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speaklevel asked

75/10 Low Voltage in Bulk

Hi, we have a 75/10 charger with a 100W panel on a boat. Two 160Ah Agm batteries. The Victron connect app shows a more or less constant voltage of 13.4 V when charging in bulk mode. No current drawn, all systems off. Discharge only at night, using lights, perhaps Diesel heater (fan). Battery in the morning quite full - 12.7V. (We do not have a shunt) Looking at the history, thats the typical day: Max 80w, 180-270 Wh, but Bulk mode only and 13,4V. I expected Voltage going up to 14.4V. And switch to Absorb abd Float. Anybody got any idea to that situation? Changing to different setups or to higher Absorb Voltage did not change anything. Neither did different TempCompensation. Thx!

battery chargingsmart solar charging behaviour
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Alexandra avatar image Alexandra ♦ commented ·
@speaklevel

And your panel voltage? VOC? If it is barely above the battery voltage not much will be going on.

I can quite honestly say though your batteries are chronically undercharged.

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speaklevel avatar image speaklevel Alexandra ♦ commented ·

Thx. We are at aprox 19.5V on the panel. Right now 40-50 Watt. Output same Watt, but 13.4V. Normally batteries are mainly charged by Landpower. Not working on shore right now. Solar is not used to fully charge, but as an “extension” of batt capacity.

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sailingaphrodite answered ·

12.7 volts in the morning is 'fully charged' on a lead acid or AGM. Have you been playing with the Expert panel as according to the manual the defaults are:

The default absorption voltage is 14.4V and the default float voltage is 13.8V.

or are you under the the blanket of cloud that has sat across the UK for months as I've also been showing low voltages.

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speaklevel avatar image speaklevel commented ·
Hi! Changes on expert panel didn’t change anything. And yes, clouds are coming and going. But even on a sunny day we are on 13.2- 13.4V output. Amps changing, but always resulting in a correct level of Watt.
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kevgermany answered ·

With low charging power provided by your panel, the low max voltage is to be expected. Voltage will only rise as the battery gets more charge in it. You're getting up to 80W, so all working properly.

You really need a bigger panel. But don't overdo it, the charger won't put out more about 140W, so 200W panel should be about right.

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speaklevel avatar image speaklevel commented ·
Thx - by the way, its a 75/15, my mistake. We’ll try to add another panel. Probably difficult due to shade. But good to know all is ok.
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kevgermany avatar image kevgermany ♦♦ speaklevel commented ·
Try to get the same panel specs. Mismatches cut output.
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