t-muehlberger
New Member
- Joined
- Jul 27, 2020
- Messages
- 13
TLDR: Want to use an old cheap server UPS because it already has battery + grid-charger + inverter built in. Also this things are really cheap usually.
Ok, so I am trying this as a hobby project and the idea is to build a rather small and rather cheap solar system. Now I get that none of this comes even close to any best practices in this space but this is just for hobby use so bear with me here.
So the Idea is to build a small solar array on the roof in order to power some devices around the house. Now I do need off-grid capabilities or battery storage since our grid here is pretty stable and the devices are not mission critical, also batteries would add more cost to the project. What I want is a system where I can plug in some devices that run on 230V mains. When the sun is out I want to use the solar power but when the sun is not so strong or during the night grid power should be used to fill the gap.
Now I know that a grid-tie system would be perfect for this but for legal reasons this is not an option here (You have to register it and have to get it installed by a professional, which adds cost and takes away hobby feeling).
Ok so here is my Idea. So basically I would be using a really small battery (lead-acid probably, cheap, simple to charge, is allowed to float). Then I would use a grid power supply set to 13.6V for example. Also a MPPT would be connected to the battery, set to voltage of 13.8V (which is higher than the gird power supply). The idea is that as soon as the sun is is there and the battery voltage rises above the Voltage of the grid power supply only solar power is used since now the voltage potential of the battery is higher than the grid charger and no power is flowing. As soon as the sun goes away or the panes produce not enough the voltage will fall back down and the grid power supply will kick in and make up for the difference. Also there is an inverter connected to the battery to power the loads. The battery would be really small in capacity, probably an old used car battery. I am not even sure if a battery would be needed in this case but I am assuming it is good for load spikes.
In my head this should work, am I wrong?
Ok, now here comes the sketchy part: I have this old server UPS lying around (also these can be had really cheap on the internet with (semi)-deffect batteries probably). If I am not mistaking this thing should already contain all the necessary parts in the correct configuration. It has a batttery, a grid charger, an inverter. Only need to pop open the cover and connect an MPPT to the battery terminals. Maybe some minor modifications.
At least in my head it would sound this simple, am I wrong? Am I missing anything?
Ok, so I am trying this as a hobby project and the idea is to build a rather small and rather cheap solar system. Now I get that none of this comes even close to any best practices in this space but this is just for hobby use so bear with me here.
So the Idea is to build a small solar array on the roof in order to power some devices around the house. Now I do need off-grid capabilities or battery storage since our grid here is pretty stable and the devices are not mission critical, also batteries would add more cost to the project. What I want is a system where I can plug in some devices that run on 230V mains. When the sun is out I want to use the solar power but when the sun is not so strong or during the night grid power should be used to fill the gap.
Now I know that a grid-tie system would be perfect for this but for legal reasons this is not an option here (You have to register it and have to get it installed by a professional, which adds cost and takes away hobby feeling).
Ok so here is my Idea. So basically I would be using a really small battery (lead-acid probably, cheap, simple to charge, is allowed to float). Then I would use a grid power supply set to 13.6V for example. Also a MPPT would be connected to the battery, set to voltage of 13.8V (which is higher than the gird power supply). The idea is that as soon as the sun is is there and the battery voltage rises above the Voltage of the grid power supply only solar power is used since now the voltage potential of the battery is higher than the grid charger and no power is flowing. As soon as the sun goes away or the panes produce not enough the voltage will fall back down and the grid power supply will kick in and make up for the difference. Also there is an inverter connected to the battery to power the loads. The battery would be really small in capacity, probably an old used car battery. I am not even sure if a battery would be needed in this case but I am assuming it is good for load spikes.
In my head this should work, am I wrong?
Ok, now here comes the sketchy part: I have this old server UPS lying around (also these can be had really cheap on the internet with (semi)-deffect batteries probably). If I am not mistaking this thing should already contain all the necessary parts in the correct configuration. It has a batttery, a grid charger, an inverter. Only need to pop open the cover and connect an MPPT to the battery terminals. Maybe some minor modifications.
At least in my head it would sound this simple, am I wrong? Am I missing anything?
