What are the correct Settings for a 160Ah 12V AGM battery

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samtutuki asked Jan 20, '19

What are the correct Settings for a 160Ah 12V AGM battery

I have 2 off 80W solar panels each connected to their own BlueSolar MPPT 75/10 regulator which are both connected to a 160Ah 12V AGM Battery on my sailboat.

When I leave the boat there is a small parasitic load (size unknown) and I have been adjusting the Absorption and Float voltages to keep the batteries charged.

I have left the absorption time with the default setting and turned the equalisation off. The Absorption voltage is set at 14.6V and the Float voltage is set to 14.4V. Both regulators have the same settings.

When I return after three days the SoC is sitting on 99% not 100%.

Can anyone please advise what Absorption voltage, Float voltage and Absorption time I should use.

Thank you.

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Answer 1 · 2019-01-20T06:39:06Z

JohnC answered · Jan 20, 2019 at 06:39 AM

Hi Sam. Unless you have a particular reason for doing so (like batt maker's recommendations), just select the charge profile for your type of batt from the menu. That'll commonly result in 14.4V (abs) and 13.8V (float). Those subject to temp compensation too, also the odd 'trick' Victron throw in free - you may not notice those unless you're graphing, but don't be concerned, they're excellent algorithms.

A parasitic load is no reason to change the settings. Find the parasite or isolate the batts if you leave the boat. Of course if it's the bilge pump, perhaps fix the leak. :)

Not sure where you're getting your SOC from, but unless you've 'tuned' it, don't take it too seriously.

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Answer 2 · 2019-01-21T00:25:37Z

samtutuki answered · Jan 21, 2019 at 12:25 AM

Thanks John.

I am getting my SoC from the Merlin Smartgauge (http://www.smartgauge.co.uk). I have used the type of gauge now on two different boats and find it to be very reliable and accurate.

I was previously using the default settings (14.4/13.8) but the battery was never fully recovering its charge after several days. I turn all my house consumers off when I leave the boat other than the bilge pump - which never runs - and the electrical control panel that drives the water and fuel tank levels.

I will reset to the figures you suggest and isolate all house loads when I am next on the boat and see what results I get after a few days.

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JohnC ♦ commented · Jan 21, 2019 at 03:25 AM

Yeh, it warrants further checking. I tend to look at Vbat after a night of standing and before pv kicks away (even turn off pv if you get there later than that). If it shows ~12.6V, then it's close to fully charged, regardless of SOC reading. Even check the V with a multimeter 'to be sure' (old Irish saying, isn't it?). :)

Your Merlin seems quite capable kit, but I've never seen one in the flesh 'down under'. But have often recommended parts of their website for learners to read. I do note the Merlin needs to be connected continuously - perhaps part of the panel you leave on?

That said, let the 75/10 do it's thing (multimeter V check too), and sort the monitor and parasites as a separate issue if you must use SOC.

Good luck with it too.

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