Battery Monitor vs Voltage

[CarlF]

I have a Victron monitor (which I like a lot as with all my Victron equipment) but the voltage consistently reads .04V low. The 2nd bank reading is correct and agrees with the multimeter. It took me a while to figure this out. I'm sure Victron would have exchanged it but it was simpler to mentally correct once I understood what was happening.

Carl

[Cheechako]

Originally Posted by John Duckworth

I have just moved aboard my cat and cannot get to grips with my batteries!

I have 4 large batteries (each +/- 150 AH).

I have Solar Charging, a generator, an inverter and 2 engines and all can ( I think) put power into the batteries.

However I have nothing that tells me what is in the batteries, and after running the generator/engines/solar, the batteries still shut off during the night with low voltage.

I am running a fridge and freezer (12V) off them but little else.

My question is.... will a battery monitor tell me what each power source is putting into the batteries? Will it then tell me how "full" they are? Will the battery monitor also tell me how much power (in amps) I am drawing from the batteries? If so, can anyone recommend a particular make and model? (I am on a VERY tight budget at the moment!)

I am reasonably competant with electrics, but is such a monitor easy to install?

Thanks
John

If I were you I would have a way to switch each charging device to the batteries. That way I would know what is charging, how well it's doing and the other stuff is isolated. This could be as simple as a robust battery on/off switch for each cable coming to the battery bank. That may be just me, but I like things with simple logic. You might have one of your charging sources draining the batteries. Then you need one monitor, anything from a basic voltmeter to a fancy battery monitor, so you can read the charging rate and other stuff if you desire. BTW: a fridge may very well deplete 4 batteries overnight, depends on your fridge, insulation and battery condition. In the process of putting these switches in you will learn your system.

[Cruisin Cat]

John,

A multimeter with clamp-on current measurement (which you can buy from around $100 up) is a really good investment to help you figure out which generating devices are in fact generating and how much, also where the current exiting your battery bank is going to. Very easy to use...just clip it over the cables coming from your generating devices and cable comngoff your battery bank/bus, then do a bit of maths to do a rough power (Amps not Ahrs) balance.

This will tell you if your generating devices are not working like you expect, or if something on your boat is consuming more current than you think or your 600Ahr battery bank has in fact lost a lot of capacity and is now only 200Ahrs for example.

[goboatingnow]

Originally Posted by Stu Jackson

Dave,

Not really. If one uses the "I'm Full!!!" output of a monitor, but hasn't correctly set the parameters, one could prematurely turn off the charger. Manually. That's covered in the Gotcha link.

And many, many folks still have Link monitors controlling Freedom inverter/chargers.

Perhaps the most important thing is to recognize that, like all electronic things, there are DEFAULT parameters that need to be set by the user to relfect THEIR PARTICULAR INSTALLATION in order for the monitor to work properly. It's usually easy for new monitor owners to figure out that your battery bank may not be the default 200 ah, and make that change. Most owners stop there.

It's not much different than setting up a new computer. Most all have DEFAULTS that are modified by owners, like the time it takes for the monitor to go into sleep mode, etc.

But, unless you DO THE MATH and recognize that if you have a fridge (5 amps) and a 400 ah house bank (2% is 8 amps) when the fridge kicks in near the end of the absorption your monitor could prematurely declare "full".

That's all that the Gotcha post was intended to present, as was well summarized by Cruisin Cat earlier in this thread:

The current threshold to recognize 100% SOC is set too low. In your case using the factory preset 4% will result in the monitor assuming 100% SOC when that is not yet reached. I suggest you go into the Setup menu and reduce the setup parameter called "It" to 0.5% or at least to 1%.

Other setup parameters that effect detection of 100% SOC are:
"Vc" - factory preset is 13.2V (on my Victron) which is way too low. I suggest you set to 14V - 14.2V (I don't remember what type of batteries you have but this setting should work for most types)

Stu

Stu. If you have a standard smart charger which is not controlled by your battery monitor. Then it matters not.

