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Old 16-06-2019, 03:51   #1
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Odd behavior with sterling ultra charge & AGM in late Absorption

My sterling pro ultra charge unit will normally charge my dual purpose 12v agm at .2C from 50%dod by itself (no loads) with no issues. It will go into float when the tail current is down to around 0.5% of capacity.
But when i have a C/20 load like fridge and lights during the late Absorption, it takes alot longer for current going into battery to taper down to 0.5%, and the absorption time is easily 2-4hours longer. To fill the last few % looks to be taking much longer when a load is going.
Does this mean the battery is on its way out or damaged?
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Old 16-06-2019, 05:40   #2
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

A c/20 load is 5%, and your charger is looking for 0.5% - that’s a big difference and easily enough to disrupt the end charge algorithm.

Odds are that’s all it is and your batteries are fine.
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Old 16-06-2019, 06:43   #3
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

Would help if you also gave the actual Ah numbers.

Many ultra owners "reboot" to extend Absorb when the settings can't hold Absorb time ling enough and go to Float prematurely.

Is your charger recent enough for California Energy Compliance, has the so-called PS mode which is actually the original battery charger mode? https://youtu.be/9wvpdp9UEfQ
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Old 16-06-2019, 09:31   #4
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

How big is your" bank" and how big is the charger?
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Old 16-06-2019, 09:43   #5
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

When your changer is on, any load placed onto the system as long as it doesnít exceed the capacity of the charger, is transparent to the battery bank.
So, no, itís not that your bank is going bad, if the loads exceed the banks capacity, even for short times, itís going to extend the time to fully charged as of course any time the charger is maxed out, the rest of the load comes from the bank
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Old 16-06-2019, 14:27   #6
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

This is the classic battery charger problem. The charger canít distinguish between current going into the battery, and current going to the loads. So ending charge at 0.5%C will never happen unless there is zero load, and in real conditions this never happens. Itís a glaring hole that is systematically ignored.

The blunt force workaround is to also have an absorb timer limiting absorb to 2-4 hrs or something like that.
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Old 16-06-2019, 15:09   #7
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Odd behavior with sterling ultra charge & AGM in late Absorption

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 ďseesĒ 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 donít think itís possible.
I donít 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.
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Old 17-06-2019, 05:05   #8
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

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Would help if you also gave the actual Ah numbers.

Many ultra owners "reboot" to extend Absorb when the settings can't hold Absorb time ling enough and go to Float prematurely.

Is your charger recent enough for California Energy Compliance, has the so-called PS mode which is actually the original battery charger mode? https://youtu.be/9wvpdp9UEfQ
Hi.
It's sterling pro 50A and 300AH in 3x 12V dual purpose.
My sterling in CEC. But i always use PS mode with custom profile.

But the actual current tapering into the battery at 14.4v is taking longer to taper right down with a small constant load, vs no load. This i don't understand.
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Old 17-06-2019, 05:23   #9
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

Letís play with some numbers.
You have 50 amps available, letís say your loads are 15 amps and your battery is accepting 10 amps. Your charger output is 25 amps and your battery doesnít see the load at all, and your charging time in the late phase is the same load or not.

However in the bulk phase, with no load the bank takes all 50 amps, but with a load of 15 amps, then the bank only gets 35 amps.
I believe what you are seeing is actually an extended bulk phase and not an extended absorption phase
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Old 17-06-2019, 07:12   #10
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

For those who want that level of info, there should be a volts and amps readout to watch during the charge cycle.

Even a logger to export data to a PC and create pretty charts is not expensive. http://luna-mate.com/product_images/...image-8645.png
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Old 17-06-2019, 07:43   #11
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

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Even a logger to export data to a PC and create pretty charts is not expensive.
Can be done for the cost of a beer in London if you already have a raspberry Pi
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Old 17-06-2019, 09:25   #12
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

And for the cost of two if you don't 8-D
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Old 17-06-2019, 10:53   #13
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

Interesting. How do you program that on the magnum ? Does it require a newer software rev ?
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Old 17-06-2019, 11:12   #14
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

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Interesting. How do you program that on the magnum ? Does it require a newer software rev ?


No, but you do need the remote, the Magnum will work without one, but you canít change anything near as I can tell without one, so the remote really isnít an option.
So you add the BMK, which stands for battery monitor kit, that gives you an amp counter battery monitor of course but having the shunt enables the termination of absorption to be based on amperage.
Once you buy the Magnum itself, things like the automatic generator start and battery monitor are decently priced.
Seems that street price for the battery monitor kit is about $125 and $110 for the automatic generator start
https://www.magnum-dimensions.com/battery-monitor-kit
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Old 17-06-2019, 11:44   #15
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Re: Odd behavior with sterling ultra charge & AGM in late Absorption

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.
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