March 5, 20233 yr Need some advice from the more seasoned folk please... I recently had a solar system installed. I’m using 3 x Freedom Won etower batteries (5kWh each), with a Victron MPII 48/5000 inverter, and 8 x 550w panels. System runs off PV first, then batteries, then grid. I included some screenshots below showing the Solar generation, and 1 showing my typical consumption profile. Typically, I generate enough from solar to run all the loads in the morning till midday, but not enough to put much back into the batteries that are sitting at 40% from the night's usage. Which means when i start using from batteries again, they batteries are only at around 60-75% charged. Which means I'm using grid again from from early the evening already. My solar yield also drops quite a bit after 2pm. So I also have to dip into the batteries a few times during the late afternoon, before being fully on batteries in the evening, till they run down to 40% again. My question is: - Do I add more panels to the current North facing roof to beef up the early morning-midday yield, making more available from morning till after lunch-ish, which will allow the batteries to recharge and last longer into the night before switching to grid? - Or do i add panels to a west facing roof, which will give me a more even yield into the late afternoon. This roof facing nicely into the direction of where the sun is from around 3pm-ish. Thanks! Solar yield profile (yellow = direct usage from solar, blue = recharging batteries) Load profile (yellow - using solar, blue, using battery, red using grid)
March 7, 20233 yr On 2023/03/05 at 10:17 AM, grapgat said: - Do I add more panels to the current North facing roof to beef up the early morning-midday yield, making more available from morning till after lunch-ish, which will allow the batteries to recharge and last longer into the night before switching to grid? That's what I would do to maximize the possible input from the panels. You could do without the battery being used in the middle of the day. Charging the batteries as soon as possible is best in my opinion as lithium doesn't like to sit around with low charge.
March 7, 20233 yr Before just buying more panels, I'd look into why you are getting a fairly low peak output of under 3kW out of your 4.4kW of panels. Any shading cast over the panels, or are they very dirty? Are your panels at a very steep angle like close to 60% What MPPT are you using? Does it have around 100A charge current?
March 8, 20233 yr Author 21 hours ago, GreenFields said: Before just buying more panels, I'd look into why you are getting a fairly low peak output of under 3kW out of your 4.4kW of panels. Any shading cast over the panels, or are they very dirty? Are your panels at a very steep angle like close to 60% What MPPT are you using? Does it have around 100A charge current? Well spotted :), I should've actually said it's 6 x 550w panels. (and using a Victron 150/85 mppt) I installed 8, but 2 of the panels hadn't been connected yet. They were connected today so I'll see what my yield looks like with all 8 going. But i figured i'd still want to add panels at some stage and wanted to sense check what the best way forward would be.
March 8, 20233 yr 22 hours ago, jumper said: You could do without the battery being used in the middle of the day. Charging the batteries as soon as possible is best in my opinion as lithium doesn't like to sit around with low charge. Not sure why you mention this. Grapgat mentioned his battery is sitting at 40% after a night's discharge. That is not a low SOC for lithium.
March 9, 20233 yr 9 hours ago, Scorp007 said: Not sure why you mention this. Grapgat mentioned his battery is sitting at 40% after a night's discharge. That is not a low SOC for lithium. I agree 40% is not too low, but they are only getting back to 65% before being discharged again and on multiple cloudy days things could be worse. I just like to keep batteries charged as much as possible (not necessarily as fast as possible) before using them again. Those are some quality (and costly) batteries, I would take very good care of them.
March 9, 20233 yr 10 hours ago, grapgat said: Well spotted :), I should've actually said it's 6 x 550w panels. (and using a Victron 150/85 mppt) I installed 8, but 2 of the panels hadn't been connected yet. They were connected today so I'll see what my yield looks like with all 8 going. But i figured i'd still want to add panels at some stage and wanted to sense check what the best way forward would be. Those 2 extra panels could change things quite a bit now. If they are managing to charge the batteries nicely then maybe the extra panels can be added to the West in future and get rid of that 3pm grid usage if you even need them anymore.
March 9, 20233 yr 12 hours ago, jumper said: I agree 40% is not too low, but they are only getting back to 65% before being discharged again and on multiple cloudy days things could be worse. I just like to keep batteries charged as much as possible (not necessarily as fast as possible) before using them again. Those are some quality (and costly) batteries, I would take very good care of them. Very interesting to read how we as Homo Sapiens do our own thing. Due to current times of LS I have such a low need to power things from the inverter. Battery sits at about 60% SOC and only powers my routers and phone charging. No need for lights for a 16h to 18h LS. I have not done any charging in 3 days. Today was a great PV day although the peak was lower than other days but my total PV system generated the most ever. This due to panels that would normally charge the batteries and have wasted power were used on my grid tied. Couple this with no LS assisted in a big way.
March 9, 20233 yr 5 minutes ago, Scorp007 said: Very interesting to read how we as Homo Sapiens do our own thing. Due to current times of LS I have such a low need to power things from the inverter. Battery sits at about 60% SOC and only powers my routers and phone charging. No need for lights for a 16h to 18h LS. I have not done any charging in 3 days. Today was a great PV day although the peak was lower than other days but my total PV system generated the most ever. This due to panels that would normally charge the batteries and have wasted power were used on my grid tied. Couple this with no LS assisted in a big way. Yeah everyone has their own way of doing things depending on their situation. I am completely off-grid and can't rely on any input except for the sun so I like to keep my battery charged as the weather here in the mountains can also be very unpredictable. I could maybe go 2 days without charging, but by then I would be freaking out 😱
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