Your comments re fridge etc are not always true. Many chargers can feed external sources while staying in absorption mode. I'm not arguing that I Your case 13.2 is too low to determine " full". Anyway the determination of " full" by most battery monitors is haphazard never simply shut down a charging source based on a battery monitor. If you have a " float" mode use it. No charger should use AmpHr counting to determing charging status.

Dave

[kiltym]

Originally Posted by Stu Jackson

How did your test work out?

Here is what I have found and observed after making some changes to the link 1000 and Freedom 15 charger.

First, I changed the charge parameters to 1% threshold and a minimum voltage of 14.2.

I personally felt that still allowing the link to realize its full based on amps going in was still valuable, but agreed that the 13.2 default value is way too low. But setting it at 15 basically removes it entirely from the calculation, which didn't seem to necessarily be correct either.

We drained our batteries down to about 11.5V, way lower then we would even normally do, but since they are new (3 months old), and have never been cycled yet, figured I would do this based on recommendations to "break-in" the batteries a bit. This equated to about 500aH being drained off the the 660aH bank (assuming the link was calibrated correctly with the batteries).

We then charged the batteries. We are in the Caribbean, and have a temp sensor also connected from the Freedom to the battery bank. However, what I noticed, was that because of this, and with the batteries heating up, the Freedom started to regulate the voltage down to about 13.7 or so. I didnt feel this was high enough. Ambient temp is about 80-85 right now. So, I disabled the temp sensor, manually set the temp to 80 on the Link 1000, and monitored the battery temp by feel to make sure things didnt get too hot. The voltage then went back up to about 14.3-14.4 to do the bulk charge. That seemed ok to me.

This took a long time. It eventually got into absorption mode, and then eventually I saw it go into float mode. However, I knew 2 things, the aH count was well over the 0, more like about 175, and the charged params also had not been met as the last time I checked it was still putting in about 24 amps into the bank. Not sure why this happened, maybe some sort of timer override is the only thing I could think of. So, I reset the charger, and it then went to absorption phase and started again to put in the 23 amps. This continued for a number of hours. The amps did decrease, but VERY slowly. Probably not even a 1amp decrease in an hour.

The other thing was I had never equalized the 6 batteries when we received them as we live at anchor and have no charge source to do this with. So I decided to cut short the charge a bit, and equalize the batteries for about 6 hours. I did turn the temp sensor back on for this step, and let it run for the 6 hours. This also reset the aH count to 0 once a negative load was sensed on the Link 1000.

Next day, put a load of 20amp-60amp on for about 8 hours. Drained about 300aH out of the battery bank.

Started the charge cycle again.

This time everything proceeded as I would expect, and the amps eventually dropped down to < 1% at the 14.35 volts, and the charger went into float mode.

I have since drained 1 aH from the bank, and turned the charger back on to see the behavior.

What I have found is the the aH counter will go > 0. So, i do not think that the Link will go to float mode based on the aH counter going to 0 as mentioned. But, the aH will go down to 5-6amps to keep the battery at 14.2-14.25, which will trigger the link to go to float.

So, my conclusions are that yes indeed the parameters need to be changed for the link to record and track accurately, but I dont think that setting the voltage to 15, and disabling this feature, is necessarily a good idea as I dont know what will cause the link to reset to float mode. But, changing the paramters to 1% and 14.2 as also suggested on this thread, seems like a very useful change.


Thanks everyone for their input and suggestions!

[John Duckworth]

I would like to thank DotDun, PBlaid, Cruising Cat, Stu Jackson, Carl F and CheeChallo for responding to my post about Battery Monitors. I have been in the Tobago Cays (and it is so very beautiful!) but without internet for the last 10 days so have been unable to reply.
Thank you all for the info, and as suggested, the Victron Battery Monitor would seem to do the job. I will hope to get it in Grenada and meanwhile will investigate all connections for possible loss of charge etc.
Many thanks for your help
John

[markpierce]

I found the gauge second from the left to be handy for monitoring battery status and current draw: