EcoWorrier
New Member
- Joined
- Mar 11, 2022
- Messages
- 3
Hi all,
I have a 85 panel array on my house roof, south oriented at optimal angle for total annual production with 230 Wp, 37Voc panels. Total size 19.55KWp.
The panels are roof-mounted (and therefore not easy to re-configure) and currently arranged in 4 (I guess 22 or 21 panel) strings feeding to two Kostal grid tied inverters. I'm 10 years into a 15 year FIT with a rate that is (currently) above market rate. I live in Luxembourg where I export ALL production (about 21MWh per year) through an export meter at the FIT rate and import my own house consumption (11MWh + an extra 4MWh expected when an EV arrives in October) through a separate import meter at market rate (currently about 60% of the FIT tariff). There are no great time of use tariffs here - only a slightly cheaper night tariff.
I'm thinking about how I can take one string and use it to charge some 48V LiFePo4 batteries for house/emergency/ EV charging at night. My problem is the high string voltage from the serial connection. The smallest string would be 21 panels x 37Voc = 777Voc. All the Victron 48V chargers say they can use an input maximum of 8 times the float voltage (54?) which comes to 432V. SMA components show 600V maximum input.
My choices seem to be:
1) Take the highest Voltage battery charger I can find and be prepared for it to disconnect daily in summer when the input voltage goes too high.
2) Somehow down-step the DC voltage to within accepted range
3) Re-config the string from serial to serial + parallel (not easy because they are roof mounted at an angle and at height and would need some scaffolding)
4) Buy some new 320Wp (current tech) panels and make a new DIY array in the garden tied to Victron components and some big LiFePo4 batteries.
4 might be easiest but is the most expensive.
Your thoughts would be appreciated
I have a 85 panel array on my house roof, south oriented at optimal angle for total annual production with 230 Wp, 37Voc panels. Total size 19.55KWp.
The panels are roof-mounted (and therefore not easy to re-configure) and currently arranged in 4 (I guess 22 or 21 panel) strings feeding to two Kostal grid tied inverters. I'm 10 years into a 15 year FIT with a rate that is (currently) above market rate. I live in Luxembourg where I export ALL production (about 21MWh per year) through an export meter at the FIT rate and import my own house consumption (11MWh + an extra 4MWh expected when an EV arrives in October) through a separate import meter at market rate (currently about 60% of the FIT tariff). There are no great time of use tariffs here - only a slightly cheaper night tariff.
I'm thinking about how I can take one string and use it to charge some 48V LiFePo4 batteries for house/emergency/ EV charging at night. My problem is the high string voltage from the serial connection. The smallest string would be 21 panels x 37Voc = 777Voc. All the Victron 48V chargers say they can use an input maximum of 8 times the float voltage (54?) which comes to 432V. SMA components show 600V maximum input.
My choices seem to be:
1) Take the highest Voltage battery charger I can find and be prepared for it to disconnect daily in summer when the input voltage goes too high.
2) Somehow down-step the DC voltage to within accepted range
3) Re-config the string from serial to serial + parallel (not easy because they are roof mounted at an angle and at height and would need some scaffolding)
4) Buy some new 320Wp (current tech) panels and make a new DIY array in the garden tied to Victron components and some big LiFePo4 batteries.
4 might be easiest but is the most expensive.
Your thoughts would be appreciated