Battery dc voltage reading on navicolor touch screen pannel

[tunc1965]

Hello all
I own Sun Odyssey 490.
Battery voltage reading on the “Navicolor” touch screen pannel is completely irrelevant.
I compare this value with actual measurements.

I get true readings once shorepower is connected or engine is on. However more important is to get true values once we are not connected.

Any commends?

Thanks

[Charlie-Bravo]

Hi, just a couple of comments, you don't say about the degree of error , quite often with digital gadgets the 0.01 seems important, but doesn't really matter, perhaps your readings are worse.

When you have the engine running and charging the batteries or shore power connected and no doubt a battery charger in action, there is a surplus of power available .
When sailing, instruments radar and fridge sucking away at the batteries, unless you have a huge solar array and wind turbines spinning you will be in a low power supply mode, and possibly slowly draining the batteries,  the difference between battery measuring locally at the batteries v at the navicolour display could be down to voltage drop of the cable run to the display, which will be more pronounced without the alternator or shore power to overcome it. 
Just rambling comments after a glass of wine or two, but thought to 'chip in ' as no one else has yet.

All the best
CB

[Trevor]

Hello tunc1965,

Welcome to the forum. I am not sure how the SO490 is wired but it may be different to our SO42DS.
If the cable from the batteries to the distribution panel is slightly undersized, when equipment is on and drawing current the voltage drop across the cable feeding the distribution panel may provide a low voltage reading. In other words the voltage drop across the cable feeding the distribution panel will make you think the batteries are low, particularly as you switch on more and more equipment. In fact the batteries are ok but the voltage is slightly low at the distribution panel.

The shore power battery charger and the alternator output if fed to the system "electrically near" the distribution panel the distribution panel would not see the voltage drop in the feeder cable.

In this case the voltage at your panel would indicate low voltage when on batteries but perfect voltage when on shore power or when engine is running.

I only present this as a hypothetical plausible story to your symptoms. In my experience Jeanneau yachts are not wired this way. The batteries, shore power charger and alternator output are all in close proximity to the batteries on our SO42DS.

Regards,

Trevor

[jalexand]

The main supply wire from the battery switches to the distribution panel in my 43DS was significantly undersized.  It was a number 6 wire an I ended upgrading it to a number zero wire.  I was having low voltage alarms on my VHF until I did this.


Jason
 

[NZL50505]

The Jeanneau standard panel gauge is notoriously inaccurate for everything from voltage to fuel and water tank levels!


I installed a separate monitor (BEP 600-DCSM if you want to be precise) which comes with correct wiring and most importantly a shunt matched to the unit. The result is that my BEP gauge gives me reading to within 0.05v of actual battery voltage. My marine electrician re-calibrated my Jeanneau panel voltage in an attempt to improve it but it's always drifting at least 0.2-0.3v above or below true reading so I ignore it now and just rely on the BEP monitor.

[apo]

We have a new SO410 with the touch screen panel. My question to you electrical experts is the we were down to 58% charge and then motor sailed for about two hours and the charge only went up to 72%. Is this what I should expect? We have a 125ah alternator and 440ah standard service batteries. The autohelm was in use and the fridge and instruments were on. 

[Trevor]

Hello apo,

That sounds about right to me. It depends upon the type of batteries you have ( lithium, AGM, wet lead acid, Gel), the size of the battery bank and the charging sources you have.

When your 125 amp capable alternator starts to charge your batteries, it will work hard to start with and soon the battery voltage will rise as the battery bank charges. When the battery voltage rises the charge current reduces. If you switch on a large load through an inverter you may use some of that alternator capacity, but when just charging your battery bank I would doubt the alternator would be working very hard for very long.

It is a lengthy process to take a large battery bank to 100% charge.

Lithium batteries can take higher charging current for longer.

From the numbers you have quoted I would think you have a normally working charging system.

Regards

Trevor

[apo]

Hi Trevor,
Thank you for the information, its good to know all is working okay. We are normally berthed in a marina so use the shore power to bring the batteries up to full charge.
Regards,
Chris

[Mistroma]

I'd agree with Trevor that your readings seem to be reasonable. There are lots of things to consider and might be worth mentioning a few things on the off chance you don't know about them.

1) 125A alternator won't be putting in 125A
Trevor has covered this one. A lot depends on the regulator but there's a good chance that your system will only put about 30-40A into the batteries initially in most situations. You can add on more for fridge, lights, instruments etc. and the alternator will increase output but only about 30-40A will actually go into the batteries to recharge.

The batteries will accept a higher charge as they become more discharged and it will taper off as they charge. The standard regulators usually taper off very quickly around 80-85% upwards. You may find that it takes many hours to get to 100% charge (poss. 8-10 hours). My own alternator output tends to drop from 40A after only 30-40 minutes and rapidly gets to 7-8A into the batteries. I keep meaning to upgrade the regulator but I have 300W solar and it isn't a big issue.

The alternator probably isn't hot rated for 125A anyway and would burn out if it was ever asked to supply 125A for a significant length of time.

2) Accuracy of state of charge indicator
I'm assuming that your meter is just a Coulomb counter with all the problems that brings. It keeps track of Amps in and out in an attempt to estimate battery state. Unfortunately, it isn't that simple. Charging efficiency changes with state of charge, battery age, chemistry, temperature, etc. It can't just say that you used 50Ah and then put 50Ah back to get back to 100%.

Hopefully your meter has been set to correct battery type, capacity when new and so on. It is probably able to guess when full charge has been reached and reset to 100% every so often in order to maintain accuracy. Errors will still remain e.g. Capacity will drop over time and also in cold weather.

3) Isolation switches
I tend to leave mine on all summer as I live on the boat. I've found that the panel gives lower and lower readings over time. I quick flip on/off for each main isolator seems to clean them up a bit and readings return to normal for several weeks. I do this vigorously a few times each summer.

Don't assume that your meter is giving a very accurate state of charge. It is just a useful guide.