terryhill avatar image
terryhill asked

75/10 staying in bulk mode

Hey guys,

I have 50watt recarc panel mounted on my carport going through 75/10 unit into a brand new 100AH AGM. (12v). This setup is intended to keep my camper trailer battery topped up when not in use.

I have noticed on the app the unit appears to be staying in bulk mode throughout the whole day.

Something doesnt seem right to me, it was a sunny day and battery was already full, i would have expected it to spend the majority of the day in FLOAT mode. Ive also noticed that the unit doesnt always do as its told. For example i have set it to FLOAT at 13.8 but i have never seen it achieve this yet. I have disconnected the panel for the time being as i dont think this unit is functioning as it should. Am i missing something here?



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2 Answers
JohnC avatar image
JohnC answered ·

Hi Terry. Your little panel isn't 'strong' enough in poor light. It's V just isn't high enough to give the mppt enough to work with, well at least for long enough.

Looking back at your data, '2 days ago' you went through a short 'abs' and 'float' too. Them's the grey light & darker sections on that day's summary. Probably a good solar day, your batt well up.

'Yesterday' must've been poor sun. It found a max of 36W, and the mppt must've run for less than an hour at that to provide a grand total of 30Wh.

'Today' better sun, but it had a little catching up to do and didn't quite make Absorb. But your batt is well charged and there's nothing whatsoever of concern that I can see.

Go hook your panel back up and let it do what it can. If you don't let it see daylight every day it won't know what day it is, so your data will confuse. The only real fix for this is to add another of those panels in series to give it a decent V to work with. Or more sun..

But it's working ok, your batts are getting a nice gentle topup, and those Wh figures are really miniscule anyway. All's well, relax..

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terryhill avatar image terryhill commented ·

Ok, ill look at a larger panel. Thankyou

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wkirby avatar image
wkirby answered ·

It will stay in bulk mode until it reaches the Absorb Voltage (probably 14.2V?). Subsequently, it will not go into float until the Absorb stage is complete.

By analysing the data in you screenshot, you can see that the battery Voltage did not reach up to the Absorb stage which I assume is set to 14.2 or 14.3V, so therefore it has stayed in the bulk stage.
On the one day "2 days ago" you can see that a maximum battery Voltage of 14.28V was recorded (Absorb Voltage) and from the graph we can see that the charger spent some time in Absorb and then the rest of the time in Float.

If there is not enough PV power to drive the battery Voltage up to the Absorb level or there is a load drawing off the system, then it will not reach the Absorb Voltage and can stay in Bulk for days.

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