Odd behavior with sterling ultra charge & AGM in late Absorption

[john61ct]

BMK is not a specific model add-on, but a class of several products that are evolving over time

[wrwakefield]

Originally Posted by PNWSalmon

I do have the BMk but for custom settings it has float voltage , absorb voltage and time and that’s about it. What you are describing seems more advanced.

Magnum makes two remotes. The 'Advanced' remote control [ARC vs. RC] offers a few additional custom battery settings [e.g., choose between timer, finish amps, or SOC for ending the Absorption cycle. The Standard model only offers an adjustable timer option.]

I have the Advanced model. I just helped another cruiser replace their standard model with the advanced just for the finer controls ending the absorption cycle...

You can identify which model you have by the button labels on the left two of five horizontal buttons across the bottom: the advanced model [ARC] labels/functions are 'Favs' and 'CTRL' [Control]; they are labeled 'Shore' and 'AGS' on the standard RC model...

In case this is helpful.

Cheers! Bill

[john61ct]

Originally Posted by wrwakefield

finish amps for ending the Absorption cycle

I have talked to owners claiming this particular feature, endAmps transition to Float

does not actually work as well as it's supposed to. What say you?

All owners I've communicated with loved absolutely everything else about tgeir Magnum gear, so not disparaging the brand

In fact I believe their attempt to implement this ideal protocol is unique to shore chargers?

[wrwakefield]

Originally Posted by john61ct

I have talked to owners claiming this particular feature, endAmps transition to Float

does not actually work as well as it's supposed to. What say you?

All owners I've communicated with loved absolutely everything else about tgeir Magnum gear, so not disparaging the brand

In fact I believe their attempt to implement this ideal protocol is unique to shore chargers?

Hi John,

Mine consistently works as expected, switching to the final phase [e.g., Float, etc.] after the BMK reads <5A for ~2 minutes. [900AH 12V DC FLA bank programmed to end Absorption @ 5A]

Others I have observed have been spot on as well. [Everyone please remember per my prior post the 'Advanced' remote control is required to program this feature.]

The few times I have heard from other cruisers that their absorption phase ends at higher amps than programmed, I discovered they didn't understand the difference between reading amps using the 'BMK meter' [measured at the shunt] vs. 'Meter' button which shows output at the inverter- and also includes house loads... Once they understood the difference, they confirmed that Absorption was ending very near their preferred setting.

One other time where a friend reported a similar anomaly, I discovered a 0.6 volt drop between his primary negative buss and the inverter 12V positive. [This threw off charge voltage settings also: the BMK meter read .6V lower than inverter output, requiring him to adjust desired voltage higher in the remote to achieve desired voltage at batteries...] Once he cleaned up the buss bar, all was well.

Another somewhat unique feature Magnum offers is selection of 3 final charge phase options: Float, Multi [float for ~4 hrs, then rest until float is needed again], and Silent [stop when absorb is finished: repeat Bulk/Absorption cycles at a programmable 'Re-bulk' setpoint. (12.8V in my case...)]

Silent mode is great for making sure my FLA bank electrolite gets stirred up, and allows my solar to contribute as it can...

I use Multi when away from the boat for extended periods [on shorepower] as it also allows for solar contribution.

Cheers! Bill

[Saltyhog]

Originally Posted by a64pilot

There is a way, but it requires a shunt. My Magnum with the BMK kit has a shunt that is connected to the bank, it of course only “sees” power that is going into or out of the bank. So I program it to go into float when my absorption rate is 3 amps, and whether the charger is putting out 100 amps or 3, when what actually is going into the battery is only 3 amps, it drops to float.
But without a shunt, I don’t think it’s possible.
I don’t know what drives the algorithm of my Sterling, but it always drops to float prematurely, you have to cycle the breaker twice to get to 100% SOC.
Of course if your tied to shore power, no concern. You will eventually get to 100% SOC even in float voltage, just takes a lot longer.

That is a *very* nice feature on your Magnum. Does anyone know if there is a similar shunt available for the Victron Multiplus. I've looked and I don't believe there is. For all the inter-module connectivity that Victron offers, this does not seem available. As Tanglewood mentioned, this is a glaring (to me anyaway) issue with most shore power battery chargers. Actually with all battery charging. Solar controllers also do not sense actual current to the battery. For all the intermodule connectivity that Victron offers, one would think this feature would be available, but I can't find it. All it would take is for the Multiplus to connect to a BMV and use its final measured current *TO* the battery to determine charge.

[john61ct]

Victron used to feature this "endAmps transition to Float" feature as driven I believe by their BMV, may have also required the GX Colour Control or Venus unit.

However with a firmware update, I think last year, that option was eliminated.

No one knows why.

[john61ct]

Originally Posted by wrwakefield

Mine consistently works as expected

Wow, fantastic, that level of detail is greatly appreciated, thanks.

> selection of 3 final charge phase options: Float, Multi [float for ~4 hrs, then rest until float is needed again], and Silent [stop when absorb is finished: repeat Bulk/Absorption cycles at a programmable 'Re-bulk' setpoint. (12.8V in my case...)]

Great flexibility there!