A kind friend lent me two smartsolar controllers and two 12v 180w panels to experiment with. I have a new Numax 105ah Leisure Battery XV31MF (lead, not lithium) to drive an electric winch and I want to charge it with the panels between uses. We don’t get direct sun all day, so I thought putting the 12v panels in parallel and keeping everything 12v would be best. Reading this forum (too late), I think this might not be great… Could I do this safely (for the battery) with the smartsolar 100 500? Or should I go 24v and use the 75 15? The battery didn’t like the 12v parallel panels on the 75 15 (it started crying. Well, weeping electrolyte anyway )
Correctly set up the MPPT should not overcharge the battery. As these have been used before were they on a 24V battery and you are now using a 12V battery. That would cause overcharging. You now need to reset them to 12V. At 12V you should have 1 panel per MPPT. Note, a 100Ah battery should be charged at around 15A, 20A at most. This could be another issue. Read the manual.
So… Thanks for the useful bit on charging at 15A (it’s a C20). I reset them to 12v (in fact it autodetected this, as per the manual, which I had actually read - it’s not that helpful on the key element as you’ll see in a moment). I think they need to be in series (and 24v!). One thing - the default battery settings are really confusing. Which Gel Deep Discharge setting would my Leisure battery be? There seems to be no way of linking battery to default battery options. All I know for certain is it isn’t Lithium! And not AGM (not shown in the Numax literature). In the end I manually set the charging voltages (from the Numax info) because the battery options weren’t obvious. Any clues?
Victron gel deep discharge 2 is a safe option for most lead acid / AGM batteries. It is always best though to set your own charge voltages based on the manufacturer information. The spiral AGM is too high for most lead acid/ AGM batteries and will overcharge.
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