rin67630
Solar Enthusiast
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.
Improving an old off-grid system
- Thread starter triplem
- Start date
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,436
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.
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
Solar Wizard
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.
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 Enthusiast
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.
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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.
Power Inverter Pure Sine Wave-3000 Watt 24V DC to 230V/240V AC Converter-2AC EU Outlets Car Inverter with Dua USB Ports-5 Meter Remote Control And Two Cooling Fans-Peak Power 6000 Watt: Amazon.co.uk: Electronics & Photo
Free delivery and returns on eligible orders. Buy Power Inverter Pure Sine Wave-3000 Watt 24V DC to 230V/240V AC Converter-2AC EU Outlets Car Inverter with Dua USB Ports-5 Meter Remote Control And Two Cooling Fans-Peak Power 6000 Watt at Amazon UK.
www.amazon.co.uk
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
Solar Wizard
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.
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?
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
life passes by too quickly to not live in freedom
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
