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Old 31-08-2014, 05:16   #16
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by Night_Sailor View Post
.

I'd be happy to delete the image if you like. I was trying to help this guy understand how shunts work. You might want to re-label your image for clarity (Engine Start) rather than the more ambiguous (Bank 2).
This is perfectly unambiguous.

One monitor. One bank. All negative connections except the bank being monitored are on the opposite side of the shunt to the monitored bank DC- terminal.

The second bank can be used for starting the engine, a second house supply, windlass or any other thing.

Some boats have a 3rd bank.
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Old 31-08-2014, 10:00   #17
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Battery monitor showing different Volts than main panel + how to setup AmpHRs

So will this victron 700?"learn" what's 100% as time goes on then?

Been keeping an eye on things today as I was out sailing. Under sail my 300watts of solar were putting in 120watts or 8amps per hour ( this was with nothing else on).

Sounds low? But I have nothing to compact it to.

Also I've noticed the 700 shows 100% full but the shore power charger is still on.
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Old 31-08-2014, 10:30   #18
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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No Simon, set the Ah rating for the full rating of the batteries. .
In order to do this correctly one must actually know the Ah capacity at the 20 hour rate. Some batteries take 30 or more cycles to attain rated capacity then steadily drop off there after.

Once yearly capacity tests are a good thing to do at a bare minimum in order to keep an Ah counter accurate.. Also most boats don't ever get "full" so if you program the rated capacity then you are discharging slightly below the 50% mark. Most battery monitors reset based on time, time at X% current and time at voltage. If this X% current is say the Victron factory setting of 4% of "C", and you have Lifeline batteries which are full at 0.5%/C @ 14.4V then you are not ever getting full and you are discharging lower than expected. Not a total deal killer but if you have rated capacity programmed in for more than a year your discharge floor gets lower and lower and lower and it snowballs until your batts are toast...

Ah counters are far from set it and forget it and the "rated" capacity changes and really needs to be ascertained once per year at a minimum...
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Old 31-08-2014, 10:41   #19
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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So will this victron 700?"learn" what's 100% as time goes on then?
No, not at all. You need to tell it what the Ah capacity, temp, Coulombic efficiency and Peukert are in order for it to be anywhere close to accurate. Using "auto sync" makes them even less accurate....

Quote:
Originally Posted by simonpickard View Post
Been keeping an eye on things today as I was out sailing. Under sail my 300watts of solar were putting in 120watts or 8amps per hour ( this was with nothing else on).

Sounds low? But I have nothing to compact it to.

Also I've noticed the 700 shows 100% full but the shore power charger is still on.



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No such thing as "amps per hour". Just semantics.. It was supplying 8A when you looked at it but solar is ever changing in output. If it ran for an hour, and held steady at 8A, then you would have returned 8 Ah's (ampere hours) to the bank...

Full on any bank is most easily determine by net current, as a % of capacity, AT absorption voltage.

So if your bank of batteries has an absorption voltage of 14.4V then when the bank is taking about 1.5% of its capacity at 14.4V you should then manually sync the monitor.

For a 400 Ah bank it looks like this:


*Voltage 14.4V = Check
Net Current Less Than 6A = Check
Reset Battery Monitor


*This must be done at absorption voltage NOT float....

Regular manual synchronizations on top of proper programming will keep your monitor as accurate as it can be...
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Old 02-09-2014, 22:58   #20
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by Maine Sail View Post
Some batteries take 30 or more cycles to attain rated capacity then steadily drop off there after.
and to make matters worse the battery companies define cycles differently than the battery monitor companies, so you cannot assume that the cycle counter you see on the battery monitor is actually showing the number of real battery cycles.
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Old 03-09-2014, 05:36   #21
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

This stuff is so hard to understand. I don't even mind it being say 10% out. All I want is the SoC to be close so I know when to recharge.

What is still puzzling me is that my solar controller can be in bulk mode when the battery monitor is saying 100% that can't be right.



