Battery Monitor vs Voltage

[Stu Jackson]

Originally Posted by kiltym

I know this. But, something has to trigger the Freedom to go into Float mode. What is this trigger?

And I am happy to keep the acceptance phase going longer as I agree this makes sense, but I want to understand what is eventually going to make the charger go into float mode and reduce the voltage so I don't boil off all my liquid.

You stated before its when aH is 0. In the Freedom manual it states its on a 1hour timer, but, this timer is not valid if the charger is attached to a Link battery monitor. But, it doesn't then say what the "trigger" is..... Just says read the Link manual, but there is nothing in there..... I do RTFM all day long, and then come here .

Yeah, I just checked the Link 2000 manual I have and it sure isn't clear. That's why I wrote the Gotcha to begin with.

That topic states: "I have changed these parameters on our Link and the results have been fantastic and exactly as Rich described. Before, our Freedom 15 Inverter/charger combo, after a daysail, would go from bulk to absorption to float within ten minutes of being plugged in. After the change to the parameters, the charger stays on absorption for a much longer time. ... Since our Link controls the charger, it is necessary for our use."

I tried it, it works. I know you're gonna try it yourself.

You have to read between the lines in the Link manual, pages 20 & 21 or 21 & 22, about the charged parameters.

That's why while the manuals may have "stuff" in them, I agree with you! That's why we have these forums!

Happy electrons!

Stu

[Stu Jackson]

How did your test work out?

[senormechanico]

Originally Posted by St. Elsewhere

If the battery was still taking 8 amps the battery was not fully charged.

My first time reading this thread and my first thought also.
I have a similar battery bank (4 6V golf carts), and my E-meter says I'm charged 100% when the battery is accepting about 2 amps at 14.2V from the solar. This is about .5% of total capacity.
The BlueSky MPPT controller keeps my 11 year old bank very happy.

[senormechanico]

Originally Posted by defjef

Bill,

Check the voltage at the terminal? What is the difference between a multi meter and a link meter which is connected to the terminals?

Granted the link reports to hundredths. But how important would thousandths be?

Is there much loss in the wiring to the link via the harness?

Is the contact of touching a meter probe as good a connection of a screwed down crimped on fitting... the later seems to have more contact.

With a modern digital meter's input resistance being 11 Megohms, I doubt the contact resistance of the meter probes would be any factor.
Same goes for the link leads. The sampling current is negligable, neglageible, negligalible, NOT ENOUGH TO WORRY ABOUT !
(lack of sailing makes your spelling go bad)

[kiltym]

Originally Posted by Stu Jackson

How did your test work out?

No time to test yet. Need to get somewhere with shore power as we live on our boat full time at anchor. Will be heading to a marina hopefully to test things out, and break in the new batteries.

Once I have something to report, I will add it to this thread.

Thanks!

[goboatingnow]

Note this issue is specific to battery monitors that control chargers. However this is a rare situation now. Very few do

Dave

[Cruisin Cat]

The comments by Senormechanico on contact resistance are correct (even though he is Senormechanico and not Senorelectico!).

Contact resistance for any voltage measurement using a modern digital multimeter or modern battery monitor are totally negligible, ie will not effect the accuracy of the reading.

Contact resistance will effect the accuracy of the reading if you are:
1. Measuring resistance of a low impedance device, eg using the ohm range on a multimeter to measure a resistance less than a few ohms...contact resistance between the probe and the device can be as high as a couple of ohms in an extreme case.
2. Measuring current going to a low impedance load if you open the circuit and put the mutimeter into the circuit (as opposed to using a clamp-on meter)

[Cheechako]

Anyone trying to use a monitor to determine amp hours remaining is going to need to adjust for what the real AH of your bank is. Or let the monitor do it. If you think each battery rated at , say, 230 AH is actually capable of exactly that.... you're dreaming. Even small electronic componants are normally rated at + or - 5%. Some are 20% and for more money you can get them closer. The manufacturing process for batteries is crude and not controlled the way these componants are. I suppose it all comes down to the accuracy of the surface area, and of the purity, of the lead melted to each cell plate. Your monitor tells you what it thinks is going on, so does your tachometer on your engine, but if you've ever had it calibrated it can be off by a couple of hundred rpm! If you buy a digital tach it will just continue to show the inaccuracy to a non-sensical 3 decimal points! The bottom line is , once you get experience with what your daily usage is, either by reading resting state voltage or a fancy meter.. you need to charge a given amount daily!

