Improving an old off-grid system

rin67630

Solar Addict
Joined
Apr 29, 2020
Messages
919
No problem. It's common knowledge that batteries need to charge at voltages higher than the rating, so all the equipment is rated for that. Everything in your car is rated at least at 14.5V, not 12V.
By the way: the advantage of using DC/DC converters to get 12V from 24V is that you always get 12V irrespective of your real battery voltage that varies from 22V to 29V and even more during equalization.
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
10,981
If you need more power, buy more panels and put them on a ground-mount. Multiple legs with diagonal bracing allows skinny pipes compared to a single pole mount.

PV panels are now the cheapest part of the system. Batteries are the most expensive.
Lead-acid batteries have a preferred/maximum charge current. Either an all-in-one or certain charge controllers that communicate with a battery shunt can regulate battery charge current while delivering much more if inverter is drawing power. e.g. PV array could be 2x to 10x the size needed for charge current and can power loads while the sun shines.
Batteries can cost 10x what PV panels do (per kWh of lifetime use), so oversize PV may be cost effective.

Having a dump load, e.g. enabling a water heater when battery gets full and AC loads are small, is a way to utilize excess PV capacity and stay within inverter capacity. A manual switch could divert AC power to shop tools when desired, enable dump load at other times.
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
2,124
Did you measure the no-load drain of your inverter ? Good ones low frequency type in the 3-4KW range easily need 10W to 20W just for idling, some a lot more. 10W idle means a full KWh wasted every 4 days. 20W, every two days.
My system can make 25kWh per day. On construction days, I might be pulling 3000-3500W out of my inverter to power everything. Why should I possibly be concerned that my inverter consumes 30W at idle? A full kWh in 4 days? I wouldn't even notice. It's not even worth measuring at my system scale. BTW, the 30W idle consumption is far lower than that of the AiO units commonly touted on this site.
 

sergea

Solar Enthusiast
Joined
Dec 15, 2020
Messages
214
Location
france
I was wondering if I could plug something like a raspberry pi or else to aggregate data for a long period of time, and get the data back with a usb or with bluetooth. Or any other devices that does that.
you could, its only overkill, go in the resource section and grab, the spread sheet to evaluate your needs.. it will gives you an indication about what you need in term of inverter, panel, and so on. That being said with a 24v 2KW inverter and a 40A reated SCC and you're done.
 

rin67630

Solar Addict
Joined
Apr 29, 2020
Messages
919
My system can make 25kWh per day. On construction days, I might be pulling 3000-3500W out of my inverter to power everything. Why should I possibly be concerned that my inverter consumes 30W at idle? A full kWh in 4 days? I wouldn't even notice. It's not even worth measuring at my system scale. BTW, the 30W idle consumption is far lower than that of the AiO units commonly touted on this site.
I agree with you, if you have got power in excess, you dont't have to worry at your home, but please don't recommend that to someone having only 2 panels on small cabin or a RV, which is the case here.

By th way: "my inverter consumes 30W at idle? A full kWh in 4 days?"
Your math is wrong: to keep it simple, 4 days are close to 100 hours. 30W idle are ~ three KWH in four days, not one !

Else, you should nor calculate with max values but by minimum values.
I don't know where you live, but here in Germany a solar system that delivers 25KWh on sunny summer days, will give you far less than 3KWh on a cloudy winter day.
Then consuming additionally 0,75KWh isn't negligible any more.
 
Last edited:

triplem

New Member
Joined
May 14, 2022
Messages
7
I was wondering if this inverter would be enough to power our tool :

Only thing is that I must make sure to receive 0.6 A to make it work + the 24 volt ?

Thanks again for all your replies and time.
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
2,124
I agree with you, if you have got power in excess, you dont't have to worry at your home, but please don't recommend that to someone having only 2 panels on small cabin or a RV, which is the case here.
The salient term here is "only 2 panels". When you can get panels for 65-75$ now, why would anyone still have only two panels. We are not talking about a camper shell here. We are talking about a cabin. I'm pretty sure that even the tiniest little cabin has space for more than just two little panels.
By th way: "my inverter consumes 30W at idle? A full kWh in 4 days?"
Your math is wrong: to keep it simple, 4 days are close to 100 hours. 30W idle are ~ three KWH in four days, not one !
Why should I possibly be concerned that my inverter consumes 30W at idle? A full 3 kWh in 4 days? I wouldn't even notice. It's not even worth measuring at my system scale. Happy now?
I don't know where you live, but here in Germany a solar system that delivers 25KWh on sunny summer days, will give you far less than 3KWh on a cloudy winter day.
Then consuming additionally 0,75KWh isn't negligible any more.

Do make enough on cloudy wet winter days. My batteries get fully charged even in the rain. I just can't irrigate the orchard. But, why would I be irrigating the orchard in the rain?
 

12VoltInstalls

…myself everything do I…
Joined
Jan 18, 2021
Messages
3,973
Location
Vermont
wondering if this inverter would be enough
I don’t know the brand but it’s unavailable
UK website

If you’re gonna buy the cheaper end but want to depend on it, look up Giandel and Reliable (QZRELB) and maybe MPPSolar and see what they have for 240VAC inverters. At least they’ll most likely work for a while. Or the high end stuff is secure; however you can buy those brands 2-5 times for that kind of money and have a backup.
 

triplem

New Member
Joined
May 14, 2022
Messages
7
I don’t know the brand but it’s unavailable
UK website

If you’re gonna buy the cheaper end but want to depend on it, look up Giandel and Reliable (QZRELB) and maybe MPPSolar and see what they have for 240VAC inverters. At least they’ll most likely work for a while. Or the high end stuff is secure; however you can buy those brands 2-5 times for that kind of money and have a backup.
I shared the uk version for the english speaker, on the french amazon it is available. But I'll look into the brands you shared. Thanks :)
 
Top