
Never fully discharged, and the little battery indicators on the battery are still green.

I've also attached another screenshot which show the voltages that the battery charger sets for bulk and float. This is taken from the mastervolt battery monitor.

Can someone please tell me if I have my voltages set correctly! By comparing the 2 values : tail voltage and charge voltage from my first screenshot which is what I need to define on my battery monitor, View attachment 54263 with the values from this screenshot.

I don't know enough about monitors to comment on that side, but regarding the batteries:

1 Those are not sealed lead acid. They are "sealed maintenance free" flooded batteries. No SLA/AGM/VRLA has the little green window indicator.
This means in any charger settings you need to treat it as ordinary wet lead acid.

2 Whether you have their leisure series or truck batteries (the only real difference between them is almost certainly the separators), 300Ah capacity of them in decent condition should supply 100A (say) for a bow thruster for a lot more than "a couple of blips" with very little voltage drop at the battery terminals.

3 Numax are OK for what they are, but they are not deep cycle traction batteries. If they have had 3 years use with regular cycling of any significant depth their capacity could be well down. Your monitor can't tell this; if it sees the defined voltage and current conditions, it assumes you have full capacity there (as I understand it).