What voltage is your solar panel applying to the batteries. (1 Viewer)

[Sandancers]

In my MH I installed a voltmeter directly across the terminals of the Hab batteries and one across the Cab battery. Therefore I am able to see the voltage on them at any time. Both batteries are lead acid, flooded, sealed.



When the engine is running they both receive 14.2 volts.

When the MH is on hook up (pre solar panel) they both got about 13.2 volts.

When I first connected the MPPT charger, a Photonic Universe type, it showed that it was giving out 15v to the battery !
The PU instruction manual said it should be giving out 14.4v at boost charge and 14.2v at float charge. Talking to their tech help they advised me to change the battery type to GEL. I did and I got the right values.
However, I was able to go into USER mode and configure the outputs downwards as I still thought they were a bit high. I changed the outputs to 14.2 for boost and 13.8 for float. Much happier now.

Then I came across the video below, from Victron. In it at 5min in the Victron man says that float voltage for lead acid batteries should be between 13.1v and 13.3v.

So which is correct ? PU at 14.2v or Victron at 13.3v for float charging?

 

[Peregrinator]

13.5v would do it, and it’s safe.

 

[VXman]

Useful link. I couldn't find a suitable preset on my Victron for AGM battery so I configured it my self. I'm in the right ball park but I have been looking for official figure for a Varta AGM lesiure battery.

 

[Peregrinator]

A charge current of 20% of the 20 hr rate for both Bulk & Absorption charge phases on AGM & GEL VRLA models.

[10% min, 20% recommended, 30% max]

t = 0.38 x (C/I)

Where:

t = Absorption Charge Time (Hours)

C = 20 hr Rated Capacity (AH) [ex: 2 strings x S6-460AGM-RE models (415 AH) = 830 AH rated capacity]

I = Charging Current (Amps) [charger output min 10% up to max 30% of 20 hr rate]

EXAMPLE:

2 strings of S6-460AGM batteries


20 hr rate = 415 AH x (2 strings) = 830 AH


I =20% of 830 AH = 166 Amps OR If the charger output limit is 120 Amps max, then 120 is used


T = 0.38 x 830/166 = 1.9 hrs OR T = 0.38 x 830/120 = 2.63 hrs

 

[autorouter]

The Victron man knows what he is talking about, I think. I'd put my money on a typo in the PU manual, should be 13.2V not 14.2V. However in the manuals I've looked at online, the float voltage is consistently stated as 13.8V.

Float voltage depends mostly on the acid concentration, and varies slightly for different battery types. AGMs have higher float voltage, and gels lower. I think 13.8V is a bit on the high side.

The other consideration is that the battery is installed in a motorhome, not isolated on a charging bench. There are items attached to the battery that are taking a small amount of power, so the float voltage is raised a bit to provide that small amount of power as well.

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[Richard n Ann]

My votronic is 13.4 float... In winter it's slightly higher