In the specs for SmartSolar MPPT 75/15 it says that PV voltage must exceed Vbat + 5v for the controller to start. What does this mean in reality?
How do I verify in the specs for a solar panel that it will ensure the SmartSolar to start charging early on a cloudy day?
Does it make a difference to buy a 24V panel rather than 12v? I have been looking at a panel that is specified with Vmpp 18v (no other voltage specified). Will that work well with the SmartSolar?
If your battery voltage is 13V the MPPT needs a PV voltage of 18V to start.
To have better low light performance you should use panels with a higher Voc or connect panels in series
The 75/15 can handle a PV voltage of up to 75V.
Voc is higher than Vmpp. It should be in the datasheet of the panels
Hello Matthias...I was looking for this exact info and didn't even have to do a search! I have two questions. 1) is the same true of a 100/30 (battV+5V)? 2) I recently learned that trying to charge two batts/BMS in series could cause problems in the batts becoming out of sync...even cause damage. I have a 24V lithium converter and am wondering if I can supply 24V from the [brand new] converter and feed two 100/30s...this way I could charge the batteries independently at 14.4V. TIA
I accidentally stumbled across this official video from Victron that tries to explain this topic which I could not find in their written Q&A:
https://www.youtube.com/watch?v=uTMVmW7GTus
I cannot say that I really understand why two 100W panels in series will produce more power in low light conditions so that it is worth starting the SmartSolar than the same two panels in parallel.
It is even more confusing when most information online talks about getting more power out if the panels are in parallel if there is shadow on only one of the panels.
If the maximum power in certain conditions is at a lower voltage, that lower voltage might be too low to charge the battery. When you have a string of panels or a panel with higher voltage, there is more room on the lower voltage side (and still be higher than the battery voltage).
If you have panels in series (string of panels) and if there is shadow on one panel or part of one panel, the shaded panel brigs down not only its own energy production (the current drops), but the energy production of the entire string (series of panels).
Strings (or panels) in parallel with that shaded string/panel are not affected.
So, if there is no shading issue (or just for a short time), it is best to wire as many panels in series as the charger allows and only after that add more strings in parallel (if the solar charger can use more panels than you have in one string).
Hi @fredrikI
Like seb71 says..
This is 'reality' for me, and not specially selected, it's this morning. 3x series panels, nameplate Vmp 108V, batts at 49.7V, horizontal pv, clear sky, no shade, 150/ mppt.
PanelV starts rising ~7:00, levels off for a short while at battV, then makes a few attempts at ~7:30 when Voc gets it's +5V. Once it can lock in the +1V it makes some A until 8:25 with Vmp 60-70V, then the sun breaks clear and Vmp jumps to where it should be.
Had I only 2x panels in a string, that Vmp up to 8:25 would be only 40V or so, not enough to hold that +1V of the tracked Vmp. Now that small A may not mean much at first sight, but a cloudy day will stretch that out too. This happens at sundown as well, and I'd rather have it than not.
Panel nameplates are a guide, but don't tell it all..
Panels like this are sold in many stores where I live. They are aimed at RV:s and quite cheap. With all this information I guess they are unsuitable for low light conditions due the low Voc?
I struggle to find a panel with the same (or higher) wattage and about the same dimensions. Any suggestions on what a good panel looks like?
Sorry for it not being English but I think you get most of it.
Maximal driftspänning (Vmp) 18,0 V
- Ström vid max effekt (Imp) 9,75 A
- Tomgångspänning (Voc) 23,12 V
- Kortslutningsström (Isc) 10,43 A
- Max effekt (Pmax): 190W
- Modulverkningsgrad: 19,3%
- InkapsladeTPT / EVA / celler / EVA / glas
- Frontglas: 3,2 mm värmebeständigt hagelresistant glas med hydrofob antireflekterande yta.
- Cell-typ: Monokristallin JA Solar PERC 5BB
- Antal celler: 36 (2 x 18)
- Eloxerad aluminiumlegerad ram, dubbelvägg
- Kabel: L 900 mm / 2,5 mm ² Ø
- Kontaktstycke: MC4
- Modulens mått: 1470 x 670 x 35 mm (LxBxH)
- Vikt: 11,20 kg
- Maximal systemspänning 1000V DC (IEC)
- Temperaturområde modul -40 ° C till +85 ° C
