Victron solar controller high charge voltage

[smac999]

Originally Posted by mikedefieslife

Well that's not what's happening. In the morning when it is 10c outside, the controller is putting out around 13.6v or similar probably due to the low sun. It is the middle of winter here. 15v doesn't seem to show up in the min/max display on the app until late afternoon. By then the temperature is closer to 18c.

Oh well anyway, I need to keep them below 15v anyhow so does that mean going against the temp comp ratings issued by Trojan?

in the morning it's still in bulk charge, it's not going to hit peak voltage untill the batteries are more full.

why are you running 400w of panel through a 20a controller??

[mitiempo]

Originally Posted by smac999

why are you running 400w of panel through a 20a controller??

I agree, a bit over panelled. You should have a 100/30 controller.

[mikedefieslife]

20a is about right. These are old panels. It is very common in the industry to ever-so-slightly over-spec the array to take into account placement/angle, clouds, winter, and efficiency losses. It's even mentioned as a consideration on the Victron website.

[Jim Cate]

why are you running 400w of panel through a 20a controller??

Not so much why, but more "how"? I too now have 400 watts of panels and I felt it necessary to buy the 100/30... it just barely meets the power spec itself.

Jim

[mikedefieslife]

Originally Posted by Jim Cate

Not so much why, but more "how"? I too now have 400 watts of panels and I felt it necessary to buy the 100/30... it just barely meets the power spec itself.

Jim

Panels are mounted on a curved surface, so they rarely deliver more than 15a

I should add that I aware that the current configuration potentially exceeds the max input current for the controller, but as it's the height of winter, it's not a problem.

The panel in spring is to replace the 100w panels with 2x200w panels each with their own controller.

[CatNewBee]

Is reconditioning enabled on the Victron controller as automatic battery maintenance? You should disable it for AGM /GEL.

[thomm225]

The Victron Connect etc many times will read a bit off. it's still only .2 volts or so which is nothing to worry about.

I believe mine reads a bit low on the connect but about right with my meter (uncalibrated)

I have my Victron disconnected right now and my PWM controller connected to one 20 W panel to maintain my batteries charge while the boat is in the yard

[noelex 77]

Originally Posted by thomm225

The Victron Connect etc many times will read a bit off. it's still only .2 volts or so which is nothing to worry about.

Thomm, you keep stating this. Why don’t you try deliberately altering the battery absorption voltage by 0.2v. For example, from 14.6 to 14.4V. I think you may be surprised by the corresponding change in the current accepted by the battery.

[thomm225]

Originally Posted by noelex 77

Thomm, you keep stating this. Why don’t you try deliberately altering the battery absorption voltage by 0.2v. For example, from 14.6 to 14.4V. I think you may be surprised by the corresponding change in the current accepted by the battery.

Sounds like a good test.

I'll try it when I reconnect the Victron in a couple months.

Today I'm painting my boot top and the section of the stern where my new (four stroke) outboard bracket will be remounted. I painted the bottom where the stands had been yesterday.

I'll also be doing a bit of touchup on the topside hull. Temp is already 50 degrees and it's only 0900

[Yellowjacket]

Originally Posted by noelex 77

…Why don’t you try deliberately altering the battery absorption voltage by 0.2v. For example, from 14.6 to 14.4V. I think you may be surprised by the corresponding change in the current accepted by the battery.

Noelex, wouldn't lowering the voltage reduce the current accepted? Or is that just in situation of line loss?

[Yellowjacket]

Originally Posted by mikedefieslife

The battery sense module is stuck to side of one of the batteries in the middle of the bank. Then the wires attached to the positive and negative of the connected pairs i.e in the middle one the cables that make the parallel.

Think I'll just dial the setting back a bit for now, as there really isn't a lot that can be done.

When talking to Victron about the 712, they were adamant that the negative be the sole connection at the battery post to get accurate readings. I don't know if this applies also to Sense device.

[john61ct]

An AH counter used to monitor a battery must be wired so **all** currents to and from the bank pass through its shunt. That does not need to mean right at the post.

Voltage closer to the post the better, but no exclusivity requirement.

Temperature best on the case body, maybe thermo coupling paste. Ideal sensor would be internal.

[noelex 77]

Originally Posted by Erik Dolson

Noelex, wouldn't lowering the voltage reduce the current accepted?

Yes, that is correct. The important time is in the absorption phase. If you reduce the absorption voltage the charge rate will go down. The battery will charge slower.

This is not a great problem if you are going to spend a long time plugged into shore power, but with the limited charging times available from solar or a generator supply, the reduced charge rate can give less usable power and/or a lower state of charge, which reduces battery life expectancy.

It is always dangerous to generalise, but if the voltage at the battery is measured, with a properly calibrated meter it is quite common for the charging voltages to be below the manufacturer’s recommendations.

There are a couple of caveats. As the charge voltage is increased, battery efficiency drops. So if you alter the absorption voltage and increase the charging current, not quite all of this extra current is being translated into usable capacity. The second factor is once the battery is full it will still accept some charge at higher voltages, but this is not translated to any more usable capacity. Another way of looking at this factor, is battery efficiency drops to zero as the battery becomes fully charged. This does fool some people who set very long absorption times believing all the current entering the battery is being converted into usable capacity.

[john61ct]

A lead battery does need to regularly get to mfg defined 100% Full state in order to maximize longevity.

Besides setting Absorb V at the high end, that needs to be held long enough to get there, even if 95% of the charge current is not being accepted for the last few hours of the charge cycle.

Of course other concurrent loads can change thing, need to keep any trivial "load dumps" from preventing that "long tail" process.

Of course going past the endAmps stopping point for too many hours too frequently can reduce AGM longevity, FLA just need to keep watered.

But that is very rare, and usually impossible with most solar setups, given the sun usually sets.

Going to Float **way too early* is very common, maybe 90+% of charge sources left at their defaults.

But cross-referencing whatever Absorb Hold Time and Absorb Return adjustments the source allows against an ammeter regularly, those two goals are not that hard to balance, as you get more familiar with usage patterns vs changing conditions, can become instinctive.

Of course the ideal is shunt-based charge regulation that transitions to Float based directly off trailing amps acceptance hitting the endAmps spec.

As a bank ages and wears, this gets harder, takes longer, and at a certain SoH% does eventually become impossible to reach the spec'd endAmps.

Nothing to do with overcharging, and may in fact indicate it's time to schedule replacing that bank.

An alternative spec to use is Deka's:

> Absorption End Point = Current change over 1 hour period of less than 0.1A

Note the*current***change** point there, no actual absolute value given for endAmps

Thus it will work even with an old worn-out no-name Wally's batt that has trouble hitting .05C

But when that batt is fresh and new, and you can't find the specific protocol from the maker, then .005C is a good default to start with, especially for FLA.

For a sub-par*AGM, maybe use .02C if you're worried about overcharging.

As a side note, if you can't easily find detailed specs like endAmps from a batt maker, it's a sure sign IMO that you should avoid*purchasing*that brand.

The point is to have an objective benchmark to hit consistently "most cycles" if possible,

rather than assuming your charge source's "going to float" is an indicator of the bank being Full.