I currently have 2 12v 130w panels wired in series to charge a 24v battery bank through a Victron blue solar 75/15 mppt controller. I only have space for one more 130w panel. Can I i wire it in series to give 36v to the controller and charge the 24v battery bank?
Hi Ti,
As long as the Voc of your array does not go over the mppt voltage limit of 75v, you will be fine.
Also note that the colder your panels get, the Voc goes up a little. Post the full specs and model of your panel, and how cold it gets at your location.
Thanks! This is the spec sheet. Panels are on a motorhome. The base is the UK but we travel to Africa and 40c and to the mountains where it’s been as low as -25c.
Hi Ti,
With those panels you can not wire 3 in series with your 75/15.
You could go 2 series, 2 parallel if you have the space. or change the mppt.
What would be an adequate size in the victron mppt controllers?
Thank you for your help, I went with the victron 100/20 to be on the safe side.
the 100/15 would have been more than enough on the safe side. 6-7 amps to be expected max.
You should be aware though, that your solar panels are in no way "12V" panels - "open circuit voltage" is the keyword here. Put 3 in series, take that value x 3 and add some margin (cold sunny weather) -> 90V -> take the 100/x MPPT
You can actually oversize the PV array for the MPPT. There is an excellent article by Victron (I like to think because of a technical inquiry from our company a few years back): https://www.victronenergy.com/blog/2014/03/28/matching-victron-energy-solar-modules-to-the-new-mppt-charge-regulators/
See "Oversizing a PV array"
So according to this, you could drive SIX (2Px3S) of these panels with a MPPT 100/15 and NINE (3Px3S) with your 100/20.