[Stu Jackson]

Originally Posted by goboatingnow

Note this issue is specific to battery monitors that control chargers. However this is a rare situation now. Very few do

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

[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

[DotDun]

Originally Posted by John Duckworth

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!)

Yes, Yes, Yes.

http://www.victronenergy.com/upload/...%20PT%20SE.pdf

http://www.victronenergy.com/upload/...05-07-2007.pdf

[Pblais]

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?

Short answer is yes, yes, yes. It's exactly what they do and not very complicated to install.

The monitor will only see what goes in and out so it will tell you a load in and a load out then integrate the loads over time to compute volume in the bank (amp hours added minus amp hours used). It's an indirect way to get the answer you really want.

You need something that can handle multiple charging sources and regulate them. Regulation for 3 engines and a solar bank unfortunately is not a "tight budget" item. It needs to see all four and then regulate the net amps of what goes into the bank. The charging profile of the batteries will determine the rate amps can be added back into the bank while the number of devices powered on will determine the load going out. Keeping the batteries above 50% and on a regular basis getting them back to 100% is the name of the game for saving money on batteries.

You have a lot of tradeoffs to make.

Getting rid of the inverter would save the most money. You now own a nice relatively big budget setup. Without a really solid regulation system you will trash batteries quickly. They of course are not cheap. You are in too deep to be on a budget now.

At this point I don't have a specific model of regulator to suggest. You need to spend the money for the best one made or put the inverter and generator aside for the time being. You don't mention what you are going to use AC electricty for. Just know that a 10 amp AC device is going to drain your entire battery bank to 50% capacity in 3 hours with no charging sources. You don't state anything that requires such a large bank or charging system. Matching the size and the load you need is really the cheapest route.

[DotDun]

Originally Posted by Pblais

Short answer is yes, yes, yes. It's exactly what they do and not very complicated to install.

The monitor will only see what goes in and out so it will tell you a load in and a load out then integrate the loads over time to compute volume in the bank (amp hours added minus amp hours used). It's an indirect way to get the answer you really want.

You need something that can handle multiple charging sources and regulate them. Regulation for 3 engines and a solar bank unfortunately is not a "tight budget" item. It needs to see all four and then regulate the net amps of what goes into the bank. The charging profile of the batteries will determine the rate amps can be added back into the bank while the number of devices powered on will determine the load going out. Keeping the batteries above 50% and on a regular basis getting them back to 100% is the name of the game for saving money on batteries.

You have a lot of tradeoffs to make.

Getting rid of the inverter would save the most money. You now own a nice relatively big budget setup. Without a really solid regulation system you will trash batteries quickly. They of course are not cheap. You are in too deep to be on a budget now.

At this point I don't have a specific model of regulator to suggest. You need to spend the money for the best one made or put the inverter and generator aside for the time being. You don't mention what you are going to use AC electricty for. Just know that a 10 amp AC device is going to drain your entire battery bank to 50% capacity in 3 hours with no charging sources. You don't state anything that requires such a large bank or charging system. Matching the size and the load you need is really the cheapest route.

Huh?

Multiple charging sources without a single control won't 'trash' batteries. (Besides, who makes such a device?) Each charging source has a regulator, regulators monitor battery voltage in order to regulate their output. Assuming the engines have factory normal 'car' alternators, they will hold the battery voltage at ~14.2-14.4v, this is not a problem assuming the engines aren't running 24/7/365. If there are 2 two simultaneous charging sources, the battery voltage will be held to the level of the one of the regulators, as the lower regulator will 'shutdown' it's charging. If there are 2 charging sources, both trying to get the battery voltage to 14.2v, they'll share the load. The batteries will only take what they need.

Assuming the monitor shunt is installed correctly, it will see the charging from all sources.

[Cruisin Cat]

Originally Posted by Pblais

Short answer is yes, yes, yes. It's exactly what they do and not very complicated to install.