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Old 03-09-2014, 07:35   #22
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by simonpickard View Post
This stuff is so hard to understand. I don't even mind it being say 10% out. All I want is the SoC to be close so I know when to recharge.

What is still puzzling me is that my solar controller can be in bulk mode when the battery monitor is saying 100% that can't be right.



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Exactly! I have the same issue with my Mastervolt battery monitor. It always reads either too pessimistic or too optimistic.

I finally just threw in the towel and installed the balmar smartguage. I am not disappointed. The data from that device 'makes sense'. Also, using just the capacity display helps my wife as she finds it much less confusing.
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Old 05-09-2014, 07:52   #23
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by simonpickard View Post
So will this victron 700?"learn" what's 100% as time goes on then?

Been keeping an eye on things today as I was out sailing. Under sail my 300watts of solar were putting in 120watts or 8amps per hour ( this was with nothing else on).

Sounds low? But I have nothing to compact it to.

Also I've noticed the 700 shows 100% full but the shore power charger is still on.

It will calibrate itself when the batteries reach fully charged which might take a few days. Mine took 3 days as I recall. Later mine got out of sync--the percentage discharge did not match the AH used. It self calibrated the next time it was fully charged. The error was very small, on the order of 1%.


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Old 05-09-2014, 07:56   #24
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by simonpickard View Post
What is still puzzling me is that my solar controller can be in bulk mode when the battery monitor is saying 100% that can't be right.

That is not right; it should be in float mode.

Recheck all your programmed parameters. Be sure you have the right voltage setting for your batteries.



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Old 05-09-2014, 07:59   #25
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

That's great to hear. So I just need to keep recharging for a few days on shore power and it'll sort itself out.

Thanks,
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Old 05-09-2014, 08:20   #26
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by Night_Sailor View Post
That is not right; it should be in float mode.

Recheck all your programmed parameters. Be sure you have the right voltage setting for your batteries

So that would be on my solar controller? I can't see a setting on the battery monitor?

For the controller it states this:

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Name:	ImageUploadedByCruisers Sailing Forum1409926775.217973.jpg
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I have 12v gels. Not sure what setting it should be on?



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Old 05-09-2014, 13:58   #27
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Re: Battery monitor showing different Volts than main panel + how to setup AmpHRs

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Originally Posted by Night_Sailor View Post
It will calibrate itself when the batteries reach fully charged which might take a few days.

Or it will simply reset prematurely because solar can easily mimic the "charged parameters" which the battery monitor resets on...

They reset on:

*Voltage
*Time at voltage
*Current
*Time at current

Solar can easily trick a battery monitor into premature resets...


Quote:
Originally Posted by Night_Sailor View Post
Mine took 3 days as I recall. Later mine got out of sync--the percentage discharge did not match the AH used.

Ah used and % charged rarely if ever line up. This is due to the Peukerts constant setting. The % charged screen uses the Peukerts constant, the Ah consumed screen does not. Therefore they can not line up and should not line up exactly...

The only way the two screens line up is if you draw the battery bank at exactly capacity divided by 20 at 75-80F. This means drawing a 400Ah bank, with the proper Peukerts constant, at 20 amps and holding that current draw steady with a battery temp of 75-80F. Then and only then will the Ah screen (CE/Consumed Energy screen for Victron) and % charged screens agree...

On most cruisng boats % charged screen will usually read higher than the CE screen shows. This is because you are most often drawing current out of the bank at less than C/20 and getting a slight bump in capacity because of it.....

Ah counters require careful user calibration. This calibration with known battery capacity (rarely not the "rating" unless new), known charge efficiency, known Peukerts constant, case temp etc., is critical for them to be even close to accurate.

Because traditional AH counters do not "learn the bank" all they can do is drift out of calibration. You as the owner must teach the battery monitor about your bank then it will be more accurate. You as the owner should also use "known full" manual resets as often as is possible because "auto synch" is very easy to trick....
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