The monitor will only see what goes in and out so it will tell you a load in and a load out then integrate the loads over time to compute volume in the bank (amp hours added minus amp hours used). It's an indirect way to get the answer you really want.

You need something that can handle multiple charging sources and regulate them. Regulation for 3 engines and a solar bank unfortunately is not a "tight budget" item. It needs to see all four and then regulate the net amps of what goes into the bank. The charging profile of the batteries will determine the rate amps can be added back into the bank while the number of devices powered on will determine the load going out. Keeping the batteries above 50% and on a regular basis getting them back to 100% is the name of the game for saving money on batteries.

You have a lot of tradeoffs to make.

Getting rid of the inverter would save the most money. You now own a nice relatively big budget setup. Without a really solid regulation system you will trash batteries quickly. They of course are not cheap. You are in too deep to be on a budget now.

At this point I don't have a specific model of regulator to suggest. You need to spend the money for the best one made or put the inverter and generator aside for the time being. You don't mention what you are going to use AC electricty for. Just know that a 10 amp AC device is going to drain your entire battery bank to 50% capacity in 3 hours with no charging sources. You don't state anything that requires such a large bank or charging system. Matching the size and the load you need is really the cheapest route.

"Short answer is yes, yes, yes. It's exactly what they do and not very complicated to install"

I wouldn't exactly say...yes, yes, yes....more like...no (see below), yes, yes.
No you cant see how much power each generating source is contributing, unless you buy a pretty complex (and no doubt pretty expensive monitor that has the facility to accept input from in your case 5 separate shunt resistors and connect 1 shunt in the -ve cable coming from each generating source. These may exist but I have never seen one.

Besides, you don't need this complexity and cost.

I live aboard my cat with almost the same setup as yours....~600Ah name plate battery capacity (see note below), 5 charging sources all with separate regulators (2 x diesel engine altinators, solar, wind, shore power charger). I also have a "normal" battery monitor which tells me total current in or out of the batteries (but not how much current is coming from each generating device), Ahrs is or out of the batteries, V, SOC, etc.


Note on "name plate battery capacity"
Someone said earlier in this thread that you should not just accept the manufacturers name plate capacity of new batteries....you should test, determine actual capacity and enter that into the battery monitor. In my view, that may be an interesting exercise if you have run out of other thing to do on your boat but otherwise not so important....the difference between actual and name plate Ah capacity will not be significant in the overall scheme unless you are trying to monitor within a very small error band.
However, if your batteries are more than a year or 2 old and/or they may not have been "cared for" properly during their service life, THIS TEST IS CRITICAL.
It is almost certain that the actual Ahr capacity will have reduced significantly from the manufacturers name plate capacity. The actual Ahr capacity of your batteries must be entered into the battery monitor (not name plate Ahr capacity) or SOC on the battery monitor will always be over stated.

You won't trash your batteries with separate regulators. You do however need to set up each regulator so they come into play as you want them to.

The only really critical thing is that if any of your regulators are shunt regulators (probably not because they are typically on wind but sometimes on solar) the voltage setting at which the shunt regulator start diverting current to the shunt resistor load must be set higher than the voltage sttings on all of your other regulators...otherwise you will have one generating device trying to put power into the batteries and the shunt regulator diverting it to the shunt resistors.

[Stu Jackson]

Originally Posted by John Duckworth

I have just moved aboard my cat and cannot get to grips with my 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 reasonably competant with electrics, but is such a monitor easy to install?

John,

Here's how easy it can be: Wiring & Installing A Battery Monitor - SailboatOwners.com

You also might be interested in the links here: Electrical Systems 101

The monitors measure amps in and amps out of your house bank, some check voltage of a second reserve bank. Only the Link 2000, as far as I know, does this for two separate banks and they stopped making those years ago.

You need controllers for the individual incoming charging sources (alternator regulator, shorepower chargers have them "built-in" while solar and wind have their own controllers).

The monitors measure incoming to the house bank, but not the individual incoming sources, so you'd have to isolate one to measure what input you're getting, but who really cares? It's the total IN that you need to know. The monitors also measure "out", your usage.

Given that, you should poke around your system and find out what your problem is, 'cuz a battery monitor isn't going to "fix" the problem you seem to be having with dead batteries. Check your battery fluids, incoming voltages when charging and all your connections.